CERES :: Browsing by Author "MacManus, David G."

Browsing by Author "MacManus, David G."

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Open Access
Advancements on the use of Filtered Rayleigh Scattering (FRS) with machine learning methods for flow distortion in aero-engine intakes
(Elsevier, 2025-01-01) Migliorini, Matteo; Doll, Ulrich; Lawson, Nicholas J.; Melnikov, Sergey M.; Steinbock, Jonas; Dues, Michael; Zachos, Pavlos K.; Röhle, Ingo; MacManus, David G.
In-flight measurements of aerodynamic quantities are a requirement to ensure the correct scaling of Reynolds and Mach number and for the airworthiness certification of an aircraft. The ability to obtain such measurement is subject to several challenges such as instrument installation, environment, type of measurand, and spatial and temporal resolution. Given expected, more frequent use of embedded propulsion systems in the near future, the measurement technology needs to adapt for the characterization of multi-type flow distortion in complex flow, to assess the operability of air-breathing propulsion systems. To meet this increasing demand for high-fidelity experimental data, the Filtered Rayleigh Scattering (FRS) method is identified as a promising technology, as it can provide measurements of pressure, temperature and 3D velocities simultaneously, across a full Aerodynamic Interface Plane (AIP). Τhis work demonstrates the application of a novel FRS instrument, to assess the flow distortion in an S-duct diffuser, in a ground testing facility. A comparison of FRS results with Stereo-Particle Image Velocimetry (S-PIV) measurements reveals good agreement of the out of plane velocities, within 3.3 % at the AIP. Furthermore, the introduction of machine learning methods significantly accelerates the processing of the FRS data by up to 200 times, offering a substantial prospect towards real time data analysis. This study demonstrates the further development of the FRS technique, with the ultimate goal of inlet flow distortion measurements for in-flight environments.
Open Access
Aerodynamic analysis of civil aeroengine exhaust systems using computational fluid dynamics
(AIAA, 2018-06-25) Otter, John J.; Goulos, Ioannis; MacManus, David G.; Slaby, Michal
As the specific thrust of civil aeroengines reduces, the aerodynamic performance of the exhaust system will become of paramount importance in the drive to reduce engine fuel burn. This paper presents an aerodynamic analysis of civil aeroengine exhaust systems through the use of Reynolds-averaged Navier–Stokes computational fluid dynamics. Two different numerical approaches are implemented, and the numerical predictions are compared to measured data from an experimental high-bypass-ratio separate-jet exhaust system. Over a fan nozzle pressure ratio range from 1.4 to 2.8, a comparison is drawn between values of the thrust coefficient calculated numerically and those obtained from experimental measurements. In addition, the effects of the freestream Mach number and extraction ratio on the aerodynamic behavior of the exhaust system are quantified and correlated to fundamental aerodynamic parameters.
Open Access
Aerodynamic design of separate-jet exhausts for future civil aero engines, Part I: parametric geometry definition and CFD approach
(ASME, 2016-03-15) Goulos, Ioannis; Stankowski, Tomasz; Otter, John; MacManus, David G.; Grech, Nicholas; Sheaf, Christopher
This paper presents the development of an integrated approach which targets the aerodynamic design of separate-jet exhaust systems for future gas-turbine aero-engines. The proposed framework comprises a series of fundamental modeling theories which are applicable to engine performance simulation, parametric geometry definition, viscous/compressible flow solution, and Design Space Exploration (DSE). A mathematical method has been developed based on Class-Shape Transformation (CST) functions for the geometric design of axi-symmetric engines with separate-jet exhausts. Design is carried out based on a set of standard nozzle design parameters along with the flow capacities established from zero-dimensional (0D) cycle analysis. The developed approach has been coupled with an automatic mesh generation and a Reynolds Averaged Navier-Stokes (RANS) flow-field solution method, thus forming a complete aerodynamic design tool for separate-jet exhaust systems. The employed aerodynamic method has initially been validated against experimental measurements conducted on a small-scale Turbine Powered Simulator (TPS) nacelle. The developed tool has been subsequently coupled with a comprehensive DSE method based on Latin- Hypercube Sampling (LHS). The overall framework has been deployed to investigate the design space of two civil aero-engines with separate jet exhausts, representative of current and future architectures, respectively. The inter-relationship between the exhaust systems' thrust and discharge coefficients has been thoroughly quantified. The dominant design variables that affect the aerodynamic performance of both investigated exhaust systems have been determined. A comparative evaluation has been carried out between the optimum exhaust design sub-domains established for each engine. The proposed method enables the aerodynamic design of separate-jet exhaust systems for a designated engine cycle, using only a limited set of intuitive design variables. Furthermore, it enables the quantification and correlation of the aerodynamic behavior of separate-jet exhaust systems for designated civil aero-engine architectures. Therefore, it constitutes an enabling technology towards the identification of the fundamental aerodynamic mechanisms that govern the exhaust system performance for a user-specified engine cycle
