Aerodynamic Design of Separate Jet Exhausts for Future Civil Aero engines—Part I: Parametric Geometry Definition and Computational Fluid Dynamics Approach

Abstract

This paper presents the development of an integrated approach which targets the aerodynamic design of separatejet exhaust systems for future gasturbine aeroengines. 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 classshape transformation (CST) functions for the geometric design of axisymmetric engines with separatejet exhausts. Design is carried out based on a set of standard nozzle design parameters along with the flow capacities established from zerodimensional (0D) cycle analysis. The developed approach has been coupled with an automatic mesh generation and a Reynolds averaged Navier–Stokes (RANS) flowfield solution method, thus forming a complete aerodynamic design tool for separatejet exhaust systems. The employed aerodynamic method has initially been validated against experimental measurements conducted on a smallscale turbine powered simulator (TPS) nacelle. The developed tool has been subsequently coupled with a comprehensive DSE method based on Latinhypercube sampling. The overall framework has been deployed to investigate the design space of two civil aeroengines with separatejet exhausts, representative of current and future architectures, respectively. The interrelationship 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 separatejet 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 separatejet exhaust systems for designated civil aeroengine architectures. Therefore, it constitutes an enabling technology toward the identification of the fundamental aerodynamic mechanisms that govern the exhaust system performance for a userspecified engine cycle.