Subjects -> ENGINEERING (Total: 2677 journals)
    - CHEMICAL ENGINEERING (235 journals)
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    - ENGINEERING (1308 journals)
    - ENGINEERING MECHANICS AND MATERIALS (452 journals)
    - HYDRAULIC ENGINEERING (56 journals)
    - INDUSTRIAL ENGINEERING (98 journals)
    - MECHANICAL ENGINEERING (115 journals)

ENGINEERING (1308 journals)            First | 1 2 3 4 5 6 7 | Last

Showing 601 - 800 of 1205 Journals sorted alphabetically
International Journal of Quality Assurance in Engineering and Technology Education     Full-text available via subscription   (Followers: 3)
International Journal of Quality Engineering and Technology     Hybrid Journal   (Followers: 4)
International Journal of Quantum Information     Hybrid Journal   (Followers: 6)
International Journal of Rapid Manufacturing     Hybrid Journal   (Followers: 3)
International Journal of Recent Contributions from Engineering, Science & IT     Open Access  
International Journal of Reliability, Quality and Safety Engineering     Hybrid Journal   (Followers: 14)
International Journal of Renewable Energy Technology     Hybrid Journal   (Followers: 8)
International Journal of Robust and Nonlinear Control     Hybrid Journal   (Followers: 10)
International Journal of Science and Innovative Technology     Open Access  
International Journal of Science Engineering and Advance Technology     Open Access  
International Journal of Sediment Research     Full-text available via subscription   (Followers: 2)
International Journal of Self-Propagating High-Temperature Synthesis     Hybrid Journal  
International Journal of Service Science, Management, Engineering, and Technology     Full-text available via subscription   (Followers: 2)
International Journal of Signal and Imaging Systems Engineering     Hybrid Journal  
International Journal of Six Sigma and Competitive Advantage     Hybrid Journal   (Followers: 4)
International Journal of Social Robotics     Hybrid Journal   (Followers: 3)
International Journal of Software Engineering and Knowledge Engineering     Hybrid Journal   (Followers: 6)
International Journal of Space Science and Engineering     Hybrid Journal   (Followers: 13)
International Journal of Speech Technology     Hybrid Journal   (Followers: 7)
International Journal of Spray and Combustion Dynamics     Full-text available via subscription   (Followers: 15)
International Journal of Student Project Reporting     Hybrid Journal   (Followers: 7)
International Journal of Surface Engineering and Interdisciplinary Materials Science     Full-text available via subscription   (Followers: 1)
International Journal of Surface Science and Engineering     Hybrid Journal   (Followers: 6)
International Journal of Sustainable Engineering     Hybrid Journal   (Followers: 4)
International Journal of Sustainable Lighting     Open Access  
International Journal of Sustainable Manufacturing     Hybrid Journal   (Followers: 4)
International Journal of Systems and Service-Oriented Engineering     Full-text available via subscription  
International Journal of Systems Assurance Engineering and Management     Hybrid Journal  
International Journal of Systems, Control and Communications     Hybrid Journal   (Followers: 6)
International Journal of Technoethics     Full-text available via subscription   (Followers: 2)
International Journal of Technology Management and Sustainable Development     Hybrid Journal   (Followers: 1)
International Journal of Technology Policy and Law     Hybrid Journal   (Followers: 7)
International Journal of Telemedicine and Applications     Open Access   (Followers: 4)
International Journal of Thermal Sciences     Hybrid Journal   (Followers: 19)
International Journal of Thermodynamics     Open Access   (Followers: 15)
International Journal of Transportation Engineering     Open Access   (Followers: 2)
International Journal of Turbomachinery, Propulsion and Power     Open Access   (Followers: 23)
International Journal of Ultra Wideband Communications and Systems     Hybrid Journal  
International Journal of Vehicle Autonomous Systems     Hybrid Journal  
International Journal of Vehicle Design     Hybrid Journal   (Followers: 6)
International Journal of Vehicle Information and Communication Systems     Hybrid Journal   (Followers: 1)
International Journal of Vehicle Noise and Vibration     Hybrid Journal   (Followers: 6)
International Journal of Vehicle Safety     Hybrid Journal   (Followers: 3)
International Journal of Virtual Technology and Multimedia     Hybrid Journal   (Followers: 2)
International Journal of Wavelets, Multiresolution and Information Processing     Hybrid Journal  
International Journal on Artificial Intelligence Tools     Hybrid Journal   (Followers: 9)
International Journal on Smart Sensing and Intelligent Systems     Open Access  
International Nano Letters     Open Access   (Followers: 6)
International Review of Applied Sciences and Engineering     Full-text available via subscription  
International Scholarly Research Notices     Open Access   (Followers: 130)
International Scientific and Vocational Studies Journal     Open Access  
International Scientific Journal of Engineering and Technology (ISJET)     Open Access  
Inventions     Open Access  
Inventum     Open Access  
Inverse Problems in Science and Engineering     Hybrid Journal   (Followers: 3)
Investiga : TEC     Open Access  
Ionics     Hybrid Journal   (Followers: 2)