Open Access
Aerodynamic effects of propulsion integration for high bypass ratio engines
(AIAA, 2017-05-26) Stankowski, Tomasz; MacManus, David G.; Robinson, Matthew; Sheaf, Christopher
This work describes the assessment of the effect of engine installation parameters such as engine position, size, and power setting on the performance of a typical 300-seater aircraft at cruise condition. Two engines with very high bypass ratio and with different fan diameters and specific thrusts are initially simulated in isolation to determine the thrust and drag forces for an isolated configuration. The two engines are then assessed in an engine–airframe configuration to determine the sensitivity of the overall installation penalty to the vertical and axial engine location. The breakdown of the interference force is investigated to determine the aerodynamic origins of beneficial or penalizing forces. To complete the cruise study, a range of engine power settings is considered to determine the installation penalty at different phases of cruise. This work concludes with the preliminary assessment of cruise fuel burn for two engines. For the baseline engine, across the range of installed positions, the resultant thrust requirement varies by 1.7% of standard net thrust. The larger engine is less sensitive with a variation of 1.3%. For an assessment over a 10,000 km cruise flight, the overall effect of the lower specific thrust engine shows that the cycle benefits of −5.8% −5.8% in specific fuel consumption are supplemented by a relatively beneficial aerodynamic installation effect but offset by the additional weight to give a −4.8% −4.8% fuel-burn reduction.
Open Access
Aerodynamic instabilities in high-speed air intakes and their role in propulsion system integration
(MDPI, 2024-01-12) Philippou, Aristia L.; Zachos, Pavlos K.; MacManus, David G.
High-speed air intakes often exhibit intricate flow patterns, with a specific type of flow instability known as ‘buzz’, characterized by unsteady shock oscillations at the inlet. This paper presents a comprehensive review of prior research, focused on unraveling the mechanisms that trigger buzz and its implications for engine stability and performance. The literature survey delves into studies concerning complex-shaped diffusers and isolators, offering a thorough examination of flow aerodynamics in unstable environments. Furthermore, this paper provides an overview of contemporary techniques for mitigating flow instability through both active and passive flow control methods. These techniques encompass boundary layer bleeding, the application of vortex generators, and strategies involving mass injection and energy deposition. The study concludes by discussing future prospects in the domain of engine-intake aerodynamic compatibility. This work serves as a valuable resource for researchers and engineers striving to address and understand the complexities of high-speed air induction systems.
Open Access
Aerodynamic interference between high-speed slender bodies
(Cranfield University, 2009-12) Chaplin, Ross; MacManus, David G.
Significant aerodynamic interference can occur between high-speed bodies in close proximity. A complex flowfield develops where shock and expansion waves from a generator body impinge upon the adjacent receiver body. The pressure and flow angularity changes which occur across these disturbances modify the body aerodynamics. The aim of this research is to quantify the aerodynamic interference effects for multi-body configurations and understand the relevant flow physics. The interference aerodynamics for slender bodies in a supersonic flow were investigated through a parametric wind tunnel study. The receiver bodies were finned and un-finned configurations. The effect of lateral and axial body separations, receiver incidence and the strength of the disturbance field were investigated. Measurements included forces and moments, surface pressures and flow visualisations. Supporting computations using steady-state, viscous predictions provided a deeper understanding of the underlying aerodynamics and flow mechanisms. Good agreement was found between the measured and predicted interference loads and surface pressures for all configurations. The interference loads are strongly dependent upon the axial impingement location of the primary shockwave. These induced loads change polarity as the impingement location moves aft over the receiver. The magnitude of the interference loads increase when the receiver is at incidence and are amplified by up to a factor of three when rear fins are attached. In general, the interference loads are larger for a stronger disturbance flowfield. The centre of pressure location is substantially affected and the static stability of the finned receiver changes in some configurations. The effect of the aerodynamic interference on the body trajectories was assessed using an unsteady, Euler prediction in combination with a 6DOF dynamic model. This shows aerodynamic ii interference can cause a collision between the bodies. Moreover, the initial interference loads dominate the subsequent body trajectories and static modelling can be used to evaluate the dynamic trajectories.
