Indian Journal of Science and Technology

Abstract

In axial compressor distortion at inlet leads to adverse pressure gradient at inlet of fan which leads to performance ­degradation and adverse effects like vibration and noise. The major distortion can lead to surge or stall in compressor. Hence, this study involves creating distortions at inlet and studying its effects on stall and performance of compressor fan. To analyze effect of distortion on compressor, an axial ducted fan is used. Study is carried out for normal flow condition, hub distortion and radial distortion conditions. Static pressure is measured in two cases. In first case, for different mass flow rate, difference in the static pressure of fan is measured, for which performance characteristic curves are plotted. In second case, normal flow inlet is distorted at operating point using above said distortion methods and difference in static pressure of fan is measured for which efficiency of fan is calculated. 60% of flow at inlet is blocked in both the cases of distortion by mechanical means using screens. Velocity across the duct at fan inlet is calculated, for which mathematical models are found. From this, average velocity from hub to tip which is necessary to find efficiency is calculated. Study shows amount of distortion not only affects stall and surge margin but also type of distortion affects surge and stall of ducted fan. Radial distortion exhibits less amount of stall margin than hub distortion for same amount of inlet flow.

Keywords: Axial Compressor, Hub Distortion, Radial Distortion, Surge and Stall