An aerodynamic optimization design method for wind turbines equipped with Gurney flaps for wind tunnel experiments

Abstract

The present invention discloses an aerodynamic optimization design method for a wind turbine equipped with a Gurney flap for a wind tunnel experiment, comprising: 1) building a model wind turbine test platform for a wind tunnel experiment; 2) equipment safety inspection; 3) opening the wind tunnel, obtaining a set wind speed, and obtaining the shaft power of the model wind turbine under the expected speed under the reference working condition; 4) designing the Gurney flap; 5) constructing a Lyapunov function for stability judgment; 6) installing the Gurney flap on the model wind turbine; 7) obtaining the shaft power of the model wind turbine equipped with the Gurney flap under the expected speed; 8) data processing and qualitative and quantitative comparison of aerodynamic optimization efficiency; 9) estimating the aerodynamic efficiency of the actual full-size wind turbine after aerodynamic optimization. The present invention is applicable to a flow control method for a wind turbine equipped with a Gurney flap, which has the characteristics of simple design, high reliability, and high safety, and can accurately obtain the aerodynamic changes of the wind turbine equipped with the Gurney flap under the expected working condition, which has important engineering significance for the aerodynamic optimization of existing wind turbines.

Description

Technical Field

[0001] The invention relates to the field of wind tunnel test and aerodynamic characteristic optimization of wind turbine attachments, and in particular to an aerodynamic optimization design method for a wind turbine equipped with a Gurney flap for wind tunnel test. Background Art

[0002] In the face of the current trend of rapid development of wind energy technology, it is difficult to meet the aerodynamic design requirements of wind turbines under various operating conditions by simply optimizing the airfoil shape. At the same time, due to the problems of imperfect technology, poor site selection and inadequate load configuration of wind turbines produced in the early stage, the power generation performance of some wind turbines is far below expectations. Therefore, it is urgent to upgrade the aerodynamic optimization of these existing wind turbines to meet higher wind energy conversion requirements. In order to solve the above problems, in recent years, many scholars have begun to install additional equipment on the original wind turbines to improve the flow state of the blades, improve the wind energy conversion efficiency and reduce the wind load and fatigue load. Flow control has the following significance in wind turbines: (1) to maximize the utilization rate of wind energy; (2) to reduce the pulsation of rotating blades, thereby reducing fatigue load and extending service life; (3) to reduce the load at extreme wind speeds, thereby reducing manufacturing costs and reducing the cost per kilowatt-hour.

[0003] At present, most active flow control methods are still in the research stage and have not been widely used in actual engineering. This is because there are some problems with existing active control technologies, such as challenges in sensor layout, separation point determination, system robustness, response rate and manufacturing cost, which limit the active control technology of wind turbine blades to achieve the expected aerodynamic optimization effect. There are relatively few related studies on the transformation of actual wind turbines and the improvement of performance, which need further in-depth exploration. In contrast, passive control methods are easier to implement in actual engineering. The Gurney flap involved in the present invention adopts a passive control method, and the transformation can be completed by installing a micro-insert at the trailing edge of the lower surface of the wind turbine blade. Compared with other technologies, the Gurney flap has the advantages of small size, simple installation, short deployment distance and less change in blade manufacturing technology. Whether it is a small wind turbine or a full-size wind turbine with a larger radius, relevant research on flow control accessories has important engineering application value. However, most of the current research on flow control accessories is based on two-dimensional airfoil sections, and there are large differences in the actual operating conditions of various types of rotating blades, resulting in inaccurate conclusions of related research. Therefore, it is of great engineering significance to explore the changes in aerodynamic characteristics of wind turbines equipped with Gurney flaps under three-dimensional rotation conditions through wind tunnel tests. Summary of the invention

[0004] The purpose of the present invention is to provide an aerodynamic optimization design method for a wind turbine equipped with a Gurney flap for wind tunnel experiments, which can overcome the above-mentioned technical problems. The method has the characteristics of simple design, high reliability and high safety. It can accurately obtain the aerodynamic changes of the wind turbine equipped with a Gurney flap under the expected working conditions, which has important engineering significance for the aerodynamic optimization of existing wind turbines.

