Experimental And Numerical Study On Supercritical H₂O/CO₂ Axial Turbo Machinery Cascade

The basic research of supercritical H₂O/CO₂mixed working fluid thermal power generation polygeneration can realize the clean and efficient use of coal energy,its core equipment is the supercritical mixed working fluid steam turbine,which plays the key role of thermal power conversion.In order to provide experimental guidance for the subsequent blade optimization design,as well as to provide important experimental basis of the supercritical H₂O/CO₂variable-condition aerodynamic experiments for other scientific researchers,it is vital to experimentally verify the aerodynamic performance of the mixed working fluid steam turbine.Combining experimental verification and numerical simulation,the aerodynamic performance of the stator blade is studied in detail.Experiments are carried out around the low-pressure seventh stage stator blade of the supercritical H₂O/CO₂mixed working fluid steam turbine.In terms of experiments,the prototype blade was modeled on a reduced scale,and the plane cascade experiment platform was built.Using five-hole probe and three-hole probe,the aerodynamic performance at 9 incidences and 2 cascade exit Mach number of the static blade cascade are investigated in a low-speed wind tunnel.Important aerodynamic parameters such as the surface static pressure coefficient、airflow angle distribution and total pressure loss coefficient of the static blade under different experiment conditions can be obtained after processing the experimental data.In terms of numerical simulation,the turbulence model is determined by comparing the numerical results with the experimental one.Air and supercritical H₂O/CO₂mixed working fluids are used as the flowing medium respectively,and numerical calculations are carried out under different inlet boundary conditions.The inlet boundary conditions are transformed by the condition conversion formula between the two flowing medium.By comparing the surface static pressure coefficient distribution of the two simulation results,the accuracy of the condition conversion formula is proved.On the basis of the accuracy of the working condition conversion formula has been verified numerically by the research group,this article has carried out experimental verification on the conversion formula for the first time.In this paper,the results indicate that the stator blade is a post-loaded blade,and the maximum pressure load position on stator blade is located at about 60%of the axial chord length.The leading edge of the blade profile is sensitive to the incidence angel.When the incidence angle is positive,the leading edge has a reverse pressure gradient;the Reynolds number of the self-mode area of the stator blade is about 265000,and the corresponding Mach number at measuring section is about 0.29Ma.After that,the profile loss coefficient basically unchanged;-5°incidence angle corresponds to the smallest profile loss.In the range of-20°～20°incidence angle,the profile loss is not sensitive.When the outlet Mach number is increased from 0.3Ma to 0.4Ma,the total pressure loss is reduced,the increase of Mach number has no obvious effect on the outlet airflow angle and the distribution of limiting streamline of surface;The passage vortex and the trailing edge shedding vortex induced by the passage vortex respectively constitute the two high loss regions on the measurement section.The two high-loss regions expand to the middle span of the stator blade as the incidence angle increases,resulting in increased end loss and outlet airflow angle;The influence of the secondary flow vortex clusters in the front of cascade flow field has certain limitations,which is basically limited to the range of 0.1 blade height.The influence is mainly reflected in the strength and position of the passage vortex,which increases the strength of passage vortex while making it closer to the wake area along the pitch direction,and closer to the end wall in the blade height direction,which indicates that secondary flow vortex clusters in the front of cascade flow field restrain the passage vortex from rising along spanwise direction to a certain extent;the working condition conversion formula has a good applicability to variable working conditions,and can be used for working condition conversion between air and supercritical H₂O/CO₂mixed working fluid under experimental conditions.