IPTEK The Journal for Technology and Science     Open Access  
Iranian Journal of Optimization     Open Access   (Followers: 2)
Iranian Journal of Science and Technology, Transactions A : Science     Hybrid Journal  
IRBM News     Full-text available via subscription  
Ironmaking & Steelmaking     Hybrid Journal   (Followers: 4)
ISA Transactions     Full-text available via subscription  
ISSS Journal of Micro and Smart Systems     Hybrid Journal   (Followers: 3)
IT Professional     Full-text available via subscription   (Followers: 24)
Iteckne     Open Access  
J-ENSITEC : Journal Of Engineering and Sustainable Technology     Open Access   (Followers: 4)
Johnson Matthey Technology Review     Open Access  
Journal of Advanced College of Engineering and Management     Open Access  
Journal of Advanced Joining Processes     Open Access  
Journal of Advanced Manufacturing Systems     Hybrid Journal   (Followers: 5)
Journal of Aerodynamics     Open Access   (Followers: 27)
Journal of Aerosol Science     Hybrid Journal   (Followers: 7)
Journal of Aerospace Engineering     Full-text available via subscription   (Followers: 67)
Journal of Alloys and Compounds     Hybrid Journal   (Followers: 16)
Journal of Analytical and Applied Pyrolysis     Hybrid Journal   (Followers: 5)
Journal of Analytical Science & Technology     Open Access   (Followers: 4)
Journal of Analytical Sciences, Methods and Instrumentation     Open Access   (Followers: 4)
Journal of Applied Engineering Sciences     Open Access   (Followers: 1)
Journal of Applied Physics     Hybrid Journal   (Followers: 69)
Journal of Applied Research and Technology     Open Access  
Journal of Applied Science and Technology     Full-text available via subscription   (Followers: 1)
Journal of Applied Sciences     Open Access   (Followers: 4)
Journal of Architectural and Engineering Research     Open Access   (Followers: 7)
Journal of Architectural Engineering     Full-text available via subscription   (Followers: 4)
Journal of Automation and Control     Open Access   (Followers: 9)
Journal of Aviation Technology and Engineering     Open Access   (Followers: 11)
Journal of Biological Dynamics     Open Access   (Followers: 1)
Journal of Biomedical Science     Open Access   (Followers: 4)
Journal of Biomolecular NMR     Hybrid Journal   (Followers: 6)
Journal of Biosciences     Open Access   (Followers: 1)
Journal of Building Pathology and Rehabilitation     Hybrid Journal  
Journal of Catalysis     Hybrid Journal   (Followers: 11)
Journal of Catalyst & Catalysis     Full-text available via subscription   (Followers: 2)
Journal of Central South University     Hybrid Journal   (Followers: 1)
Journal of Chemical and Petroleum Engineering     Open Access   (Followers: 1)
Journal of China Coal Society     Open Access  
Journal of China Universities of Posts and Telecommunications     Full-text available via subscription  
Journal of Cleaner Production     Hybrid Journal   (Followers: 26)
Journal of Coastal and Riverine Flood Risk (JCRFR)     Open Access   (Followers: 3)
Journal of Cold Regions Engineering     Full-text available via subscription   (Followers: 3)
Journal of Combinatorial Designs     Hybrid Journal   (Followers: 4)
Journal of Combustion     Open Access   (Followers: 40)
Journal of Computational and Nonlinear Dynamics     Full-text available via subscription   (Followers: 6)
Journal of Computational and Theoretical Nanoscience     Full-text available via subscription  
Journal of Computational Biology     Hybrid Journal   (Followers: 9)
Journal of Computational Design and Engineering     Open Access   (Followers: 1)
Journal of Computational Electronics     Hybrid Journal   (Followers: 5)
Journal of Computational Multiphase Flows     Open Access   (Followers: 1)
Journal of Computing and Information Science in Engineering     Full-text available via subscription   (Followers: 1)
Journal of Coupled Systems and Multiscale Dynamics     Full-text available via subscription  
Journal of Dairy Science     Open Access   (Followers: 12)
Journal of Delta Urbanism     Open Access   (Followers: 4)
Journal of Display Technology     Hybrid Journal   (Followers: 3)
Journal of Dynamic Systems, Measurement, and Control     Full-text available via subscription   (Followers: 14)
Journal of Dynamical and Control Systems     Hybrid Journal   (Followers: 7)
Journal of Earthquake Engineering     Hybrid Journal   (Followers: 14)
Journal of Elasticity     Hybrid Journal   (Followers: 7)
Journal of Electroceramics     Hybrid Journal  
Journal of Electromagnetic Waves and Applications     Hybrid Journal   (Followers: 10)
Journal of Electronic Testing     Hybrid Journal   (Followers: 2)
Journal of Electronics Cooling and Thermal Control     Open Access   (Followers: 9)
Journal of Electrostatics     Hybrid Journal   (Followers: 2)
Journal of Energy Engineering     Full-text available via subscription   (Followers: 7)
Journal of Energy Resources Technology     Full-text available via subscription   (Followers: 4)
Journal of Engineering     Open Access  
Journal of Engineering     Open Access   (Followers: 2)
Journal of Engineering and Applied Science     Open Access  
Journal of Engineering and Technological Sciences     Open Access   (Followers: 3)
Journal of Engineering Design     Hybrid Journal   (Followers: 17)
Journal of Engineering Education     Hybrid Journal   (Followers: 7)
