Development of High Specific Speed Mixed Flow Compressors

Abstract

The results of a study on the aerodynamic performance of a high specific speed, mixed flow compressor are presented. The specific speed was N. = 450 to 550 (m³/min) ½ (rpm) (m⁻¾ ), with approximately a 2.0 pressure ratio per stage. The flow path from the outlet of the mixed flow impeller was inclined in the axial direction and entered into a curved diffuser. A theoretical flow analysis and a performance test were performed. The slip factor for this type of compressor should be predicted by a different formula from that used for centrifugal compressors. Distributions of the flow velocity, temperature and pressure were measured, using a highly sensitive pressure transducer and a total temperature probe. The flow field, including the end wall boundary layer, was surveyed. The losses and the flow condition of the unsteady flow were analyzed. The compressor of N (Subscript s) = 450 to 500 showed high efficiency and handled a flowrate of about twice as much as a conventional centrifugal compressor. This development contributes tremendously in reducing the compressor size.