Effects of turbofan engine nozzle flows on nozzle pressure coefficients in a high-lift aircraft configuration

Abstract

Increasing the bypass ratio of turbofan engines requires the fan pressure ratio (FPR) to reduce, if the net thrust is required to remain constant. The fan stream propulsive efficiency and normally also that of the complete engine increases. When performing in-flight thrust and drag measurements, the static pressure field can influence the engine operating characteristics, which, under the assumptions made during measurements, can lead to a bias error in the thrust-drag book keeping. Using CFD analysis on the Common Research Model- High Lift (CRM-HL), this bias error is quantified for both a Through-Flow Nacelle (TFN) and Turbofan Propulsion Simulator (TPS) for a variety of angles of attack and FPRs. The results show a clear sensitivity of the bias error for both variables. Finally, recommendations for improved measurements during book keeping to avoid this bias error are made.