Journal of Engineering for Gas Turbines and Power     Full-text available via subscription   (Followers: 15)
Journal of Engineering Mathematics     Hybrid Journal   (Followers: 2)
Journal of Engineering Mechanics     Full-text available via subscription   (Followers: 16)
Journal of Engineering Physics and Thermophysics     Hybrid Journal   (Followers: 2)
Journal of Engineering Research     Open Access   (Followers: 1)
Journal of Engineering Research and Reports     Open Access  
Journal of Engineering Technology and Applied Sciences     Open Access  
Journal of Engineering Thermophysics     Hybrid Journal   (Followers: 4)
Journal of Engineering, Design and Technology     Hybrid Journal   (Followers: 17)
Journal of Engineering, Project, and Production Management     Open Access  
Journal of Environmental & Engineering Geophysics     Hybrid Journal   (Followers: 2)
Journal of Environmental Engineering     Full-text available via subscription   (Followers: 49)
Journal of Environmental Engineering and Landscape Management     Open Access   (Followers: 8)
Journal of Environmental Engineering and Science     Hybrid Journal   (Followers: 2)
Journal of Experimental Nanoscience     Hybrid Journal  
Journal of Fire Sciences     Hybrid Journal   (Followers: 6)
Journal of Flood Risk Management     Hybrid Journal   (Followers: 14)
Journal of Flow Control, Measurement & Visualization     Open Access   (Followers: 1)
Journal of Fluids Engineering     Full-text available via subscription   (Followers: 30)
Journal of Fourier Analysis and Applications     Hybrid Journal   (Followers: 3)
Journal of Fuel Cell Science and Technology     Full-text available via subscription   (Followers: 2)
Journal of Functional Analysis     Full-text available via subscription   (Followers: 3)
Journal of Fundamental and Applied Sciences     Open Access  
Journal of Geological Research     Open Access   (Followers: 1)
Journal of Geotechnical and Geoenvironmental Engineering     Full-text available via subscription   (Followers: 31)
Journal of Geotechnical Engineering     Full-text available via subscription   (Followers: 4)
Journal of Geovisualization and Spatial Analysis     Hybrid Journal  
Journal of Global Optimization     Hybrid Journal   (Followers: 6)
Journal of Graduate School of Natural and Applied Sciences of Mehmet Akif Ersoy University     Open Access  
Journal of Hazardous Materials Advances     Open Access  
Journal of Healthcare Engineering     Open Access   (Followers: 3)
Journal of Heat Transfer     Full-text available via subscription   (Followers: 68)
Journal of Humanitarian Engineering     Open Access   (Followers: 1)
Journal of Hydraulic Engineering     Full-text available via subscription   (Followers: 28)
Journal of Hyperspectral Remote Sensing     Open Access   (Followers: 23)
Journal of Imaging     Open Access   (Followers: 3)
Journal of Industrial and Production Engineering     Hybrid Journal   (Followers: 4)
Journal of Industrial Engineering and Management     Open Access   (Followers: 5)
Journal of Industrial Safety Engineering     Full-text available via subscription   (Followers: 6)
Journal of Inequalities and Applications     Open Access  
Journal of Infrared, Millimeter and Terahertz Waves     Hybrid Journal   (Followers: 3)
Journal of Infrastructure Preservation and Resilience     Open Access   (Followers: 1)
Journal of Institute of Science and Technology     Open Access  
Journal of Intelligent and Connected Vehicles     Open Access   (Followers: 1)
Journal of Intelligent Systems : Theory and Applications     Open Access  
Journal of International Maritime Safety, Environmental Affairs, and Shipping     Open Access   (Followers: 1)
Journal of Iron and Steel Research International     Hybrid Journal   (Followers: 7)
Journal of Irrigation and Drainage Engineering     Full-text available via subscription   (Followers: 24)
Journal of King Saud University - Engineering Sciences     Open Access  
Journal of KONBiN     Open Access   (Followers: 5)
Journal of Liquid Chromatography & Related Technologies     Hybrid Journal   (Followers: 7)
Journal of Management in Engineering     Full-text available via subscription   (Followers: 9)
Journal of Manufacturing Science and Engineering     Full-text available via subscription   (Followers: 32)
Journal of Manufacturing Systems     Full-text available via subscription   (Followers: 3)
Journal of Manufacturing Technology Management     Hybrid Journal   (Followers: 3)
Journal of Mechanical Design and Testing     Open Access   (Followers: 4)
Journal of Mechatronics     Full-text available via subscription   (Followers: 3)
Journal of Mega Infrastructure & Sustainable Development     Hybrid Journal  
Journal of Metallurgy     Open Access   (Followers: 9)
Journal of Mining Institute     Open Access  
Journal of Motor Behavior     Hybrid Journal   (Followers: 8)
Journal of Multivariate Analysis     Hybrid Journal   (Followers: 15)
Journal of Nanoengineering and Nanomanufacturing     Full-text available via subscription  
Journal of Nanoparticle Research     Hybrid Journal   (Followers: 3)
Journal of Nanoscience     Open Access  
Journal of Nanoscience and Nanotechnology     Full-text available via subscription   (Followers: 8)
Journal of NanoScience, NanoEngineering & Applications     Full-text available via subscription  
Journal of Nanotechnology     Open Access   (Followers: 10)
Journal of Nanotechnology in Engineering and Medicine     Full-text available via subscription   (Followers: 4)

