Study On Plateau Adaptability Of A Centrifugal Compressor

For a compressor system of six-cylinder diesel engine with turbocharger， thecentrifugal compressor working at high altitude was analyzed theoretically and a numericalsimulation method of compressor working on plateau conditions was proposed byinvestigating the change of air properties with the altitude. Based on this method, theinfluence of the plateau conditions to the performance of compressor was investigated.According to the changes in performance of compressor working at high altitude, thespecial design conditions and requirements were proposed for the original compressor. Inorder to design a centrifugal compressor being more adapt to the plateau environment, thedesign methods and improvement measures of compressor was investigated. The specificcontents are as follows:Firstly, for the flow characteristics of the compressor, the effects of different inletconditions were investigated by using theory and numerical simulation. Based on theplateau environment, the overall performance of compressor working on plain and plateauinlet conditions were compared by using the flow characteristic figure. From the numericalanalysis of internal flow field characteristics, the cause for the change of compressorperformance was studied.Secondly, For a vehicular turbocharger working at high altitude, commoncharacteristics of the centrifugal compressor was analyzed theoretically and numericalsimulation was conducted for the compressor to investigate the influence of plateaucondition at low Reynolds numbers. By changing compressor inlet conditions, theperformance of the compressor was compared with the use of equivalent flow rate andequivalent speed. The influence of changes of inlet temperature and pressure to thecompressor equivalent properties was analyzed to get the accurate methods of predictingthe compressor characteristics at high altitude.Finally, from detailed numerical calculations and analysis of original compressor, thedesign strategies of impeller and volute were proposed according to design conditions andrequirements of the compressor working on plateau conditions. By using new designmethods and design software, new impeller and volute was designed. In order to increase the surge margin, a new compressor with inlet recirculation casing treatment was designed.Through common characteristics and numerical simulation, the overall performance ofdifferent compressors was compared. From the numerical analysis of internal flow fieldcharacteristics, the cause for the change of compressor performance was studied. Theresults suggested that: With the inlet recirculation casing treatment, the flow range wasenhanced, but the compressor performance drop a lot. Without the inlet recirculation casingtreatment, the surge margin and pressure ratio increased in the new compressor and theproblem of surging can be prevented when engine working on plateau conditions at lowspeeds with the new design.