NUMERICAL AND EXPERIMENTAL INVESTIGATION OF STEADY FLOW DISTORTION IN DROOPED TURBOFAN INTAKES

In some civil aero engines, steady flow distortion in turbofan intakes is often caused by the non-axisymmetric geometry, mostly droop and scarf, and the trend of shortening the nacelle exacerbates this distortion. Much analysis of previous research has established models for numerically predicting the propagation of modes through the region of steady flow distortion, but experimental measurements of the internal flow field in the intake remain challenging. The main objective of this paper is to demonstrate the feasibility of experimentally investigating the steady flow distortion in drooped turbofan intakes, providing a framework for a deeper understanding of the flow mechanisms in these intakes. Firstly, based on two types of geometrical shape, droop and scarf, three different geometries of intakes are designed, and the steady flow distortions they generate are compared using computational fluid dynamics (CFD). Secondly, the generation mechanism of steady-state distortion will be briefly discussed. Finally, this study designs fan experiments under static inlet conditions. The experiments are conducted on an aspirated fan test rig, and total pressure and static pressure measurements are recorded with a 5-hole Aero-Probe. The research results indicate that the fan experiment is successful in capturing this steady flow distortion. Both droop and scarf type intakes cause minor steady flow distortion at the outlet of the intake, which rapidly decays in the duct.