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International Journal of Turbomachinery, Propulsion and Power
Number of Followers: 23  Open Access journalISSN (Online) 2504-186X Published by MDPI  [84 journals]
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- IJTPP, Vol. 7, Pages 12: Flow in Pillow-Plate Channels for High-Speed
Turbomachinery Heat Exchangers
Authors: Stephan Sundermeier, Maximilian Passmann, Stefan aus der Wiesche, Eugeny Y. Kenig
First page: 12
Abstract: In numerous turbomachinery applications, e.g., in aero-engines with regenerators for improving specific fuel consumption (SFC), heat exchangers with low-pressure loss are required. Pil low-plate heat exchangers (PPHE) are a novel exchanger type and promising candidates for high-speed flow applications due to their smooth profiles avoiding blunt obstacles in the flow path. This work deals with the overall system behavior and gas dynamics of pillow-plate channels. A pillow-plate channel was placed in the test section of a blow-down wind tunnel working with dry air, and compressible flow phenomena were investigated utilizing conventional and focusing schlieren optics; furthermore, static and total pressure measurements were performed. The experiments supported the assumption that the system behavior can be described through a Fanno–Rayleigh flow model. Since only wavy walls with smooth profiles were involved, linearized gas dynamics was able to cover important flow features within the channel. The effects of the wavy wall structures on pressure drop and Mach number distribution within the flow path were investigated, and a good qualitative agreement with theoretical and numerical predictions was found. The present analysis demonstrates that pressure losses in pillow-plate heat exchangers are rather low, although their strong turbulent mixing enables high convective heat transfer coefficients.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2022-03-22
DOI: 10.3390/ijtpp7020012
Issue No: Vol. 7, No. 2 (2022)
- IJTPP, Vol. 7, Pages 13: Two-Dimensional Investigation of the Fundamentals
of OGV Buffeting
Authors: Jonah Harris, Bharat Lad, Sina Stapelfeldt
First page: 13
Abstract: The increased demands of compact modern aero engine architectures have highlighted the problem of outlet guide vane (OGV) buffeting in off-design conditions. This structural response to aerodynamic excitations is characterised by increased vibration, risking structural fatigue. Investigations focused on understanding, mitigation and avoidance are therefore of high priority. OGV buffet is a type of transonic buffet caused by unsteady shock movement, but the exact parameters driving it are not fully understood. To try and understand them, this paper examines the buffet of a quasi-2D OGV geometry. Parametric studies of the incidence angle and inlet Mach number were performed. Forcing frequencies for both studies were found to be close to the experimentally detected frequency of vibration in the first bow mode, which demonstrates that buffet is driven by quasi-2D flow features. Increasing the inlet Mach number increased the dominant forcing frequency, whereas increasing the incidence yielded little change. Profiles of unsteady pressure amplitudes were shown to smoothly increase in magnitude with an increasing incidence and inlet Mach number.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2022-04-02
DOI: 10.3390/ijtpp7020013
Issue No: Vol. 7, No. 2 (2022)
- IJTPP, Vol. 7, Pages 14: A Reliable Update of the Ainley and Mathieson
Profile and Secondary Correlations
Authors: Yumin Liu, Patrick Hendrick, Zhengping Zou, Frank Buysschaert
First page: 14
Abstract: Empirical correlations are still fundamental in the modern design paradigm of axial turbines. Among these, the prominent Ainley and Mathieson correlation (Ainley D. and Mathieson G., 1951, “A Method of Performance Estimation for Axial-Flow Turbines,” ARC Reports and Memoranda No. 2974) and its derivatives, plays a crucial role. In this paper, the underlying assumptions of the aforementioned models are discussed by means of a descriptive review, whilst an attempt is made to enhance their reliability and, potentially, accuracy in performance estimations. Closer investigation reveals an intriguing misuse of the lift coefficient in the secondary loss. In light of this, an enhanced model that, notably, builds upon the Zweifel criterion and the vortex penetration depth concept is developed and discussed. The obtained accuracy is subsequently assessed through CFD computations, employing a database comprising 109 cascades. The results indicate a 50% probability of achieving the ±15% error interval, which is twice as good as the most recent Aungier model (Aungier R., 2006, “Turbine Aerodynamics: Axial-Flow and Radial-Inflow Turbine Design and Analysis”, ASME Press, New York). Furthermore, the reliability of the proposed model is demonstrated by a reconstruction of the Smith chart, on the one hand, and a performance analysis, on the other. The reconstruction exhibits contours that conform to the original. The results of the performance study are compared with the CFD solutions of eight cascades working in off design conditions and confirm the need of the additionally included turbine design parameters, such as the axial velocity and the meanline radius ratios.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2022-04-21
DOI: 10.3390/ijtpp7020014
Issue No: Vol. 7, No. 2 (2022)
- IJTPP, Vol. 7, Pages 15: Acoustoelastic Modes in Rotor-Cavity Systems: An
Overview on Frequency Shift Effects Supported with Measurements
Authors: Unglaube, Brillert
First page: 15
Abstract: With an increase in fluid densities in centrifugal compressors, fluid-structure interaction and coupled acoustoelastic modes receive growing attention to avoid machine failure. Besides the vibrational behavior of the impeller, acoustic modes building up in the side cavities need to be understood to ensure safe and reliable operation. In a coupled system, these structure and acoustic dominant modes influence each other. Therefore, a comprehensive overview of frequency shift effects in rotor-cavity systems is established based on findings in the literature. Additionally, experimental results on coupled mode pairs in a rotor-cavity test rig with a rotating disk under varying operating conditions are presented. Measurement results for structure dominant modes agree well with theoretical predictions. The development of a forward and a backward traveling wave is demonstrated for each mode in case of disk rotation. Conducted experiments reveal the occurrence of weakly and strongly coupled mode pairs as frequency shifts are observed that cannot solely be explained by “uncoupled mode effects”, such as the added mass, speed of sound, and stiffening effect, but indicate an additional coupling effect. However, the hypothesis of a bigger frequency shift for stronger coupled modes cannot be corroborated consistently. Only for the strongly coupled four nodal diameter mode pair in the “wide cavity” setup, a coupling effect is clearly visible in the form of mode veering.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2022-05-06
DOI: 10.3390/ijtpp7020015
Issue No: Vol. 7, No. 2 (2022)
- IJTPP, Vol. 7, Pages 16: Machine Learning Methods in CFD for
Turbomachinery: A Review
Authors: James Hammond, Nick Pepper, Francesco Montomoli, Vittorio Michelassi
First page: 16
Abstract: Computational Fluid Dynamics is one of the most relied upon tools in the design and analysis of components in turbomachines. From the propulsion fan at the inlet, through the compressor and combustion sections, to the turbines at the outlet, CFD is used to perform fluid flow and heat transfer analyses to help designers extract the highest performance out of each component. In some cases, such as the design point performance of the axial compressor, current methods are capable of delivering good predictive accuracy. However, many areas require improved methods to give reliable predictions in order for the relevant design spaces to be further explored with confidence. This paper illustrates recent developments in CFD for turbomachinery which make use of machine learning techniques to augment prediction accuracy, speed up prediction times, analyse and manage uncertainty and reconcile simulations with available data. Such techniques facilitate faster and more robust searches of the design space, with or without the help of optimization methods, and enable innovative designs which keep pace with the demand for improved efficiency and sustainability as well as parts and asset operation cost reduction.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2022-05-13
DOI: 10.3390/ijtpp7020016
Issue No: Vol. 7, No. 2 (2022)
- IJTPP, Vol. 7, Pages 1: Design and Parametric Analysis of a Supersonic
Turbine for Rotating Detonation Engine Applications
Authors: Noraiz Mushtaq, Gabriele Colella, Paolo Gaetani
First page: 1
Abstract: Pressure gain combustion is a promising alternative to conventional gas turbine technologies and within this class the Rotating Detonation Engine has the greatest potential. The Fickett–Jacobs cycle can theoretically increase the efficiency by 15% for medium pressure ratios, but the combustion chamber delivers a strongly non-uniform flow; in these conditions, conventionally designed turbines are inadequate with an efficiency below 30%. In this paper, an original mean-line code was developed to perform an advanced preliminary design of a supersonic turbine; self-starting capability of the supersonic channel has been verified through Kantrowitz and Donaldson theory; the design of the supersonic profile was carried out employing the Method of Characteristics; an accurate evaluation of the aerodynamic losses has been achieved by considering shock waves, profile, and mixing losses. Afterwards, an automated Computational Fluid Dynamics (CFD) based optimization process was developed to find the optimal loading condition that minimizes losses while delivering a sufficiently uniform flow at outlet. Finally, a novel parametric analysis was performed considering the effect of inlet angle, Mach number, reaction degree, peripheral velocity, and blade height ratio on the turbine stage performance. This analysis has revealed for the first time, in authors knowledge, that this type of machines can achieve efficiencies over 70%.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2022-01-04
DOI: 10.3390/ijtpp7010001
Issue No: Vol. 7, No. 1 (2022)
- IJTPP, Vol. 7, Pages 2: Preliminary Design Guidelines for Considering the
Vibration and Noise of Low-Speed Axial Fans Due to Profile Vortex Shedding
Authors: Gábor Daku, János Vad
First page: 2
Abstract: This paper presents a critical overview on worst-case design scenarios for which low-speed axial flow fans may exhibit an increased risk of blade resonance due to profile vortex shedding. To set up a design example, a circular-arc-cambered plate of 8% relative curvature is investigated in twofold approaches of blade mechanics and aerodynamics. For these purposes, the frequency of the first bending mode of a plate of arbitrary circular camber is expressed by modeling the fan blade as a cantilever beam. Furthermore, an iterative blade design method is developed for checking the risky scenarios for which spanwise and spatially coherent shed vortices, stimulating pronounced vibration and noise, may occur. Coupling these two approaches, cases for vortex-induced blade resonance are set up. Opposing this basis, design guidelines are elaborated upon for avoiding such resonance. Based on the approach presented herein, guidelines are also developed for moderating the annoyance due to the vortex shedding noise.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2022-01-07
DOI: 10.3390/ijtpp7010002
Issue No: Vol. 7, No. 1 (2022)
- IJTPP, Vol. 7, Pages 3: Retrofittable Solutions Capability for Gas Turbine
Compressors
Authors: Martina Ricci, Stefano Gino Mosele, Marcello Benvenuto, Pio Astrua, Roberto Pacciani, Michele Marconcini
First page: 3
Abstract: The increasing introduction of renewable energy capacity has changed the perspective on the operation of conventional power plants, introducing the necessity of reaching extreme off-design conditions. There is a strong interest in the development and optimization of technologies that can be retrofitted to an existing power plant to enhance flexibility as well as increase performance and lower emissions. Under the framework of the European project TURBO-REFLEX, a typical F-class gas turbine compressor designed and manufactured by Ansaldo Energia has been studied. Numerical analyses were performed using the TRAF code, which is a state-of-the-art 3D CFD RANS/URANS flow solver. In order to assess the feasibility of lower minimum environmental load operation, by utilizing a reduction in the compressor outlet mass-flow rate, with a safe stability margin, two different solutions have been analyzed: blow-off extractions and extra-closure of Variable Inlet Guide Vanes. The numerical steady-state results are compared and discussed in relation to an experimental campaign, which was performed by Ansaldo Energia. The purpose is to identify the feasibility of the technologies and implementation opportunity in the existing thermal power plant fleet.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2022-01-11
DOI: 10.3390/ijtpp7010003
Issue No: Vol. 7, No. 1 (2022)
- IJTPP, Vol. 7, Pages 4: Acknowledgment to Reviewers of IJTPP in 2021
Authors: IJTPP Editorial Office IJTPP Editorial Office
First page: 4
Abstract: Rigorous peer-reviews are the basis of high-quality academic publishing [...]