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Similar Journals
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International Journal of Spray and Combustion Dynamics
Journal Prestige (SJR): 0.481
Citation Impact (citeScore): 1
Number of Followers: 15  
 
  Full-text available via subscription Subscription journal
ISSN (Print) 1756-8277 - ISSN (Online) 1756-8285
Published by Sage Publications Homepage  [1174 journals]
  • The flame displacement speed: A key quantity for turbulent combustion and
           combustion instability

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      Authors: Paul Palies
      Pages: 4 - 16
      Abstract: International Journal of Spray and Combustion Dynamics, Volume 14, Issue 1-2, Page 4-16, March–June 2022.
      Future combustion power and propulsion systems may operate in premixed regime enabling reduced fuel burn and reduced pollutant emissions. The turbulent premixed regime in those future combustion systems is likely to be in the corrugated regime where modeling the flame as a thin interface propagating into the fresh gas is made possible. The flame displacement speed is thus a key quantity for turbulent combustion in this regime. This quantity is also important for combustion instabilities. Indeed, the flame displacement speed [math] combined to the flow speed [math] determines the flame surface location by determining the flame surface speed [math]. The flame surface location has shown to play a major role on combustion instabilities. Research work have also demonstrated the role of the flame displacement speed on the flame response which is used for subsequent combustion instability prediction. In this context, the derivation of flame speed models and flame transfer function models based on this quantity are required. This paper presents the theoretical derivation of flame transfer function coefficients for swirling premixed flames in this context. The derivation is based on the definition of the flame speed for turbulent flame, its perturbed form for oscillating flow, and the kinematic flame-flow speed budget. The obtained results are compared to previous literature data and discussed. The effect of the flame angle, id est the effect of the swirl number on the flame response is also investigated. This works motivates detailed local measurements and simulations to evaluate flow-flame speed budget terms.
      Citation: International Journal of Spray and Combustion Dynamics
      PubDate: 2022-06-06T02:44:12Z
      DOI: 10.1177/17568277221081298
      Issue No: Vol. 14, No. 1-2 (2022)
       
  • Autoignition flame transfer matrix: Analytical model versus large eddy
           simulations

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      Authors: Francesco Gant, Alexis Cuquel, Mirko R. Bothien
      Pages: 72 - 81
      Abstract: International Journal of Spray and Combustion Dynamics, Volume 14, Issue 1-2, Page 72-81, March–June 2022.
      Modern gas turbines need to fulfil increasingly stringent emission targets on the one hand and exhibit outstanding operational and fuel flexibility on the other. Ansaldo Energia GT26 and GT36 gas turbine models address these requirements by employing a combustion system in which two lean premixed combustors are arranged in series. Due to the high inlet temperatures from the first stage, the second combustor stage predominantly relies on autoignition for flame stabilization. In this paper, the response of autoignition flames to temperature, pressure and velocity excitations is investigated. The gas turbine combustor geometry is represented by a backward-facing step. Based on the conservation equations an analytical model is derived by solving the linearized Rankine-Hugoniot conditions. This is a commonly used analytical approach to describe the relation of thermodynamic quantities up- and downstream of a propagation stabilized flame. In particular, the linearized Rankine-Hugoniot jump conditions are derived taking into account the presence of a moving discontinuity as well as upstream entropy inhomogeneities. The unsteady heat release rate of the flame is modelled as a linear superposition of flame transfer functions, accounting for velocity, pressure, and entropy disturbances, respectively. This results in a 3[math]3 flame transfer matrix relating both primitive acoustic variables and the temperature fluctuations across the flame. The obtained analytical expression is compared to large eddy simulations with excellent agreement. A discussion about the contribution of the single terms to the modelling effort is provided, with a focus on autoignition flames.
      Citation: International Journal of Spray and Combustion Dynamics
      PubDate: 2022-06-06T02:47:08Z
      DOI: 10.1177/17568277221086261
      Issue No: Vol. 14, No. 1-2 (2022)
       
  • Large-eddy simulation and challenges for projection-based reduced-order
           modeling of a gas turbine model combustor

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      Authors: Nicholas Arnold-Medabalimi, Cheng Huang, Karthik Duraisamy
      Pages: 153 - 175
      Abstract: International Journal of Spray and Combustion Dynamics, Volume 14, Issue 1-2, Page 153-175, March–June 2022.
      Computationally efficient modeling of gas turbine combustion is challenging due to the chaotic multi-scale physics and the complex non-linear interactions between acoustic, hydrodynamic, and chemical processes. A large-eddy simulation, referred to as the full order model (FOM), is performed for a gas turbine model combustor with turbulent combustion effects modeled using a flamelet-based method. Modal analysis reveals a high degree of correlation with averaged and instantaneous high-frequency particle image velocimetry fields. The dynamics of the precessing vortex core is quantitatively characterized using dynamic mode decomposition. The governing equations of the FOM are projected onto a low-dimensional linear manifold to construct a reduced-order model (ROM). A discretely-consistent least squares projection is used to guarantee global stability. The ROM provides an accurate reconstruction of the combustion dynamics within the training region, but faces a significant challenge in future state predictions. This limitation is mainly due to the increased projection error, which in turn is a direct consequence of the highly chaotic nature of the flow field, involving a wide range of dispersed coherent structures. This shortcoming is overcome using an adaptive basis method which yields accurate predictions of dynamics beyond the training region consistent with the FOM. Formal projection-based ROMs have not been applied to a problem of this scale and complexity, and achieving accurate and efficient ROMs is a grand challenge problem. A production-ready ROM method will significantly decrease the computational cost of the flame dynamics as well as the portability of this prediction to smaller-scale computers.
      Citation: International Journal of Spray and Combustion Dynamics
      PubDate: 2022-06-06T02:36:44Z
      DOI: 10.1177/17568277221100650
      Issue No: Vol. 14, No. 1-2 (2022)
       
  • Atomization characteristics of a bluff body-assisted sonic twin-fluid
           atomizer

