Theoretical analysis of the effect of water and ethanol injection on axial compressor instabilities

Two types of instabilities that occur in compression systems rotating stall and surge have an adverse effect on the compressor performance. Several techniques have been explored to minimize the effect of these instabilities. It has been observed that injection of a liquid into the compressor not only improves thermodynamic efficiencies but also results in stabilizing the system. Therefore, water and ethanol injection has been investigated as an effective tool for controlling these compressor instabilities. In the present paper a modified Moore–Greitzer model has been proposed for wet compression-based system using water and ethanol. Under this work the effect of injection of water (1) at various stages of compressor, (2) at different altitudes and (3) by varying amounts has also been presented. The effect of various parameters on wet compression such as (a) Optimum stage for liquid injection (b) Optimum amount of liquid injection and (c) Effect of altitude on liquid injection is also examined in the present work which shows that the liquid injection helps in improving the performance of compression systems in terms of increase in the stall margin and pressure rise coefficient.