Abstract
A proof of concept is provided by computational fluid dynamic simulations of a new recirculating type casing treatment. This treatment aims at extending the stable operating range of highly loaded axial compressors, so to improve the safety of sorties of high-speed, high-performance aircraft powered by high specific thrust engines. This casing treatment, featuring an axisymmetric recirculation channel, is evaluated on the NASA rotor 37 test case by steady and unsteady Reynolds Averaged Navier Stokes (RANS) simulations, using the realizable k-ε model. Flow blockage at the recirculation channel outlet was mitigated by chamfering the exit of the recirculation channel inner wall. The channel axial location from the rotor blade tip leading edge was optimized parametrically over the range −4.6% to 47.6% of the rotor tip axial chord c z . Locating the channel at 18.2% c z provided the best stall margin gain of approximately 5.5% compared to the untreated rotor. No rotor adiabatic efficiency was lost by the application of this casing treatment. The investigation into the flow structure with the recirculating channel gave a good insight into how the new casing treatment generates this benefit. The combination of stall margin gain at no rotor adiabatic efficiency loss makes this design attractive for applications to high-speed gas turbine engines.
Highlights
IntroductionThe stable operation of high-speed jet engines for military aircraft has become more challenging to achieve, where engines are used in combination with advanced stealth inlet ducts, which may cause a severe flow distortion through the inlet
Stable engine operations are essential to ensure a safe aircraft sortie
Houghton and Day [6,7] made a parametric design study of a circumferential groove type casing treatment for a subsonic single-stage axial compressor. They varied the groove axial position, the groove depth, and the number of the grooves. Their experiments showed that a deep groove with a depth of 0.27 axial chords gives a better stall margin than a shallower groove with a depth of 0.14 axial chords
Summary
The stable operation of high-speed jet engines for military aircraft has become more challenging to achieve, where engines are used in combination with advanced stealth inlet ducts, which may cause a severe flow distortion through the inlet. A casing treatment is an alternative or complementary approach to increase the axial compressor stall margin. Houghton and Day [6,7] made a parametric design study of a circumferential groove type casing treatment for a subsonic single-stage axial compressor. They varied the groove axial position, the groove depth, and the number of the grooves. Sakuma et al [8] applied a single circumferential groove to the casing wall of the National Aeronautics and Space Administration (NASA) axial compressor rotor 37
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