On the Evaluation of Reynolds Number and Relative Surface Roughness Effects on Centrifugal Compressor Performance Based on Systematic Experimental Investigations

Abstract

This paper summarizes the results of systematic investigations into the Reynolds number effects. It is based on performance map measurements carried out on a compressor test rig which was constructed primarily for this purpose. The measurements were performed for stages with different flow coefficients (0.004 ≦ φ1 ≦ 0.05), with different gases (air, nitrogen, helium, freon) and in the inlet pressure range 0.2 bar ≦ p1 ≦ 40 bar. By analogy with the turbulent flow in technically rough pipes, semi-empirical correlations are derived concerning the effects of the Reynolds number and the relative surface roughness on the characteristic performance parameters (efficiency, flow coefficient, head coefficient, work coefficient). For the detailed design calculation of individual stages, provision is made for the different effects on the hydraulic flow losses and the disk friction losses. Simplified correlations are given for the conversion of characteristics measured during thermodynamic performance tests. The correlations are applied to various single and multistage compressors, and the results compared with measured performance characteristics in the Reynolds number range 6 × 103 ≦ Ret ≦ 1.1 × 107. The good correspondence obtained forms the basis for recommending the application of these simplified relationships for the improvement of centrifugal compressor performance test codes (e.g. ASME PTC-10 and ISO TC 118).