[0005] The aerodynamic optimization design method involved in the present invention is implemented as follows: an aerodynamic optimization design method for a wind turbine equipped with a Gurney flap for a wind tunnel experiment, comprising the following steps:

[0006] Step 1) Using 3D modeling software to model and 3D print various components of the model wind turbine, and building a model wind turbine test platform for wind tunnel experiments;

[0007] Step 2) Check the safety of equipment and experimental environment, including: whether the connection fasteners are loose; whether the wind turbine is fixedly installed; whether the signal acquisition circuit is correctly connected and operating normally, and ensure that the inside of the wind tunnel is clean;

[0008] Step 3) opening the wind tunnel to obtain a set wind speed; obtaining the shaft power of the model wind turbine under the reference working condition at the expected speed, and closing the wind tunnel;

[0009] Step 4) designing a Gurney flap, establishing an aerodynamic model of a model wind turbine equipped with a Gurney flap, and preliminarily obtaining a relationship between a power coefficient of the model wind turbine equipped with a Gurney flap and a flap height;

[0010] Step 5) constructing a Lyapunov function using the difference between the actual speed and the expected speed, and determining whether the derivative of the function is negative, to determine whether the designed model wind turbine with the Gurney flap installed can operate stably;

[0011] Step 6) installing a Gurney flap on the model wind turbine;

[0012] Step 7) repeating step 3) to obtain the shaft power of the model wind turbine with the Gurney flap installed at the desired speed, and closing the wind tunnel;

[0013] Step 8) data processing and comparison;

[0014] Step 9) Estimate the aerodynamic efficiency of the actual full-scale wind turbine after aerodynamic optimization.

[0015] In order to ensure the stable operation of the wind turbine, when there is a deviation between the incoming wind speed and the rated wind speed or there is uncertainty in the sampling, the wind turbine shaft power needs to be maintained within a range close to a constant value. Therefore, this design method uses the height of the Gurney flap to change the aerodynamic characteristics of the blade, and uses the difference between the actual speed and the rated speed as the feedback quantity to achieve the stable operation of the wind turbine.

[0016] As a further improvement of the present invention, the step 4) uses formula (1) combined with blade element momentum theory to preliminarily obtain the relationship between the power coefficient and flap height of the model wind turbine equipped with a Gurney flap; and uses formula (2) to establish an aerodynamic model of the model wind turbine equipped with a Gurney flap.

[0017] C p =K 1 (ω r )+K 2 (ω r )h (1)

[0018]

[0019] Where, J is the moment of inertia; K r is the viscous friction coefficient; ρ is the air density; ω r is the actual wind wheel speed; U 0 is the incoming flow velocity; η is the wind turbine electrical conversion efficiency, h is the Gurney flap height; R is the rotor radius; C p The wind energy utilization rate of the model wind turbine equipped with Gurney flap; K 1 (ω r ) and K 2 (ω r ) is the same as ω r The related polynomial is used to fit the wind wheel speed ω r The wind energy utilization rate at that time.

[0020] As a further improvement of the present invention, in step 5), the difference between the actual speed and the expected speed is used to construct the Lyapunov function V 1 ;

[0021]

[0022] In the formula, e 1 is the state variable, i.e., the difference between the actual speed and the expected speed; is the expected wind wheel speed; r is the actual wind rotor speed; in the test, the actual wind rotor speed obtained by the Hall sensor for speed measurement minus the expected wind rotor speed (i.e., the set value) is used to accurately obtain the state variable e 1 The value of the rotation speed is limited, and the change in the wind speed in the wind tunnel and the uncertainty in the sampling of the test model cause the change in the rotation speed to be within a limited range.

[0023] As a further improvement of the present invention, in step 5), the model wind turbine with Gurney flaps installed can be stably operated by verifying the designed model wind turbine with Gurney flaps by combining formula (4) with blade element momentum theory;

[0024]

[0025] Where: K r is the viscous friction coefficient; ρ is the air density; U 0 is the incoming flow velocity; η is the wind turbine electrical conversion efficiency, h is the Gurney flap height; R is the rotor radius; K 1 (ω r ), K 2 (ω r ), and For r , The related polynomial is used to represent the wind wheel speed value ω r and The wind energy utilization rate at that time.