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2022-01-31
DOI: 10.3390/ijtpp7010004
Issue No: Vol. 7, No. 1 (2022)
- IJTPP, Vol. 7, Pages 5: A Low Order Flow Network Model for Double-Wall
Effusion Cooling Systems
Authors: van de Noort, Ireland
First page: 5
Abstract: The high pressure turbine nozzle guide vane of a modern aeroengine experiences large heat loads and thus requires both highly effective internal and external cooling. This can be accomplished with double-wall effusion cooling, which combines impingement, pin-fin and effusion cooling. The combination of three cooling mechanisms causes high pressure losses, increasing potential for the migration of coolant towards low pressure regions, subsequently starving effusion holes on the leading edge of coolant supply. This paper presents a low order flow network model to rapidly assess the pressure and mass flow distributions through such cooling schemes for a flexible set of geometric and flow conditions. The model is subsequently validated by a series of experiments with varying mainstream pressure gradients. Results from the model are used to indicate design parameters to reduce the effect of coolant migration, and to minimise the risk of destructive hot gas ingestion.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2022-02-02
DOI: 10.3390/ijtpp7010005
Issue No: Vol. 7, No. 1 (2022)
- IJTPP, Vol. 7, Pages 6: Trapped Acoustic Modes in an Axial Multi-Stage
Compressor Leading to Non-Synchronous Blade Vibrations
Authors: Anne-Lise Fiquet, Stéphane Aubert, Nicolas Buffaz, Agathe Vercoutter, Christoph Brandstetter
First page: 6
Abstract: Non-synchronous blade vibrations have been observed in an experimental multi-stage high-speed compressor setup at part-speed conditions. A detailed numerical study has been carried out to understand the observed phenomenon by performing unsteady full-annulus Reynolds-Averaged Navier–Stokes (RANS) simulations of the whole setup using the solver elsA. Several operating conditions have been simulated to observe this kind of phenomena along a speedline of interest. Based on the simulation results, the physical source of the non-synchronous blade vibration is identified: An aerodynamic disturbance appears in a highly loaded downstream rotor and excites a spinning acoustic mode. A “lock-in” phenomenon occurs between the blade boundary layer oscillations and the spinning acoustic mode. The establishment of axially propagating acoustic waves can lead to a complex coupling mechanism and this phenomenon is highly relevant in understanding the multi-physical interactions appearing in modern compressors. It is shown that aerodynamic disturbances occurring downstream can lead to critical excitation of rotor blades in upstream stages due to an axially propagating acoustic wave. The paper includes the analysis of a relevant transient test and a detailed analysis of the numerical results. The study shows the capability and necessity of a full-annulus multistage simulation to understand the phenomenon.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2022-02-04
DOI: 10.3390/ijtpp7010006
Issue No: Vol. 7, No. 1 (2022)
- IJTPP, Vol. 7, Pages 7: Aeroelastic Stability of Combined Plunge-Pitch
Mode Shapes in a Linear Compressor Cascade
Authors: George Hill, Julian Gambel, Sabine Schneider, Dieter Peitsch, Sina Stapelfeldt
First page: 7
Abstract: Modern aeroengine designs strive for peak specific fuel and thermal efficiency. To achieve these goals, engines have more highly loaded compressor stages, thinner aerofoils, and blended titanium integrated disks (blisks) to reduce weight. These configurations promote the occurrence of aeroelastic phenomena such as flutter. Two important parameters known to influence flutter stability are the reduced frequency and the ratio of plunge and pitch components in a combined flap mode shape. These are used as design criteria in the engine development process. However, the limit of these criteria is not fully understood. The following research aims to bridge the gap between semi-analytical models and modern compressors by systematically investigating the flutter stability of a linear compressor cascade. This paper introduces the plunge-to-pitch incidence ratio, which is defined as a function of reduced frequency and pitch axis setback for a first flap (1F) mode shape. Using numerical simulations, in addition to experimental validation, aerodynamic damping is computed for many modes to build stability maps. The results confirm the importance of these two parameters in compressor aeroelastic stability as well as demonstrate the significance of the plunge-to-pitch incidence ratio for predicting the flutter limit.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2022-02-14
DOI: 10.3390/ijtpp7010007
Issue No: Vol. 7, No. 1 (2022)
- IJTPP, Vol. 7, Pages 8: Reynolds Sensitivity of the Wake Passing Effect on
a LPT Cascade Using Spectral/hp Element Methods†
Authors: Andrea Cassinelli, Andrés Mateo Mateo Gabín, Francesco Montomoli, Paolo Adami, Raul Vázquez Vázquez Díaz, Spencer J. Sherwin
First page: 8
Abstract: Reynolds-Averaged Navier–Stokes (RANS) methods continue to be the backbone of CFD-based design; however, the recent development of high-order unstructured solvers and meshing algorithms, combined with the lowering cost of HPC infrastructures, has the potential to allow for the introduction of high-fidelity simulations in the design loop, taking the role of a virtual wind tunnel. Extensive validation and verification is required over a broad design space. This is challenging for a number of reasons, including the range of operating conditions, the complexity of industrial geometries and their relative motion. A representative industrial low pressure turbine (LPT) cascade subject to wake passing interactions is analysed, adopting the incompressible Navier–Stokes solver implemented in the spectral/hp element framework Nektar++. The bar passing effect is modelled by leveraging a spectral-element/Fourier Smoothed Profile Method. The Reynolds sensitivity is analysed, focusing in detail on the dynamics of the separation bubble on the suction surface as well as the mean flow properties, wake profiles and loss estimations. The main findings are compared with experimental data, showing agreement in the prediction of wake traverses and losses across the entire range of flow regimes, the latter within 5% of the experimental measurements.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2022-02-22
DOI: 10.3390/ijtpp7010008
Issue No: Vol. 7, No. 1 (2022)
- IJTPP, Vol. 7, Pages 9: Experimental Validation of an Analytical
Condensation Model for Application in Steam Turbine Design
Authors: Lapp, Schuster, Hecker, Brillert
First page: 9
Abstract: This paper presents experimental data on shear-stress-driven liquid water films on a horizontal plate formed by the condensation of superheated steam. The experimental results were obtained in the Experimental Multi-phase Measurement Application (EMMA) at the University of Duisburg-Essen. The liquid film thickness was spatially and temporally investigated with an optical measurement system. Furthermore, the resulting local heat transfer coefficient in the case of film condensation was determined for a variety of steam velocities and temperatures. Subsequently, the presented data are compared to the results of an analytical condensation model for shear-stress-driven liquid films developed by Cess and Koh. Thus, the model is qualitatively validated, with explicable remaining disparities between the model and experiment that are further discussed. The presented results are an important contribution to the contemporary research into steady-state, single-component multiphase flow considering phase-change phenomena including heat transfer.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2022-03-03
DOI: 10.3390/ijtpp7010009
Issue No: Vol. 7, No. 1 (2022)
- IJTPP, Vol. 7, Pages 10: Stall Margin Improvement in an Axial Compressor
by Continuous and Pulsed Tip Injection
Authors: Joseph Moubogha Moubogha, Gabriel Margalida, Pierric Joseph, Olivier Roussette, Antoine Dazin
First page: 10
Abstract: Stall and surge are strong limitations in the operating range of compressors and thus one of the major limits of jet engine performance. A promising way to push the stability limit of compression machines is to inject a small amount of flow at the blade tip to alter the physical mechanism responsible for stall onset. This study focuses on the experimental performance of such a system. To do so, an axial compressor test bench was equipped with 40 actuators connected to an auxiliary pressurised air supply system. They were able to generate high-speed jet blowing just at the tip of the rotor blades. The opening of each actuator was controlled by an electromagnetic valve. This allowed generating continuous or pulsed jets with frequencies up to 500 Hz at different duty cycles. The performance of the control system was investigated for various control strategies, where the injected flow rate, the injection angle, the number of injectors, the jet frequency and the duty cycle were systematically varied. This paper is concluded by a study of the energy balance of the system for various configurations. To the best of the authors’ knowledge, this constitutes a rarely seen analysis in the literature.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2022-03-16
DOI: 10.3390/ijtpp7010010
Issue No: Vol. 7, No. 1 (2022)
- IJTPP, Vol. 7, Pages 11: The Profile Loss of Additive Manufactured Blades
for Organic Rankine Cycle Turbines
Authors: Leander Hake, Felix Reinker, Robert Wagner, Stefan aus der Wiesche, Markus Schatz
First page: 11
Abstract: Results from an experimental profile loss study are presented of an additive manufactured linear turbine cascade placed in the test section of a closed-loop organic vapor wind tunnel. This test facility at Muenster University of Applied Sciences allows the investigation of high subsonic and transonic organic vapor flows under ORC turbine flow conditions at elevated pressure and temperature levels. An airfoil from the open literature was chosen for the cascade, and the organic vapor was Novec 649TM. Pitot probes measured the flow field upstream and downstream of the cascade. The inflow turbulence level was 0.5%. The roughness parameters of the metal-printed blades were determined, and the first set of flow measurements was performed. Then, the blade surfaces were further finished, and the impact of roughness on profile losses was assessed in the second flow measurement set. Although the Reynolds number level was relatively high, further surface treatment reduces the profile loss noticeably in organic vapor flows through the printed cascade.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2022-03-21
DOI: 10.3390/ijtpp7010011
Issue No: Vol. 7, No. 1 (2022)
- IJTPP, Vol. 6, Pages 40: Experimental Study of the Leakage Flow in an
Axial-Flow Fan at Variable Loading
Authors: Edward Canepa, Andrea Cattanei, Mehrdad Moradi, Alessandro Nilberto
First page: 40
