 Subjects -> AERONAUTICS AND SPACE FLIGHT (Total: 124 journals)
| A B C D E F G H I J K L M N O P Q R S T U V W X Y Z | | The end of the list has been reached or no journals were found for your choice. |
|
|
- Evaluation of an automatic continuous high-lift system in a flight
simulator study with airline pilots-
Free pre-print version: Loading...
Rate this result:
What is this?
Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract In the INTELWI LuFo research project, TU Berlin is investigating an automatic, continuously operating high-lift system for passenger aircraft. Today’s commercial aircraft operate the high-lift systems in fixed steps. Typically, five fixed steps result from the different requirements for take-off and landing. For each flap position, there is a speed of best glide. Since aircraft decelerate during landing, they usually fly outside the optimum point. This is improved by a continuous flap system, as it continuously adjusts the flap position depending on the current flight condition. Flight simulation studies allow modelling and evaluation of new flight control functions at an early stage of development. This paper evaluates the flight simulator study for the assessment of the Automatic Continuous Moving Slat/Flap System with a focus on the pilots’ assessment. Ten airline pilots took part in the study in the SEPHIR flight simulator at TU Berlin. The approach scenarios vary with regard to the energy content of the approach since the high-lift system influences the energy management. The evaluation is based on questionnaires answered by the pilots after each approach. The participating pilots particularly emphasised the reduction of the workload and the pleasant integration of the continuous flap function into the existing cockpit procedures. According to the participating pilots, there is potential for improvement and further scenarios to investigate the functions behaviour in the event of failures in systems that affect flap operation.
PubDate: 2023-12-08
- Comparison of shock-buffet dynamics on a supercritical airfoil with and
without a pitching degree of freedom-
Free pre-print version: Loading...
Rate this result:
What is this?
Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract With the goal of understanding the dynamics of the transonic flow around an OAT15A airfoil model, velocity field measurements were performed by means of high repetition rate particle image velocimetry. The experiments were performed at free-stream Mach numbers from 0.70 to 0.77 and at a Reynolds number of Re \(_\textrm{c}\approx 3\times 10^6\) . The variation of the Mach number allowed for an investigation in the pre-buffet, buffet and close to buffet-offset regime. A fixed version and a spring mounted version of the model were used to investigate the effect of the pitching degree of freedom on the shock buffet. The dominant structural frequency of the airfoil’s pitch motion was adjusted to be in the range of the natural buffet frequency of the flow with inhibited pitching motion of the model. Flow field measurements with an acquisition rate of \(4\,\) kHz allowed for the detection and analysis of the shape and the motion of the compression shock. With released pitching degree of freedom, shock buffet started at a lower Mach number and showed a larger amplitude for the shock oscillation. Furthermore, the shock motion appeared more harmonic compared to the model without pitching degree of freedom. For a Mach number of \(M_\infty =0.72\) and 0.74, the change of the angle of attack and the shock location correlated strongly with each other. From the measurements, the phase lag between both quantities during the coupled motion could be determined. From the correlation of the shock position at different heights, it can be concluded that the shock motion is controlled by events at the shock foot. The movement of the upper shock part is only a reaction to the movement of the lower part.
PubDate: 2023-11-24
- Utilisation of semantic technologies for the realisation of data-driven
process improvements in the maintenance, repair and overhaul of aircraft
components-
Free pre-print version: Loading...
Rate this result:
What is this?
Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract Aircraft components are subject to numerous, complex and often manual maintenance, repair and overhaul (MRO) procedures to ensure long operating cycles. In order to remain competitive in the long term, in spite of increased cost pressure, MRO service providers must improve the efficiency of their processes through the targeted use of internal knowledge sources. Techniques from the fields of Artificial Intelligence (AI) and Data Mining (DM) have already proven their potential in diverse domains. However, the application of such data-driven approaches is also associated with some hurdles that need to be eliminated in advance. Data are generated at the business process level, known as Information Technology (IT, e.g. Enterprise Resource Planning (ERP) systems), as well as at the equipment level, known as Operational Technology (OT, e.g. test equipment). The integration of both forms the basis for improving the maintenance activities of diagnostics and maintenance scheduling. However, creating a unified view and understanding of the manifold data related to the maintenance process is a major problem due to the heterogeneous data sources and formats included. In this context, the use of Semantic Technologies (ST) can be helpful to overcome these challenges and provide the foundation for improved data management. The objective of this contribution is to introduce an ontology that delineates fundamental domain concepts, facilitating the augmentation of maintenance process data for individual aircraft components with pertinent contextual information. The result is being applied within the scope of a proof of concept aimed at supporting the coherent digital services diagnostics and short-term maintenance planning.
PubDate: 2023-11-21
- Conceptual design of a pilot assistance system for customised noise
abatement departure procedures-
Free pre-print version: Loading...
Rate this result:
What is this?
Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract The departure of an aircraft is commonly the flight phase with the highest thrust level in a flight, which leads to considerable noise levels on the ground. The departure procedures are characterised by the thrust reduction altitude, the acceleration altitude, and the control of airspeed and aircraft configuration within each take-off segment. Thrust reduction and acceleration altitudes are typically constant and are not adjusted to particular operational key parameters (e.g., take-off mass, reduced take-off thrust) or weather conditions. However, the parameters differ between individual flights and affect flight performance as well as the noise levels on the ground. This paper presents the conceptual design of a pilot assistance system which aims to reduce the noise on the ground by identifying a custom thrust reduction and acceleration altitude for existing noise abatement departure procedures. The pilot assistance system is based on an aircraft simulation model and a noise simulation and is aimed to be utilised during pre-flight planning on ground. A key part of the noise evaluation is that the local population distribution around the airport is considered. An overview of the ongoing research at the German Aerospace Center is provided. The conceptual design and preliminary results are presented and discussed using an exemplary take-off for three wind conditions.
PubDate: 2023-11-18
- Bio-inspired altitude changing extension to the 3DVFH* local obstacle
avoidance algorithm-
Free pre-print version: Loading...
Rate this result:
What is this?
Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract Obstacle avoidance is critical for unmanned aerial vehicles (UAVs) operating autonomously. Obstacle avoidance algorithms either rely on global environment data or local sensor data. Local path planners react to unforeseen objects and plan purely on local sensor information. Similarly, animals need to find feasible paths based on local information about their surroundings. Therefore, their behavior is a valuable source of inspiration for path planning. Bumblebees tend to fly vertically over far-away obstacles and horizontally around close ones, implying two zones for different flight strategies depending on the distance to obstacles. This work enhances the local path planner 3DVFH* with this bio-inspired strategy. The algorithm alters the goal-driven function of the 3DVFH* to climb-preferring if obstacles are far away. Prior experiments with bumblebees led to two definitions of flight zone limits depending on the distance to obstacles, leading to two algorithm variants. Both variants reduce the probability of not reaching the goal of a 3DVFH* implementation in Matlab/Simulink. The best variant, 3DVFH*b-b, reduces this probability from 70.7 to 18.6% in city-like worlds using a strong vertical evasion strategy. Energy consumption is higher, and flight paths are longer compared to the algorithm version with pronounced horizontal evasion tendency. A parameter study analyzes the effect of different weighting factors in the cost function. The best parameter combination shows a failure probability of 6.9% in city-like worlds and reduces energy consumption by 28%. Our findings demonstrate the potential of bio-inspired approaches for improving the performance of local path planning algorithms for UAV.
PubDate: 2023-11-18
- A mixed-method approach to investigate the public acceptance of drones
-
Free pre-print version: Loading...
Rate this result:
What is this?
Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract Drones may play an essential role in future traffic. As with every innovation, not only is the technical maturity decisive for its success, but also whether the general public will accept it. This paper uses a mixed-method approach combining quantitative and qualitative methods to investigate social acceptance concerning drones. The study included 20 participants and comprised a virtual simulation, a team task, and a group discussion. This way, different aspects of drone acceptance were investigated. On the one hand, a simulative approach was tested to explore the visual perception of drone flights in an urban setting. On the other hand, the acceptance of various drone applications such as civil protection, parcel delivery, and air taxis was studied. Furthermore, this research identified requirements for coordinating and managing future drone traffic. This paper combines two acceptance models from the literature as a theoretical framework: an adoption of Chamata’s and Winterton’s Technical Acceptance Model by Krempel and the Unacceptability–Acceptance Scale by Hofinger.
PubDate: 2023-11-16
- Trim Strategies and Dynamic Cross-Coupling During Aerial Refueling
-
Free pre-print version: Loading...
Rate this result:
What is this?
Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract This paper presents a multi-modal analysis framework which is used to examine the aerodynamic interactions between a tanker aircraft and a receiver during AAR for the purposes of predicting receiver dynamic modes and associated flying qualities. The data produced under this framework can then be used to predict handling qualities during the AAR task given appropriate handling qualities data. This work is motivated by the need to rapidly clear tanker–receiver pairs for safe operation in the event of multilateral operation between groups with different refueling platforms. The framework uses a vortex panel method with an actuator disk propulsion model to predict air velocities in the tanker wake. A vortex panel representation of the receiver is then combined with a closed-form aerodynamic model to find the trim points at various locations in the tanker’s wake. The closed-form aerodynamic model is used for speed of analysis and for better results at higher aerodynamic angles. This analysis framework is applied to the case of a C-130 tanker with a F/A-18 receiver. Two different trim strategies are examined: one where the yaw angle of the fighter is zero degrees, and the other where the roll angle of the fighter is zero degrees. The positional stability of the receiver is examined, finding areas of positional stability within the bounds of the tanker’s wingspan. A simplified controller model is combined with 6-DOF, 9-state equations to predict the closed-loop natural modes at the trim points within the tanker wake. The closed-loop eigenvalues of the 9-state system are not predicted to change appreciably during refueling compared to steady-level flight, and the examination of the eigenvectors shows cross-coupling effects. It is theorized that a purely eigenvalue-based analysis will be insufficient to predict handling qualities during AAR using existing decoupled approaches due to this cross-coupling.
PubDate: 2023-11-10
- Experimental investigation of performance and soot emissions of oxygenated
fuel blends in a small aero engine-
Free pre-print version: Loading...
Rate this result:
What is this?
Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract Recent studies show that mixing jet fuel with oxygenated fuels has an impact on exhaust gas soot formation. Soot particles are an environmental hazard with an impact on air quality around airports, and possibly influencing ice crystal nucleation, leading to contrail and ice cloud (cirrus) formation. These ice clouds significantly warm up the atmosphere by reflecting heat radiation back to Earth and, at the same time, being transparent to incoming sunlight. Many investigations concentrate on reducing aviation’s CO2 footprint, but only a few account for reducing soot emissions in aero engines. This study examines the potential of blending Jet A-1 with oxygenated fuels to decrease soot particle formation in aero engines. For this, blends with 5 vol% and 20 vol% of ethanol, and 5 vol% of a polyoxymethylene dimethyl ether 3–5 mix (OME3-5 mix) are investigated in an Allison 250-C20B turboshaft engine with the help of a condensation particle counter (CPC). The results show tendencies in soot particle reduction, which, in most cases, is larger than the volumetric percentage of the oxygenated fuel within the blend.
PubDate: 2023-11-07
- Experimental investigation on the turbulent wake flow in fully established
transonic buffet conditions-
Free pre-print version: Loading...
Rate this result:
What is this?
Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract The transonic flight regime is often dominated by transonic buffet, a highly unsteady and complex shock-wave/boundary-layer interaction involving major parts of the flow field. The phenomenon is associated with a large-amplitude periodic motion of the compression shock coupled with large-scale flow separation and intermittent re-attachment. Due to the resulting large-scale variation of the global flow topology, also the turbulent wake of the airfoil or wing is severely affected, and so are any aerodynamic devices downstream on which the wake impinges. To analyze and understand the turbulent structures and dynamics of the wake, we performed a comprehensive experimental study of the near wake of the supercritical OAT15A airfoil in transonic buffet conditions at a chord Reynolds number of \(2\times 10^{6}\) . Velocity field measurements reveal severe global influences of the buffet mode on both the surface-bound flow field on the suction side of the airfoil and the wake. The flow is intermittently strongly separated, with a significant momentum deficit that extends far into the wake. The buffet motion induces severe disturbances and variations of the turbulent flow, as shown on the basis of phase-averaged turbulent quantities in terms of Reynolds shear stress and RMS-values. The spectral nature of downstream-convecting fluctuations and turbulent structures are analyzed using high-speed focusing schlieren sequences. Analyses of the power spectral density pertaining to the vortex shedding in the direct vicinity of the trailing edge indicate dominant frequencies one order of magnitude higher than those associated with shock buffet ( \(St_c=\mathcal {O}({1})\) ) vs. \(St_c=\mathcal {O}({0.1})\) ). It is shown that the flapping motion of the shear layer is accompanied by the formation of a von Kármán-type vortex street of fluctuating strength. These wake structures and dynamics will impact any downstream aerodynamic devices affected by the wake. Our study, therefore, allows conclusions regarding the incoming flow of devices such as the tail plane.
PubDate: 2023-11-02
- Liquid hydrogen storage design trades for a short-range aircraft concept
-
Free pre-print version: Loading...
Rate this result:
What is this?
Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract Preliminary design trades for the liquid hydrogen storage system of a short-range aircraft are presented. Two promising insulation methods, namely rigid foam and multilayer insulation, are identified as main design drivers. In addition, the maximal pressure and the shape of the hydrogen storage tank influence the aircraft performance and the insulation efficiency. In this study, the hydrogen storage tanks are integrated in wing pods. The main effects driven by the design parameters are addressed using conceptual and preliminary methods: models are carried out for the storage mass, additional drag, propeller efficiency loss and the dynamical thermodynamic behavior of the liquid hydrogen storage. These effects are coupled making an integrated design method necessary. For the sizing of the liquid hydrogen storage, a multidisciplinary workflow is set up including the aircraft sensitivities on the design mission block fuel. The trade-off study reveals the opposing trend between insulation efficiency and aircraft performance. For the insulation architecture based on rigid foam, the penalties implied by the storage tank on aircraft level and the penalties due to vented hydrogen can be balanced and result in minimal block fuel for the design mission. The application of multilayer insulation avoids venting during the design mission, but has an increased penalty on the aircraft performance compared to rigid foam insulation. Besides the criterion of minimal block fuel, the dormancy time is compared, indicating the thermal efficiency. Applying multilayer insulation, the dormancy time can be increased significantly calling for a discussion of operational requirements for hydrogen-powered aircraft.
PubDate: 2023-10-25
- Extended reality (xR) flight simulators as an adjunct to traditional
flight training methods: a scoping review-
Free pre-print version: Loading...
Rate this result:
What is this?
Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract Over the next 20 years, it is predicted that an additional 760,000 new pilots will be needed to meet the growing demands of the global aviation industry. With current training capability, this may be difficult to achieve. A potential means of improving the efficiency and lowering the cost of flight training, which arguably may be prohibitively expensive to many potential trainee pilots, is to use extended reality simulation in place of traditional flight simulators and aircraft for at least some of the required training. To provide a better understanding of the possibilities in this regard, and where current research has advanced, a scoping review was undertaken. In total, 18 studies were identified as meeting the inclusion criteria. It was concluded that extended reality technology has the potential to be successfully employed in flight training—saving time and money, whilst also enabling increased training capability, although some potential limitations were identified. The interest in this technology, combined with evidence pointing to its potential usefulness in flight training, suggests that further examination in this area by academia and industry is warranted.
