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 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.

Effects of Aircraft Integration on Compact Nacelle Aerodynamics

“…The tool encompasses dierent modules to build a fully parametric powerplant using intuitive Class Shape Transformations (iCST). The full conguration comprises the CRM airframe [33], nacelle [5,20], intake [23], exhaust [34] and pylon [35] (Figure 2). The exhaust after-body is designed to be conical.…”

“…The design of the core nozzle and plug is carried out on the basis of alleviating any ow separation on the pylon heat-shield downstream of the core nozzle exit. To establish the owcapacities for sizing the bypass and core exhaust nozzles, the engine cycle was designed with a zero-dimensional cycle modelling tool [36] to provide representative conditions for an Ultra-High BPR engine [34]. The pylon is constructed as a series of aerofoil sections that are mounted on the vertical direction and designed to avoid adverse ow features [35].…”

Multi-objective optimisation of short nacelles for high bypass ratio engines

“…The intake and exhaust system were also dened employing CST curves. The bypass and core ducts were set with the Geometric Engine Modeler Including Nozzle Installation (GEMINI) tool [35,24]…”

“…Diversity is ensured through the use of a distance operator which penalizes clus- Although previous work has indicated that the exhaust performance can be sensitive to the nacelle trailing edge β nac [35]…”

Aspects of aero-engine nacelle drag

“…A UHBPR cycle was developed for an engine of BPR = 17.8 to cruise at a freestream Mach number of 0.82 and MFCR of 0.75 using a simulation tool for modelling engine thermodynamic performance, Turbomatch [30]. The in house software GEMINI was used to create a representative nacelle and separate jet exhaust geometry for this engine cycle [31]. Table 1 summarises the difference in design approaches taken in the four nacelles.…”