Open Access
Aerodynamic interference for aero-engine installations
(AIAA, 2016-01-02) Stankowski, Tomasz P.; MacManus, David G.; Sheaf, Christopher; Grech, Nicholas
Open Access
Aerodynamic Interference on Finned Slender Body
(American Institute of Aeronautics and Astronautics, 2016-04-28) Chaplin, Ross; MacManus, David G.; Leopold, Friedrich; Martinez, Bastien; Gauthier, Thibaut; Birch, Trevor
Aerodynamic interference can occur between high-speed slender bodies when in close proximity. A complex flowfield develops where shock and expansion waves from a generator body impinge upon the adjacent receiver body and modify its aerodynamic characteristics in comparison to the isolated case. The aim of this research is to quantify and understand the multibody interference effects that arise between a finned slender body and a second disturbance generator body. A parametric wind tunnel study was performed in which the effects of the receiver incidence and axial stagger were considered. Computational fluid dynamic simulations showed good agreement with the measurements, and these were used in the interpretation of the experimental results. The overall interference loads for a given multibody configuration were found to be a complex function of the pressure footprints from the compression and expansion waves emanating from the generator body as well as the flow pitch induced by the generator shockwave. These induced interference loads change sign as the shock impingement location moves aft over the receiver and in some cases cause the receiver body to become statically unstable. Overall, the observed interference effects can modify the subsequent body trajectories and may increase the likelihood of a collision.
Open Access
Aerodynamic investigations of ventilated brake discs.
(Professional Engineering Publishing, 2005-01-01T00:00:00Z) Parish, D.; MacManus, David G.
The heat dissipation and performance of a ventilated brake disc strongly depends on the aerodynamic characteristics of the flow through the rotor passages. The aim of this investigation was to provide an improved understanding of ventilated brake rotor flow phenomena, with a view to improving heat dissipation, as well as providing a measurement data set for validation of computational fluid dynamics methods. The flow fields at the exit of four different brake rotor geometries, rotated in free air, were measured using a five-hole pressure probe and a hot-wire anemometry system. The principal measurements were taken using two-component hot-wire techniques and were used to determine mean and unsteady flow characteristics at the exit of the brake rotors. Using phase-locked data processing, it was possible to reveal the spatial and temporal flow variation within individual rotor passages. The effects of disc geometry and rotational speed on the mean flow, passage turbulence intensity, and mass flow were determined. The rotor exit jet and wake flow were clearly observed as characterized by the passage geometry as well as definite regions of high and low turbulence. The aerodynamic flow characteristics were found to be reasonably independent of rotational speed but highly dependent upon rotor geometry.
Open Access
Aerodynamic optimisation of civil aero-engine nacelles by dimensionality reduction and multi-fidelity techniques
(Emerald, 2022-09-30) Tejero, Fernando; MacManus, David G.; Hueso Rebassa, Josep; Sanchez Moreno, Francisco; Goulos, Ioannis; Sheaf, Christopher
Purpose - Aerodynamic shape optimisation is complex due to the high dimensionality of the problem, the associated non-linearity and its large computational cost. These three aspects have an impact on the overall time of the design process. To overcome these challenges, this paper develops a method for transonic aerodynamic design with dimensionality reduction and multi-fidelity techniques. Design/methodology/approach - The developed methodology is used for the optimisation of an installed civil ultra-high bypass ratio aero-engine nacelle. As such, the effects of airframe-engine integration are considered during the optimisation routine. The active subspace method is applied to reduce the dimensionality of the problem from 32 to 2 design variables with a database compiled with Euler CFD calculations. In the reduced dimensional space, a co-Kriging model is built to combine Euler lower-fidelity and RANS higher-fidelity CFD evaluations. Findings - Relative to a baseline aero-engine nacelle derived from an isolated optimisation process, the proposed method yielded a non-axisymmetric nacelle configuration with an increment in net vehicle force of 0.65% of the nominal standard net thrust. Originality - This work investigates the viability of CFD optimisation through a combination of dimensionality reduction and multi-fidelity method, and demonstrates that the developed methodology enables the optimisation of complex aerodynamic problems.