Abstract: The present paper reports a 2D-PIV (particle image velocimetry) study of the effect of the operating point on the leakage flow in a low-speed ring fan. First, the flow pattern has been studied at 12 operating points covering the whole characteristic curve. At very low loading, the leakage flow streams along the rotor ring and is directly reingested; then, a separation bubble attached to the ring forms that, approaching the design point, modifies in a flow streaming radially outward. As the loading further increases, a separated flow region appears in the blade tip region that finally merges with the leakage flow. A further, more detailed study has been performed at eight operating points in the neighborhood of the design one. Very small loading variations may yield the leakage flow pattern modification, but no intermittence is present during the transition, as instantaneous flow patterns of any intermediate type continuously alternate. These results provide a consistent explanation for the ones of previous acoustic measurements.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-10-20
DOI: 10.3390/ijtpp6040040
Issue No: Vol. 6, No. 4 (2021)
- IJTPP, Vol. 6, Pages 41: The High-Speed Cascade Wind Tunnel at the
Bundeswehr University Munich after a Major Revision and Upgrade
Authors: Reinhard Niehuis, Martin Bitter
First page: 41
Abstract: Since its first operation in 1956 at DFL Braunschweig and after its movement to Munich, the High-Speed Cascade Wind Tunnel (HGK) at Bundeswehr University Munich is intensively used for fundamental and application-oriented research on aero-thermodynamics of turbomachinery bladings. Numerous systematic airfoil design studies were performed over the last decades. Thanks to the HGK facility, which enables thorough and detailed cascade testing at turbomachinery-relevant conditions, many of those airfoils for different purposes finally made it into turbomachinery applications. Nowadays, the HGK still provides very useful contributions to the understanding of the complicated flow in compressor and turbine bladings, and thereby extends the knowledge on relevant physical phenomena. As a consequence of the intense usage, this unique test facility was subject to a major revision and upgrade. The performed changes are presented within this paper including an overview on new capabilities in terms of the extended operating range, the data acquisition system, and the recently available measurement equipment.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-10-29
DOI: 10.3390/ijtpp6040041
Issue No: Vol. 6, No. 4 (2021)
- IJTPP, Vol. 6, Pages 42: Turbine Broadband Noise Predictions Using
Linearised Frequency Domain Navier-Stokes Solvers
Authors: Ricardo Blázquez-Navarro, Roque Corral
First page: 42
Abstract: A linear frequency domain Navier-Stokes solver is used to retain the influence of turning, thickness, and main geometric parameters on turbine broadband noise. The methodology has been applied to predict the broadband interaction noise produced by a representative low-speed low-pressure turbine section. The differences in the spectra with respect to those yielded by state-of-the-art flat plate based methodologies are up to 6 dB. The differences are caused by multiple effects that semi-analytical methodologies do not account for. The most important are blade thickness and turning, which have been studied separately to quantify their impact on the broadband noise footprint. The influence of changing the turbine operating conditions has been discussed as well. The outlet sound pressure level scales with the third and second power of the inlet and outlet Mach number, respectively, for constant turbulence intensity, within most of the frequency range considered.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-11-12
DOI: 10.3390/ijtpp6040042
Issue No: Vol. 6, No. 4 (2021)
- IJTPP, Vol. 6, Pages 43: Experimental and Numerical Analysis of a
Compressor Stage under Flow Distortion
Authors: Alberto Baretter, Benjamin Godard, Pierric Joseph, Olivier Roussette, Francesco Romanò, Raphael Barrier, Antoine Dazin
First page: 43
Abstract: On many occasions, fan or compressor stages have to face azimuthal flow distortion at inlet, which affects their performance and stability. These flow distortions can be caused by external events or by some particular geometrical features. The aim of this work is to propose a joined numerical and experimental analysis of the flow behavior in a single axial compressor stage under flow distortion. The distortions are generated by different grids that are placed upstream to the rotor. Experimentally, the flow analysis is based on the measurements obtained by a series of unsteady pressure sensors flush-mounted at the casing of the machine rotor. URANS computations are conducted using the elsA software. The flow distortion is simulated by a drop of stagnation pressure ratio at the inlet boundary condition. The study is focusing first on the ability of a pressure drop, imposed as an inlet boundary condition in CFD, to reproduce accurately the effect of a flow distortion. The analysis is conducted using singular value decomposition (SVD) and dynamic mode decomposition (DMD). A special attention is then paid, on the experimental level, to the arising of rotating stall, from the onset of the instability up to completely developed stall cells.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-11-23
DOI: 10.3390/ijtpp6040043
Issue No: Vol. 6, No. 4 (2021)
- IJTPP, Vol. 6, Pages 44: Data Driven Modal Decomposition of the Wake
behind an NREL-5MW Wind Turbine
Authors: Stefania Cherubini, Giovanni De Cillis, Onofrio Semeraro, Stefano Leonardi, Pietro De Palma
First page: 44
Abstract: The wake produced by a utility-scale wind turbine invested by a laminar, uniform inflow is analyzed by means of two different modal decompositions, the proper orthogonal decomposition (POD) and the dynamic mode decomposition (DMD), in its sparsity-promoting variant. The turbine considered is the NREL-5MW at tip-speed ratio λ=7 and a diameter-based Reynolds number of the order 108. The flow is simulated through large eddy simulation, where the forces exerted by the blades are modeled using the actuator line method, whereas tower and nacelle are modeled employing the immersed boundary method. The main flow structures identified by both modal decompositions are compared and some differences emerge that can be of great importance for the formulation of a reduced-order model. In particular, a high-frequency mode directly related to the tip vortices is found using both methods, but it is ranked differently. The other dominant modes are composed by large-scale low-frequency structures, but with different frequency content and spatial structure. The most energetic 200 POD modes account for ≈20% only of the flow kinetic energy. While using the same number of DMD modes, it is possible to reconstruct the flow field to within 80% accuracy. Despite the similarities between the set of modes, the comparison between these modal-decomposition techniques points out that an energy-based criterion such as that used in the POD may not be suitable for formulating a reduced-order model of wind turbine wakes, while the sparsity-promoting DMD appears able to perform well in reconstructing the flow field with only a few modes.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-11-25
DOI: 10.3390/ijtpp6040044
Issue No: Vol. 6, No. 4 (2021)
- IJTPP, Vol. 6, Pages 45: Transport of Swirling Entropy Waves through an
Axial Turbine Stator
Authors: Andrea Notaristefano, Paolo Gaetani
First page: 45
Abstract: The transport of entropy waves and their impact on the stage aerodynamics are still open questions. This paper shows the results of an experimental campaign that focuses on the swirling entropy waves advection through an axial turbine stator. The research aims at quantifying the aerodynamic impact of the swirling entropy waves on the first nozzle and characterizing their transport. The disturbance is generated by a novel entropy wave generator that ensures a wide set of different injection parameters. The device injects the disturbance axially, four different clocking positions are investigated. Measurements show a severe temperature attenuation of the swirling entropy wave at stator outlet. The high temperature location changes with the injection position as a result of the different interaction with the stator secondary flows. Depending on the injection position, the aerodynamic flow field is strongly perturbed by the injected swirl profile, instead the entropy wave effect is negligible.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-11-26
DOI: 10.3390/ijtpp6040045
Issue No: Vol. 6, No. 4 (2021)
- IJTPP, Vol. 6, Pages 46: Numerical Steady and Transient Evaluation of a
Confined Swirl Stabilized Burner
Authors: Federica Farisco, Luisa Castellanos, Jakob Woisetschläger, Wolfgang Sanz
First page: 46
Abstract: Lean premixed combustion technology became state of the art in recent heavy-duty gas turbines and aeroengines. In combustion chambers operating under fuel-lean conditions, unsteady heat release can augment pressure amplitudes, resulting in component engine damages. In order to achieve deeper knowledge concerning combustion instabilities, it is necessary to analyze in detail combustion processes. The current study supports this by conducting a numerical investigation of combustion in a premixed swirl-stabilized methane burner with operating conditions taken from experimental data that were recently published. It is a follow-up of a previous paper from Farisco et al., 2019 where a different combustion configuration was studied. The commercial code ANSYS Fluent has been used with the aim to perform steady and transient calculations via Large Eddy Simulation (LES) of the current confined methane combustor. A validation of the numerical data has been performed against the available experiments. In this study, the numerical temperature profiles have been compared with the measurements. The heat release parameter has been experimentally and numerically estimated in order to point out the position of the main reaction zone. Several turbulence and combustion models have been investigated with the aim to come into accord with the experiments. The outcome showed that the combustion model Flamelet Generated Manifold (FGM) with the k-ω turbulence model was able to correctly simulate flame lift-off.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-11-30
DOI: 10.3390/ijtpp6040046
Issue No: Vol. 6, No. 4 (2021)
- IJTPP, Vol. 6, Pages 21: Experimental Aerodynamic and Aeroelastic
Investigation of a Highly-Loaded 1.5-Stage Transonic Compressor with
Tandem Stator
Authors: Jonas Foret, Daniel Franke, Fabian Klausmann, Alexandra Schneider, Heinz-Peter Schiffer, Bernd Becker, Hauke Müller
First page: 21
Abstract: This paper experimentally investigates a highly-loaded 1.5-stage transonic axial compressor, which comprises a variable inlet guide vane, a BLISK rotor, and a variable stator in tandem arrangement. A detailed comparison between the newly designed compressor stage and a reference stage with a conventional stator design was conducted by using extensive instrumentation. Thus, steady and unsteady phenomena—focusing on the aerodynamic and aeroelastic behavior—were analyzed. Due to the new stator vane design, a higher aerodynamic stator vane loading was pursued, while the vane count was reduced. This, in turn, allowed a rotor design with an increased work coefficient. This experimental study revealed several effects of the optimized compressor stage in terms of both performance and the corresponding aerodynamics, as well as the aeroelastic behavior.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-06-22
