Numerical Study Of Flow Characteristics And Performance Inside Centrifugal Impeller

Centrifugal compressors play an important role in lots of fields, and amount of energy is used to operate. Analyzing the characteristics of centrifugal compressor flow field, improving structure, raising efficiency, are the main topics of centrifugal compressors research. With the development of computer technology, numerical simulation method becomes an important way of analyzing the flow of centrifugal compressors.In this paper, a centrifugal compressor, with the impeller tip diameter 0.4m and Mach number 0.86, was studied. Poly-means were used here to complete the geometric modeling and meshing of whole flow field of the centrifugal compressor stage. Compared to other modeling methods, it was easier to create the model of geometry structure and generate high quality mesh in the paper. Basing on this, the inner flow of stage from surging to blocking flows was calculated here. Then the charts of polytrophic efficiency and energy head coefficient of centrifugal compressor were presented. From the polytrophic efficiency chart, it showed that the highest value of polytrophic efficiency was 0.8647 corresponding flow coefficient 0.12047.The flow field characteristics of centrifugal compressor in three key operating conditions were discussed respectively. The flow coefficients of small flow rate condition, design condition and large flow rate condition were 0.1045, 0.1205 and 0.1460. In different conditions, with the increasing of flow rate, the flow in impeller and diffuser became worse; from hub to shroud, flow turned more complexity. In return channel, there were less separation areas in large flow rate condition than small flow rate condition and design condition. Variety of static pressure contour in any area corresponded with that of velocity. In all conditions, there were a low pressure area in the hub of impeller, and two high pressure areas in the hub of bend and the shroud of return channel. The flow in these areas might cause more energy loss of centrifugal compressor.The flow loss in diffuser, bend and return channel part was analyzed. The chart of loss percentage showed that, in small flow rate conditions, with the flow rate increasing, the flow loss became small, there was a lowest loss percentage near design condition; in large flow rate conditions, with the flow rate increasing, the flow loss became large again.The Analysis of the flow characteristics of centrifugal compressor in this paper provided a numerical foundation of analyzing the effect of centrifugal compressor structure to flow field and reducing the flow loss of the stage, it is helpful for further study and able to instruct the designing of centrifugal compressor and solving engineering problems.