CN105201728B - A kind of design method of horizontal axis tidal current energy hydraulic turbine combination airfoil fan - Google Patents

Abstract

The invention discloses a design method for combined airfoil blades of a horizontal axis tidal current energy water turbine. The method separately studies the hydrodynamic performance of conventional airfoils and bionic airfoils. Combined with the bionic airfoil, a combined airfoil blade with superior performance is designed; the 3D digital model of the fish fin is obtained, and the cross-sectional profiles at different positions are selected as the bionic fin airfoil, and the bionic fish is selected by the analysis software. Fin airfoil, and derive the two-dimensional coordinates of the bionic airfoil and the required conventional airfoil, optimize the leaf element of the designed blade, obtain the parameters of each blade element, and compare the bionic airfoil and the required conventional airfoil with the blade The two-dimensional coordinates of the airfoil are converted into three-dimensional coordinate data, which are imported into the three-dimensional design software for lofting processing, and finally the combined airfoil blade is generated; this method makes the hydrodynamic performance of the combined airfoil blade more superior , significantly improving the energy-gaining efficiency of the turbine.

Description

A Design Method for Composite Airfoil Blades of Horizontal Axis Tidal Energy Turbine

technical field

The invention relates to a design method of a hydraulic turbine blade, in particular to a design method of a combined airfoil blade of a horizontal axis tidal current energy hydraulic turbine.

Background technique

In recent years, the development of ocean energy has penetrated into various fields. As a clean and renewable energy, tidal current energy has been extensively studied. Tidal current energy has the advantages of reliability, periodicity, sustainability, and wide distribution. It will It will play an important role in the future energy. In order to utilize the tidal current energy, the hydro turbine is the main capture device of the tidal current energy. Therefore, how to improve the energy harvesting efficiency of the tidal current energy hydro turbine has become a key factor affecting the popularization and application of tidal current energy generation. Therefore, the research and development of the hydro turbine is becoming more and more important. are getting more and more attention.

The blade is the core component of the turbine, and the airfoil is the basis of the blade, so the choice of the blade airfoil will directly affect the energy harvesting efficiency of the turbine. Due to the late appearance of horizontal axis turbines, there is currently no set of methods fully applicable to the design of blades of horizontal axis tidal energy turbines. However, due to its similar form to wind turbines, more mature wind turbine blade design methods are mostly used at home and abroad. However, there are large differences in density, viscosity, flow velocity and other factors between the two working media, resulting in low energy gain efficiency of the turbine obtained according to the design method of wind turbine blades. Therefore, how to design a blade that meets the characteristics of the working medium is a key issue to improve the energy-capturing efficiency of the horizontal-axis tidal energy turbine. Patent CN 104408260 A provides a tidal current energy turbine blade airfoil design method, which is based on a genetic optimization algorithm and comprehensively considers all aspects of the hydrofoil airfoil design of the turbine, and can obtain the best hydrofoil according to the requirements of different water areas and marine environments It has the advantages of broad representation of feasible solutions, group searchability, random searchability and globality, and can obtain the global optimal solution.

Applying bionics to blade design is a new direction of development. Studies have shown that applying the natural characteristics of bird wings to the design of horizontal axis wind turbine blades can significantly improve their energy harvesting efficiency. At the same time, marine fish have undergone natural evolution for hundreds of millions of years, and their body structure characteristics and movement methods can well adapt to life in water, and have excellent hydrodynamic performance. Studies have shown that the movement coordination of fish fins plays a vital role in hydrodynamic performance, so fish bionics research has aroused the interest of many researchers, and has achieved good application in the field of underwater propulsion technology, which is the level of The design of bionic blades of axial tidal current energy turbines has brought new enlightenment. However, the function of fins is mainly used for body propulsion and balance control, which is quite different from the rotary motion of water turbines. Therefore, it is not suitable to use the profiling method to design blades with exactly the same shape as fish fins.

Contents of the invention

In view of the above problems, the purpose of the present invention is to provide a design method for a combined airfoil blade of a horizontal axis tidal current energy turbine, which uses a combination of a bionic airfoil and a conventional airfoil to form a combined airfoil blade, so that the hydrodynamic performance of the blade is more superior , improve the energy-gathering efficiency of the water turbine to make up for the deficiencies of the existing technology.

The horizontal axis tidal current energy turbine blade design method provided by the present invention adopts the classic WILSON theory and the blade element momentum theory to study the hydrodynamic performance of the conventional airfoil and the bionic airfoil respectively. According to the role of each blade element in the blade, the conventional Combining the blade airfoil with the bionic airfoil, a composite airfoil blade with superior performance is designed.