[0026] In the experiment, the actual wind rotor speed is obtained by measuring the speed of the Hall sensor, and the expected wind rotor speed (i.e., the set value) is subtracted from the actual wind rotor speed to accurately obtain the state variable e 1 The value of the rotation speed is limited, and the change in the wind speed in the wind tunnel and the uncertainty in the sampling of the test model cause the change in the rotation speed to be within a limited range.

[0027] As a further improvement of the present invention, the Gurney flap in step 6) adopts photocuring 3D printing technology to cure the photosensitive resin raw material into a rectangular strip, and is vertically fixed to the trailing edge of the pressure surface of the model wind turbine rotor by epoxy resin glue, and the radial installation position of the Gurney flap is at the middle section of the blade of the rotor. Considering that the model wind turbine used for wind tunnel testing is generally small, the corresponding Gurney flap size is also relatively small, and the flap height is an important factor affecting the aerodynamic characteristics of the wind turbine, the present invention adopts more precise photocuring 3D printing technology. Compared with molten deposition, its surface has no texture and higher precision, and the photosensitive resin material has higher precision, is not brittle, has a smooth surface, and has no supporting material contact points; at the same time, the three-dimensional rotation effect on the horizontal axis wind turbine is jointly generated by the centrifugal force and the Coriolis force in the boundary layer. The centrifugal force will cause radial flow in the blade root separation zone, and further lead to the generation of chord-wise Coriolis force. The chord-wise Coriolis force can effectively offset part of the chord-wise adverse pressure gradient, thereby slowing down the flow separation. The Gurney flap is installed in the middle of the blade because the blade root is at a higher local angle of attack than the blade tip, which makes flow separation more likely to occur. As a flow control accessory, the Gurney flap plays a major role in the area before the stall angle of attack in the linear section of the lift coefficient. In addition, for the middle section of the blade, the three-dimensional rotation effect and tip loss have little effect on its aerodynamic characteristics, that is, its flow characteristics are closer to two-dimensional flow. Therefore, the Gurney flap has a positive effect at this position. In addition, due to the strong influence of the tip vortex at the blade tip, the cross-sectional angle of attack is significantly reduced, resulting in significant aerodynamic force losses. Therefore, the lift ratio of the Gurney flap at this position is also relatively limited.

[0028] As a further improvement of the present invention, the shaft power in step 3) and step 7) is measured indirectly: the shaft power is fitted by measuring the actual rotation speed and output current, and the output current is accurately obtained by a zero-phase digital filter, and the passband boundary frequency and stopband boundary frequency of the filter are 1 times and 2 times the rotation frequency of the wind wheel, respectively. For the rotation speed and current measured in the wind tunnel, the change of the current is faster and more drastic. The use of a filter can eliminate the electromagnetic interference and high-frequency noise of the motor in the wind tunnel test, and extract useful signal components from it, so as to analyze the real-time signal more quickly and eliminate the phase difference; the zero-phase digital filter used in the present invention has the advantages of high precision, high reliability, programmable change of characteristics or multiplexing, and easy integration, and can achieve characteristics that cannot be achieved by analog filters, such as linear phase, zero phase, etc.; at the same time, considering that in the actual wind tunnel test, the model wind turbine is affected by its own rotation, and at this time, in the frequency domain distribution, the energy near the rotation frequency is higher. For this reason, the passband boundary frequency of the filter is set to 1 times the rotation frequency, and the stopband boundary frequency is set to 2 times the rotation frequency during design.

