Fluid Dynamic Analysis And Optimization Method For Vertical-axis Turbine: Improvement And Application

The exploitation and utilization of wind and tidal power energy is the hot issue of newenergy field. Wind and tidal power energy of our country has rich reserves, having great valuein tapping and utilizing. During the exploitation and utilization of wind and tidal powerenergy, turbines are the energy conversion device, one type of which is vertical-axis turbine.The simple structure, the making of the blade and the convenient maintenance of the wholedevice make it especially suit for the main energy recharge of the island economic body.Since the flow fields produced in the rotation process of the vertical-axis turbine bladesare quite complex, a lot of problems still remain unsolved. Besides, the fluid dynamiccharacter of vertical-axis turbine directly determine the energy conversion efficiency and theblade load; therefore, there is great need to develop an effective method, used for fluidperformance prediction, blade load analysis and engineering design optimization, which is ofgreat importance in studying the property of this turbine and the mechanism of flow fieldformation, increasing the turbine power coefficient, and guiding engineering practice.Based on the project of “The key technology research and demonstration of150Kw tidalpower station” of national science and technology support plan, this thesis studies thevertical-axis turbine in the exploitation and utilization of wind and tidal power energy, aimingat studying the fluid performance prediction, blade load analysis and performanceoptimization of such turbine.Chapter One introduces the basic principle and structure form of the mainstreamvertical-axis generating set, and the research progress of the fluid dynamical analysis andoptimization method of vertical-axis turbine at home and abroad. Chapter Two sets up thekinematics and dynamics of rotors of vertical-axis turbine, explains the working principle ofthe turbine, defines the parameters of geometry, kinematics and dynamics, and brieflyanalyzes the influences of tip speed ratio and blade deflection angle on turbine powercoefficient. Chapter Three sets up the stream-tube model based on momentum theorem, thencompares the results with the experiment data of wind turbine published in literature and tidalpower turbine developed and tested by the studying team, points out the application scope anddefects of stream-tube model, modifies the curve of turbine power coefficient in the dynamical stall area and second effect area, and then sets up the stream-tube model inturbulence and simulates the changes of blade load with time. Chapter Four develops finitevortex model based on predecessor’s work and a kutta condition with pressure differencebetween upper and lower airfoil trailing edges combining vortex model. Finite vortex model canbe used to calculate the airfoil force of multi blades under unsteady motion. Chapter Four alsoanalyzes mechanisms of jamming between vortex and blades, analyzes the manner in whichnewly born vortex parameter, vortex core diameter and wake merger through the examples ofsome classical motions such as sudden start of aerofoil and pitching and heaving of aerofoil,simulates nonlinear wake structure in the Knoller-Betz effect when blades do intermediate andhigh frequency heaving motion. Chapter Five uses finite vortex model to realize loadforecasting of fixed pitch turbine and variable pitch turbine, and the method is proved to havebetter precision by comparing calculation results with model experiment results. Chapter Fivealso analyzes how the fluid characteristics of fixed pitch turbine influence by the parameterssuch as speed ratio, setting angle of blade and solidity. Finally it proposes a method toimprove energy utilization rate and reduce load fluctuation load fluctuation of blade by theexample of cycloidal variable pitch turbine. Chapter Six proposes the problem of optimalblade angular deviation to realize the maximum energy utilization efficiency under thecondition of fixed speed ratio, reveal the change law of optimal blade angular deviation underthe condition of different speed ratios. Validated by viscosity CFD method, the angulardeviation change law can increases the energy utilization rate by30%in the whole range oftip speed ratio...