Research On Rotor/Stator Matching Of Single Stage Centrifugal Compressor

Centrifugal compressor is the key power equipment in many fields of our national economy,but consumes a lot of energy.Continuously improving the research and design level of centrifugal compressor is an important link to meet the increasingly requirements of high load and efficiency of centrifugal compressor in various fields in the future.Centrifugal compressor includes impeller,diffuser,volute and other components.However,due to the limitation of computer technology,the numerical study of centrifugal compressor mostly focuses on a single component,ignoring the matching of upstream and downstream components,which leads to the limitation of the research results.Moreover,the interference between the components would shift the operating condition of compressor components,and it is difficult to ensure that all components are operating at the optimum conditions,so that the overall performance cannot achieve the desired target;Meanwhile,the deviation of the operating conditions may cause some components to enter the choke or surge zone earlier,resulting in a narrow range of entire operating conditions.In recent years,more and more researchers have begun to focus on the matching of centrifugal compressor components.However,most of them focus on the matching between impeller and diffuser or between impeller and volute.There are few studies on the matching of impeller,diffuser and volute.In this paper,numerical simulation method was used to study the matching of a centrifugal impeller,long vaned diffuser and volute.Firstly,the frozen rotor method and stage method based on structured/unstructured hybrid grid technology were employed to solve the boundary matching problem of grid multi-reference frame.The grid number was reduced according to the flow characteristics and the grid independence was verified to ensure the simulation accuracy.The influence of blade solidity of long vaned diffuser on matching of diffuser and centrifugal impeller was explored.By changing the number of diffuser blades,chord length and inlet radius,the effect of blade solidity on the maximum efficiency and operating range of centrifugal compressor was obtained.These three parameters have little effect on the overall stage efficiency of centrifugal compressor,while have large influence on the operating range.At the same time,the flow characteristics of diffuser under different solidity were analysed to explore the mechanism of the change of centrifugal compressor efficiency and operating range.Finally,the basic parameters of the optimized diffuser under the best matching were obtained.On this basis,the optimized diffuser and centrifugal impeller were used to further discuss the matching of centrifugal impeller,diffuser and volute.Three volutes with different structural forms were analyzed: asymmetric circular volute,symmetric circular volute and trapezoidal volute.The total pressure loss coefficient and static pressure recovery coefficient were applied to evaluate the performance of the volute.The streamline and static pressure distributions at four different sections of three different volutes were analyzed in detail.It is concluded that the total pressure loss coefficient of the trapezoidal section volute is minimum and the static pressure recovery coefficient is the largest in the whole operating condition.That is to say,the flow loss in trapezoidal volute is relatively small,and the expansion capacity of the volute is relatively good.The whole stage matching research obtained the intrinsic mechanism of the interference among each component and estabilished the matching criteria.The relation of the matching and performance of the centrifugal compressor provides the theoretical basis for design of the centrifugal compressor.The whole stage matching in the compressor optimization could reduce the shift of the performance curve.Meanwhile,the whole stage efficiency and stable operation range can be improved.