DOI: 10.3390/ijtpp6030021
Issue No: Vol. 6, No. 3 (2021)
- IJTPP, Vol. 6, Pages 22: Experimental Investigation of the Unsteady
Stator/Rotor Wake Characteristics Downstream of an Axial Air Turbine
Authors: Daniel Duda, Tomáš Jelínek, Petr Milčák, Martin Němec, Václav Uruba, Vitalii Yanovych, Pavel Žitek
First page: 22
Abstract: A feasibility study of velocity field measurements using the Particle Image Velocimetry (PIV) method in an axial air turbine model is presented. The wakes past the blades of the rotor wheel were observed using the PIV technique. Data acquisition was synchronized with the shaft rotation; thus, the wakes were phase averaged for statistical analysis. The interaction of the rotor blade wakes with the stator ones was investigated by changing the stator wheel’s angle. The measurement planes were located just behind the rotor blades, covering approximately 3 cm × 3 cm in axial × tangential directions. The spatial correlation function suggests that the resolution used is sufficient for the large-scale flow-patterns only, but not for the small ones. The scales of fluctuations correspond to the shear layer thickness at the mid-span plane but, close to the end-wall, they contain larger structures caused by the secondary flows. The length-scales of the fluctuations under off-design conditions display a dependence on the area of the stator and rotor wakes cross-sections, which, in turn, depend on their angle. The obtained experimental data are to be used for the validation of mathematical simulation results in the future.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-06-28
DOI: 10.3390/ijtpp6030022
Issue No: Vol. 6, No. 3 (2021)
- IJTPP, Vol. 6, Pages 23: Modelling the Condensation Phenomena within the
Radial Turbine of a Fuel Cell Turbocharger
Authors: Tim Wittmann, Sebastian Lück, Christoph Bode, Jens Friedrichs
First page: 23
Abstract: Radial turbines used in automotive fuel cell turbochargers operate with humid air. The gas expansion in the turbine causes droplets to form, which then grow through condensation. The associated release of latent heat and decrease in the gaseous mass flow strongly influence the thermodynamics of the turbine. This study aims to investigate these phenomena. For this purpose, the classical nucleation theory and Young’s growth law are integrated into a Euler–Lagrange approach. The main advantages of this approach are the calculation of individual droplet trajectories and a full resolution of the droplet spectrum. The results indicate an onset of nucleation at the blade tip and in the tip gap, followed by nucleation over the entire blade span, depending on the humidity at the turbine inlet. With a saturated turbine inflow, condensation causes the outlet temperature to rise to almost the same level as at the inlet. In addition, condensation losses reduce the efficiency and the latent heat released by condensation leads to significant thermal throttling.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-07-08
DOI: 10.3390/ijtpp6030023
Issue No: Vol. 6, No. 3 (2021)
- IJTPP, Vol. 6, Pages 24: Pulsed Flow Turbine Design Recommendations
Authors: Florian Hermet, Nicolas Binder, Jérémie Gressier, Gonzalo Sáez-Mischlich
First page: 24
Abstract: A preliminary analysis of turbine design, fit for pulsed flow, is proposed in this paper. It focuses on an academic 2D configuration using inviscid flows, since pressure loads due to wave propagation are several orders of magnitude higher than friction and viscous effects do not significantly impinge on the inviscid part, as previously shown by Hermet, 2021. As such, a large parametric study was carried out using the design of experiments methodology. A performance indicator adapted to unsteady environment is carefully defined before detailing the factors chosen for the design of experiments. Since the number of factors is substantial, a screening design to identify the factors influence on the output is first established. The non-influential factors are then omitted in a more quantitative study of the output law. The surface response calculation allows determining the factor level favouring the best output. Consequently, the main trends in the turbine design driven by a pulsed flow can be stated.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-07-08
DOI: 10.3390/ijtpp6030024
Issue No: Vol. 6, No. 3 (2021)
- IJTPP, Vol. 6, Pages 25: Prediction of Transient Pressure Fluctuations
within a Low-Pressure Turbine Cascade Using a Lanczos-Filtered Harmonic
Balance Method
Authors: Jan Philipp Heners, Stephan Stotz, Annette Krosse, Detlef Korte, Maximilian Beck, Damian Vogt
First page: 25
Abstract: Unsteady pressure fluctuations measured by fast-response pressure transducers mounted in a low-pressure turbine cascade are compared to unsteady simulation results. Three differing simulation approaches are considered, one time-integration method and two harmonic balance methods either resolving or averaging the time-dependent components within the turbulence model. The observations are used to evaluate the capability of the harmonic balance solver to predict the transient pressure fluctuations acting on the investigated stator surface. Wakes of an upstream rotor are generated by moving cylindrical bars at a prescribed rotational speed that refers to a frequency of f∼500 Hz. The excitation at the rear part of the suction side is essentially driven by the presence of a separation bubble and is therefore highly dependent on the unsteady behavior of turbulence. In order to increase the stability of the investigated harmonic balance solver, a developed Lanczos-type filter method is applied if the turbulence model is considered in an unsteady fashion.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-07-09
DOI: 10.3390/ijtpp6030025
Issue No: Vol. 6, No. 3 (2021)
- IJTPP, Vol. 6, Pages 26: Analysis of a Linear Model for Non-Synchronous
Vibrations Near Stall
Authors: Christoph Brandstetter, Sina Stapelfeldt
First page: 26
Abstract: Non-synchronous vibrations arising near the stall boundary of compressors are a recurring and potentially safety-critical problem in modern aero-engines. Recent numerical and experimental investigations have shown that these vibrations are caused by the lock-in of circumferentially convected aerodynamic disturbances and structural vibration modes, and that it is possible to predict unstable vibration modes using coupled linear models. This paper aims to further investigate non-synchronous vibrations by casting a reduced model for NSV in the frequency domain and analysing stability for a range of parameters. It is shown how, and why, under certain conditions linear models are able to capture a phenomenon, which has traditionally been associated with aerodynamic non-linearities. The formulation clearly highlights the differences between convective non-synchronous vibrations and flutter and identifies the modifications necessary to make quantitative predictions.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-07-09
DOI: 10.3390/ijtpp6030026
Issue No: Vol. 6, No. 3 (2021)
- IJTPP, Vol. 6, Pages 27: Numerical Prediction of the Aerodynamics and
Acoustics of a Tip Leakage Flow Using Large-Eddy Simulation
Authors: David Lamidel, Guillaume Daviller, Michel Roger, Hélène Posson
First page: 27
Abstract: A Large-Eddy Simulation of the tip leakage flow of a single airfoil is carried out. The configuration consists of a non-rotating, isolated airfoil between two horizontal plates with a gap of 10 mm between the tip of the airfoil and the lower plate. The Mach number of the incoming flow is 0.2, and the Reynolds number based on the chord is 9.3 × 105. The objective of the present study is to investigate the best way to compute both the aerodynamics and acoustics of the tip leakage flow. In particular, the importance of the inflow conditions on the prediction of the tip leakage vortex and the airfoil loading is underlined. On the other hand, the complex structure of the tip leakage vortex and its convection along the airfoil was recovered due to the use of a mesh adaptation based on the dissipation of the kinetic energy. Finally, the ability of the wall law to model the flow in the tip leakage flow region was proven in terms of wall pressure fluctuations and acoustics in the far-field.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-07-13
DOI: 10.3390/ijtpp6030027
Issue No: Vol. 6, No. 3 (2021)
- IJTPP, Vol. 6, Pages 28: Influence of the Rotor-Driven Perturbation on the
Stator-Exit Flow within a High-Pressure Gas Turbine Stage
Authors: Paolo Gaetani, Giacomo Persico
First page: 28
Abstract: In stator–rotor interaction studies on axial turbines, the attention is commonly focused on the unsteady rotor aerodynamics resulting from the periodic perturbations induced by the stator flow structures. Conversely, less interest has been historically attracted regarding the influence of the rotor on the flow released by the stator, correlated to propagation of the blade potential field upstream of the rotor leading edge. In this paper, experiments in the research high-pressure turbine of the Laboratory of Fluid-Machines of the Politecnico di Milano, performed by applying a fast-response aerodynamic pressure probe, alongside fully-3D time-accurate CFD simulations of the flow, are combined with the aim of discussing the rotor-to-stator interaction. While rotating, the rotor induces periodic perturbations on the pressure and velocity field in the stator–rotor gap, altering the evolution of the total quantities and the flow rate discharged by each stator channel and eventually triggering energy-separation effects which result in total pressure and total temperature oscillations in the stator-exit flow. Such oscillations were found to rise up to almost ±10% of the stage total temperature drop.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-07-13
DOI: 10.3390/ijtpp6030028
Issue No: Vol. 6, No. 3 (2021)
- IJTPP, Vol. 6, Pages 29: Flow and Ingestion in a Turbine Disc Cavity under
Rotationally-Dominated Conditions
Authors: Anna Bru Revert, Paul F. Beard, John W. Chew
First page: 29
Abstract: An investigation of hot gas ingestion driven by the disc pumping effect in a chute seal was conducted at the Oxford Rotor Facility. Measurements of mean pressure, unsteady pressure and gas concentration have been logged and analysed under different operating conditions. The sensitivity of mean cavity pressure coefficient, frequency spectra of the unsteady pressures and sealing effectiveness to changing conditions of purge flow, annulus flow, rotor disc speed and seal clearance have been studied. The steady pressures revealed the development of two vortices in the cavity, induced by the sharp change in geometry of the stator wall. The increased shear at the interface between these two vortices strengthened the unsteady activity at this location. The addition of mainstream flow improved the sealing capability of the chute seal under certain operating conditions. The excitation of further frequencies when an axisymmetric annulus flow was introduced suggests a complex interaction between annulus and purge flows.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-07-20
