Theory And Its Applied Research Of Wind Turbine Blade Airfoil Profile Using Air Weight Analogy To Pressure Difference

With the serious development and use of fossil energy,the global carbon dioxide emissions are increasing,the greenhouse effect is intensifying,and it is urgent to seek new energy sources.As an inexhaustible clean resource,wind energy is gradually being taken seriously,and wind turbines are important devices for capturing wind energy and converting it into electrical energy,in which blades play a vital role,airfoil as an important part of the composition of the blade,the domain scholars are actively exploring research and development,committed to the design of the high-efficiency airfoil.At present,mainstream wind turbine blade airfoils mainly include NACA series,DU series,and FFA-W airfoil series,etc.,however the acquisition of original theory and data of these airfoils are still in the confidential stage,so the Country and Enterprises and Universities are committed to the establishment of airfoil theory,hoping to fundamentally obtain precious airfoil data,and at the same time improve the airfoil theory in the simulation practice.In this paper,the interaction between flowing air and wind turbine blade airfoil is fully studied,we find that:in fact,the air flowing in the horizontal plane is caused by the pressure difference between the front and rear air masses,which is also the case while the airflow flowing on the airfoil surface,the pressure on the airfoil surface is different from place to place,and it is precisely because of this pressure difference that urge the airflow flowing on the airfoil surface.However,the airflow flowing situation on the airfoil surface is complicated,and the measurement of the differential pressure between the front and rear air masses is difficult to achieve.After in-depth research found:Does the flow of air masses in a horizontal plane under pressure difference have the same effect as the flow of air masses in a vertical plane under weight?And the weight of the air mass can easily be calculated.Therefore,the main works of this paper are as follows:(1)In this paper,a method of air weight analogy to pressure difference is proposed:That is,the air flowing under the action of pressure difference in the horizontal plane is analogied as the air flowing under the weight of air in the vertical plane in a vacuum.(2)The wind turbine blade airfoil theory is established by the method of air weight analogy to differential pressure in(1).The core idea of the theory is:assuming that the entire system is in a vacuum,there is a curve in the vertical plane that when air mass to slide along the curve from one point to another point under the effect of gravity causes the time used be shortest,setting the curve as the profile of the airfoil,using the line connection of two-point as the chord length of airfoil,thus the curve can capture much more air mass,so that it will convert more wind energy captured into mechanical energy during this time.(3)The mathematical expression of the airfoil profile is obtained by the theory of air weight analogy to pressure difference.Based on the airfoil profile,the wind turbine blade airfoil(called SJX airfoil here)is constructed.(4)The superiority of the airfoil designed in this paper is verified by Fluent simulation The result shows that the lift coefficient of the SJX airfoil is higher than the three similar airfoils selected in the airfoil library in the range of-4°～6° angle of attack,compared with the NACA2409-34 airfoil,the maximum lifting rate of lift coefficient is 49.35%;the lift to drag ratio of SJX airfoil has obvious advantage when the angle of attack change from-40～4°,compared with the other three airfoils,the maximum lifting rate of lift to drag ratio is 64.21%.(5)Applied research:A 1MW wind turbine blade is designed with SJX airfoil,in order to verify its aerodynamic performance,compared with the blade designed with NACA2409-34 airfoil selected from the airfoil library,and the multi-working condition flow field simulation is carried out.The result shows that at the rated wind speed of 12m/s,the former’s output power is 984786.39W,the latter’s output power is 956,769.42W,and the power is increased by 2.84%.It is indicated that the wind turbine based on SJX airfoil designed can achieve higher output power,which is closer to the design power and can significantly improve the energy conversion rate,verified the feasibility of the theory.