[0029] As a further improvement of the present invention, the expression for estimating the aerodynamic efficiency of the actual full-scale wind turbine after aerodynamic optimization in step 9) is shown in formula (5);

[0030]

[0031] In the formula, C p The wind energy utilization rate of the model wind turbine equipped with Gurney flap; C p_full Wind energy utilization rate of full-size wind turbine equipped with Gurney flap; Re _full is the Reynolds number corresponding to the estimated full-size wind turbine rotor diameter as the characteristic length; Re _model is the Reynolds number corresponding to the characteristic length of the rotor diameter of the model wind turbine used in the test; n 1 、n 2 The power factor is obtained by calculating the power coefficient of the full-size wind turbine without Gurney flaps at the same tip speed ratio and the power coefficient of the model wind turbine obtained by wind tunnel test at the reference working condition. Since changing the Reynolds number of the airfoil operation has an important influence on the performance of the wind rotor blade, in addition to the steady-state aerodynamic force and the transition position, it will also affect the boundary layer thickness, flow separation area and size, and dynamic stall characteristics. Therefore, it is necessary to estimate the aerodynamic characteristics of the wind turbine airfoil under high Reynolds numbers. The method described in the present invention can improve the accuracy of the prediction of the performance of the blade during design, reduce the error of the aerodynamic characteristics of the blade caused by the influence of the Reynolds number, and thus reduce the risk of insufficient design safety margin and material waste.

[0032] As a further improvement of the present invention, the model wind turbine test platform is installed inside the wind tunnel test section, and a 10W power resistor of 1kΩ and a button switch are connected in parallel to the model wind turbine control circuit. The button switch adopts a two-pin and two-gear form. When the model wind turbine operates normally, the button switch is in a normally open state. When an accident occurs in the test, the loss is reduced by pressing the button switch and reducing the wind speed.

[0033] The present invention adopts the above technical scheme, and compared with the prior art, it has the following beneficial effects: the present invention provides an aerodynamic optimization design method for a wind turbine equipped with a Gurney flap for a wind tunnel experiment, establishes an aerodynamic model of a model wind turbine equipped with a Gurney flap, and constructs a Lyapunov function using the difference between the actual rotational speed and the expected rotational speed, and by judging whether the function derivative is negative, it can efficiently determine whether the designed Gurney flap can operate stably within the disturbance range, thereby ensuring that the designed wind turbine equipped with a Gurney flap is safe and reliable; the present invention is suitable for a flow control method for a wind turbine equipped with a Gurney flap, and the method has the characteristics of simple design, good reliability and high safety. By means of wind tunnel measurement, the aerodynamic changes of the model wind turbine equipped with a Gurney flap under the expected working condition can be accurately obtained. At the same time, the present invention takes into account the influence of the Reynolds number, so that the aerodynamic changes of the actual full-size wind turbine after the Gurney flap is installed can be estimated, which has important engineering significance for the aerodynamic optimization of existing full-size wind turbines. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 The present invention is a flow chart of an aerodynamic optimization design method for a wind turbine equipped with a Gurney flap for wind tunnel experiments.

[0035] Figure 2 It is a structural schematic diagram of the model wind turbine test platform in the present invention.

[0036] Figure 3 This is a graph of wind turbine output current actually measured and filtered in the present invention.

[0037] Figure 4 It is a design flow chart of the Gurney flap in the present invention.

[0038] Figure 5 This is a relationship diagram between the power coefficient and flap height of a model wind turbine equipped with a Gurney flap, which is initially obtained in the present invention.

[0039] Figure 6 The graph is a relationship curve between the incoming wind speed and the shaft power of the wind turbine equipped with a Gurney flap in the present invention in working condition 1.

[0040] Figure 7 The graph is a relationship curve between the incoming wind speed and the shaft power of the wind turbine equipped with a Gurney flap in the present invention in working condition 2.

[0041] Figure 8 It is a schematic diagram of the installation position of the Gurney flap in the present invention.

[0042] Fig. 9 It is a shaft power comparison curve diagram of the model wind turbine in the present invention under the reference working condition and the model wind turbine equipped with a Gurney flap.

[0043] Fig.10 This is a relationship diagram of the expression for estimating the aerodynamic efficiency of an actual full-size wind turbine in the present invention.