DOI: 10.3390/ijtpp6030029
Issue No: Vol. 6, No. 3 (2021)
- IJTPP, Vol. 6, Pages 30: Loss Characterization of a Conventional Variable
Inlet Guide Vane
Authors: Roman G. Frank, Christian Wacker, Reinhard Niehuis
First page: 30
Abstract: Variable inlet guide vanes (VIGVs) are most commonly used as the major control unit of integrally geared centrifugal compressors (IGCCs). In order to enhance the efficient operating range of the compressor, the loss mechanisms and utilization limits of state-of-the-art VIGVs need to be better understood. Field measurements in the wake of a typical, commercially used configuration were therefore conducted at the VIGV test facility of the Bundeswehr University Munich. The investigations were carried out at application oriented subsonic flow conditions and stagger angles from 50∘ to 90∘ covering the full low-loss operating range, including the limits of efficient operation. For a precise local loss characterization, an inflow correlation was developed and applied to consider total pressure inhomogeneities caused by the radial inflow velocity profile and minor circumferential velocity deviations. Contrary to previous research efforts, not only the profile losses, but also the secondary flow losses induced by the open blade tips and wall-blade interactions were resolved in full detail. For this reason, a more precise and comprehensive loss assessment of realistic VIGV cascades is acquired.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-07-26
DOI: 10.3390/ijtpp6030030
Issue No: Vol. 6, No. 3 (2021)
- IJTPP, Vol. 6, Pages 31: Experimental Study on Flow Behavior of Unshrouded
Impeller Centrifugal Pumps under Inlet Air Entrainment Condition
Authors: Minquan Liao, Qiaorui Si, Meng Fan, Peng Wang, Zhonghai Liu, Shouqi Yuan, Qianglei Cui, Gérard Bois
First page: 31
Abstract: Results on overall pump head and efficiency performance, pressure pulsation and high speed camera visualization of flow patterns behavior are presented for different inlet air-water void fractions at a given rotational speed. With the increase of inlet void fractions and decrease of the flow rates, the size of bubbles increase and tend to agglomerate in specific impeller passage locations along the blade chord. The starting point of pump breakdown is related to a strong inward reverse flow occurring in a specific location near the shroud gap of the impeller and volute tongue region. Using a constant air void fraction value of 2%, pressure pulsation frequency results are analyzed in relation with local flow mixture patterns and flow rate modification.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-07-28
DOI: 10.3390/ijtpp6030031
Issue No: Vol. 6, No. 3 (2021)
- IJTPP, Vol. 6, Pages 32: Flow Coefficient and Reduced Frequency Effects on
Wake-Boundary Layer Interaction in Highly Accelerated LPT Cascade
Authors: Edward Canepa, Davide Lengani, Alessandro Nilberto, Daniele Petronio, Daniele Simoni, Marina Ubaldi, Pietro Zunino
First page: 32
Abstract: The paper presents a detailed analysis of particle image velocimetry (PIV) measurements performed in a turbine cascade representative of highly accelerated low-pressure turbine (LPT) blades. Two cameras have been simultaneously used to observe a great portion of the suction side boundary layer with the highest possible spatial resolution, thus allowing us to solve the interaction process between impinging upstream wakes and the blade boundary layer. Four unsteady inflow conditions, characterized by different incoming wake reduced frequencies and flow coefficients, have been examined at fixed Reynolds number. The highly resolved flow fields have been processed to explore reduced frequency and flow coefficient effects on the boundary layer unsteady transition process and, consequently, on loss production. For a deep physical insight on the mechanisms responsible for loss generation, proper orthogonal decomposition (POD) has been applied at different phases of the wake passing period. This has provided the dominant structures affecting the cascade aerodynamics during the wake period. Moreover, the examination of POD modes has allowed us to show the effects induced by the parameter variation on the turbulent kinetic energy production and thus to the unsteady loss production mechanisms.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-08-04
DOI: 10.3390/ijtpp6030032
Issue No: Vol. 6, No. 3 (2021)
- IJTPP, Vol. 6, Pages 33: Dimensionless Numbers Relationships for Outer Air
Seal of Low Pressure Turbine
Authors: Pałkus, Strzelczyk
First page: 33
Abstract: The dimensional analysis and the numerical parametric study of the typical outer air seal from a low-pressure turbine were performed in the framework of the presented paper. The most crucial variables for the flow through the outer air seal were identified and further dimensionless numbers were derived. The dependent quantities resulting from the analysis were: the axial Reynolds number (formulated with the bulk velocity, corresponding to the mass flow through the seal), the outlet swirl ratio (incorporating the exit flow angle, important for mixing) and the windage heating (related to the internal losses). Additionally, the discharge coefficient was cross-checked enabling further comparison with the available literature. The comprehensive numerical parametric study included all important contributors for the flow through the seal with a parameter operating range appropriate for engine outer air seals.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-08-24
DOI: 10.3390/ijtpp6030033
Issue No: Vol. 6, No. 3 (2021)
- IJTPP, Vol. 6, Pages 34: Improvement of the Parallel Compressor Model and
Application to Inlet Flow Distortion
Authors: Emmanuel Benichou, Nicolas Binder, Yannick Bousquet, Xavier Carbonneau
First page: 34
Abstract: This paper introduces a semi-analytical approach which enables one to deal with distorted inflow in axial fans or compressors. It is inspired by the classical parallel compressor (PC) theory but relies on a local flow-loading coefficient formalism. It is applied to non-uniform flow conditions to study the aerodynamic behavior of a low-speed fan in response to upstream flow distortion. Experimental measurements and 3D RANS simulations are used to evaluate the prediction of fan performance obtained with the local PC method. The comparison proves that, despite its simplicity, the present approach enables to correctly capture first order phenomena, offering interesting perspectives for an early design phase if different fan geometries are to be tested and if the upstream distortion maps are available.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-08-25
DOI: 10.3390/ijtpp6030034
Issue No: Vol. 6, No. 3 (2021)
- IJTPP, Vol. 6, Pages 35: Effect of Different Subgrid-Scale Models and
Inflow Turbulence Conditions on the Boundary Layer Transition in a
Transonic Linear Turbine Cascade
Authors: Ettore Bertolini, Paul Pieringer, Wolfgang Sanz
First page: 35
Abstract: The aim of this work is to study the influence of different subgrid-scale (SGS) closure models and inflow turbulence conditions on the boundary layer transition on the suction side of a highly loaded transonic turbine cascade in the presence of high free-stream turbulence using large eddy simulations (LES) of the MUR237 test case. For the numerical simulations, the MUR237 flow case was considered and the incoming free-stream turbulence was reproduced using the synthetic eddy method (SEM). The boundary layer transition on the blade suction side was found to be significantly influenced by the choice of the SGS closure model and the SEM parameters. These two aspects were carefully evaluated in this work. Initially, the influence of three different closure models (Smagorinsky, WALE, and subgrid-scale kinetic energy model) was evaluated. Among them, the WALE SGS closure model performed best compared to the Smagorinsky and KEM models and, for this reason, was used in the following analysis. Finally, different values of the turbulence length scale, eddies density, and inlet turbulence for the SEM were evaluated. As shown by the results, among the different parameters, the choice of the turbulence length scale plays a major role in the transition onset on the blade suction side.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-08-27
DOI: 10.3390/ijtpp6030035
Issue No: Vol. 6, No. 3 (2021)
- IJTPP, Vol. 6, Pages 36: Unsteady Simulation of a Transonic Turbine Stage
with Focus on Turbulence Prediction
Authors: Sanz, Scheier
First page: 36
Abstract: The flow in a transonic turbine stage still poses a high challenge for the correct prediction of turbulence using an eddy viscosity model. Therefore, an unsteady RANS simulation with the k-ω SST model, based on a preceding study of turbulence inlet conditions, was performed to see if this can improve the quality of the flow and turbulence prediction of an experimentally investigated turbine flow. Unsteady Q3D results showed that none of the different turbulence boundary conditions could predict the free-stream turbulence level and the maximum values correctly. Luckily, the influence of the boundary conditions on the velocity field proved to be small. The qualitative prediction of the complex secondary flows is good, but there is lacking agreement in the prediction of turbulence generation and destruction.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-08-27
DOI: 10.3390/ijtpp6030036
Issue No: Vol. 6, No. 3 (2021)
- IJTPP, Vol. 6, Pages 37: Influence of Spanwise and Streamwise Film Hole
Spacing on Adiabatic Film Effectiveness for Effusion-Cooled Gas Turbine
Blades
Authors: Matthew Courtis, Alexander Murray, Ben Coulton, Peter Ireland, Ignacio Mayo
First page: 37
Abstract: To meet the challenges of increased thermal loads and performance demands on aero-engine turbine blades, more advanced cooling techniques are required. This study used a modification of the well-known Goldstein equation to predict film effectiveness for an individual film cooling hole and applied the Sellers’ superposition method to apply these films across effusion-cooled configurations. In doing so, it tackles a relatively unchallenged problem of film holes in close spanwise proximity. An experimental set-up utilised infrared cameras to assess the film effectiveness of nine geometries of varying spanwise and streamwise spacings. Higher porosity led to increased thermal protection, and the spanwise spacing had the most profound impact, with film effectiveness approaching 0.9. Additionally, greater uniformity in the spanwise direction was observed. The modified Goldstein-Sellers method showed good agreement with experimental results although lateral mixing was underestimated. This method represents a tool that could be easily implemented in the industry for rapid assessment of novel cooling geometries.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-08-31
