Browsing by Author "Stankowski, Tomasz"
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Item 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 T.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 cycleItem 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 T.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.Item Open Access The aerodynamic effects of VHBR engine installation to the Common Research Model(American Institute of Aeronautics and Astronautics, 2017-05-26) Stankowski, Tomasz; MacManus, David G.; Robinson, MatthewThis 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 by-pass 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 penalising forces. To complete the cruise study a range of engine power settings were 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 varied by 1.7% of standard net thrust. The larger engine was less sensitive with a variation of 1.3%. For an assessment over a 10000km cruise flight the overall effect of the lower specific thrust engine showed that the cycle benefits of –5.8% in specific fuel consumption was supplemented by a relatively beneficial aerodynamic installation effect but offset by the additional weight to give a -4.8% fuel burn reduction.Item Open Access Civil turbofan engine exhaust aerodynamics: impact of bypass nozzle after-body design(Elsevier, 2017-09-11) Goulos, Ioannis; Stankowski, Tomasz; MacManus, David G.; Woodrow, Philip; Sheaf, Christopher T.It is envisaged that the next generation of civil large turbofan engines will be designed for greater bypass ratios when compared to contemporary architectures. The underlying motivation is to reduce specific thrust and improve propulsive efficiency. Concurrently, the aerodynamic performance of the exhaust system is anticipated to play a key role in the success of future engine architectures. The transonic flow topology downstream of the bypass nozzle can be significantly influenced by the after-body geometry. This behavior is further complicated by the existence of the air-flow vent on the nozzle after-body which can have an impact on the performance of the exhaust system. This paper aims to investigate the aerodynamics associated with the geometry of the bypass nozzle after-body and to establish guidelines for the design of separate-jet exhausts with respect to future large turbofan engines. A parametric geometry definition has been derived based on Class-Shape Transformation (CST) functions for the representation of post-nozzle-exit components such as after-bodies, plugs, and air-flow vents. The developed method has been coupled with an automatic mesh generation and a Reynolds Averaged Navier–Stokes (RANS) flow solution method, thus devising an integrated aerodynamic design tool. A cost-effective optimization strategy has been implemented consisting of methods for Design Space Exploration (DSE), Response Surface Modeling (RSM), and Genetic Algorithms (GAs). The combined approach has been deployed to explore the aerodynamic design space associated with the bypass nozzle after-body geometry for a Very High Bypass Ratio (VHBR) turbofan engine with separate-jet exhausts. A detailed investigation has been carried out to expose the transonic flow mechanisms associated with the effect of after-body curvature combined with the impact of the air-flow vent. A set of optimum curved after-body geometries has been obtained, with each subsequently compared against their respective conical representation. The obtained results suggest that no significant performance improvements can be obtained through curving the nozzle after-body relative to the case of a conical design. However, it is shown that the application of surface curvature has the potential to unlock new parts in the design space that allow analysts to reduce the required after-body length without any loss in aerodynamic performance. The developed approach complements the existing tool-set of enabling technologies for the design and optimization of future large aero-engines, consequently leading to increased thrust and reduced Specific Fuel Consumption (SFC).