In order to achieve the above object, the concrete technical scheme that the present invention takes is:

A method for designing combined airfoil blades of a horizontal axis tidal current energy turbine, characterized in that it comprises the following steps:

1) Use a 3D scanner to obtain the 3D digital model of the fin specimen, that is, the point cloud data of the fin;

2) The above point cloud data is processed by reverse engineering software to obtain the 3D digital model of the fin, and the cross-sectional profiles at different positions of the fin along the length direction of the fin are arbitrarily selected as the bionic fin airfoil;

3) Compare the intercepted bionic fin airfoil with multiple conventional airfoils of the turbine at different Reynolds numbers through airfoil professional analysis software, and select the bionic fin airfoil with the largest lift-to-drag ratio when the optimal Reynolds number is reached , and derive the two-dimensional coordinates of the airfoil and each conventional airfoil, that is, the two-dimensional coordinates of the bionic airfoil and the two-dimensional coordinates of each conventional airfoil;

4) According to the design requirements, determine the parameters such as the power of the turbine, the number of blades, the rated flow rate, the tip speed ratio, the rated speed of the impeller, and the diameter of the impeller;

5) According to the parameters obtained in step 4), use the conventional blade design method to design the blade, determine the length of the designed blade, and divide the length into k -1 equal parts, and then obtain k cross-sections, namely leaf elements, through The numerical analysis software optimizes the above k leaf elements respectively to obtain the parameters of each leaf element;

6) According to the design requirements and the role of different positions of the blade, the bionic fin airfoil and different conventional airfoils in step 3) are selected to correspond to each blade element in step 5), and each airfoil obtained in step 3) The two-dimensional coordinates are transformed into three-dimensional coordinates according to the leaf element parameters in step 5);

7) Import the airfoil 3D coordinate data obtained above into the 3D design software, carry out lofting processing, and finally generate the composite airfoil blade.

The specific method for obtaining the bionic fin airfoil in the step 2) is: divide the fin n equally along the length direction of the fin to obtain n-1 bionic fin airfoils, wherein the size of n is determined by the The length and the number of bionic airfoils to be selected are determined.

The conventional airfoil described in step 3) is the NACA series airfoil.

The specific steps of the leaf element optimization described in step 5) are: according to the design requirements, use the conventional blade design method to design the blade, and divide the designed blade into k -1 equal parts along the length direction, that is, obtain k leaf element ; study each leaf element separately, and assume that the radius of the i -th leaf element is r _i , use the numerical analysis software to write program codes for the objective function, constraint equation and solution equation respectively; through the optimization toolbox of the numerical analysis software Call the above program code to calculate parameters such as radius, tip speed ratio, axial factor, circumferential factor, tip loss factor, inflow angle, chord length, twist angle, etc. of each blade element.

The two-dimensional coordinates of the airfoil in step 6) are transformed into three-dimensional coordinate data of the airfoil through translation transformation, scaling transformation, rotation transformation and offset transformation along the Z axis.

The advantages of the present invention: the blade design in the present invention adopts the combination of the bionic fin airfoil and the conventional airfoil, which can better adapt to the characteristics of the working medium, thus having a higher energy harvesting efficiency; Different parts from the root to the blade tip play different roles in the energy-capturing process of the blade. The combined airfoil blade designed by selecting different airfoils has been proved by experiments that the invention can significantly improve the energy-capturing efficiency and reliability of the blade; In sea conditions with different flow velocities and directions, the design method provided by the present invention can be used to select different bionic airfoils and conventional airfoils to design combined airfoil blades, thereby obtaining higher energy harvesting efficiency.

Description of drawings

Fig. 1 is an example diagram of a cross-sectional airfoil of a shark tail fin in an embodiment of the present invention.

Fig. 2 is the airfoil diagram of different positions of the shark caudal fin in the embodiment of the present invention.

Fig. 3 is an example diagram of hydrodynamic performance analysis of several bionic shark tail fin airfoils in the embodiment of the present invention.

Fig. 4 is an example diagram of the airfoil selection of the combined airfoil blade in the embodiment of the present invention.

Fig. 5 is an example diagram of a composite airfoil blade in an embodiment of the present invention.

Among them, 1-NACA63-018 airfoil; 2-NACA0015 airfoil; 3-bionic shark tail fin airfoil; 4-NACA2412 airfoil; 5-NACA2410 airfoil.

detailed description

In order to make the object, technical solution and advantages of the present invention clearer, the implementation of the present invention will be further described through specific examples below in conjunction with the accompanying drawings.

In this embodiment, the tail fin of a shark is used as the acquisition model of the bionic airfoil, and the specific operation method in this embodiment is also applicable to the acquisition of other fish fins for the bionic airfoil and the design of combined airfoil blades.

