Performance Prediction of Centrifugal Compressor Based on Performance Test, Similarity Conversion and CFD Simulation

Abstract

One centrifugal compressor is applied for refrigeration and its working substance is R134a. The operating points obtained by using similar conversion at different rotation speeds are compared with the numerical results. They keep consistent with each other while the rotation speeds are lower, but the error between them will become large with the increasing of the rotation speed. Then the operating points are obtained when the working substance is air by using two similar conversion methods separately. Based on the comparison, it can be obtained that the result of keeping the specific volume ratio of inlet and outlet is more accurate than the result of maintaining Ma number. Then the test result is compared with the similarity result and the numerical result when the working substance is air. It is obtained that the similarity result is more consistent with the test result better than the numerical result and the trend of efficiency and pressure ratio change with the flow rate is consistent with the test result. In the process of similar conversion, the efficiency η is no useful for similitude design and it has less influence on the conversion result.

Similarity model for predicting the performance of an R718 compressor

“…When the similarity law is applied to a centrifugal compressor whose working fluid is air, and the working fluid of the compressor is replace with R134a, a recent study found that the performance was similar when the number of Mach was below the critical point. 18 In another study, after analyzing the general specifications of a centrifugal compressor, the most efficient operating point of the compressor is identified with a speed diagram for each pressure ratio using the law of similarity to effectively design a compressor. 19 Therefore, using the law of similarity, the performance is similar even if the geometry and rotation speed of the impeller is different.…”