PubDate: 2023-10-20
- Practical examples for the flight data compatibility check
-
Free pre-print version: Loading...
Rate this result:
What is this?
Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract Accurate information about aircraft speed, altitude, and aerodynamic flow angles is essential for evaluating aircraft performance and handling qualities. These quantities are determined from air data measurements taken by sensors normally located near the aircraft cockpit. Since these sensors are affected by the distorted flow field around the fuselage, a correction must be applied. Before the first flight, a set of calibration parameters is usually determined from wind tunnel experiments or CFD calculations. However, the Data Compatibility Check (DCC) method allows a more accurate air data sensor calibration during the certification flight test. This method reconstructs air data quantities from inertial acceleration, angular rate measurements and the flight path. By comparing the reconstructed quantities with the measured ones, the structure and parameters of air data sensor models can be identified. In this paper, an introduction to the data compatibility check method and the setup used in a flight test for system identification is given. The DCC is applied on data gathered from a test campaign with the new DLR research aircraft Dassault Falcon 2000LX ISTAR. Use cases for the calibration of the nose boom airflow vanes and the correction of sensors during large sideslip maneuvers will be presented in this paper.
PubDate: 2023-10-11
- Conceptual design of a middle-of-the-market airliner
-
Free pre-print version: Loading...
Rate this result:
What is this?
Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract The middle of the market is a term that was established to address the commercial aircraft market segment that encompasses long-haul sectors from 3500 to 5000 nm, and airplanes with single-class passenger capacity between 220 and 250. Until now, this segment has not been extensively explored, and some airlines have shown interest in purchasing airplanes better suited to their needs in this segment. Airplanes that incorporate the latest technology already existing in narrow-body aircraft will benefit from increased engine fuel efficiency and other airframe musts. The present work investigates the optimum aircraft design for the medium category above 150–280 passenger capacity and its economic operation. For this purpose, a multi-objective optimization framework was designed to determine the best aircraft design that fits into this concept's range and capacity specifications. A surrogate model based on artificial neural networks was developed for the estimation of aerodynamic coefficients. An optimization task with a higher fidelity engine model was also carried out for searching for optimal classic designs. The results raised an important discussion about the benefits and drawbacks of a trijet configuration for transport airplanes with a capacity of over 200 passengers.
PubDate: 2023-10-09
- Model-based design and multidisciplinary optimization of complex system
architectures in the aircraft cabin-
Free pre-print version: Loading...
Rate this result:
What is this?
Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract The aviation industry is currently facing major challenges due to environmental and socio-economic trends toward sustainable and digitalized aviation. Revolutionary, more powerful and efficient technologies must be rapidly integrated into aircraft, while aircraft manufacturers must demonstrate the required safety. To support the implementation of new concepts, the DLR Institute of System Architectures in Aeronautics is researching methods for end-to-end digitalization from the preliminary design phase to assembly and production. In this context, Model-Based Systems Engineering (MBSE) and Multidisciplinary Design Optimization are important approaches for the development of complex systems. This paper presents a method for the end-to-end use of digital models for multidisciplinary optimization of system architectures. The Systems Modeling Language (SysML) is used to represent the system architecture. The focus is on the cabin and cabin systems, since they are highly coupled to other aircraft systems and have dynamic, customer-specific configuration requirements. The system architecture in SysML is instantiated and configured by the interface to the aircraft fuselage and cabin design parameter sets in the Common Parametric Configuration Schema. The subsequent coupling of the generated system architecture model with the cabin system design model developed in Matlab allows a multidisciplinary optimization of the system properties. A sensitivity analysis is performed using the Passenger Service Unit as an example. The effects of different cabin configurations on the system architecture are investigated and interdisciplinary synergies are identified and analyzed. The results of this analysis are discussed in this paper.
PubDate: 2023-10-05
- Real-time power flow analysis and management for a long-endurance solar
UAV during continuous flight-
Free pre-print version: Loading...
Rate this result:
What is this?
Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract One of the primary challenges for Unmanned Aerial Vehicle (UAV) developers is to improve their endurance while in the air, as their typical flight time is limited to a few hours. One widely used technology to enhance their endurance is harnessing solar energy to power UAV and charge their batteries in flight. This article presents the development of a real-time simulation environment to enable the continuous flight of the Sky Sailor solar UAV. Through the utilization of a solar irradiance model, a solar panel model, real-time power generation is calculated. Simultaneously, the UAV’s full dynamic model, along with the autopilot and propulsion system model, is employed to determine the energy consumption at each moment. The energy management algorithm then compares the acquired energy with the power consumed, and in cases of surplus energy, it is efficiently stored in the battery for nighttime usage. Simulations show that continuous flight of the drone can be achieved during the summer season, when the daylight hours are long enough to fully charge the battery, With the ability to fly continuously during this period, the UAV can be used in various areas, such as monitoring forest fires, agricultural fields, beaches, and security monitoring for oil companies and their life bases in deserts.
PubDate: 2023-10-05
- High-resolution vibroacoustic characterization of DLR’s Falcon
2000LX ISTAR aircraft-
Free pre-print version: Loading...
Rate this result:
What is this?
Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract In the framework of CleanSky2’s Airframe project DA9, engine tonal noise is a cooperation between Dassault Aviation and DLR. The project aims to enhance the understanding and mitigation of engine-related tonal noise in the aircraft cabin. The presented work was done to get an in-depth understanding of the vibroacoustic behavior of DLR’s Falcon 2000LX ISTAR aircraft. A two and a half weeks long vibroacoustic ground test was conducted utilizing artificial shaker excitation and operational engine excitation. The responses were measured using a roving grid of accelerometers at more than 1200 positions, meaning a subset of about 250 sensors were installed at every given time and then moved along the fuselage in a predetermined way to get a high-resolution measurement of aircrafts fuselage. The accelerometer data were than processed to show operational deflections shapes and calculate experimental structural intensity vector fields to analyze the energy transfer through the structure for optimized placement of active or passive counter measures. Specifically, the transport of tonal frequencies generated by the engines was analyzed.
PubDate: 2023-10-01
- Experimental and numerical analysis of the aerodynamics and vortex
interactions on multi-swept delta wings-
Free pre-print version: Loading...
Rate this result:
What is this?
Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract The flow field around a generic multi-swept delta wing configuration is investigated under transonic flow conditions, both experimentally and numerically. A special focus is on the analysis of vortex/vortex and vortex/shock interactions at moderate angles of attack. In the present study, the Mach number is varied between \(\textrm{Ma} = {0.50}\) and \(\textrm{Ma} = {1.41}\) and the angle of attack is varied between \(\alpha = 8^\circ\) and \(\alpha = 28^\circ\) . Numerical results are validated using experimental surface pressure data from pressure taps, as well as forces and moments based on strain gauge measurements. For selected cases, velocity field data from particle image velocimetry (PIV) measurements are available as well. Over a broad range of angle of attack and Mach number, strong vortex/vortex interactions, including vortex braiding and vortex merging, occur. The location of vortex merging is moving downstream with increasing angle of attack and increasing Mach number. Additionally, at \(\textrm{Ma} = {0.85}\) , vortex/shock interaction occurs above the wing. For moderate angles of attack, shock-induced vortex breakdown is observed.
PubDate: 2023-10-01
- Sensorless motor control for electro-mechanical flight control actuators
-
Free pre-print version: Loading...
Rate this result:
What is this?
Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract Electro-mechanical flight control actuators have become a viable option as a replacement for conventional hydraulic actuators in future more electric aircraft. A rotor angle measurement is generally required for field-oriented control of the electrical machine and usually obtained from a safety-critical resolver. It contributes, however, to a rising local hardware complexity with a negative impact on space allocation, weight, motor inertia, reliability, and cost. This paper investigates sensorless control strategies that might substitute the resolver with an accurate estimate value. A hybrid observer is implemented that allows position control without an angle sensor at all speeds. In the high speed domain, the extended electromotive force of the permanent magnet synchronous machine is used for angle estimation. In the low speed domain, including standstill, anisotropy properties of the motor are exploited by applying the alternating injection method. The performance of the control algorithm is evaluated on an aileron actuator test rig for a large civil aircraft.