Based on the shark tail fin as the bionic object, the design method of the combined airfoil blade of the horizontal axis tidal current energy turbine includes the following steps:

1) Use a 3D scanner to obtain a 3D digital model of the shark's caudal fin, that is, the point cloud data of the shark's caudal fin;

2) Process the above point cloud data through reverse engineering software to obtain a three-dimensional digital model of the shark caudal fin, as shown in Figure 1;

3) According to the length of the shark tail fin, it is divided into 8 equal parts, and the cross-sectional contours at 7 positions are obtained as the bionic shark tail fin airfoil, as shown in Figure 2;

4) Through the airfoil professional analysis software, compare the hydrodynamic performance of the intercepted 7 tail fin airfoils with the conventional airfoils of the NACA series of horizontal axis tidal energy turbines at different Reynolds numbers, and select the best Reynolds that meets the design requirements. Count the tail fin airfoil with the largest lift-to-drag ratio, and derive the two-dimensional coordinates of the airfoil and the conventional airfoils, that is, the two-dimensional coordinates of the bionic airfoil and the two-dimensional coordinates of the conventional airfoils; When the number is 80000, when the angle of attack is 10° and 6.5° respectively, the airfoils at the 37.5% and 12.5% positions of the bionic shark tail fin have a larger lift-to-drag ratio (Cl/Cd), which is different from that when the angle of attack is 8.5° The maximum lift-to-drag ratio of NACA63-412 airfoil is close;

5) According to the design requirements, determine the rated power P of the turbine, the number of blades B , the rated flow rate V _rated , the tip speed ratio λ , the rated speed n of the impeller, the energy capture coefficient C _p of the turbine, and the diameter D of the impeller. The formula for calculating the power of the turbine is :

,

Among them, ρ is the seawater density;

6) According to the parameters obtained in step 5), the blades are designed using conventional blade design methods, and then the leaf elements are optimized by numerical analysis software to obtain the parameters of each leaf element. The specific steps are as follows:

(1) According to the design requirements, use the conventional blade design method to design the blade, determine the length of the blade, and divide the length into k -1 equal parts, and then obtain k cross-sections, namely leaf elements;

(2) Study each leaf element separately, set the radius of the i -th leaf element as r _i , and use numerical analysis software to write program codes for the objective function, constraint equation and solution equation;

(3) Call the above program code through the optimization toolbox of the numerical analysis software to calculate the radius, tip speed ratio, axial factor, circumferential factor, tip loss factor, inflow angle, chord length, twist Angle and other parameters;

7) First, according to the design requirements and the role of different positions of the blade, select the conventional airfoil and the optimal tail fin airfoil obtained in step 4) corresponding to each blade element in step 6), and according to the blade element parameters in step 6), The two-dimensional coordinates of each airfoil obtained in step 4) are converted into three-dimensional coordinate data through translation transformation, scaling transformation, rotation transformation and offset transformation along the Z axis; the selection of each part of the airfoil in the blade is based on the following method:

a. As shown in Figure 4, the airfoil at the root of the blade needs to bear most of the torque when the blade rotates. Based on the analysis and comparison of the conventional airfoils of the NACA series, the NACA63-018 airfoil (1) with a relatively large thickness is selected;

b. As shown in Figure 4, the airfoil at the transition between the blade root and the middle of the blade must bear a small amount of torque and also play the role of blade capacitation. The NACA0015 airfoil (2) with a relative thickness of 15% is selected;

c. As shown in Figure 4, the middle part of the blade is the key part of capacitation. Select the bionic shark tail fin airfoil (3) with the largest lift-to-drag ratio obtained in step 4). After analysis, its relative thickness is 13.4%, and the relative thickness is average. Smaller than the relative thickness of the root and transition, enabling a smooth design of the blade;

d. As shown in Figure 4, the airfoil at the transition part from the middle of the blade to the blade tip needs to meet the requirements of good energy-gaining performance and small tip loss, and the NACA2412 airfoil (4) with a relative thickness of 12% is selected;

e. As shown in Figure 4, for the airfoil at the blade tip, in order to minimize the influence of the blade tip vortex on the blade’s capacitation, the NACA2410 airfoil (5) with a relative thickness of 10% is selected;

8) In the 3D design software, perform lofting processing on the 3D coordinate data obtained above to generate a combined airfoil blade, as shown in Figure 5.

Install 3 combined airfoil blades on the turbine, adjust the pitch angle under the design conditions, test and record the power generation of the turbine at different pitch angles, and then calculate the energy-capturing efficiency of the turbine; after analyzing the measured data, use The highest energy-gaining efficiency of the turbine with combined airfoil blades is 0.368. Under the same working conditions, the energy-gaining efficiency of the turbine with NACA63-8XX airfoil blades is 0.346. The energy efficiency is higher, so it can be seen that the energy harvesting efficiency of the combined airfoil is obviously better than that of the conventional airfoil.