Open Access
Aerodynamic optimisation of civil aero-engine nacelles by dimensionality reduction and multi-fidelity techniques
(Unknown, 2022-03-30) Tejero, Fernando; MacManus, David G.; Hueso Rebassa, Josep; Sanchez Moreno, Francisco; Goulos, Ioannis; Sheaf, Christopher
Aerodynamic shape optimisation is complex due to the high dimensionality of the problem, the associated nonlinearity and its large computational cost. These three aspects have an impact on the overall time of the design process. To overcome these challenges, this paper develops a method for transonic aerodynamic design with dimensionality reduction and multi-fidelity techniques. It is used for the optimisation of an installed civil ultra-high bypass ratio aero-engine nacelle. As such, the effects of airframe-engine integration are considered during the optimisation routine. The active subspace method is applied to reduce the dimensionality of the problem from 32 to 2 design variables with a database compiled with Euler CFD calculations. In the reduced dimensional space, a co-Kriging model is built to combine Euler lower-fidelity and RANS higher-fidelity CFD evaluations. Relative to a baseline aero-engine nacelle derived from an isolated optimisation process, the proposed method yielded a non-axisymmetric nacelle configuration with an increment in net vehicle force of 0.65% of the nominal standard net thrust. This work demonstrates that the developed methodology enables the optimisation of complex aerodynamic problems.
Open Access
Aerodynamic optimization of the exhaust system of an aft-mounted boundary layer ingestion propulsor
(2022-03-28) Matesanz García, Jesús; Piovesan, Tommaso; MacManus, David G.
Novel aircraft propulsion configurations require a greater integration of the propulsive system with the airframe. As a consequence of the closer integration of the propulsive system, higher levels of flow distortion at the fan face are expected. This distortion will propagate through the fan and penalize the system performance. This will also modify the exhaust design requirements. Hence, the aerodynamic design of the exhaust system becomes crucial to reduce the penalties of the distortion on the system performance. This work defines a methodology for the optimization of exhaust systems for novel embedded propulsive systems. As the case study a 2D axisymmetric aft mounted annular boundary layer ingestion (BLI) propulsor is used. An automated CFD approach is applied with a parametric definition of the design space. A throughflow body force model for the fan is implemented and validated for 2D axisymmetric and 3D flows. A multi-objetive optimization based on evolutionary algorithms is used for the exhaust design. A maximum benefit of approximately 0.32% on the total aircraft required thrust was observed by the application of compact exhaust designs. Furthermore, for the embedded system, is observed that the design of the compact exhaust and the nacelle afterbody have a considerable impact on the aerodynamic performance. To the author’s knowledge, this is the first detailed optimization of an exhaust system on an annular aft-mounted BLI propulsor.
Open Access
Aerodynamic optimization of the exhaust system of an aft-mounted boundary layer ingestion propulsor
(Emerald, 2022-12-15) Matesanz García, Jesús; Piovesan, Tommaso; MacManus, David G.
Purpose Novel aircraft propulsion configurations require a greater integration of the propulsive system with the airframe. As a consequence of the closer integration of the propulsive system, higher levels of flow distortion at the fan face are expected. This distortion will propagate through the fan and penalize the system performance. This will also modify the exhaust design requirements. This paper aims to propose a methodology for the aerodynamic optimization of the exhaust for novel embedded propulsive systems. To model the distortion transfer, a low order throughflow fan model is included. Design/methodology/approach As the case study a 2D axisymmetric aft-mounted annular boundary layer ingestion (BLI) propulsor is used. An automated computational fluid dynamics approach is applied with a parametric definition of the design space. A throughflow body force model for the fan is implemented and validated for 2D axisymmetric and 3D flows. A multi-objective optimization based on evolutionary algorithms is used for the exhaust design. Findings By the application of the optimization methodology, a maximum benefit of approximately 0.32% of the total aircraft required thrust was observed by the application of compact exhaust designs. Furthermore, for the embedded system, it is observed that the design of the compact exhaust and the nacelle afterbody have a considerable impact on the aerodynamic performance. Originality/value This paper presents a novel approach for the exhaust design of embedded propulsive systems in novel aircraft configurations. To the best of the authors’ knowledge, this is the first detailed optimization of the exhaust system on an annular aft-mounted BLI propulsor.
