Measurement And Calculation Of Internal Flow Field Characteristics In Centrifugal Compressor Under Uniform And Distorted Inlet Condition

Centrifugal compressor is widely used in military and civil fields as a core component of vehicle engine turbochargers and turboshaft engine.Owing to the asymmetric structure of the volute,the internal flow field in a centrifugal compressor is circumferentially non-uniform.Furthermore,a bent inlet pipe is widely used in the centrifugal compressor inlet,which caused the inlet distortion for practical engineering applications.The inlet distortion also affect the internal flow field distribution,therefore,the performance and stability of the compressor will also change.In this study,a centrifugal compressor with a volute is investigated.The internal flow field characteristics and the influence of the inlet distortion on internal flow field were discussed in detail under two different inlet conditions.Steady experiments were carried out under straight pipe and 270 degree elbow inlet conditions.By analyzing the experimental data,it can be seen that,with the decrease of the flow rate,in addition to the high pressure region induced by the volute,a static pressure increase region exists in the certain circumferential position,which are referred to as the static pressure bulge region.The phenomenon of the static pressure bulge not only occurs on the left of peak efficiency point at low flow rate conditions,but also exist on the right of peak efficiency point at high flow rate conditions.With the decrease of flow rate,the degree of static pressure bulge is gradually strengthened,and the static pressure bulge region gradually increased on the circumferential and streamwise direction,thereby forming two obvious pressure bulge regions inside the impeller and diffuser.The phenomenon of the static pressure bulge first occurs the approximately circumferential 270° position.On the streamwise direction,the static pressure bulge regions first occur at P4 inside the compressor and P11 inside the diffuser,respectively.Compared to the straight pipe inlet condition,the static pressure increase weakens the degree of static pressure bulge under the270° bent pipe inlet distortion condition.However,the degree of the static pressure bulge will increase and become more obvious on the earliest occurrence position of the static pressure bulge region.In order to obtain the pressure measurement around the casing wall conveniently and accurately,a data acquisition program was written in Lab VIEW,and the data acquisition program was applied to the experiments using the PCI-1713 data acquisition card and the terminal board from Yanhua company.To analyze the influence of inlet distortion on the compressor stall,the unsteady full-annulus simulation results were obtained under the two types of inlet pipe conditions at the speed of 80kr/min in the compressor.By comparing spatial and temporal distribution characteristics of the impeller inlet flow field in the stall progress,It can be seen that the inlet distortion caused by the 270° bent pipe makes the stall inception circumferential position to change from the circumferential 120° position to the circumferential 60°position.Furthermore,the inlet distortion makes the stall inception occurs earlier and the compressor enters stall more quickly,thereby causing the compressor performance deterioration.