Research On The Performance Prediction Model And Aerodynamic Design Method Of Centrifugal Compressors

The centrifugal compressor has the advantages of simple structure and high single-stage pressure ratio,and is widely applied in the field of energy and power.Stage pressure ratio,isentropic efficiency and operation range always is the vital parameters to evaluate the centrifugal compressor performance.Due to their speed,and ease of use,1D and 2D performance prediction method is the important part of the centrifugal compressor aerodynamic design.However,their prediction accuracy depends on the empirical models such as loss correlations,slip factor model and stall-onset prediction model,and there are certain limitations on accuracy and applicability.This study improved the 1D and 2D performance prediction method by modifying the empirical models,including the loss correlations selection method,the slip factor model and the stall-onset prediction model.Combined with blade design technology,a more complete aerodynamic design method for centrifugal compressors was established.The main contents of this dissertation are:?1?Establish and improve 1D performance prediction methods based on empirical loss correlations.The study reviewed the main loss mechanisms and corresponding loss correlations.According to the inlet tip relative Mach number and specific speed,a new method to select loss correlations was proposed by testing multiple loss correlations.This method was validated by experimental results on eight centrifugal compressors in public and one in-house.The performance predicted by the proposed method was in close agreement with the experimental results.Compared with the conventional set,the proposed method was superior.?2?Establish and improve the S_2m thoughflow preformance prediction method based on streamline curvature method.The slip factor model is an important parameter in the S_2mm method.The Qiu slip factor model has not considered the suppressive effect of secondary flow on the slip,resulting in uncertainty in the scope of application and prediction ability.This study numerically investigated the slip factor characteristics with mass flow.An improved slip factor model for centrifugal compressor was developed.A secondary flow term was added to the Qiu model to correct the slip factor.A S_2m method was established using the current slip factor model.Compared with the Qiu model,the current slip factor model showed higher accuracy.Therefore,the S_2m method established in the study was superior.?3?Propose a 1D stall-onset prediction model?Model II?based on tip leakage flow mechanism.The conventional stall-onset prediction model?Model I?lacks theoretical basis and has low prediction accuracy,based on the statistical analysis of experimental data.Firstly,this study numerically investigated the characteristics of the tip leakage flow.It confirmed that the interface between the tip leakage flow and the main flow spills from the blade leading edge when the centrifugal compressor stalls.Then,1D-TT Model was proposed to predict the tip leakage vortex trajectory based on the Chen model and blade loading calculation method.Finally,1D prediction model was developed to determine the stall-onset point for subsonic centrifugal compressors,where the interface between the tip leakage flow and the main flow spills from the blade leading edge.In this model,the momentum balance analysis was applied to identify the position of the interface according to Cameron and Ye's method.The parameter of the tip leakage vortex trajectory in Model II was determined by 1D-TT Model.The effective origin of the tip leakge flow was correlated with the rotational speed and tip clearance.The effectiveness of Model II was validated with the experimental and CFD results.Compared with the conventional model?Model I?,Model II showed better accuracy.?4?Research on aerodynamic design method of centrifugal compressor.This study combined the performance prediction methods established in the previous three chapters with the blade design techniques to establish aerodynamic design methods for centrifugal compressors.Three centrifugal compressor design and numerical verification were conducted with this design method.The results showed that the aerodynamic design method was fast and effective.