Research On Multi-objective Optimization Of Aerodynamic Performance For Centrifugal Compressors

Centrifugal compressors are widely used in fields of petrochemical,energy,aeronautics,transportation and so on.Traditional design-modification method for centrifugal compressors is time consuming.In addition it is difficult to obtain a global optimal solution.This design process is difficult to meet the demand of design cycle and aerodynamic performance.Therefore optimization is required to solve this issue.A centrifugal compressor model stage is composed of an impeller,a diffuser and a return channel.The impeller is the most important part.Its performance directly affects the efficiency,pressure ratio and flow field uniformity of the stage.The return channel is also an important part,which has influence on the aerodynamic performance of multistage centrifugal compressors.Loss in the return channel affects the performance of the stage.The flow field uniformity at the outlet of the return channel affects the inlet condition of the next stage.Subsequently this influences the aerodynamic performance and flow filed uniformity of the next centrifugal compressor stage.Therefore,the impeller and return channel should be optimized while optimizing the centrifugal compressor stage in order to get a better design scheme with higher efficiency and more uniform flow field.According to previous researches,numerical optimization methods had been widely used in turbomachinery rotating parts.However,the methods are rarely used in multistage centrifugal compressors.Hence this paper design a parameterized model of the impeller and return channel,then the parametric models is optimized under variable operating conditions.According to previous researches,numerical optimization methods have been widely used in turbomachinery.However,the method is rarely used in multistage centrifugal compressors.Hence this paper designs a parameterized model of the impeller and return channel,then the parametric model is optimized under variable operating conditions.Taking two-stage centrifugal compressors with a first stage of 0.2 large flow coefficient as a research object,the impeller and return channel of the first stage are optimized by parameterization,CFD simulations and optimization method.One solution with better aerodynamic performance is obtained.By comparing the flow field of the original model and the optimized one,the aerodynamic performance of the optimized one is better than that of the original model.The whole stage polytropic efficiency of the two-stage compressor is improved by 0.98% in the design condition.Moreover,the whole stage efficiency is also improved under variable operating conditions.Based on the findings obtained from the 0.2 flow coefficient model stage,a 0.22 flow coefficient centrifugal compressor is modified.Results show that the optimized design has better aerodynamic performance than the original one.The above results show that the optimization method used for centrifugal compressor model stages is applicable and reliable.Through further investigation of the original design and the optimized design,it is found that reasonable variation of the bend configuration at the outlet of the return channel can improve the flow field uniformity at the stage outlet.These conclusions will provide technical reference and theoretical guide for the design of large flow multistage centrifugal compressors and return channels.