Investigation On Aerodynamic Design And Flow Characteristics Of Centrifugal Compressor Using Helium And Xenon

With the scientific research extended to deep space and deep sea of human,traditional power conversion devices can’t meet the requirements of use due to its low energy density and short battery life.The closed Brayton cycle using mixture of helium and xenon has high energy density and long battery life,and the mixture fluid improves the physical properties of helium gas which is difficult to compress,and reserves many advantages such as high stability and no pollution.The application of Brayton cycle power has broad prospects in the future development.Centrifugal compressors are the core components of the closed Brayton cycle using the mixture of helium and xenon.There are many related designs and flow mechanism research,but most of them are designed and studied with traditional centrifugal compressors using air as working fluid.There are few researches on the design methods and theories of centrifugal compressors using mixture of helium and xenon.And The internal flow mechanism is still unclear and needs further study.Based on the above background issues,the main research contents of this paper are as follows:Firstly,the investigation on aerodynamic design of the centrifugal compressor’s impeller and diffuser was carried out.The influence of the relative speed ratio of the impeller and the expansion angle of the diffuser on the performance of the compressor and the internal flow field characteristics was studied.The performance and internal performance of the centrifugal compressor using the mixture of helium and xenon under full flow working conditions were analyzed.The difference between the selection rules of the design parameters of the centrifugal compressor using different fluids and the flow characteristics of the centrifugal compressor using mixture of helium and xenon are revealed.Secondly,for the most important flow problem in the impeller,leakage flow,the independent change of the radial/axial tip of the centrifugal compressor using mixture of helium and xenon and the influence of the tip shape distribution on the tip leakage flow and performance were studied.The centrifugal compressor blade was summarized.The influence of the height and shape of the tip on its performance,the research results indicate that the decreasing tip clearance distribution increases the efficiency of the impeller in the small tip by 0.23% and the big tip by 0.168%.Finally,considering the high cost of the mixed fluid,the preliminary research on the alternative fluid centrifugal compressor can be carried out,and a similar method based on the actual temperature of environment is proposed to analyze the internal flow and performance similarity between the impeller of centrifugal compressor and the full-flow centrifugal compressor under five working fluids such as air,argon,helium,nitrogen and mixture of helium and xenon.The preliminary results show that argon has higher similarity in the Mach number distribution,blade load distribution and loss distribution in the centrifugal compressor,and is lower than that of the mixture of helium and xenon.Because of lower flow losses and slightly higher overall efficiency,so it is considered that argon has an alternative effect on the mixture of helium and xenon in the centrifugal compressor.In this paper,the research on the design method of centrifugal compressor using mixture of helium and xenon,the analysis of full-flow characteristics,the summary of tip flow characteristic and the exploration of alternative fluids provide reference for the design of centrifugal compressor using mixture of helium and xenon.It also provides a theoretical basis for the search for alternative working fluids in turbomachinery using special fluid.