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      Authors: Raghav Sikka, Knut Vågsæther, Dag Bjerketvedt, Joachim Lundberg
      Abstract: International Journal of Spray and Combustion Dynamics, Ahead of Print.
      This study examines the gas dynamic effect and atomization behaviour of the sonic bluff body-assisted twin-fluid atomizer with three distinct geometry configurations based on cone distances (Lc) as 6.0 mm, 8.0 mm, and 10.0 mm. The atomization characteristics of these atomizers employing a 280 µm annular liquid sheet with a central bluff body (cone) are compared based on a range of air and liquid flow rates. The spray-bluff body impacted secondary atomization was characterized through volume-normalized droplet size distribution (DSD) & cumulative droplet distribution, excentricity plots, Sauter mean diameter (SMD), and relative span factor (Δ). When plotted for a given liquid flow rate, the DSD & cumulative droplet distribution becomes more uniform with the increase in the airflow rate independent of the cone distance (Lc). Excentricity plots exhibited high excentricity droplets at the spray centreline and a large fraction of nearly spherical droplets at off-centre spray locations. SMD and RSF (Δ) showed opposite trends when plotted against the air-to-liquid ratio (ALR) as SMD increases while RSF decreases with radial locations, respectively. When plotted for all radial locations, Sauter mean diameter (D32) and relative span factor (Δ) show a cluster formation. Larger SMD values correspond to lower RSF (Δ) values and vice-versa.
      Citation: International Journal of Spray and Combustion Dynamics
      PubDate: 2022-05-31T03:33:51Z
      DOI: 10.1177/17568277221104924
       
  • Proceedings of the Symposium on Thermoacoustics in Combustion

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      Authors: Mirko Bothien
      First page: 3
      Abstract: International Journal of Spray and Combustion Dynamics, Ahead of Print.

      Citation: International Journal of Spray and Combustion Dynamics
      PubDate: 2022-05-11T07:48:41Z
      DOI: 10.1177/17568277221099785
       
  • Nonlinear flame response modelling by a parsimonious set of ordinary
           differential equations

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      Authors: Gregor Doehner, Matthias Haeringer, Camilo F. Silva
      First page: 17
      Abstract: International Journal of Spray and Combustion Dynamics, Ahead of Print.
      In this work we present a parsimonious set of ordinary differential equations (ODEs) that describes with satisfactory precision the linear and non-linear dynamics of a typical laminar premixed flame in time and frequency domain. The proposed model is characterized by two ODEs of second-order that can be interpreted as two coupled mass-spring-damper oscillators with a symmetric, nonlinear damping term. This non-linear term is identified as function of the rate of displacement following [math]. The model requires only four constants to be calibrated. This is achieved by carrying out an optimization procedure on one input and one output broadband signal obtained from high-fidelity numerical simulations (CFD). Note that the Transfer Function (FTF) or describing function (FDF) of the flame under investigation are not known a-priori, and therefore not used in the optimization procedure. Once the model is trained on CFD input and output time series, it is capable of recovering with quantitative accuracy the impulse response of the laminar flame under investigation and, hence, the corresponding frequency response (FTF). If fed with harmonic signals of different frequency and amplitude, the trained model is capable of retrieving with qualitative precision the flame describing function (FDF) of the studied flame. We show that the non-linear term [math] is essential for capturing the gain saturation for high amplitudes of the input signal. All results are validated against CFD data.
      Citation: International Journal of Spray and Combustion Dynamics
      PubDate: 2022-05-19T04:44:38Z
      DOI: 10.1177/17568277221094760
       
  • Iterative solvers for the thermoacoustic nonlinear eigenvalue problem and
           their convergence properties

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      Authors: Georg A. Mensah, Philip E. Buschmann, Alessandro Orchini
      First page: 30
      Abstract: International Journal of Spray and Combustion Dynamics, Ahead of Print.
      The spectrum of the thermoacoustic operator is governed by a nonlinear eigenvalue problem. A few different strategies have been proposed by the thermoacoustic community to tackle it and identify the frequencies and growth rates of thermoacoustic eigenmodes. These strategies typically require the use of iterative algorithms, which need an initial guess and are not necessarily guaranteed to converge to an eigenvalue. A quantitative comparison between the convergence properties of these methods has however never been addressed. By using adjoint-based sensitivity, in this study we derive an explicit formula that can be used to quantify the behaviour of an iterative method in the vicinity of an eigenvalue. In particular, we employ Banach’s fixed-point theorem to demonstrate that there exist thermoacoustic eigenvalues that cannot be identified by some of the iterative methods proposed in the literature, in particular fixed-point iterations, regardless of the accuracy of the initial guess provided. We then introduce a family of iterative methods known as Householder’s methods, of which Newton’s method is a special case. The coefficients needed to use these methods are explicitly derived by means of high-order adjoint-based perturbation theory. We demonstrate how these methods are always guaranteed to converge to the closest eigenvalue, provided that the initial guess is accurate enough. We also show numerically how the basin of attraction of the eigenvalues varies with the order of the employed Householder’s method.
      Citation: International Journal of Spray and Combustion Dynamics
      PubDate: 2022-05-09T11:57:29Z
      DOI: 10.1177/17568277221084464
       
  • Analytical modelling of flame transfer functions for technically premixed
           flames