Open Access
Aerodynamics of a compact nacelle at take-off conditions
(IEEE, 2023-06-08) Swarthout, Avery E.; MacManus, David G.; Tejero, Fernando; Matesanz García, Jesús; Goulos, Ioannis; Boscagli, Luca; Sheaf, Christopher
Next generation ultra-high bypass ratio turbofans may have larger fan diameters than the previous generation of aircraft engines. This will potentially increase the nacelle diameter and may incur penalties to the weight and drag of the powerplant. To offset these penalties, a more compact nacelle may be used. Compact nacelles may be more sensitive to boundary layer separation at the end-of-runway conditions, particularly at an off-design windmilling operating point. Additionally, the flow separation on the external cowl surface is likely to be influenced by the integration between the powerplant, pylon and airframe. The publicly available NASA high lift common research model (HL-CRM) with take-off flap and slat settings was modified to accommodate an ultra-high bypass ratio powerplant. The powerplant has an intake, separate jet exhaust, external cowl and pylon. Boundary layer separation on the external cowl of the compact powerplant is assessed at end-of-runway rated take-off and take-off windmilling scenarios. Additionally, the lift curve and Cp distributions of the high lift common research model (HL-CRM) are compared for rated take-off and take-off windmilling engine mass flows. Overall, the nacelle boundary layer separates from the nacelle highlight at windmilling conditions when the engine mass flow is relatively low. The mechanism of separation at windmilling conditions is diffusion driven and is initiated on the nacelle aft-body. The pylon has a small impact on the overall mechanism of separation. However, the wing and high-lift devices of the HL-CRM introduce local separation on the external cowl. The HL-CRM wing with the installed powerplant stalls at a similar angle (αa/c = 16°) to the HL-CRM with the through flow nacelle available in the open literature. Compared with the nominal take-off condition, the maximum lift coefficient of the HL-CRM airframe was reduced by about 2% under windmilling engine mass flows.
Open Access
Aerodynamics of aero-engine installation
(AIAA, 2016-01-02) Stankowski, Tomasz P.; MacManus, David G.; Sheaf, Christopher; Grech, Nicholas
Small internal combustion engines, particularly those ranging in power from 1 kW to 10 kW, propel many remotely piloted aircraft (RPA) platforms that play an increasingly significant role in the Department of Defense. Efficiency of these engines is low compared to conventional scale engines and thermal losses are a significant contributor to total energy loss. Existing thermal energy loss models are based on data from much larger engines. Whether these loss models scale to the engine size class of interest, however, has yet to be established. The Small Engine Research Bench (SERB) was used to measure crank angle resolved gas temperature inside the combustion chamber of a small internal combustion engine (ICE). A 55 cc, two stroke, spark-ignition ICE was selected for this study. The engine was modified for optical analysis using sapphire rods 1.6 mm in diameter on opposite sides of the combustion chamber. The engine modification was found to have no measurable impact on indicated mean effective pressure or heat rejection through the cylinder. FTIR absorption thermometry was used to collect mid-infrared absorption spectra. The FTIR was allowed to scan continuously while simultaneously recording the scanning mirror position and crank angle associated with each data point, then data was re-sorted by crank angle. Measured spectra were compared with lines generated using CDSD-4000 and HITEMP line list databases. The line of best fit corresponded to the mean gas temperature through the combustion chamber. In this way temperature was determined as a function of crank angle for three operating conditions: 4,300, 6,000, and 7,500 revolutions per minute, all at wide open throttle. High cycle-to-cycle variation in the regions of combustion and gas exchange degraded temperature measurements at the affected crank angles. Future research will attempt to improve signal to noise in these measurements.
