Exploring mechanism of stall margin enhancement of subsonic axial-flow compressor through steady micro tip injection

Aim. Suder et al dealt with the same problem with numerical simulation only^[5]; in our opinion, the mechanism they offer, lacking experimental support, is representative of several brave but unsuccessful first attempts at exploring this very difficult subject. We believe that the mechanism we offer, with some experimental support, is a step forward. In the full paper, we explain in detail the results of our exploration; in this abstract, we just add some pertinent remarks to listing the four topics of explanation: (1) test setup and the design of injector, (2) the analysis of the test results, (3) the method of numerical simulation, and (4) the results of numerical simulation and their analysis; under topic 1, we explain a new type of injector with the help of Fig.1 in the full paper; in topic 2, we point out that, for the tested rotor, our experimental results demonstrate that the stalling mass flow can be reduced by 7.69% using an injected mass flow equivalent to 0.064% of the design mass flow at 53% design speed; in topic 3, we point out that time-dependent CFD simulations were conducted with a view to identifying the physical mechanism that accounts for the beneficial effects of the steady micro tip injection on the performance and stability of the subsonic axial-flow compressor; also under topic 3, Fig.3 in the full paper shows the performance of the rotor of the tested subsonic axial-flow compressor; in topic 4, we give detailed analyses of the flow visualization at the tip that expose the different tip flow topologies for the cases without tip injection and with tip injection as shown in Fig.4 in the full paper. It is found that the physical mechanisms responsible for extending the compressor stall margin is repositioning the tip clearance vortex trajectory further towards the trailing edge of the blade passage and delaying the movement of incoming/tip clearance flow interface to the leading edge plane.