The Design And Performance Optimization Of Air Turbine In SCPPVC System On The Basis Of Genetic Algorithm

According to the Bates theory,momentum theory and blade element theory and on the basis of Wilson design method,the genetic algorithm is used as the optimization tool to conduct a systematic design of blades of the turbine in the system.By resorting to numerical calculation and experimental analysis,the performance of the turbine blades has been studied and improved from two aspects: aerodynamic performance and energy conversion efficiency,which has verified the accuracy of the numerical calculation results and ensured the feasibility of genetic algorithm in optimizing the turbine blade.The thesis would make a comparison of the blades before and after optimization in the pressure field,velocity field,output power and other aspects and take an analysis of its reasons so as to further improve its aerodynamic performance.With the adoption of genetic algorithm,by taking annual electricity generated as an objective function,the structure of air turbine blades in SCPPVC system has achieved optimized design.In the process of design,NACA63-215 aerofoil with a high ratio of lift-drag ratio is adopted,and on the basis of the principle of joint exchange coordinates,by resorting to three-dimensional model software,the three-dimensional solid modeling of the two wind turbine blades before and after optimization is established.The result shows that: the overall length of the blade chord length is increased since the genetic algorithm is used for optimization design.This change can increase the sweep area of the blade and the speed of the impeller.Due to the optimized design,the torsional angle of the blade is reduced,which can reduce the starting torque of the impeller and increase the strength at the blade root,thereby improving the operational safety when the impeller rotates.CFD flow field simulation software is used in have a simulating calculation ofaerodynamic performance of air turbine blades and its energy conversion efficiency in vertical chimney power generation system,further analyzing the changes rising from aerodynamic performance and flow field of the turbine before and after optimization.According to the result: when the wind velocity of inflow is 5 m/s,the output power of two air turbines optimized,on the basis of Wilson design theory and with the adoption of genetic algorithm,increases first and then decrease with the increase of the number of turbine blades.The output power reaches its maximum when the number of blades is 7;The pressure difference between the front and back of blades increases first and then decrease with the increase of the number of turbine blades;When the wind velocity increases from 5 m/s to 9 m/s,the output power of air turbines with 3 to 8blades optimized by genetic algorithm increases rapidly and since the optimization of blades by genetic algorithm,the output power of air turbines has been increased in vertical chimney power generation system as a whole,which has proved the effectiveness of genetic algorithm in achieving the optimization design of air turbine blades in vertical chimney power generation system.The method of numerical simulation calculation is adopted in studying the impact of tip speed ratio on power and the finding indicates: torque of air turbine increases first and then decrease with the increase of tip speed ratio.When the tip speed ratio is1.8,the energy conversion efficiency of the designed air turbine reaches its peak.The blades of the air turbine designed by the Wilson theory and optimized by genetic algorithm calculation have been made by resorting to 3D printing technology and combining with 3D solid modeling,whose performance has been researched in the experimental system of vertical chimney power generation.According to the result:when the wind velocity of inflow is 5m/s and the number of blades in air turbine is 7,the output power of air turbine reaches its peak,the pressure difference between the front and back of blades is also the biggest and the variation tendency of differential pressure and power is nearly accordant.All of these has verified the effectiveness of numerical simulation calculation method and further stated the application of genetic algorithm in optimizing blades can improve aerodynamic performance of air turbine blades.Optimizing air turbine blades by genetic algorithm can slightly reduce torsional angle of blade root of air turbine,which can reduce starting torque of the turbine,effectively reducing start-up wind speed of blades and intensifying the stress of the blade root to ensure a safe operation of blades.When the inflow wind velocity remainsthe same,a strong elevating force can be generated from the upper surface and the lower surface of the airfoil section of blades and the air flow is fully and evenly attached around the blades;the output power of air turbine optimized by genetic algorithm has been increased by 3%-32% compared with before.When the number of blades is 5,the output power of the air turbine increases most significantly;when the number of blades is 7 and tip velocity ratio is 1.8,the output power of the air turbine is the highest.