Numerical Optimization of a Stall Margin Enhancing Recirculation Channel for an Axial Compressor

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.

Areas of Investigation into Air Intake Systems for the Impact on Compressor Performance Stability in Aircraft Turbine Engines

“…Preliminary work of Kawase and Rona [23] in this area confirms that the use of recirculation channels reduces losses in the blade tip area and has a positive effect on compressor stability. This is done mainly by mitigating the flow leakage between the concave and convex sides of the airfoil.…”

Enhancement of aerodynamic performance of axial compressors utilizing natural aspiration through optimized casing circumferential slot

“…Rotational speed [r/min Modern compressors of gas turbine engines, utilized in aircraft or other applications, are regularly developed to increase their efficiency and to achieve higher total pressure ratios with less degradation of their performance 1 . This is usually accompanied by increasing the stage loading which causes the engine weight and length to decrease 2 .…”

CFD Investigation of an Axial Compressor with Casing Treatment for the Enhancement of the Stall Margin

“…They reported that TLV delaying the deterioration of the tip flow field and increased rotor performance. Kawase and Aldo [20] used recirculation channel to enhance the stall margin of axial compressor. The results demonstrated that 18.2 % axial position of fluid improve the stall margin by 5.5%.…”