PubDate: 2023-09-25
- A contribution to the investigation of acoustic interferences in aircraft
distributed propulsion-
Free pre-print version: Loading...
Rate this result:
What is this?
Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract The objective of this work is to better understand the acoustic interferences created by distributed propulsion engines based on an approach that combines RANS simulation results for the aerodynamic prediction and analytical models to calculate acoustics. A multi-propeller configuration without wing is considered for this investigation. The propeller geometry and the operating conditions are realistic for a regional transport airplane. In the first part of the paper, the results obtained by two different and independent prediction methods are compared. One method is well-established and serves as validation for the second, low-order method, which is better suited for design-to-noise applications since it requires less details as input and is computationally faster by several orders of magnitude. The good agreement between both methods, obtained for a single propeller as well as for the distributed propeller configuration, is exploited in the second part of the paper to investigate the role of acoustic interferences. Taking acoustic interferences into account drastically affects the directivity of the tonal emission. Compared to the results obtained by considering the propellers as if they were uncorrelated, the far-field sound pressure levels can be significantly lower at the radiation nodes or amplified up to the theoretical limit of 9 dB calculated for eight propellers. The directivity patterns depend on the relative initial angular positions of the propellers. When these positions are randomly varied according to the uniform probability density distribution model, the mean result (expectation) is the same as if the propellers were considered as uncorrelated. Finally, the results show that the probability that the acoustic level is lower than the mean value is higher than 50% because of the positive skewness of the probability distribution of the resulting pressure amplitude. Even though the propeller–propeller and propeller–wing interactions were not considered, the essence of the findings is expected to remain valid for more complex configurations because those interactions are rotor phase-locked.
PubDate: 2023-09-20
DOI: 10.1007/s13272-023-00679-6
- Numerical investigation of a Coandă-based fluidic thrust vectoring
system for subsonic nozzles-
Free pre-print version: Loading...
Rate this result:
What is this?
Please help us test our new pre-print finding feature by giving the pre-print link a rating.
A 5 star rating indicates the linked pre-print has the exact same content as the published article.
Abstract: Abstract The numerical investigation of a novel subsonic thrust concept for fluidic thrust vectoring (FTV) of jet engines is the subject of this publication. FTV possibly offers advantages over conventional mechanical thrust vector control such as decreased complexity, mass and maintenance costs. The operating principle of the FTV nozzles under investigation at the Institute of Jet Propulsion is based on the Coandă effect. The applied concept of thrust vectoring uses dedicated secondary flow channels which are mounted in parallel around the nozzle inner cone or the nozzle wall. If required, bleed air, provided by extraction from the engine compressor or from an external source, is injected at a specific nozzle pressure ratio at the nozzle throat \(A_8\) through these secondary ducts, resulting in the redirection of the secondary jet towards the convex Coandă surface. The interaction between the primary mass flow and the secondary jet leads to a redirection of the primary exhaust mass flow of the engine and thus to a vectoring of the exhaust flow. In this paper, the influence of different nozzle geometric parameters and different operating points are investigated within an extensive parametric study applied to a convergent two-dimensional thrust vectoring nozzle using computational fluid dynamics tools. Thrust vector deflection of up to \({20}^{\circ }\) at a maximum secondary to primary mass flow ratio of \(10 \%\) is achieved. Reducing this mass flow rate to \(5 \%\) still yields vectoring angles of up to \({15}^{\circ }\) whereby similar deflection angles compared to conventional mechanical thrust vectoring systems are achievable.
PubDate: 2023-09-05
DOI: 10.1007/s13272-023-00677-8
|
Hybrid journal (It can contain Open Access articles)
