Differences in Formation Mechanism of Static Pressure Circumferential Distribution of Centrifugal Compressor Under Different Operating Conditions

Abstract

The casing-wall static pressure of the centrifugal compressor behaves the double-peak distribution in the circumference at small flow rates (SM) but the single-peak distribution at large flow rates (LM). A previous study shows that the double-peak distribution is induced by the redistribution of impeller outlet flow rates. In this paper, by using the similar simplified method of directly imposing pressure boundary to the diffuser outlet, the original reason for the formation process difference of pressure distribution in the circumference at different operating conditions is further investigated. The results show that at LM, under the combined action of the specific downstream pressure distribution and the flow performance of the compressor itself, alternating low/high velocity airflow zones similar to those at SM cannot be established in the diffuser when the impeller outlet flow rates are redistributed. Therefore, the static pressure can only express the single-peak distribution in the circumference. In fact, whether the static pressure exhibits the double-peak or single-peak distribution in the circumference depends on whether the impeller outlet flow mutation can destroy the original flow balance. When the flow mutation is dominant, the double-peak distribution is created, whereas when the original flow balance is prevailing, the single-peak distribution is formed.