Abstract
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 axisymmetric 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. 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 subdomains 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 toward the identification of the fundamental aerodynamic mechanisms that govern the exhaust system performance for a user-specified engine cycle.
Highlights
1.1 BackgroundWithin the context of civil aviation, there is a continuing need to improve the operational performance and environmental impact of integrated aircraft–poweplant systems
Computational Fluid Dynamics (CFD) solutions have been obtained for a total of 5 meshes using progressively increasing grid fidelity
4 Conclusions An integrated approach has been developed which targets the aerodynamic design of separate-jet exhaust systems for future gas-turbine aero-engines
Summary
Within the context of civil aviation, there is a continuing need to improve the operational performance and environmental impact of integrated aircraft–poweplant systems. This entails, among others, the introduction of more fuel efficient, costeffective, and environmentally friendly aircraft engines. With respect to the envisaged propulsor designs of future turbofan engines, it is anticipated that modern configurations will employ higher values of By-Pass Ratio (BPR = mbypass ) combined with lower Fan Pressure Ratios (FPR) to lower mcore specific thrust and improve propulsive efficiency [6]. It is expected that future large turbofan engines will employ a BPR of the order of 15+ at Design Point (DP) mid-cruise conditions. A rise in BPR results in higher gross to net propulsive force ratio
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