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      Authors: Fernando Biagioli, Alessandro Innocenti, Ammar Lamraoui, Khawar J Syed
      First page: 42
      Abstract: International Journal of Spray and Combustion Dynamics, Ahead of Print.
      The linear response to harmonic acoustic excitation of the total heat release rate in technically premixed flames (Flame Transfer Function, FTF) is studied in case of an ideal swirl burner. The analysis is based on the linearization of the production rate for the mean reaction progress variable modelled with a turbulent flame speed closure. Three main components of the FTF are identified which are generated by: I) direct fluctuations in the fuel mixture fraction (formation enthalpy contribution), II) direct fluctuations in the turbulent flame speed and III) flame surface area fluctuations driven by velocity and turbulent flame speed fluctuations. The velocity fluctuation is separated into an irrotational acoustic displacement and a rotational convective component. The effect of the rotational velocity component on the FTF is modelled here in a semi-empirical way, related to swirl number fluctuations at the flame base due to the phase shift between convected tangential velocity fluctuations and acoustically propagating axial velocity fluctuations. It is finally shown that fuel mixture fraction fluctuations can be generated not only by air mass flow rate fluctuations but also by fuel flow rate fluctuations which depend upon the air side impedance at the fuel injection location. It is shown that this impedance changes with the geometry of the plenum placed upstream the burner affecting in this way also the FTF.
      Citation: International Journal of Spray and Combustion Dynamics
      PubDate: 2022-04-22T06:51:58Z
      DOI: 10.1177/17568277221094403
       
  • On the convective wave equation for the investigation of combustor
           stability using FEM-methods

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      Authors: Gerrit Heilmann, Thomas Sattelmayer
      First page: 55
      Abstract: International Journal of Spray and Combustion Dynamics, Ahead of Print.
      Solving the Helmholtz equation with spatially resolved finite element method (FEM) approaches is a well-established and cost-efficient methodology to numerically predict thermoacoustic instabilities. With the implied zero Mach number assumption all interaction mechanisms between acoustics and the mean flow velocity including the advection of acoustic waves are neglected. Incorporating these mechanisms requires higher-order approaches that come at massively increased computational cost. A tradeoff might be the convective wave equation in frequency domain, which covers the advection of waves and comes at equivalent cost as the Helmholtz equation. However, with this equation only being valid for uniform mean flow velocities it is normally not applicable to combustion processes. The present paper strives for analyzing the introduced errors when applying the convective wave equation to thermoacoustic stability analyses. Therefore, an acoustically consistent, inhomogeneous convective wave equation is derived first. Similar to Lighthill’s analogy, terms describing the interaction between acoustics and non-uniform mean flows are considered as sources. For the use with FEM approaches, a complete framework of the equation in weak formulation is provided. This includes suitable impedance boundary conditions and a transfer matrix coupling procedure. In a modal stability analysis of an industrial gas turbine combustion chamber, the homogeneous wave equation in frequency domain is subsequently compared to the Helmholtz equation and the consistent Acoustic Perturbation Equations (APE). The impact of selected source terms on the solution is investigated. Finally, a methodology using the convective wave equation in frequency domain with vanishing source terms in arbitrary mean flow fields is presented.
      Citation: International Journal of Spray and Combustion Dynamics
      PubDate: 2022-03-24T04:45:27Z
      DOI: 10.1177/17568277221084470
       
  • Stability criteria of two-port networks, application to thermo-acoustic
           systems

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      Authors: Mohammad Kojourimanesh, Viktor Kornilov, Ines Lopez Arteaga, Philip de Goey
      First page: 82
      Abstract: International Journal of Spray and Combustion Dynamics, Ahead of Print.
      System theory methods are developed and applied to introduce a new analysis methodology based on the stability criteria of active two-ports, to the problem of thermo-acoustic instability in a combustion appliance. The analogy between thermo-acoustics of combustion and small-signal operation of microwave amplifiers is utilized. Notions of unconditional and conditional stabilities of an (active) two-port, representing a burner with flame, are introduced and analyzed. Unconditional stability of two-port means the absence of autonomous oscillation at any embedding of the given two-port by any passive network at the system's upstream (source) and downstream (load) sides. It has been shown that for velocity-sensitive compact burners in the limit of zero Mach number, the criteria of unconditional stability cannot be fulfilled. The analysis is performed in the spirit of a known criterion in microwave network theory, the so-called Edwards-Sinsky's criterion. Therefore, two methods have been applied to elucidate the necessary and sufficient conditions of a linear active two-port system to be conditionally stable. The first method is a new algebraic technique to prove and derive the conditional and unconditional stability criteria, and the second method is based on certain properties of Mobius (bilinear) transformations for combinations of reflection coefficients and scattering matrix of (active) two-ports. The developed framework allows formulating design requirements for the stabilization of operation of a combustion appliance via purposeful modifications of either the burner properties or/and of its acoustic embeddings. The analytical derivations have been examined in a case study to show the power of the methodology in the thermo-acoustics system application.
      Citation: International Journal of Spray and Combustion Dynamics
      PubDate: 2022-04-12T08:01:09Z
      DOI: 10.1177/17568277221088465
       
  • Spray response on a model prefilmer under unsteady airflows of various
           frequencies

