| The process of fossil exploit and utilization has caused the aggravation of the ecological damage and environmental pollution.With this problem,in order to achieve energy sustainable development,it is an inevitable choice for human to improve energy efficiency of thermal power generation systems,which is able to further make emission and the cost of production decrease.The Brayton cycle with the supercritical CO2 as the working medium has various advantages.It can be widely used in different fields and has a good prospects.However,there still are many difficulties for the design of its core components,the centrifugal compressor.In terms of these difficulties which should be solved,in this topic,the research on the internal flow of the centrifugal compressor in the supercritical CO2 is conducted.The aim to improve the aerodynamic performance of the flow-through component is set.The technology and theories including the internal-flow aerodynamic design theory of the actual gas in the centrifugal compressor,and the analysis and solution technology of the CFD multi-phase flow are applied so as to achieve expected design index.Meanwhile,the influence of centrifugal impeller outlet geometric angle and wrap angle on the compression performance and internal flow is explored.Under supercritical and transcritical conditions,the combined pressurization physical mechanism of centrifugal force and channel area change is studied.And the related rules between the passage geometry and flow matching is discussed.At first,this study gives the one-dimensional and quasi-three-dimensional design methods,the full three-dimensional numerical methods and physical property processing methods for centrifugal compressor impellers.With these methods,it verified the supercritical centrifugal compressor design method and completed the one-dimensional and quasi-three-dimensional design of a supercritical centrifugal compressor.On the basis of the three-dimensional blade building program and the CFD simulation calculation technology developed by the laboratory,this topic completed the three-dimensional design of the centrifugal impeller and predicted the final performance.After these processes,a centrifugal compressor with the mass flow rate of 3.55kg/s at the design point,total pressure ratio of 1.832 and adiabatic efficiency of 91.1% is obtained.The key data of aerodynamic performance and internal flow structure information were obtained,and the compression performance,blade load and flow structure of the supercritical CO2 centrifugal compressor were analyzed.Taking a supercritical CO2 centrifugal compressor as a prototype,this study got different geometric models of the centrifugal compressor impeller by changing the wrap angle and the geometric angle at the outlet plane.After that,a full three-dimensional numerical simulation calculation was performed to explore the influence of the main geometric parameters on the compression performance of the centrifugal compressor.It is resulted that the working mass flow rate range of the centrifugal compressor is different with different wrap angles.As the increase of the wrap angle,the high mass flow rate area of the centrifugal compressor gradually decreases,and the range of decrease gradually increases.The wrap angle has an effect on the compression performance of the centrifugal compressor mainly under the high mass flow rate condition and the design condition and instead of the low mass flow rate condition.It is also shown that outlet geometric angles has little impact on the working mass flow rate range of centrifugal compressors.In the four kind of centrifugal impellers with different outlet geometric angles,the one with the outlet geometric angle of 60 degree has higher total pressure ratio and the total pressure ratio of compressors gradually decreases as the outlet geometric angle gradually increases.Near the designed mass flow rate,the total pressure ratio changes by about 0.06,whose change rate is about 3.3%,when the outlet geometric angle changes 10 degree. |
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