A modified streamwise body force model of fan with distorted inflow for rapid propulsion-airframe integrated simulation

Abstract

Streamwise Body Force Model (SBFM) could be used to simulate the force of blade on the airflow, resulting in rapid propulsion-airframe integrated simulation. However, when subjected to inlet distortion, the upstream flow field of fan stage is redistributed, which causes inaccurate prediction of fan stage performance. As inspired by the upstream influence of compressor, this paper aims to present a modification strategy for SBFM method to predict the compressor performance under circumferential inlet distortion without any knowledge of compressor geometry. Based on the linearized motion equation, the Upstream Influence Model (UIM) is introduced to predict the upstream flow field redistribution. Then the theoretical Mach number at Aerodynamic Interface Plane (AIP) position is calculated and selected to determine the corresponding body force coefficients based on the functional relationship between body force coefficients and Mach number, thus the upstream influence of compressor could be accurately quantified and the Modified Streamwise Body Force Model (MSBFM) could be established. Two studied cases are calculated with different methods and the upstream flow fields are analyzed. The prediction error of MSBFM method for compressor adiabatic efficiency is less than 3%, and the calculation efficiency is improved 20 times under the condition of ensuring computing accuracy. The MSBFM method has the potential for rapid propulsion-airframe integrated simulation.