Browsing by Author "Otter, John J."
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Item 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, MichalAs 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.Item Open Access Design and analysis of non-axisymmetric installed aero-engine exhaust systems(Elsevier, 2020-09-17) Otter, John J.; Goulos, Ioannis; Christie, Robert; MacManus, David G.In order to increase propulsive efficiency, and hence reduce fuel consumption, future aero-engines are expected to operate with higher bypass ratios and larger fan diameters relative to current in-service engines. As such, propulsion systems are likely to be more closely-coupled with the airframe which is expected to accentuate detrimental aerodynamic interference effects between the engine and airframe. It is therefore crucial that the design of future aero-engine exhaust systems is considered as part of an engine-airframe configuration in order to ensure that the expected benefits of high BPR engines are realised. This work presents the aerodynamic performance and evaluation of a set of novel exhaust systems within complete engine-airframe configurations. The introduction of non-axisymmetric exhaust systems was shown to mitigate the aerodynamic penalties associated with closely-coupled propulsion systems at cruise conditions. Relative to an axisymmetric baseline configuration, the introduction of non-axisymmetric bypass and core nozzles were found to increase the net vehicle force of the engine-airframe configuration by 0.8% and 0.6% respectively. As a result of this work, it can be concluded that non-axisymmetric exhaust systems represent a viable method for reducing aircraft cruise fuel burn.Item Open Access Design optimisation of separate-jet exhausts for the next generation of civil aero-engines(ISABE, 2017-09-08) Goulos, Ioannis; Otter, John J.; Stankowski, Tomasz; MacManus, David G.; Grech, Nicholas; Sheaf, ChristopherThis paper presents the development and application of a computational framework for the aerodynamic design of separate-jet exhaust systems for Very-High-Bypass-Ratio (VHBR) gas-turbine aero-engines. An analytical approach is synthesised comprising a series of fundamental modelling methods. These address the aspects of engine performance simulation, parametric geometry definition, viscous/compressible flow solution, design space exploration, and genetic optimisation. Parametric design is carried out based on minimal user-input combined with the cycle data established using a zero-dimensional (0D) engine analysis method. A mathematical approach is developed based on Class-Shape Transformation (CST) functions for the parametric geometry definition of gas-turbine exhaust components such as annular ducts, nozzles, after-bodies, and plugs. This proposed geometry formulation is coupled with an automated mesh generation approach and a Reynolds Averaged Navier–Stokes (RANS) flow-field solution method, thus forming an integrated aerodynamic design tool. A cost-e ective Design Space Exploration (DSE) and optimisation strategy has been structured comprising methods for Design of Experiment (DOE), Response Surface Modelling (RSM), as well as genetic optimisation. The integrated framework has been deployed to optimise the aerodynamic performance of a separate-jet exhaust system for a large civil turbofan engine representative of future architectures. The optimisations carried out suggest the potential to increase the engine’s net propulsive force compared to a baseline architecture, through optimum re-design of the exhaust system. Furthermore, the developed approach is shown to be able to identify and alleviate adverse flow-features that may deteriorate the aerodynamic behaviour of the exhaust system.Item Open Access Installation aerodynamics of civil aero-engine exhaust systems(Elsevier, 2019-04-02) Otter, John J.; Stankowski, Tomasz; Robinson, Matthew; MacManus, David G.Without careful consideration of aerodynamic installation effects on exhaust system performance the projected benefits of high bypass ratio engines may not be achievable. This work presents a computational study of propulsion system integration in order to quantify the effect that aircraft installation has on the aerodynamic performance of separate-jet aero-engine exhaust systems. Within this study the sensitivity of exhaust nozzle performance metrics to aircraft incidence and under wing position were investigated for two engines of different specific thrust. Upon installation, thrust generation was found to be beneficial or detrimental relative to an isolated engine depending on the position of the engine relative to the wing leading edge. The dominant installation effect was observed on the exhaust afterbodies and, over the range of engine positions investigated at cruise conditions, the installed modified velocity coefficient was shown to vary up to 1 % relative to an isolated engine. Furthermore, due to variations in the core nozzle mass flow rate by up to 10% relative to an isolated engine, it is concluded that aerodynamic installation effects need to be taken into consideration when sizing the core nozzle in order to ensure engine operability.Item Open Access Multi-fidelity assessment of exhaust systems for complete engine-airframe integrations(Unknown, 2020-02-28) Hueso Rebassa, Josep; Tejero, Fernando; Otter, John J.; Goulos, Ioannis; MacManus, David G.For podded underwing configurations, the goal of specific fuel consumption reduction has led to engine designs with larger fan diameters and higher bypass ratios to increase propulsive efficiency. As a consequence of this trend, the aerodynamic interference with the airframe is increased. Non-axisymmetric exhaust geometries could minimise such interference for coupled configurations. Class Shape Transformation functions are used to define 3D podded engine geometries that are installed on a transonic aircraft configuration. The complete system is assessed at mid-cruise conditions of a representative long-range cruise operation. The assessment is conducted by multi-fidelity computational fluid dynamics computations that are Euler inviscid and Reynolds Averaged Navier Stokes turbulent methods. The correlation between the different fidelities is analysed and a multi-fidelity co-kriging model is developed. The model is applied to predict the behaviour of installed non-axisymmetric exhaust systems and results into a 33% computational benefit compared to single-fidelity surrogates.Item Open Access Parametric design of non-axisymmetric separate-jet aero-engine exhaust systems(Elsevier, 2019-07-16) Otter, John J.; Christie, Robert; Goulos, Ioannis; MacManus, David G.; Grech, NicholasFuture civil air vehicles are likely to feature propulsion systems which are more closely integrated with the airframe. For a podded underwing configuration, this close coupling is expected to require non-axisymmetric design capabilities for the aero-engine exhaust system. This work presents the development of a novel parametric representation of non-axisymmetric aero-engine exhaust system geometries based on Intuitive Class Shape Transformation (iCST) curves. An exhaust design method was established and aerodynamic analyses of a range of non-axisymmetric configurations was demonstrated. At typical flight conditions, the introduction of non-axisymmetric separate jet nozzles was shown to increase the engine net propulsive force by 0.12% relative to an axisymmetric nozzle.