DOI: 10.3390/ijtpp6030037
Issue No: Vol. 6, No. 3 (2021)
- IJTPP, Vol. 6, Pages 38: Design Parameter Influence on Losses and
Downstream Flow Field Uniformity in Supersonic ORC Radial-Inflow Turbine
Stators
Authors: Cappiello, Tuccillo
First page: 38
Abstract: The design of organic Rankine cycle (ORC) turbines often requires dealing with transonic flows due to the cycle efficiency requirements and the matching of the temperature profiles with heat sources and sinks, as well as the nature of organic fluids, often featuring high molecular weight. Consequently, the use of convergent–divergent turbine stators has been widely established as a solution in the published literature for use in both axial- and radial-inflow machines. With respect to the latter layout in particular, the available design guidelines are still limited. The present work shows the results of an investigation into a series of ORC radial-inflow convergent–divergent nozzles that differ with respect to the vane count and the designed metal angle of the outlet. These stators were designed by fitting the divergent portion of a sharp-edged minimum-length nozzle, designed by means of the method of characteristics (MoC) adapted to dense gases, into a radial-inflow turbine stator. The geometries were analysed by means of steady-state RANS CFD calculations, and the results were used to assess the influence of the design parameters on the nozzle losses and downstream flow field uniformity, showing that conflicting trends exist between optimum stator efficiency and optimum downstream flow field uniformity.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-09-06
DOI: 10.3390/ijtpp6030038
Issue No: Vol. 6, No. 3 (2021)
- IJTPP, Vol. 6, Pages 39: Machine Learning Based Sensitivity Analysis of
Aeroelastic Stability Parameters in a Compressor Cascade
Authors: Marco Rauseo, Mehdi Vahdati, Fanzhou Zhao
First page: 39
Abstract: Aeroelastic instabilities such as flutter have a crucial role in limiting the operating range and reliability of turbomachinery. This paper offers an alternative approach to aeroelastic analysis, where the sensitivity of aerodynamic damping with respect to main flow and structural parameters is quantified through a surrogate-model-based investigation. The parameters are chosen based on previous studies and are represented by a uniform distribution within applicable intervals. The surrogate model is an artificial neural network, trained and tested to achieve an error within 1% of the test data. The quantity of interest is aerodynamic damping and the datasets are obtained from a linearised aeroelastic solver. The sensitivity of aerodynamic damping with respect to the input variables is obtained by calculating normalised gradients from the surrogate model at specific operating conditions. The results show a quantitative comparison of sensitivity across the different input parameters. The outcome of the sensitivity analysis is then used to decide the most appropriate action to take in order to induce stability in unstable operating conditions. The work is a preliminary study, carried out on a simplified two dimensional compressor cascade and it is aimed at proving the validity of a data-driven approach in studying the aeroelastic behaviour of turbomachinery. To the best of the authors’ knowledge, this is the first time a data-driven flutter model has been investigated. The initial results are encouraging, indicating that this approach is worth pursuing in the future. The presented framework can be used as a redesign tool to enhance the flutter stability of an existing blade.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-09-15
DOI: 10.3390/ijtpp6030039
Issue No: Vol. 6, No. 3 (2021)
- IJTPP, Vol. 6, Pages 6: Steady-State Fluid-Solid Mixing Plane to Replace
Transient Conjugate Heat Transfer Computations during Design Phase
Authors: Lucian Hanimann, Luca Mangani, Ernesto Casartelli, Elmar Gröschel, Magnus Fischer
First page: 6
Abstract: The demand for increased turbomachinery performance, both, towards higher pressures and temperatures, leads to high thermal-loads of specific components and can critically affect mechanical integrity. In the particular case of rotating-disk configurations, like the back-side of wheels or in cavities, a very efficient way for cooling is jet impingement. An example for this situation are high pressure-ratio turbochargers, where cooling of the impeller disk (back wall) is introduced to achieve tolerable thermal loads. From the physical point of view, jet impingement on a rotating wall generates an unsteady heat transfer situation. On the other end, accurate values of time-averaged temperatures would be sufficient for design purposes. In general, obtaining circumferentially time-averaged solutions requires transient analysis of the conjugate heat transfer (CHT) process to account for the mean effect of jet cooling on solids. Such analysis is computationally expensive, due to the difference in information propagation time-scale for the solid and the fluid. In this paper, a new approach to directly compute circumferentially time-averaged (i.e., steady-state) temperature distributions for rotating-disk CHT problems is presented based on an adaption of the well known fluid-fluid mixing plane approach.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-03-30
DOI: 10.3390/ijtpp6020006
Issue No: Vol. 6, No. 2 (2021)
- IJTPP, Vol. 6, Pages 7: A Consistent and Implicit Rhie–Chow
Interpolation for Drag Forces in Coupled Multiphase Solvers
Authors: Lucian Hanimann, Luca Mangani, Marwan Darwish, Ernesto Casartelli, Damian M. Vogt
First page: 7
Abstract: The use of coupled algorithms for single fluid flow simulation has proven its superiority as opposed to segregated algorithms, especially in terms of robustness and performance. In this paper, the coupled approach is extended for the simulation of multi-fluid flows, using a collocated and pressure-based finite volume discretization technique with a Eulerian–Eulerian model. In this context a key ingredient in this method is extending the Rhie–Chow interpolation technique to account for the unique flow coupling that arises from inter-phase drag. The treatment of this inter-fluid coupling and the fashion in which it interacts with the velocity-pressure solution algorithm is presented in detail and its effect on robustness and accuracy is demonstrated using 2D dilute gas–solid flow test case. The results achieved with this technique show substantial improvement in accuracy and performance when compared to a leading commercial code for a transonic nozzle configuration.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-04-01
DOI: 10.3390/ijtpp6020007
Issue No: Vol. 6, No. 2 (2021)
- IJTPP, Vol. 6, Pages 8: Differential Throttling and Fluidic Thrust
Vectoring in a Linear Aerospike
Authors: Michele Ferlauto, Andrea Ferrero, Matteo Marsicovetere, Roberto Marsilio
First page: 8
Abstract: Aerospike nozzles represent an interesting solution for Single-Stage-To-Orbit or clustered launchers owing to their self-adapting capability, which can lead to better performance compared to classical nozzles. Furthermore, they can provide thrust vectoring in several ways. A simple solution consists of applying differential throttling when multiple combustion chambers are used. An alternative solution is represented by fluidic thrust vectoring, which requires the injection of a secondary flow from a slot. In this work, the flow field in a linear aerospike nozzle was investigated numerically and both differential throttling and fluidic thrust vectoring were studied. The flow field was predicted by solving the Reynolds-averaged Navier–Stokes equations. The thrust vectoring performance was evaluated in terms of side force generation and axial force reduction. The effectiveness of fluidic thrust vectoring was investigated by changing the mass flow rate of secondary flow and injection location. The results show that the response of the system can be non-monotone with respect to the mass flow rate of the secondary injection. In contrast, differential throttling provides a linear behaviour but it can only be applied to configurations with multiple combustion chambers. Finally, the effects of different plug truncation levels are discussed.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-04-21
DOI: 10.3390/ijtpp6020008
Issue No: Vol. 6, No. 2 (2021)
- IJTPP, Vol. 6, Pages 9: Near-Wall Flow in Turbomachinery
Cascades—Results of a German Collaborative Project
Authors: David Engelmann, Martin Sinkwitz, Francesca di Mare, Björn Koppe, Ronald Mailach, Jordi Ventosa-Molina, Jochen Fröhlich, Tobias Schubert, Reinhard Niehuis
First page: 9
Abstract: This article provides a summarizing account of the results obtained in the current collaborative work of four research institutes concerning near-wall flow in turbomachinery. Specific questions regarding the influences of boundary layer development on blades and endwalls as well as loss mechanisms due to secondary flow are investigated. These address skewness, periodical distortion, wake interaction and heat transfer, among others. Several test rigs with modifiable configurations are used for the experimental investigations including an axial low speed compressor, an axial high-speed wind tunnel, and an axial low-speed turbine. Approved stationary and time resolving measurements techniques are applied in combination with custom hot-film sensor-arrays. The experiments are complemented by URANS simulations, and one group focusses on turbulence-resolving simulations to elucidate the specific impact of rotation. Juxtaposing and interlacing their results the four groups provide a broad picture of the underlying phenomena, ranging from compressors to turbines, from isothermal to non-adiabatic, and from incompressible to compressible flows.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-05-08
DOI: 10.3390/ijtpp6020009
Issue No: Vol. 6, No. 2 (2021)
- IJTPP, Vol. 6, Pages 10: A Comparison of Single-Entry and Multiple-Entry
Casing Impingement Manifolds for Active Thermal Tip Clearance Control
Authors: Priyanka Dhopade, Benjamin Kirollos, Peter Ireland, Leo Lewis
First page: 10
