Abstract
Performance of small turbocharger compressors is greatly affected by their size and size related Reynolds number. Although the effect of Reynolds number on compressors’ efficiency is well known, the effects of Reynolds number have on other performance and design parameters of these compressors are little recognized in open literature. This paper reports the effects of Reynolds number and size on peak efficiency and surge flow of turbocharger compressors, studies the influences of Reynolds number on optimum compressor blade count. Test results show that when a compressor is scaled up (Reynolds number increases), its stability is generally reduced, and vice versa when scaled down. How this feature can be utilised in compressor design is discussed, and an example is given to show how compressor efficiency and flow range may be improved when scaling down by employing a more stable vaneless diffuser and reducing impeller blade number. Finally, the effect of Reynolds number on blade number selection for different sizes of a compressor is studied through CFD and test, and based on these experiences and the theory of flow on flat plate, a design guide line is proposed for the optimum blade numbers in compressor scaling for both impellers with and without splitter.
