Experimental study of a centrifugal compressor with two successive and counter-rotating impellers

In many industries, reducing the size of the compression system represents a significant goal for designers. In fact, increasing the power density of the compressor actually means lowering production costs. The chief purpose of this study is to compare, in terms of aerodynamic performances, a centrifugal compressor consisting of an impeller and a volute, to an innovative concept based on the principle of two successive impellers and designed to work in counter-rotation. To simplify the experimental research in this study, the volute of the conventional compressor is maintained for the new design. The conventional impeller has been replaced by two successive impellers having the same meridian profile, and whose diameter of the rear impeller is identical to that of the conventional impeller. The impellers design of the counter-rotation stage was carried out granting to an approach proposed here. The numerical results underline the advantage of the innovative compressor, in terms of power density, compared to the conventional design. The numerical forecasts also agree significantly with the results of experimental tests got on a test bench exclusively designed for compressors. Experimental optimization of the rotational speed ratio of the two counter-rotating impellers has demonstrated the possibility of increasing the compression ratio and efficiency over a wide range of flow. © Published under licence by IOP Publishing Ltd.