Abstract: In this paper, we compare using computational fluid dynamics the aero-thermal performance of two candidate casing manifolds for supplying an impingement-actuated active tip clearance control system for an aero-engine high-pressure turbine. The two geometries are (a) single-entry: an annular manifold fed at one circumferential location; (b) multiple-entry: a casing manifold split into four annular sectors, with each sector supplied separately from an annular ring main. Both the single-entry and multiple-entry systems analysed in this paper are idealised versions of active clearance control systems in current production engines. Aero-thermal performance is quantitatively assessed on the basis of the heat transfer coefficient distribution, driving temperature difference for heat transfer between the jet and casing wall and total pressure loss within the high-pressure turbine active clearance control system. We predict that the mean heat transfer coefficient (defined with respect to the inlet temperature and local wall temperature) of the single-entry active clearance control system is 77% greater than the multiple-entry system, primarily because the coolant in the multiple-entry case picks up approximately 40 K of temperature from the ring main walls, and secondarily because the average jet Reynolds number of impingement holes in the single-entry system is 1.2 times greater than in the multiple-entry system. The multiple-entry system exhibits many local hot and cold spots, depending on the position of the transfer boxes, while the single-entry case has a more predictable aero-thermal field across the system. The multiple-entry feed system uses an average of 20% of the total available pressure drop, while the feed system for the single-entry geometry uses only 2% of the total available pressure drop. From the aero-thermal results of this computational study, and in consideration of holistic aero-engine design factors, we conclude that a single-entry system is closer to an optimal solution than a multiple-entry system.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-05-14
DOI: 10.3390/ijtpp6020010
Issue No: Vol. 6, No. 2 (2021)
- IJTPP, Vol. 6, Pages 11: Analysis of the Unsteady Flow Field in a Steam
Turbine Control Valve using Spectral Proper Orthogonal Decomposition
Authors: Christian Windemuth, Martin Lange, Ronald Mailach
First page: 11
Abstract: A significant share of the conversion of thermal into electrical energy is realized by steam turbines. Formerly designed for continuous operation, today’s requirements include extended part load operation that can be accompanied by highly unstable flow conditions and vibrations within the control valve of the turbine. The prediction of the flow at part load conditions requires large computational efforts with advanced turbulence modeling in order to compute the flow at a reasonable accuracy. Due to the unsteadiness of the flow, the evaluation of the numerical results itself is a major challenge. The turbulent structures require statistical approaches, of which the use of Spectral Proper Orthogonal Decomposition (SPOD) has proven itself as a powerful method. Within this paper, the application of the method on a critical operating point with a temporal excitation of pressure oscillations observed in the experiments with dry air is presented. Using SPOD, the dominating flow phenomena were isolated and flow structures visualized.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-05-21
DOI: 10.3390/ijtpp6020011
Issue No: Vol. 6, No. 2 (2021)
- IJTPP, Vol. 6, Pages 12: A Parametric Study on the LES Numerical Setup to
Investigate Fan/OGV Broadband Noise
Authors: Jean Al-Am, Vincent Clair, Alexis Giauque, Jérôme Boudet, Fernando Gea-Aguilera
First page: 12
Abstract: In the present paper, large eddy simulations are performed to study two different mechanisms of Fan/OGV broadband noise: airfoil self-noise and turbulence interaction noise. Firstly, the current study focuses on the prediction of airfoil self-noise from a thin plate with a sharp trailing edge and a chord-based Reynolds number of the order of 106. The boundary layer is tripped to trigger transition to turbulence, and a parameter study is performed to study the influence of the near-wall modeling, grid topology and refinement in the near-wall and wake regions, the spanwise domain extent, and the tripping method. Empirical and analytical models, as well as available DNS data are used for validation purposes. Secondly, the interaction noise from a thin plate impinged by an incoming synthetic turbulent flow is studied. For both cases, far-field acoustic spectra are compared to Amiet’s models for leading and trailing edge noise showing a good agreement.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-05-26
DOI: 10.3390/ijtpp6020012
Issue No: Vol. 6, No. 2 (2021)
- IJTPP, Vol. 6, Pages 13: Experimental Investigation of Centrifugal Flow in
Rotor–Stator Cavities at High Reynolds Numbers >108
Authors: Tilman Schröder, Sebastian Schuster, Dieter Brillert
First page: 13
Abstract: The designers of radial turbomachinery need detailed information on the impact of the side chamber flow on axial thrust and torque. A previous paper investigated centripetal flow through narrow rotor–stator cavities and compared axial thrust, rotor torque and radial pressure distribution to the case without through-flow. Consequently, this paper extends the investigated range to centrifugal through-flow as it may occur in the hub side chamber of radial turbomachinery. The chosen operating conditions are representative of high-pressure centrifugal compressors used in, for example, carbon capture and storage applications as well as hydrogen compression. To date, only the Reynolds number range up to Re=2·107 has been investigated for centrifugal through-flow. This paper extends the range to Reynolds numbers of Re=2·108 and reports results of experimental and numerical investigations. It focuses on the radial pressure distribution in the rotor–stator cavity and shows the influence of the Reynolds number, cavity width and centrifugal mass flow rate. It therefore extends the range of available valid data that can be used to design radial turbomachinery. Additionally, this analysis compares the results to data and models from scientific literature, showing that in the higher Reynolds number range, a new correlation is required. Finally, the analysis of velocity profiles and wall shear delineates the switch from purely radial outflow in the cavity to outflow on the rotor and inflow on the stator at high Reynolds numbers in comparison to the results reported by others for Reynolds numbers up to Re=2·107.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-05-26
DOI: 10.3390/ijtpp6020013
Issue No: Vol. 6, No. 2 (2021)
- IJTPP, Vol. 6, Pages 14: Numerical Investigation of the Performance Impact
of Stator Tilting Endwall Designs on a Mixed Flow Turbine
Authors: Yang Gao, Jens Fridh, Richard Morrison, Pangbo Ren, Stephen Spence
First page: 14
Abstract: This paper numerically investigates stator endwall designs for a mixed flow turbine. One key design parameter studied is the tilting angle of the stator endwall. By examining stator designs with different tilting angles, the aim of this paper is to improve the efficiency of the studied mixed flow turbine at low velocity ratio working conditions. The performance curve at the design speed was chosen for the comparison between the baseline design and the tilted endwall designs. First, the numerical predictions for the baseline design were validated with experimental data. Then, to understand the mechanism of the performance variation between the different designs, the internal flow field was analyzed in detail. It was found that the tilting stator endwall could form a geometric “kink” in the endwall profiles. On the shroud side, certain designs with such kink caused local flow separations upstream the rotor leading edge. This separation could have the effect of reducing the intensity of the tip leakage vortex and the exit kinetic energy losses at the rotor outlet and may also improve the performance of the exhaust diffuser. As a result, the peak of the efficiency curve shifted toward lower velocity ratio. If the turbine stage incorporated a downstream exhaust diffuser, the optimal design in this study showed a shift of the velocity ratio of the peak efficiency point from 0.62 to 0.60 compared with the baseline. The maximum efficiency improvement was 1.3% points, which occurred at low velocity ratio. Meanwhile, the peak efficiency was 0.2% points higher than the baseline. If the exhaust diffuser was removed, a similar shift of the efficiency curve was observed but less efficiency gain was achieved at the low velocity ratio condition. A preliminary unsteady simulation was also conducted for the optimal design in this study.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-05-28
DOI: 10.3390/ijtpp6020014
Issue No: Vol. 6, No. 2 (2021)
- IJTPP, Vol. 6, Pages 15: Centrifugal Compressor Polytropic
Performance—Improved Rapid Calculation Results—Cubic Polynomial
Methods
Authors: Matt Taher, Fred Evans
First page: 15
Abstract: This paper presents a new improved approach to calculation of polytropic performance of centrifugal compressors. This rapid solution technique is based upon a constant efficiency, temperature-entropy polytropic path represented by cubic polynomials. New thermodynamic path slope constraints have been developed that yield highly accurate results while requiring fewer computing resources and reducing computing elapsed time. Applying this thermodynamically sound cubic polynomial model would improve accuracy and shorten compressor performance test duration at a vendor’s shop. A broad range of example case results verify the accuracy and ease of use of the method. The example cases confirm the cubic polynomial methods result in lower calculation uncertainty than other methods.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-05-28
DOI: 10.3390/ijtpp6020015
Issue No: Vol. 6, No. 2 (2021)
- IJTPP, Vol. 6, Pages 16: Experiments of Transpiration Cooling Inspired
Panel Cooling on a Turbine Blade Yielding Film Effectiveness Levels over
95%
Authors: Augustin Wambersie, Holt Wong, Peter Ireland, Ignacio Mayo
First page: 16
Abstract: Panels were tested at different locations around the turbine blade, on both suction and pressure surfaces. Three different surface porosities were also tested. Results demonstrated that the approach can be very successful with high levels of film cooling effectiveness, exceeding 95%, achieved using low coolant mass flow rates. Increasing the surface porosity also proved to be an important parameter in the panel’s performance. Additionally, staggering the film holes lead to significant positive interactions between individual films, resulting in much improved panel performance.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-06-04
DOI: 10.3390/ijtpp6020016
Issue No: Vol. 6, No. 2 (2021)
- IJTPP, Vol. 6, Pages 17: A Machine Learning Approach to Improve Turbulence
Modelling from DNS Data Using Neural Networks
Authors: Yuri Frey Marioni, Enrique Alvarez de Toledo Ortiz, Andrea Cassinelli, Francesco Montomoli, Paolo Adami, Raul Vazquez
First page: 17
Abstract: In this paper, we investigate the feasibility of using DNS data and machine learning algorithms to assist RANS turbulence model development. High-fidelity DNS data are generated with the incompressible Navier–Stokes solver implemented in the spectral/hp element software framework Nektar++. Two test cases are considered: a turbulent channel flow and a stationary serpentine passage, representative of internal turbo-machinery cooling flow. The Python framework TensorFlow is chosen to train neural networks in order to address the known limitations of the Boussinesq approximation and a clustering based on flow features is run upfront to enable training on selected areas. The resulting models are implemented in the Rolls-Royce solver HYDRA and a posteriori predictions of velocity field and wall shear stress are compared to baseline RANS. The paper presents the fundamental elements of procedure applied, including a brief description of the tools and methods and improvements achieved.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-06-04
