Research
Numerical Studies on Centrifugal Impeller Performance with Different Lean Combinations
Centrifugal compressors are designed for a given operating pressure and mass flow rate. These machines are often run at off design operating conditions depending on the requirement from industrial to Aerospace applications. The need to maintain relatively high efficiency under off design conditions with adequate stall margin makes the compressor design more challenging. These necessities demand for improvement in the flow conditions through the impeller by optimizing the vane shape. Much of the research was carried out on impeller vane shape to minimize the wake regions at impeller exit and one such effort was to introduce a blade lean at impeller inlet and exit. Investigation from the experimental studies revealed the authors that the introduction of lean at exit suppressed the wake flow regions and henceforth improved the impeller performance either with improved pressure rise or with increased stall margin. Though many of the research studies have proven the influence of lean on the change in the Centrifugal impeller performance, the study was pertained to a lean with a combination of positive inlet and exit leans or negative inlet and exit leans that has shown no change in surge margin improvement. Moreover, the study was pertained to a transonic impeller and the flow investigations are confined to two operating conditions only. Considering the authors knowledge/experience on usage of lean, our current research is aimed to investigate the performance of a subsonic impeller that has a combination of positive inlet and negative exit lean. This impeller model is further compared for performance with the other two different impeller models viz., an impeller with negative exit lean and the impeller with zero lean. All these three different lean angle combinations are focused to understand the aerodynamic performance, stability margin for steady state operation and flow behavior throughout the operating range. The performance results revealed a noticeable improvement
