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

Abstract

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.

The Use of Enhanced Nozzle Maps for Gas-Turbine Performance Modelling

“…Nozzle gross thrust coefficient maps were used for the by-pass and the core-nozzle. These maps were produced using a simplified nozzle configuration for different operational and geometrical parameters using computational fluid dynamics (CFD) method [9].…”

“…Sutherland's law was utilized for the calculations of dynamic viscosity [10], kinetic theory for the thermal conductivity and temperature-based polynomial correlation to estimate the specific heat [10]. Several cases were run after implementing the grid and domain sensitivity study [9]. The extracted data in terms of the pressure forces, drag and friction forces were used to calculate the nozzle gross thrust, in addition to the nozzle fluxes [9].…”

“…Several cases were run after implementing the grid and domain sensitivity study [9]. The extracted data in terms of the pressure forces, drag and friction forces were used to calculate the nozzle gross thrust, in addition to the nozzle fluxes [9].…”

“…For the BP nozzle geometry, the development of the maps is based on the gross thrust coefficient (Cfg) (Equation 1) [11] that was extracted from CFD calculations. Cfg is represented by the ratio of the actual gross thrust that is extracted from the aerodynamic analysis (Equation 2), Where The derived value of the gross thrust coefficient (Cfg) includes the impact of the geometry variation on the pressure-thrust term.…”

“…Therefore, instead of the typical current one-dimensional maps that illustrate the NPR impact only for a single nozzle configuration [7,8], the multidimensional effect of the flow has been quantified. In the current work, two samples of the used maps are presented, while a detailed description is offered at Al-Akam et al [11,12].…”