Design And Analysis Of Supercritical Carbon Dioxide Radial-inflow Turbine

In order to alleviate the excessive consumption of fossil energy and reduce the pollution caused by fossil energy combustion,renewable energy has been more and more widely used.Electric energy storage technology can effectively use renewable energy,that is,it can solve the problem of renewable energy gridconnection,and can eliminate the hidden danger of lack of power supply at peak power consumption,and play a role in peak shaving and valley filling.Turbine is an important part of the power cycle in the energy storage system,and its performance has a great impact on the performance of the entire cycle.Compared with axial flow turbines,the enthalpy reduction of radial-inflow turbines is large,and higher efficiency can be achieved under the design conditions of small flow rates.Compared with air,carbon dioxide(Carbon Dioxide,CO2)has good physical properties and is an energy storage medium with great development potential.Therefore,this paper takes the S-CO2(Supercritical Carbon Dioxide,S-CO2)radial-inflow turbine as the research object,calculates its thermal parameters and geometric parameters,and analyzes the performance of the designed turbine.The main research contents include turbine theoretical design,performance analysis under design conditions and performance analysis under variable working conditions,among which the performance analysis under design conditions mainly includes turbine flow field analysis,geometric parameter influence analysis on turbine performance and turbine blade strength performance analysis.(1)The theoretical design mainly carried out thermal calculation,geometric parameter calculation and three-dimensional model design.The thermal calculation mainly determines the angle and speed of the inlet and outlet air flow of the turbine dynamic and static impeller through theoretical formulas and empirical parameters;The geometric design is to determine the geometric dimensions of the static impeller and the moving impeller according to the angle and speed of the inlet and outlet air flow of the moving and static impeller;The three-dimensional model design is to determine the specific shape of the moving and static blades,and then combine the geometric parameters of the impeller for three-dimensional modeling.(2)The analysis of the turbine flow field under the design conditions mainly explores the flow field inside the turbine under the design conditions.The temperature,pressure,velocity and Mach number in the turbine field were analyzed,and it was found that the temperature and pressure changes were gentle,no large mutations occurred along the flow channel,no obvious separation and vortex occurred in the velocity streamline,and the working fluid flowed mainly at subsonic speed in the flow field.Reasonable distribution of temperature,pressure,speed and Mach number verifies that the turbine has good aerodynamic performance.(3)The influence of geometric parameters on turbine performance under design conditions mainly explored the effects of blade top gap,number of moving blades and number of static blades on turbine performance.The results show that the increase of the leaf top gap will lead to the decrease of turbine efficiency,and the leaf top gap should be reduced as much as possible.There is an optimal number of blades for the efficiency of moving blades for turbine,which is 9;For the influence of the number of static blades on the turbine performance,select the number of blades close to the minimum number of static blades taking into account the total-total efficiency(total-total efficiency refers to the adiabatic efficiency obtained when the outlet kinetic energy can be effectively used)and the total-static efficiency(the total-static efficiency refers to the adiabatic efficiency obtained when the outlet kinetic energy is not utilized).(4)Under the design conditions,the strength performance analysis of turbine blades mainly analyzes the equivalent force experienced by turbine blades.The results show that the equivalent force of the moving and static blades is much less than the yield strength of the material,and the minimum safety factor is greater than the recommended minimum safety factor of 1.6,which meets the strength requirements.(5)When analyzing the operation of turbine variable working conditions,it is found that the power is positively correlated with the inlet temperature,and the flow rate is negatively correlated with the inlet temperature.When the radialinflow turbine inlet pressure increases from 16 MPa to 24 MPa,the total-total efficiency and total-static efficiency decrease with the increase of the turbine inlet pressure,and the working fluid flow rate increases from 22.065 kg/s to 33.259 kg/s,and the increase rate gradually decreases,and the output power continues to increase.When the outlet pressure increases,the flow rate decreases from 30.755 kg/s to 29.182 kg/s,and the output power decreases from 3.796 MW to 2.973 MW,and the turbine total-static efficiency and the total-total efficiency continue to increase.When the speed continues to increase,the efficiency of the radial-inflow turbine gradually increases,and with the increase of the speed,the speed of efficiency increase slows down.