A Study On Fluid Analysis And Structure Modification For Low Mass Flow Rate Centrifugal Compressor

To solve the problems of daily worse environment and lack of energy caused by over exploitation of fossil energy,"The 13th Five Year Plan"by Chinese Government,has proposed to deepen energy revolution,to strive hard to promote energy production and change ways of utilization,to optimize the structure of energy supply and to construct of low-carbon clean,safe efficient modern energy system.Now,the biomass energy has become the fourth-largest energy only next to energy of coal,power generation of biomass energy will play a more important role in the energy structure,and the proportion of biomass power generation will be higher in the future market.However,the power output of the micro plant is low in the field of distributed power supply and the demand of the centrifugal compressor's mass flow rate is low.To maintain the same speed with the plant,the speed of the centrifugal compressor is limited.The thesis'sneed of the compressor is 30000r/min and the pressure ratio need is 3.But direct 3-D design method from the very beginning and similarity theory design method find it hard to meet such severe requirements.To overcome such a problem,this thesis find necessary to study on the designing of single stage centrifugal compressor,this thesis's main content includes as follows:Firstly,the thesis has introduced the CFD numerical simulation method based on the platform of FLUENT,and has finished the calculation of a centrifugal compressor provided by some a company by using such method as well.Also,the calculation result has been compared to the experiment data,which certificate the reliability of the numerical simulation method.Secondly;the thesis has conducted the study of design centrifugal impeller based on the existing resource of centrifugal.The design of centrifugal impeller departs in two tips.The first tip is designing the inducer.Aim to reduce the loss of the energy created by air dash into the head of the inducer,and a design method which designs inducer type line to make fluid flow as far as possible consistent with inducer drainage of geometric modelling was proposed according to its working condition mass rate of flow and speed.The second tip focused on the blades,which introduced how to construct a blade and modify different back sweep angles to promote pressure ratio,define the final angle of the blades.Thirdly,the thesis has developed the shape of meridian plane according to promoting pressure ratio and decreasing the mass flow rate respectively based on the impeller designed.Meanwhile,the article has designed the splitters and proposed a new method of splitters'construction.In the end,the thesis discussed the effect of different kinds of splitters and confirmed the best choice of them.And then,the thesis conducted modification of r2 and r3/r2,after combined analysis of characteristic performance curve and detailed fluid distribution of the centrifugal,the thesis confirmed the best choice of the modifications.