The Effect of Impeller Tip Clearance on the Performance of a MGT Mixed Flow Compressor Stage Fitted with a Crossover Diffuser

Abstract Mixed flow compressor stage designs are becoming increasingly popular for use in Micro Gas Turbine (MGT) engines. Due to manufacturing constraints and structural considerations, such compressors typically feature unshrouded impeller designs. A numeric investigation of the effect impeller-shroud tip clearance on performance a MGT mixed fitted with crossover diffuser is presented. Three baseline test designed using an in-house-developed application based one-dimensional mean line theory. These cover wide range design mass rates, speeds, meridional exit (mixed flow) angles. The each evaluated at 0.1 mm, 0.3 0.6 mm. Commercial CFD software used verify results various configurations. It found that increase negatively impacts both (total-to-total pressure ratio efficiency) choke margin. Conversely, stall margin increases clearance.