Computational fluid dynamics-based approach for low-order models of propelling nozzle performance

At the preliminary design stage for an aero-engine, the evaluation of the nozzle performance is an important aspect as it affects the overall engine cycle behaviour. Currently, there is a lack of systematic, extensive data on the nozzle performance and its dependence on the geometric and aerodynamic aspects. This paper presents a method that can be used to build characteristic maps for a nozzle as a function of a number of geometric and aerodynamic parameters. The proposed method encompasses the design of a nozzle configuration, a parameterisation of the nozzle pressure ratio, nozzle contraction ratio, plug half-angle (β), mesh generation, and an aerodynamic assessment using the Favre-averaged Navier–Stokes method. The method has been validated against experimental performance data of a plug nozzle configuration and then used for the aerodynamic assessment. The derived nozzle maps show that the thrust coefficient (Cfg) for this type of nozzle is significantly sensitive to the combined effect of the variation of the proposed parameters on the nozzle performance. These maps were used to build low-order models to predict Cfg, using response surface methods. The performance was assessed, and the results show that these low-order methods are capable of providing Cfg estimates with sufficient accuracy for use in preliminary design assessments.