Numerical And Experimental Research Of Wet Compression On Centrifugal Compressor In CAES

The compressed air energy storage(CAES)technology can achieve large-scale,long-term energy storage,and can be widely used in power grid peak regulation,renewable energy,distributed energy,etc.At present,it is one of the most promising large-scale physical energy storage technologies.The compressor is one of the core components in the CAES system,and its characteristics directly determine the overall system performance and economy.The centrifugal compressor is a common one in the CAES system.which must meet the demand of high efficiency at various operation conditions.The compressor operates at the humid air condition and the inlet fogging is considered as an technology about energy-saving and efficiency-enhancement,which has been verified in gas turbine.According to these characteristics and technologies,the typical stage of a largescale CAES centrifugal compressor is chosen as the research object and the wet compression study on the research object is carried out,which includes two parts: inlet humidity and inlet fogging.Through the establishment of the corresponding compressor performance correction model,a theoretical study on the law and mechanism of performance impact was conducted.Through the design of wet compression experimental scheme and the establishment of its experimental system,the experimental research was carried out.Later,a three-dimensional numerical flow analysis was performed for the whole stage characteristics.The main research contents and conclusions are as follows:1.Theoretical study on wet compression.Based on the similarity criterion and considering the influence of compressibility and Reynolds number comprehensively,the performance correction model of inlet air humidity was constructed.The equivalent adiabatic index and gas constant of wet compression and approximate performance convertion were coupled,and the droplet evaporation model and droplet behavior modification were added to establish the performance correction model of inlet fogging.The results show that the increase of humidity declines the total pressure ratio and specific compression work and the preformance curve shifts towards smaller mass flow.The inlet fogging can improve total pressure ratio and isothermal efficiency and its effects enlarge with the increase of fogging ratio and decrease of droplet diameter.The influence essence of inlet humidity and fogging are the change of gas constant and equivalent adiabatic index,respectively.2.Experimental study on wet compression.Based on the double-stage intercooling closed experimental platform of centrifugal compressor,the nozzle test rig,air inlet humidification and air inlet spray experimental system were designed and built,and a complete experimental measurement and control scheme was developed.The nozzle performance test,inlet humidity and inlet spray performance experiment of centrifugal compressor were carried out.The performance curves of the centrifugal compressor under different inlet humidity and inlet fogging conditions were obtained and the theoretical model was verified.3.Numerical study on wet compression.According to the characteristics of wet compression,the corresponding numerical research method was established and verified.Numerical studies on typical air inlet humidity and air inlet fogging were carried out.The results show that for inlet humidity,the increase of humidity enlarge the inlet flow angle.For inlet fogging,the evaporative cooling reduce the compression work,but droplet motion increase it,and the evaporative flow increment can also affect the compression work.In addition,the evaporative cooling reduce the flow angle at diffuser inlet,leading to diffuser stall,which narrows the stable operating range.