Stability Enhancement of a Low Speed Axial Compressor with Tip Injection

摘要

This study presents stability enhancement of a 4-stage low speed axial compressor enhancement by tip injection. Tip injection was actuated by 2 external blowers and the air was injected steadily through the Coanda-shaped nozzles. With tip injection, the compressor operation range has been extended by 4.9% relative to the case without injection. To analyze stall margin improvement, Spatial Fourier Transform (SFT) has been performed. The coefficient of SFT (SFC) is a complex number, containing information about the magnitude and the phase of SFC. When a modal, or long length scale, disturbance occurs, the magnitude of SFC increases abruptly and the phase of SFC increases linearly with time. By analyzing the distribution of the magnitude and the phase of SFC, the stall onset point has been verified. Thus, the stall onset points have been determined for varying injection flow rates, and the precise extension of the operation range has been calculated. Furthermore, the injection flow rate has been changed during injection process to examine the possibility of attaining an additional flow extension. It has been verified that increasing the injection rate can bring about operation range extension, and reducing the amount of injection flow rate.