Open Access
Aerodynamics of aero-engine installation
(Sage Publications, 2016-02-24) Stankowski, Tomasz P.; MacManus, David G.; Sheaf, Christopher; Christie, Robert
This paper describes current progress in the development of methods to assess aero-engine airframe installation effects. The aerodynamic characteristics of isolated intakes, a typical transonic transport aircraft as well as a combination of a through-flow nacelle and aircraft configuration have been evaluated. The validation task for an isolated engine nacelle is carried out with concern for the accuracy in the assessment of intake performance descriptors such as mass flow capture ratio and drag rise Mach number. The necessary mesh and modelling requirements to simulate the nacelle aerodynamics are determined. Furthermore, the validation of the numerical model for the aircraft is performed as an extension of work that has been carried out under previous drag prediction research programmes. The validation of the aircraft model has been extended to include the geometry with through flow nacelles. Finally, the assessment of the mutual impact of the through flow nacelle and aircraft aerodynamics was performed. The drag and lift coefficient breakdown has been presented in order to identify the component sources of the drag associated with the engine installation. The paper concludes with an assessment of installation drag for through-flow nacelles and the determination of aerodynamic interference between the nacelle and the aircraft.
Open Access
The aerodynamics of aero-engine Nacalles.
(2018-02) Robinson, Matthew H.; MacManus, David G.
This thesis deals with the aerodynamics of aero-engine nacelles with a focus on the influence of a short and slim nacelle design on the drag performance. As turbofan engines are designed with increasingly reduced specific thrusts in order to improve propulsive efficiency, the fan diameter tends to grow. With a larger fan, the engine weight and nacelle drag grow which may offset the benefit from the reduced specific thrust. It is imperative to determine if a reduced length and thickness nacelle, compared to a conventional design, will enable the viable use of these reduced specific thrust aero-engine designs. The research aims to answer this question with a focus on cruise drag, spillage drag, drag rise and windmill performance of isolated and installed short, and slim nacelles. An innovative optimisation process was developed with a computational fluid dynamics process included as a means to evaluate nacelle drag. This was applied to different nacelle designs in a novel design space to optimise for cruise and off-design performance with a multi-objective genetic algorithm. The optimisation routine was extensively tested and verified against a number of analytical functions to ensure it could adequately approximate optimal Pareto sets. The optimisation of both axisymmetric and non-axisymmetric nacelles was carried out on drag, spillage and drag rise Mach number as well as on two metrics which control the pressure distribution of the nacelle. Optimal nacelles were then chosen to study the influence of nacelle incidence, the windmill condition and installation onto an aircraft on the drag performance and to provide a new quantification of these impacts. The optimisation demonstrated that under cruise conditions it is possible to have compact nacelle designs that offer reductions in drag. For example, a nacelle with a 23% reduction in length resulted in a 22% reduction in nacelle drag. However, these compact designs are more sensitive to off design condition. Specifically the spillage drag at a required drag rise Mach number of 0.87 could be 9 times higher for the reduced length nacelle. Nonetheless, it is possible to create a nacelle at the shortest length tested which had spillage of less than 6% of the cruise drag and met all requirements on drag rise to cruise at a Mach number of 0.85. This was enabled by an increase in the trailing edge radius such that it was equal to the highlight radius which improved the wave drag characteristics. Whilst the shortened nacelle was viable at low incidence, the increased wave drag resulted in the drag benefit relative to the conventional design being negated by an incidence of 6 degrees. In addition, this reduced length nacelle experienced separation at the end of runway windmill condition at 22 degrees, which is below the requirement of 30 degrees. Once installed on an aircraft the impact of reducing the nacelle length was a decrease in overall cruise aircraft drag of 3%. These studies demonstrate that there is a significant cruise benefit available from a short nacelle but that the off design conditions, most notably windmill requirements, will need to be addressed.
Open Access
Aerodynamics of propulsion system integration for modern aero-engines.
(2016-09) Stańkowski, Tomaz Piotr; MacManus, David G.
