Steady performance measurements of a turbofan engine with inlet distortions containing co- and counterrotating swirl from an intake diffuser for hypersonic flight

The influence of distorted inlet flow on the steady and unsteady performanc e of turbofan engine, which is a component of an air-breathing combined pro pulsion system for a hypersonic transport aircraft is reported in this pape r. The performance and stability of this propulsion system depend on the be havior of the turbofan engine. The complex shape of the intake duct causes inhomogeneous flow at the engine inlet plane, where total pressure and swir l distortions are present. The S-bend intakes are installed axisymmetricall y left and right into the hypersonic aircraft, generating axisymmetric mirr or-inverted flow patterns. Since all turbo engines of the propulsion system have the same direction of rotation, one distortion corresponds to a corot ating swirl at the low pressure compressor (LPC) inlet while the mirror-inv erted image counterpart represents a counterrotating swirl. Therefore the i nfluence of the the distortions on the performance and stability of the 'CO ' and 'COUNTER' rotating turbo engine are different. The distortions were g enerated separately by nit appropriate simulator at the inlet plane of a LA RZAC 04 engine. The results of low-frequency measurements at different engi ne planes yield the relative variations of thrust and specific fuel consump tion and hence the steady engine performance. High-frequency measurements w ere used to investigate the different influence of CO and COUNTER inlet dis tortions on the development of LPC instabilities.