[0044] Fig.11 This is a trend diagram of the wind turbine speed change when the button switch is pressed urgently in the present invention. DETAILED DESCRIPTION

[0045] The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0046] like Figure 1 As shown, a method for aerodynamic optimization design of a wind turbine equipped with a Gurney flap for a wind tunnel experiment includes the following steps:

[0047] Step 1) Using 3D modeling software to model and 3D print various components of the model wind turbine, and building a model wind turbine test platform for wind tunnel experiments;

[0048] The model wind turbine test platform built is as follows Figure 2 As shown, it includes a wind wheel 2-1, a micro generator 2-2, a Hall sensor 2-3, a motor bracket 2-4, a tower 2-5, a base 2-6 and a signal acquisition circuit 2-7. The signal acquisition circuit 2-7 includes an adjustable load 2-7-1, a sampling resistor 2-7-2, a power resistor 2-7-3 and a push button switch 2-7-4; the adjustable load 2-7-1, the sampling resistor 2-7-2 and the two wires output by the micro generator 2-2 are electrically connected in series, and the power resistor 2-7-3 and the push button switch 2-7-4 are connected in parallel to the control loop.

[0049] Before the test, the wind rotor, motor bracket and base were three-dimensionally modeled, and the tower was made of a steel rod with a diameter of 16mm. The wind rotor diameter was set to 40cm, and the blades of the wind rotor were made of DTU-LN221 airfoil with a thickness of 21%; the wind rotor was connected to the shaft of the micro-generator, and the micro-generator was WS-31ZYT57-R; the Hall sensor was 3-wire DC NPN type M4; the adjustable load was BOURNS-3590S-2-101L; the sampling resistor was 0.05 ohm, 1% precision resistor; the power resistor was 10W 1kΩ power resistor; the switch was two-pin two-gear; the model wind turbine test platform was installed inside the wind tunnel test section.

[0050] Step 2) Check the safety of equipment and experimental environment, including: whether the connecting fasteners are loose; whether the wind turbine is fixedly installed; whether the signal acquisition circuit is correctly connected and operating normally; and ensure that the inside of the wind tunnel is clean;

[0051] Step 3) Open the wind tunnel, adjust the frequency of the control cabinet to obtain a set wind speed of 7.12 m / s; obtain the shaft power of the model wind turbine under the baseline working condition (without Gurney flap installed) at the expected speed, and close the wind tunnel;

[0052] The present invention adopts an indirect measurement method. First, the relationship between shaft power and output current and rotation speed is obtained. Then, the corresponding relationship between multiple groups of different rotation speeds and currents and the shaft power of the micro-generator used in the test is measured, and polynomial fitting is performed. The actual wind wheel speed obtained by the Hall sensor is obtained by measuring the voltage value across the sampling resistor and dividing it by the resistance value of the sampling resistor, and combining zero-phase digital filtering to accurately obtain the output current; in this embodiment, the passband boundary frequency and stopband boundary frequency of the filter are set to 1 times and 2 times the wind wheel rotation frequency, respectively. When the wind turbine speed is set to 1518r / min, the wind turbine tip speed ratio is 4.46, and the rotation frequency is 25.3Hz; at this time, the pass-band and stop-band boundary frequencies of the filter are 25.3Hz and 50.6Hz, respectively, and the actual measured output current sampling frequency is 10000Hz. Due to the presence of a commutator in the micro motor itself, and the friction between the brush and the commutator has many high-frequency burrs, the results before filtering are difficult to analyze. Figure 3 It can be seen that the result after zero-phase digital filtering is relatively smooth and can be used to fit the model wind turbine shaft power.

[0053] Step 4) designing a Gurney flap, establishing an aerodynamic model of a model wind turbine equipped with a Gurney flap, and preliminarily obtaining a relationship between a power coefficient of the model wind turbine equipped with a Gurney flap and a flap height;

[0054] like Figure 4 The figure shows the design process of the Gurney flap. To ensure the stable operation of the wind turbine, when there is a deviation between the incoming wind speed and the rated wind speed or there is uncertainty in the sampling, the shaft power of the wind turbine needs to be maintained within a range close to a constant value. In order to increase the power, this design method uses the addition of a Gurney flap to change the aerodynamic characteristics of the blade, and uses the difference between the actual speed and the rated speed as the feedback, thereby achieving stable and more efficient operation of the wind turbine.