DOI: 10.3390/ijtpp6020017
Issue No: Vol. 6, No. 2 (2021)
- IJTPP, Vol. 6, Pages 18: Modelling Turbine Acoustic Impedance
Authors: James Brind, Graham Pullan
First page: 18
Abstract: We quantify the sensitivity of turbine acoustic impedance to aerodynamic design parameters. Impedance boundary conditions are an influential yet uncertain parameter in predicting the thermoacoustic stability of gas turbine combustors. We extend the semi-actuator disk model to cambered blades, using non-linear time-domain computations of turbine vane and stage cascades with acoustic forcing for validation data. Discretising cambered aerofoils into multiple disks improves reflection coefficient predictions, reducing error by up to an order of magnitude compared to a flat plate assumption. A parametric study of turbine stage designs using the analytical model shows acoustic impedance is a weak function of degree of reaction and polytropic efficiency. The design parameter with the strongest influence is flow coefficient, followed by axial velocity ratio and Mach number. We provide the combustion engineer with improved tools to predict impedance boundary conditions, and suggest thermoacoustic stability is most likely to be compromised by change in turbine flow coefficient.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-06-07
DOI: 10.3390/ijtpp6020018
Issue No: Vol. 6, No. 2 (2021)
- IJTPP, Vol. 6, Pages 19: Experimental Aerodynamic and Aeroelastic
Investigation of a Transonic Compressor Rotor with Reduced Blade Count
Authors: Daniel Franke, Daniel Möller, Maximilian Jüngst, Heinz-Peter Schiffer, Thomas Giersch, Bernd Becker
First page: 19
Abstract: This study investigates the aerodynamic and aeroelastic characteristics of a transonic axial compressor, focusing on blade count reduced rotor behavior. The analysis is based on experiments, conducted at the Transonic Compressor Darmstadt test rig at Technical University of Darmstadt and compulsory simulations. In order to obtain measurement data for the detailed aerodynamic and aeroelastic investigation, extensive steady and unsteady instrumentation was applied. Besides transient measurements at the stability limit to determine the operating range and limiting phenomena, performance measurements were performed, presenting promising results with respect to the capabilities of blade count reduced rotors. Close to the stability limit, aerodynamic disturbances like radial vortices were detected for both rotors, varying in size, count, speed and trajectory. Comparing the rotor configurations results in different stability limits along the compressor map as well as varying aeromechanical behavior. Those effects can partially be traced to the variation in blade pitch and associated aerodynamics.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-06-11
DOI: 10.3390/ijtpp6020019
Issue No: Vol. 6, No. 2 (2021)
- IJTPP, Vol. 6, Pages 20: Continuous Adjoint-Based Optimization of an
Internally Cooled Turbine Blade—Mathematical Development and Application
Authors: Xenofon Trompoukis, Konstantinos Tsiakas, Varvara Asouti, Marina Kontou, Kyriakos Giannakoglou
First page: 20
Abstract: This paper presents an adjoint-based shape optimization framework and its demonstration in a conjugate heat transfer problem in a turbine blading. The gradient of the objective function is computed based on the continuous adjoint method, which also includes the adjoint to the turbulence model. Differences in the gradient resulting from making the frozen turbulence assumption are discussed. The developed software was used to optimize both the blade shape of the internally cooled linear C3X turbine blade and the position of cooling channels aiming at (a) minimum total pressure drop of the hot gas flow and (b) minimum highest temperature within the blade. A two-step optimization procedure was used. A free-form parameterization tool, based on volumetric NURBS, controls the blade airfoil contour, while the cooling channels are free to move following changes in the coordinates of their centers. Geometric and flow constraints are included in the performed optimizations, keeping the cooling channels away from the airfoil sides and retaining the turbine inlet capacity and flow turning.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-06-15
DOI: 10.3390/ijtpp6020020
Issue No: Vol. 6, No. 2 (2021)
- IJTPP, Vol. 6, Pages 1: Acknowledgment to Reviewers of IJTPP in 2020
Authors: IJTPP Editorial Office IJTPP Editorial Office
First page: 1
Abstract: Peer review is the driving force of journal development, and reviewers are gatekeepers who ensure that IJTPP maintains its standards for the high quality of its published papers [...]
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-01-25
DOI: 10.3390/ijtpp6010001
Issue No: Vol. 6, No. 1 (2021)
- IJTPP, Vol. 6, Pages 2: Fuzzy Controller Structures Investigation for
Future Gas Turbine Aero-Engines
Authors: D. F., Jafari
First page: 2
Abstract: The Advisory Council for Aeronautics Research in Europe (ACARE) Flight Path 2050 focuses on ambitious and severe targets for the next generation of air travel systems (e.g., 75% reduction in CO2 emissions per passenger kilometer, a 90% reduction in NOx emissions, and 65% reduction in noise emission of flying aircraft relative to the capabilities of typical new aircraft in 2000). In order to meet these requirements, aircraft engines should work very close to their operating limits. Therefore, the importance of advanced control strategies to satisfy all engine control modes simultaneously while protecting them from malfunctions and physical damages is being more crucial these days. In the last three decades, fuzzy controllers (FCs) have been proposed as a high potential solution for performance improvement of the next generation of aircraft engines. Based on an analytic review, this paper divides the trend of FCs design into two main lines including pure FCs (PFC) and min–max FCs (MMFC). These two main architectures are then designed, implemented on hardware, and applied in a case study to analyze the advantages and disadvantages of each structure. The analysis of hardware-in-the-loop (HIL) simulation results shows that the pure FC structure would be a high potential candidate for maneuverability and response time indices improvement (e.g., military applications); while min–max FC architecture has a great potential for future civil aero-engines where the fuel consumption and steady-state responses are more important. The simulation results are also compared with those of industrial min–max controllers to confirm the feasibility and reliability of the fuzzy controllers for real-world application. The results of this paper propose a general roadmap for fuzzy controllers’ structure selection for new and next generation of aircraft engines.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-02-22
DOI: 10.3390/ijtpp6010002
Issue No: Vol. 6, No. 1 (2021)
- IJTPP, Vol. 6, Pages 3: Review of a Custom-Designed Optical Sensing System
for Aero-Engine Applications
Authors: Rubén Fernández, Josu Amorebieta, Iker García, Gotzon Aldabaldetreku, Joseba Zubia, Gaizka Durana
First page: 3
Abstract: Fibre bundle-based reflective optical sensors are good candidates for parameter monitorisation in aero engines. Tip clearance is one of those parameters of great concern that is necessary to monitor. Within this optical technology, the evolution experienced by a custom-designed optical sensor is presented from its first configuration up to the fifth one. The performance of the last configuration is compared with those of other two optical sensors that are also based on a fibre bundle design. The comparison has been carried out in an experimental program in a transonic wind tunnel for aero engines. The proven high resolution and sensitivity of the last configuration of the optical sensor opens up the possibility to detect blade defects, cracks, etc. that could otherwise be hard to track.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-02-25
DOI: 10.3390/ijtpp6010003
Issue No: Vol. 6, No. 1 (2021)
- IJTPP, Vol. 6, Pages 4: Axial Compressor Mean-Line Analysis: Choking
Authors: Ioannis Kolias, Alexios Alexiou, Nikolaos Aretakis, Konstantinos Mathioudakis
First page: 4
Abstract: A mean-line compressor performance calculation method is presented that covers the entire operating range, including the choked region of the map. It can be directly integrated into overall engine performance models, as it is developed in the same simulation environment. The code materializing the model can inherit the same interfaces, fluid models, and solvers, as the engine cycle model, allowing consistent, transparent, and robust simulations. In order to deal with convergence problems when the compressor operates close to or within the choked operation region, an approach to model choking conditions at blade row and overall compressor level is proposed. The choked portion of the compressor characteristics map is thus numerically established, allowing full knowledge and handling of inter-stage flow conditions. Such choking modelling capabilities are illustrated, for the first time in the open literature, for the case of multi-stage compressors. Integration capabilities of the 1D code within an overall engine model are demonstrated through steady state and transient simulations of a contemporary turbofan layout. Advantages offered by this approach are discussed, while comparison of using alternative approaches for representing compressor performance in overall engine models is discussed.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-02-26
DOI: 10.3390/ijtpp6010004
Issue No: Vol. 6, No. 1 (2021)
- IJTPP, Vol. 6, Pages 5: A New Loss Generation Body Force Model for
Authors: Syamak Pazireh, Jeffrey J. Defoe
First page: 5
Abstract: Body force models of fans and compressors are widely employed for predicting performance due to the reduction in computational cost associated with their use, particularly in nonuniform inflows. Such models are generally divided into a portion responsible for flow turning and another for loss generation. Recently, accurate, uncalibrated turning force models have been developed, but accurate loss generation models have typically required calibration against higher fidelity computations (especially when flow separation occurs). In this paper, a blade profile loss model is introduced which requires the trailing edge boundary layer momentum thicknesses. To estimate the momentum thickness for a given blade section, an artificial neural network is trained using over 400,000 combinations of blade section shape and flow conditions. A blade-to-blade flow field solver is used to generate the training data. The model obtained depends only on blade geometry information and the local flow conditions, making its implementation in a typical computational fluid dynamics framework straightforward. We show good agreement in the prediction of profile loss for 2D cascades both on and off design in the defined ranges for the neural network training.
Citation: International Journal of Turbomachinery, Propulsion and Power
PubDate: 2021-03-11
DOI: 10.3390/ijtpp6010005
Issue No: Vol. 6, No. 1 (2021)