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      Authors: Thomas Christou, Björn Stelzner, Nikolaos Zarzalis
      First page: 98
      Abstract: International Journal of Spray and Combustion Dynamics, Ahead of Print.
      An appealing concept for jet engine combustors is the Lean Premixed Prevaporized (LPP) combustor, which operates at high pressures. The low NOx emissions achieved by lean combustion are one of the targets for modern aircraft engines. However, these types of combustors can introduce thermoacoustic instabilities that can potentially damage the engine and reduce its lifespan. Since the potential instabilities on the fuel spray characteristics, i.e. the spray mass flux, can affect the flame stability, the need arises to investigate the spray response under an unsteady airflow.For this study, a model prefilmer was experimentally investigated to produce a two-dimensional droplet flow without swirl flow. An acoustic forcing in the range of 100–500 Hz was introduced into the airflow, characterized by a hot wire Constant Temperature Anemometry (CTA) setup. Droplet characteristics, namely the droplet diameter distribution and velocity, were determined using a Phase Doppler Anemometry (PDA) setup, while the acquired data were phase-averaged in one period of the airflow oscillation. The influence of the excitation frequency and the air-to-liquid ratio (ALR) on the spray was studied: the spray responded to the acoustic excitation and therefore critical performance parameters, such as the spray mass flux, oscillated indicating potential problems regarding the flame stability.
      Citation: International Journal of Spray and Combustion Dynamics
      PubDate: 2022-05-09T11:57:42Z
      DOI: 10.1177/17568277221092987
       
  • Response of spray number density and evaporation rate to velocity
           oscillations

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      Authors: Sagar Kulkarni, Camilo F. Silva, Wolfgang Polifke
      First page: 107
      Abstract: International Journal of Spray and Combustion Dynamics, Ahead of Print.
      A theoretical investigation of the effect of gas velocity oscillations on droplet number density and evaporation rate is presented. Oscillations in gas velocity cause a number density wave, i.e. an inhomogeneous, unsteady variation of droplet concentration. The number density wave, as it propagates downstream at the mean flow speed, causes modulation of the local evaporation rate, creating a vapour wave with corresponding oscillations in equivalence ratio. The present work devises an analytical formulation of these processes. Firstly, the response of a population of droplets to oscillations in the gas velocity is modelled in terms of a number density wave. Secondly, the formulation is extended to incorporate droplet evaporation, such that an analytical expression for the evaporation rate modulation is obtained. Subsequently, the droplet 1D convection-diffusion transport equation with the calculated evaporation source term is solved using an appropriate Green’s function to determine the resulting equivalence ratio perturbations. The dynamic response of equivalence ratio fluctuations to velocity oscillations is finally characterized in terms of a frequency-dependent transfer function. The aforementioned analytical approach relies on a number of simplifying approximations, nevertheless it was validated with good agreement against 1D Euler-Lagrange CFD simulations.
      Citation: International Journal of Spray and Combustion Dynamics
      PubDate: 2022-03-31T03:20:35Z
      DOI: 10.1177/17568277221085957
       
  • Impact of shear-coaxial injector hydrodynamics on high-frequency
           combustion instabilities in a representative cryogenic rocket engine

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      Authors: Wolfgang Armbruster, Justin Hardi, Michael Oschwald
      First page: 118
      Abstract: International Journal of Spray and Combustion Dynamics, Ahead of Print.
      The excitation mechanism of a thermoacoustic instability in a 42-element research rocket thrust chamber with representative operating conditions with respect to European cryogenic rocket engines is investigated in detail. From previous research it was known that the chamber 1T mode can be excited by persistent heat release rate oscillations which are modulated by the resonant modes of the liquid oxygen injectors. The excitation source of the longitudinal injector eigenmodes is investigated in this study. Fibre-optical probes measuring the OH* dynamics from the recess volume of two injectors showed additional frequency content which could neither be explained by the chamber acoustics, nor the acoustics of the injection system. Instead, the temporal evolution of these frequencies correlate with the oxidizer flow velocity. In this work we show that the additional flame modulation originates from a hydrodynamic effect in the injection system. Even though the exact process cannot be precisely identified, an effect designated orifice whistling at the injector inlet orifice seems to be a likely candidate. Combining the new results with previous publications about this combustor, it is now possible to explain past and present observations in terms of the hydrodynamic and thermoacoustic conditions which are necessary for the combustion instability to appear. The conditions, which lead to an injection-driven excitation of the 1T mode are matching frequencies of the 2L mode of the injectors and the chamber 1T mode as well as a Strouhal number between 0.2 and 0.4 based on the length and flow velocity of the injector inlet orifice.
      Citation: International Journal of Spray and Combustion Dynamics
      PubDate: 2022-04-27T08:06:09Z
      DOI: 10.1177/17568277221093848
       
  • Observation of reactive shear layer modulation associated with
           high-frequency transverse thermoacoustic oscillations in a gas turbine
           reheat combustor experiment

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      Authors: Jonathan McClure, Frederik M. Berger, Michael Bertsch, Bruno Schuermans, Thomas Sattelmayer
      First page: 131
      Abstract: International Journal of Spray and Combustion Dynamics, Ahead of Print.
      This paper presents the investigation of high-frequency thermoacoustic oscillations and associated flame dynamics in an experimental gas turbine reheat combustor at atmospheric pressure. Examination of dynamic pressure measurements reveals bursts of high-frequency periodic oscillations which appear randomly amidst stochastic fluctuations in the reheat combustor. Analysis of the flame dynamics during these bursts of periodic behaviour reveals that increased heat release in the reactive shear layers of the reheat flame is associated with greater thermoacoustic driving potential. This redistribution of heat release is likely due to the stochastic nature of auto-ignition kernel formation. To determine the underlying flame-acoustic coupling mechanism behind the driving potential, phase-resolved flame dynamics over the acoustic cycle are investigated which reveal the presence of an oscillatory heat release pattern associated with the first transverse eigenmode. An in-phase interaction between the acoustic field and these heat release oscillations in the shear layer regions indicates that this phenomenon likely constitutes a thermoacoustic driving mechanism. This is an important step towards the development of models for high-frequency thermoacoustic driving mechanisms relevant to reheat combustion systems, which will allow accurate prediction and mitigation of thermoacoustic instabilities in future designs.
      Citation: International Journal of Spray and Combustion Dynamics
      PubDate: 2022-03-31T03:23:36Z
      DOI: 10.1177/17568277221088192
       