Over the past years, the fan diameter of a turbofan engine for commercial aircraft tended to increase and based on the requirement to improve the propulsive efficiency it is expected that the engine diameter will continue to increase. In this context, the issue of the integration of a larger powerplant with the airframe is a major concern. It is anticipated that the increase of engine diameter will eventually lead to an increase of the drag due to the engine installation, which could potentially outweigh the benefits of very high by-pass ratio cycles. This research aims to quantify the aerodynamic sensitivity to the key parameters of engine installation such as engine position, size and power-setting for prospective large turbofans. A numerical study with the use of Computational Fluid Dynamics was completed to determine the effect of engine position, size and power setting on the performance of a typical 300 seater aircraft with podded engines at cruise condition. Two engines with very-high by-pass ratio and with different fan diameters and specific thrusts were simulated in isolation and in range of positions under the wing. In addition, the detailed breakdown of the interference force was investigated to determine the contribution of aerodynamic forces based on the components such as wing, nacelle and fuselage. The assessment of the flowfields was done to determine the aerodynamic origins of beneficial or penalising forces and to explain the observed trends in the aerodynamic forces. The work concluded with the evaluation of the fuel burn reduction for the larger engine configuration. Over the long-haul cruise phase, the cycle benefits for the large engine with low specific thrust deteriorated from -5.8% reduction in fuel burn to -4.8% as compared with the baseline engine due to the effect of engine weight and throttle dependent aerodynamic forces. It was also found that the large engine was less sensitive to the engine position. Over the same range of positions, the sensitivity of 1.7% of reference thrust for the baseline engine reduced to 1.3% sensitivity for the 1.23 times larger engine. Overall, to aid the preliminary design of prospective large turbofans, a model for the quantification of the engine installation effect was proposed based on the available dataset. The model aims to outline the general trend in the determination of engine installation at the early stage of the preliminary design. A basic verification of the model was completed with an agreement of 1.25 aircraft drag count in the prediction of the overall installation effect based on the available dataset.
Open Access
Aerodynamics of vortex ingestion for aero-engines
(Cranfield University, 2013-12) McLelland, Grant; MacManus, David G.
The potential impact of inlet flow distortion on the stability and performance of aircraft engines remains a key concern for engine-airframe integration. Current and future configurations, such as Unmanned Combat Air Vehicles (UCAVs), and possible civil aircraft with large rear-mounted engines, feature closely-coupled intake and airframe aerodynamics. Such configurations are susceptible to the ingestion of streamwise vorticity generated upstream on the aircraft. There is a dearth of understanding of this ingestion process which, crucially, determines the nature of the flow distortion presented to the turbomachinery. To assess the risk of engine stability and performance deterioration, it is therefore necessary to understand and model the vortex ingestion process. This research provides a novel application of Stereoscopic Particle Image Velocimetry (Stereo PIV) to obtain quantitative measurements of a streamwise vortex inside a contracting intake capture streamtube. The experiments were conducted in the 8’x6’ lowspeed wind tunnel using a 1/30th scale intake model. Vortex generators were employed to create a streamwise vortex in the flow upstream of the intake. The streamtube contraction levels, vortex generator type, and vortex generator configuration were varied to establish fundamental understanding on the flow physics of vortex ingestion. The vortex experiences notable levels of intensification as it passes through the contracting streamtube. The evolution of the vortex is strongly dependent on the streamtube contraction levels, the initial characteristics of the vortex prior to ingestion, and the trajectory that the vortex follows inside the capture streamtube. In addition, detailed studies have been performed using Computational Fluid Dynamics (CFD) to establish an approach to simulate vortex ingestion flows. A number of guidelines have been developed using experimental measurements to ensure that the flow physics of vortex ingestion are captured. This approach permits vortex ingestion simulations to be performed to evaluate the inlet flow distortion characteristics in full-scale intake flows.
Open Access
Analysis and control of resonant cavity flows
(Cranfield University, 2013) Roberts, David; MacManus, David G.
Recently, the trend for the internalisation of stores within an aircraft fuselage has led to a renewed interest in the field of cavity aero-acoustics. Many modern military aircraft, including recent unmanned combat configurations, are designed with internal stores carriage. Housing stores within a weapon bay cavity has the two fold benefit to the aircraft: reduced excrescence drag, and a smaller radar signature. However, open cavities exposed to a grazing flow can exhibit large resonant pressure fluctuations which may damage stores or components within the cavity. The aim of this research is to investigate the fundamental flow characteristics of open cavities and to develop passive palliative concepts to control the unsteady pressure fluctuations within resonant cavity flows. The fundamental flow characteristics of two scale cavities were investigated experimentally: a 1/40th scale model under transonic conditions (0.80