Pre-Whirl

PRE-WHIRL

pre-whirl is known as the air to rotate and used to minimize the velocity before entering in to the impeller blade, it does not effect the mass of air flow and velocity of flow for reducing the reduce shock waves.due to running of centrifugal compressor with  a high speed  in gas turbine and jet engine this causes the shock waves in the flow passage. The shock waves are determined in terms of match number and given by the relation.

Due to high resolutions the tangential velocity at the impeller is very high, which causes the impeller wave curved part to break away at the edges,by the axial entry of air.due to high speed of air flow it increases the shock waves and energy loss.