Improvement of Moderately Loaded Transonic Axial Compressor Performance Using Low Porosity Bend Skewed Casing Treatment

Dilipkumar Bhanudasji Alone,A M Pradeep,Janaki Rami Reddy Mudipalli,Shobhavathy M Thimmaiah,Srinivasan Ramamurthy,Venkat S Iyengar,S Satish Kumar

doi:10.1155/2014/625876

Abstract

This paper presents experimental results of a single stage transonic axial flow compressor coupled with low porosity bend skewed casing treatment. The casing treatment has a plenum chamber above the bend slots. The depth of the plenum chamber is varied to understand its impact on the performance of compressor stage. The performance of the compressor stage is evaluated for casing treatment and plenum chamber configurations at two axial locations of 20% and 40%. Experimental results reveal that the stall margin of the compressor stage increases with increase in the plenum chamber volume. Hot-wire measurements show significant reduction in the turbulence intensity with increase in the plenum chamber volume compared to that with the solid casing at the stall condition. At higher operating speeds of 80% and at 20% axial coverage, the stall margin of the compressor increases by 20% with half and full plenum depth. The improvement in the peak stage efficiency observed is 4.6% with half plenum configuration and 3.34% with the full plenum configuration. The maximum improvement in the stall margin of 29.16% is obtained at 50% operating speed with full plenum configurations at 40% axial coverage.

Highlights

Instabilities in the compression systems of aero engines are the greatest issues of concern for all the gas turbine community
The stall margin improvement (SMI) above the solid casing is evaluated at different operating speeds and for all the configurations of the casing treatment
Experimental studies on bend skewed casing treatment of 21% porosity have been carried out to study the impact of plenum chamber volume on the performance of a single stage transonic axial flow compressor

Summary

Introduction

Instabilities in the compression systems of aero engines are the greatest issues of concern for all the gas turbine community. It was observed that the mere presence of a porous casing around the rotor tip was sufficient to cause a marked improvement in the stable flow range This led to the development of casing treatment and a series of investigations were initiated by NASA [3,4,5] to evaluate the effect of various treatment geometries on stall margin and overall performance of axial compressors. Takata and Tsukuda [7] carried out experiments on a low speed, single stage compressor with axial as well as skewed slot casing inserts and with varying rotor tip clearances They were the first to report clear evidence of the importance of orientation of skewed grooves on the improvement of stall range and performance. The variation of the inlet axial velocity in the tip region at stall condition is studied using a single component hot wire probe for the solid casing and casing treatment

Descriptions of the Research Facility

Casing Treatment Configurations

Results and Discussions

Conclusions