Study On The Diffuser Of Centrifugal Compressor

In the current national economic life,centrifugal compressors have played a significant role in all kinds of works.It has become an indispensable part of people's lives.Meanwhile,because of the continuous consumption of natural resources,the compressors are required to have a better performance and a higher efficiency.For decades,the worldwide researchers have made a great contribution in optimizing the design of various parts of the compressor,of which a considerable part of the work concentrated in the impeller part of the compressor.The optimization of the stator is also increasing over time.However,in most of the research work,the model is simplified,and the influence of seal clearance on the flow is neglected,this will make a big difference between the numerical simulation result and the real experiment result.Therefore,the numerical simulation and flow analysis of the model stage with the real seal gap have certain reference value for the practical engineering application.In this paper,the numerical simulation method is used to analyze the model stage of a refrigeration centrifugal compressor.The NUMECA software is used in this project.The main content is divided into four parts:First,according to the data of the impeller,diffuser and the return channel,three-dimensional model was established and analyzed through numerical simulation method;Second,after the simulation and analysis of the model stage,it is found that in the case of the 110% flow rate,the efficiency and pressure ratio are significantly decreased.The influence of the installation angle of the original blade on the flow is investigated through the post-processing part.It is found that the flow separation on the suction side of the blade is caused by the negative impact angle when the flow rate increases.So the installation angle of the diffuser blade is adjusted and the flow at large flow rate is analyzed in detail.The results show that increasing the inlet angle of diffuser can improve the flow condition of the model at high flow rate;Third,the inlet part of the diffuser is analyzed in detail.In order to investigate the influence of different shapes on the clearance leakage and the flow of the main channel,the real model of the main channel and the seal cavity is established.It is found that the existence of the sealed cavity has a great impact on the flow,and the shape of the diffuser inlet has a certain disturbance to the internal flow through the real model of the main channel and the sealed cavity part.Based on that,the improvement of the diffuser inlet has been proposed.The results show that reducing the inlet area of the diffuser can effectively reduce the influence of the sealed cavity on the flow of the main channel,improve the efficiency and pressure ratio of the model,but also increase the sealing leakage;Forth,a new type of diffuser-bend-return channel blade is proposed,and a preliminary model is built on the basis of the original blade.