Small-scale ORC Axial Turbine Aerodynamic Optimization Design And Performance Analysis

With the rapid development of China’s economy,China’s energy structure based on fossil energy has revealed more and more serious drawbacks,and energy transformation has become one of the urgent problems to be solved.Clean energy and industrial waste heat have received increasing attention due to their wide range of sources and extremely low pollution.However,these energy sources tend to have lower temperatures and lower heat flux density.The efficiency of using the traditional steam Rankine cycle is lower,and the use of the Organic Rankine cycle is one of the measures to improve the conversion efficiency.In this paper,the low-power axial flow turbine in the organic Rankine cycle is taken as the object,and the flow optimization design and performance analysis are carried out.Based on the one-dimensional design method of traditional steam turbines,this paper combines the physical properties of organic working fluids with the AMDCKO loss model to organize the one-dimensional design method of organic working fluid axial turbines.And then,One-dimensional design program it is written using Matlab.Then,by using the genetic algorithm,the design of the one-dimensional structural parameters of the turbine was optimized with efficiency as the goal,and the optimized turbine efficiency was 85.96%.According to the design parameters obtained by one-dimensional optimization design,stator and rotor flow paths were modeled and meshed,and the CFD simulation was performed on the single-stage axial turbine.The simulation results show that the flow in the turbine is uniform and the overall performance is good,but there is a certain uneven pressure distribution in the rotor flow path.Comparing the simulation results with the one-dimensional design results,the relative errors of the selected parameters are all within the acceptable range,which proves the rationality of the design results.Based on the original blade shape,the response surface method was used to optimize rotor blade shape.Through the single parameter sensitivity analysis,8 control parameters of the Bezier curve parameterized model were selected,among which 4 were used as the optimization independent variables.The Box-Behnken method was used to design 29 sets of schemes and CFD simulation was carried out.After analyzing the results by Design Expert,rotor profile with the highest efficiency was determined.The optimized blade shape has an efficiency improvement of 1.68% compared with the original blade type.In addition,the flow field inside the turbine is more uniform.Finally,the performance analysis of the turbine obtained by the optimized design was carried out.The CFD software was used to calculate the flow field state and the change of the equal entropy efficiency when the rotating speed change and the mass flow change were respectively calculated.Through analysis,the turbine is most sensitive to changes in rotating speed.Overall,the change in speed will cause an increase in the vortex,and the change in mass flow will affect the turbine output,the exhaust parameters,and the pressure distribution in the flow path.