| In the background of the rapid development of wind energy,it has attracted more and more attention about how to improve the reliability of the wind turbine,maintainability and ability against various extreme climatic conditions.And the research on wind turbine that is suitable in cold weather conditions is an important research field in recent years.However,the icing problem is the main problem in the condition of cold climate.The icing of wind turbine is the physical process that the liquid water in the air is frozen and accumulated on the surface of the wind turbine in the cold weather.Icing on the surface of the blade will reduce the lift of the airfoil and increase the resistance.Icing on the blade will change the load distribution,the impact of structural strength and fatigue life.In addition,the falling ice from blade also will bring hidden trouble of security.Icing distribution on the blade of horizontal axis wind turbine research results in references at home and abroad have been researched by using a quasi three dimensional numerical simulation on icing distribution for large scale wind turbine which has been constructed.Also the wind tunnel test system was constructed,and the icing distribution of rotating blades model was obtained.The main work and innovative achievements are as follows:(1)The quasi three dimensional icing numerical simulation method which is suitable for horizontal axis wind turbine rotor blade has been proposed,and the numerical simulation study has been carried out on the quasi three dimensional icing distribution on horizontal axis wind turbine rotor blade.Based on the theory and method of two-dimensional cloud and icing calculation,the method of numerical simulation of wind turbine blade was proposed.The numerical simulation of a 1.5 MW horizontal axis wind turbine under different operating temperature,liquid water content,average particle diameter of water droplet and icing time was carried out.The main conclusions of the research can be summarized as following: 1)using this method to calculate the icing distribution of rotating blade,and summed up two kinds of typical ice type,that is streamlined and horn type ice;the icing area of blade leaf apex in front of the tip of 50%~70%,with the increasing of icing time,ice type unchanged at the same section of span wise position on the airfoil,only expanded based on the original shape of the ice and the expansion was close in unit time.When the ambient temperature and liquid water content were certain,it can be inferred that the ice shape of the airfoil,and medium volume droplet diameter droplets had a weak influence on the icing pattern.When the ambient temperature was high,the greater the content of liquid water,the easier the formation of horn type ice.And the lower of the ambient temperature and the smaller of the liquid water content,the easier to form streamlined ice;the greater of the liquid water content and average particle diameter,the nearier development of blade root icing area.2)Established the ice shape evaluation method of wind turbine is irregular,the influences of the environmental temperature,liquid water content and medium volume droplet diameter feature the largest amount of ice thickness,ice area and ice volume.The results can provide a useful reference for the development of icing control strategy and the design of ice control system.(2)A new type of icing wind tunnel test system has been designed,and its performance has been verified.Based on the lasting stable low temperature environment in northeast region,the formation of icing wind tunnel test system using the natural low temperature based on the conventional open jet wind tunnel,installation of the spray system and airway structure.The temperature of the test section,the uniformity of the flow field,the liquid water content and the average particle diameter of the water droplet were measured.The main conclusions of the research can be summarized as following: 1)When the outside temperature is stable,the temperature of ice tunnel test section is stable.The distribution of wind velocity in the test section is more uniform.For the liquid water content distribution and a uniform area is generated in the central part of the section of the test section,and a multiple of similar annular regions are formed around the central area.The droplet diameter of the spray system is between 30?m~50?m,which can meet the requirement of icing test of wind turbine to a certain extent.2)Using the system to test the distribution of fixed blade icing,and comparing with the numerical simulation results.When the angle of attack and the liquid water content is small,the results of numerical simulation were coincident with the experimental results.However,due to the large angle of attack,,to obtain the steady flow field is difficult and the numerical simulation method cannot be used to calculate it.Similarly,when the liquid water content is large,the numerical simulation can get the irregular ice shape,but the deviation was larger than that of the experimental results,which indicates that the numerical simulation method could not completely calculate the icing of the blade under the working conditions.Therefore,the icing test of wind tunnel is still an essential research method for the icing of wind turbine blades.The design of the test system provides a new test method for wind turbine and other models.