Influence of transonic Flow on the Thrust Determination of TPS during Wind Tunnel measurements

Abstract

The drag determination of powered configurations equipped with Turbine-Powered-Simulators (TPS) at transonic speeds in the wind tunnel is basically the problem of correct net thrust determination, since neither drag nor thrust can be measured directly. For thrust evaluation the Standard-Bookkeeping-Method (SBM) is applied, which computes the gross thrust from measured quantities and coefficients, which are obtained during static engine calibration. In wind tunnel experiments, peculiar drag behaviour was observed in terms of the effect of power settings and the influence of different bypass ratios (BPR). Within this contribution analysis using CFD are performed to demonstrate the influence of external flow on the gross thrust for an isolated TPS. From the obtained results the shortcomings of the SMB at transonic external flow are identified and thrust corrections to the SBM are derived. The application of the corrections to the measured Lilienthal-polars stress the necessity of a valid bookkeeping procedure for transonic Mach numbers.