The above implementation examples only illustrate the principles and methods of the design, and are not intended to limit the present invention. Anyone who understands the technology and principle can modify and change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications and changes made by those skilled in the art without departing from the spirit and technical ideas disclosed in the present invention should still be covered by the claims of the present invention.

Claims (4)

1. a design method of horizontal axis tidal current energy water turbine composite airfoil blade, is characterized in that, comprises the following steps: 1) Use a 3D scanner to obtain the 3D digital model of the fin specimen, that is, the point cloud data of the fin; 2) The above point cloud data is processed by reverse engineering software to obtain the 3D digital model of the fin, and the cross-sectional profiles at different positions of the fin along the length direction of the fin are arbitrarily selected as the bionic fin airfoil; 3) Compare the intercepted bionic fin airfoil with multiple conventional airfoils of the turbine at different Reynolds numbers through airfoil professional analysis software, and select the bionic fin airfoil with the largest lift-to-drag ratio when the optimal Reynolds number is reached , and derive the two-dimensional coordinates of the airfoil and each conventional airfoil, that is, the two-dimensional coordinates of the bionic airfoil and the two-dimensional coordinates of each conventional airfoil; 4) According to the design requirements, determine the power of the turbine, the number of blades, the rated flow rate, the tip speed ratio, the rated speed of the impeller and the diameter of the impeller; 5) According to the parameters obtained in step 4), the blade is designed using the conventional blade design method, the length of the designed blade is determined, and the length is divided into k + 1 equal parts. At this time, k cross-sections, namely leaf elements, are obtained. The numerical analysis software optimizes the above k leaf elements respectively to obtain the parameters of each leaf element; 6) According to the design requirements and the role of different positions of the blade, select the bionic fin airfoil and the conventional airfoil in step 3) to correspond to each blade element in step 5), and use the two-dimensional The coordinates are converted into three-dimensional coordinates according to the blade element parameters in step 5); the airfoil of each part of the blade is selected according to the following method: the airfoil at the blade root needs to bear most of the torque when the blade rotates, and the NACA series conventional airfoil The analysis and comparison of the NACA63-018 airfoil with a relatively large thickness is selected; the airfoil at the transition part between the blade root and the middle of the blade has to bear a small part of the torque and also play the role of blade energy capture, and the airfoil with a relative thickness of 15% is selected. NACA0015 airfoil; the middle part of the blade is the key part of capacitation. Select the bionic shark tail fin airfoil obtained in step 3) with the largest lift-to-drag ratio. After analysis, its relative thickness is 13.4%, which is smaller than the relative thickness of the root and transition parts. The thickness of the blade can realize the smooth design of the blade; the airfoil at the transition part from the middle of the blade to the blade tip needs to meet the requirements of good energy-gaining performance and small loss of the blade tip, and the NACA2412 airfoil with a relative thickness of 12% is selected; at the blade tip Part of the airfoil, in order to minimize the impact of the blade tip vortex on the blade’s energy capture, choose the NACA2410 airfoil with a relative thickness of 10%; 7) Import the airfoil 3D coordinate data obtained above into the 3D design software, carry out lofting processing, and finally generate the composite airfoil blade. 2. The method for designing combined airfoil blades of water turbines as claimed in claim 1, wherein the specific method for obtaining the bionic fin airfoil in step 2) is: divide the fin n equally along the length direction of the fin, namely n −1 bionic fin airfoils are obtained, wherein the size of n is determined by the length of the fin and the number of bionic airfoils to be selected. 3. The method for designing combined airfoil blades of hydraulic turbines according to claim 1, wherein the specific steps of blade element optimization described in step 5) are: according to the design requirements, the blades are designed using conventional blade design methods, and the The designed leaf is divided into k -1 equal parts along the length direction, that is, k leaf elements are obtained; each leaf element is studied separately, and assuming that the radius of the i -th leaf element is r _i , the objective function, Write program codes for constraint equations and solution equations; call the above program codes through the optimization toolbox of the numerical analysis software to calculate the radius, tip speed ratio, axial factor, circumferential factor, tip loss factor, Inflow angle, chord length, twist angle. 4. The design method of hydro turbine combined airfoil blade as claimed in claim 1, characterized in that, the two-dimensional coordinates of the airfoil in step 6) are converted by translation transformation, scaling transformation, rotation transformation and offset transformation along the Z axis is the three-dimensional coordinate data of the airfoil.