  • Hybrid CFD/low-order modeling of thermoacoustic limit cycle oscillations
           in can-annular configurations

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      Authors: Matthias Haeringer, Wolfgang Polifke
      First page: 143
      Abstract: International Journal of Spray and Combustion Dynamics, Ahead of Print.
      We propose a hybrid strategy for modeling non-linear thermoacoustic phenomena, e.g. limit-cycle (LC) oscillations, in can-annular combustion systems. The suggested model structure comprises a compressible CFD simulation limited to the burner/flame zone of one single can, coupled to a low-order model (LOM) representing the remaining combustor. In order to employ the suggested strategy for modeling non-linear phenomena like LC oscillations, the LOM must capture non-linear flame dynamics in the cans, which are not resolved by CFD. Instead of identifying such non-linear flame models in preliminary simulations, we aim at learning the non-linear dynamics “on-the-fly”, while simulating the self-excited system under consideration. Based on the observation of flame dynamics in the CFD domain, the parameters of the employed non-linear models are estimated during run time. The present study reveals that block-oriented models, which comprise a linear dynamic part followed by a static non-linear function, are well suited for this purpose.The proposed hybrid model is applied to a laminar can-annular combustor. Results agree well with the monolithic CFD simulation of the entire combustor, while the computational cost is drastically reduced. The employed flame models, whose parameters are identified during the simulation of the self-excited LC oscillation, represent well the relevant non-linear dynamics of the considered flame.
      Citation: International Journal of Spray and Combustion Dynamics
      PubDate: 2022-03-24T04:44:55Z
      DOI: 10.1177/17568277221085953
       
  • Comparison of the flame dynamics of a premixed dual fuel burner for
           kerosene and natural gas

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      Authors: Jan Kaufmann, Manuel Vogel, Jannes Papenbrock, Thomas Sattelmayer
      First page: 176
      Abstract: International Journal of Spray and Combustion Dynamics, Ahead of Print.
      In this study, the flame dynamics of swirl stabilized lean premixed combustion is investigated for kerosene and natural gas operation. A natural gas swirl burner is retrofitted with a twin-fluid nozzle to allow performing all experiments with the identical burner hardware. The mixture preparation complexity is stepwise increased from perfectly premixed natural gas to technically premixed natural gas and lastly technically premixed kerosene combustion. Flame transfer functions (FTFs) for the three configurations are presented and compared with each other. This approach allows to experimentally decompose the FTF and isolate the contributions of equivalence ratio fluctuations and droplet dynamics. Furthermore, FTF data for a systematic variation of equivalence ratio and air mass flow in kerosene operation is presented and the impact of spray quality and convective delay time on the FTF is discussed. For all operation points, stationary flame images are provided and evaluated as basis for the FTF interpretation. Additionally, [math] emissions are measured in order to determine the degree of premixing in kerosene operation. Through a systematic FTF comparison, it was found that the frequency range in which droplets react to acoustic forcing can be read from the FTF phase. The spray quality was found to have a significant impact on the FTF whereas a change in the convective delay time does not affect the FTF.
      Citation: International Journal of Spray and Combustion Dynamics
      PubDate: 2022-04-12T08:01:28Z
      DOI: 10.1177/17568277221091405
       
  • Robust combustor design based on flame transfer function modification

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      Authors: Jakob G. R. von Saldern, Johann Moritz Reumschüssel, Jan Paul Beuth, Christian Oliver Paschereit, Kilian Oberleithner
      First page: 186
      Abstract: International Journal of Spray and Combustion Dynamics, Ahead of Print.
      Operation under stable conditions is an important prerequisite for gas turbine safety. While recent studies have focused primarily on acoustic design to avoid thermoacoustic instabilities, in the present study we shift the focus to improving stability margins by flame transfer function (FTF) modification. The flame transfer function of premixed flames is affected by various mechanisms such as variations in equivalence ratio, swirl fluctuations and shear layer instabilities. These mechanisms can be influenced by modifying parameters such as fuel distribution, injection location, swirl number or gas composition. Based on the Nyquist stability method we formulate criteria for how and at what frequencies the flame transfer function needs to be modified, in order to increase the stability margins of a thermoacoustic system. Gain and phase margin as well as the sensitivity function serve as measures of stability. The criteria are limited to single frequencies, which allows experimental FTF optimization with manageable effort. In the second part of this study it is shown that the Nyquist method can also be used as an efficient and compact way to determine whether the uncertainties of subsystems can affect the overall stability, without requiring eigenvalue calculations.
      Citation: International Journal of Spray and Combustion Dynamics
      PubDate: 2022-04-28T07:41:54Z
      DOI: 10.1177/17568277221088422
       
  • Erratum to “impact of burner plenum acoustics on the sound emission of a
           turbulent lean premixed open flame”

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      Abstract: International Journal of Spray and Combustion Dynamics, Ahead of Print.

      Citation: International Journal of Spray and Combustion Dynamics
      PubDate: 2021-05-26T04:53:21Z
      DOI: 10.1177/17568277211008631
       
 
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