(3)The icing distribution of the blade segment of the rotating wind turbine has been studied.On the basis of the existing icing wind tunnel test system with natural low temperature,the rotating vane test platform is added to form the icing wind tunnel test system of rotating blades.Wind tunnel tests of rotating blade icing at different rotating speeds were carried out under different icing conditions.The main conclusions of the research can be summarized as followings:1)The rotating cylinder ice distribution were obtained by orthogonal test of rotating cylindrical dimensionless icing area and regression equation dimensionless ice stagnation thickness,the forecast and test results have high consistency,and provide the experimental basis for the study ofrotating blade icing.2)For rotating aluminum blades,in all,it had significant effect of speed to the ice type of aluminium alloy rotating blade,when the speed was low,the ice thickness was uniform.When the speed was high,the ice in the leading edge of blade increased,and the ice in the trailing edge of blade reduced.Icing time has a little influence on blade ice type,but with the increasing of time,the amount of ice was increased.There existed significant difference between symmetrical airfoil and non-symmetrical airfoil on ice shape,non-symmetrical airfoil would freeze in the leading edge and the trailing edge of blade.The dimensionless ice area,dimensionless ice thickness increased with the increasing of icing time,and the variations of other typical characteristics were small;the different speed had a significant effect on ice typical characteristics,and decided its development trend.There were two icing areas of non symmetrical airfoil under certain condition,and the analysis needed to add the amount of additional characteristic.3)For glass steel blade,its icing rule was same as the rule of aluminium alloy blade,regression model equation was obtained by orthogonal test on the dimensionless ice area and non-regression equation dimensionless ice stagnation thickness,and the test is highly coincident with model.The work of this paper laied the foundation for the research on the icing test of large scale wind turbine rotor blades.(4)This paper also has studied the icing distribution scaling method of the horizontal axis wind turbine blade,and put forward a kind of wind tunnel test system which was placed on the eccentric axis.The existing ice related theory of similarity research was analyzed,using the scaling method of rotating blade,a kind of eccentrically placed around the shaft rotating blade icing wind tunnel test system was put forward,which broadened the scope of icing wind tunnel test parameters,and improved the test ability of icing wind tunnel,and the rotary blade icing scaling method in wind turbine blade icing feasibility study was verified.The main conclusions of the research can be summarized as followings: 1)An eccentrically placed around the shaft rotating blade icing wind tunnel test system was proposed,which improved the experimental model of the circumferential speed without changing the icing wind tunnel test section size,so that it could be carried out in more icing test mode.The parameters of the new icing test system were measured,the test system could meet the demand of rotating blade icing test.Comparison of the ice shape and rotating cylindrical rotating blades before and after the improvement was conducted,the high degree of overlap,and the improved system could take rotating blade icing test.2)The rotating blade icing scaling method in the study on the feasibility of icing wind turbine rotating blades was verified,frost and ice state scaling parameters 0.5 and 0.25 was given.The test parameters of the ice shape were obtained by numerical scaling,and the scaling of the ice shape with original conditions was high.Using the icing scaling method,wind turbine blade airfoil,the actual blade fragment length of the chord model could be used 0.21 m from the axis of rotation 0.5m ice distribution to predict the chord length 0.84 m from the axis of rotation at 38.1m ice distribution.The improved system of icing wind tunnel could test on the similar test conditions.This research belongs to the basic research of wind turbine icing field,which can providetheoretical and experimental basis to the subsequent wind disaster prediction,icing warning and icing control system development.Based on the icing distribution obtained in this study,it can be used to evaluate the performance of the wind turbine under icing condition,provided basic parameters on the design and development of ice control system.Using the icing test system developed in this study,the existing wind turbine model can be further optimized,and the development of ice control device can be verified.The furture research on all sizes of actual ice wind turbine can be carried out based on the eccentric placed around the axis of the rotating blade icing wind tunnel test system proposed in this study and the similar method of icing wind turbine. |
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