[0055] First, the aerodynamic model of the model wind turbine with Gurney flap installed is established, as shown in formula (1-1):

[0056]

[0057] Where, J is the moment of inertia; K r is the viscous friction coefficient; ρ is the air density; ωr is the actual wind wheel speed; U 0 is the incoming flow velocity; η is the wind turbine electrical conversion efficiency, h is the Gurney flap height; R is the rotor radius; M is the wind turbine aerodynamic torque; E is the wind turbine electromagnetic torque; C p The wind energy utilization rate of the model wind turbine equipped with Gurney flaps is obtained by using formula (1) combined with blade element momentum theory to preliminarily obtain the relationship between the power coefficient of the model wind turbine equipped with Gurney flaps and the flap height;

[0058] C p =K 1 (ω r )+K 2 (ω r )h (1)

[0059] In the formula, K 1 (ω r ) and K 2 (ω r ) is the same as ω r Related polynomials are used to fit the wind wheel speed ω r The wind energy utilization rate at that time. Substitute equation (1) into equation (1-1) to establish the aerodynamic model of the model wind turbine with Gurney flap installed;

[0060]

[0061] At the same time, the blade element momentum theory method is used to estimate the shaft power output of the model wind turbine equipped with the Gurney flap according to the present invention. The specific implementation steps are as follows:

[0062] Step 1: The lift and drag coefficients of the DTU-LN221 airfoil with Gurney flaps of 1.5% and 3% relative chord heights are obtained by numerical calculation;

[0063] Step 2: Initialize the rate of change of the incoming flow velocity after passing through the wind wheel (the ratio of the axial induced velocity at the wind wheel to the incoming flow velocity in front of the wind wheel, i.e., the axial induction factor) and the ratio of the tangential rotation angular velocity of the airflow to the impeller rotation angular velocity (i.e., the tangential induction factor);

[0064] Step 3: Calculate the angle of attack at each blade element section;

[0065] Step 4: Obtain the lift coefficient and drag coefficient of the two-dimensional airfoil section with the Gurney flap installed, and calculate the tangential force and normal force;

[0066] Step 5: Calculate the axial induction factor and the tangential induction factor;

[0067] Step 6: If the values ​​of the axial induction factor and the tangential induction factor are greater than 0.2, return to step 2; otherwise, complete the calculation of the shaft power of the model wind turbine with the Gurney flap installed and convert it into a dimensionless power coefficient. Figure 5 This is a relationship diagram between the power coefficient and flap height of the model wind turbine equipped with a Gurney flap obtained preliminarily in the method of the present invention. At this time;

[0068] C p =K 1 (ω r )+K 2 (ω r )h

[0069]

[0070] It can be seen from the figure that the shaft power of the wind turbine first increases and then decreases with the increase of the tip speed ratio, which is in line with the actual law of the three-blade wind turbine. There is a maximum power coefficient point near the expected speed of 160rad / s, and in the high speed area, with the increase of the flap height, the power coefficient has a small upward trend.

[0071] Step 5) Use the difference between the actual speed and the expected speed to construct the Lyapunov function, and by judging whether the derivative of the function is negative, determine whether the designed model wind turbine with the Gurney flap can operate stably; Use the difference between the actual speed and the expected speed in formula (3) to construct the Lyapunov function V 1 ;

[0072]

[0073] In the formula, e 1 is the state variable, i.e., the difference between the actual speed and the expected speed; is the expected wind wheel speed; r is the actual wind rotor speed; in the test, the actual wind rotor speed obtained by the Hall sensor for speed measurement minus the expected wind rotor speed (i.e., the set value) is used to accurately obtain the state variable e 1 The value of the rotation speed is limited, and the change in the wind speed in the wind tunnel and the uncertainty in the sampling of the test model cause the change in the rotation speed to be within a limited range.

[0074] Obviously, the function V 1 Positive definite, if the system is stable, then the function derivative is negative definite, for V 1 The derivatives of are:

[0075]

[0076] make Because J is the moment of inertia and is a positive number, and It must also be a positive number, then:

[0077]

[0078] Simplifying formula (3-2), we can get;

[0079]

[0080] Where: K r is the viscous friction coefficient; ρ is the air density; U 0 is the incoming flow velocity; η is the wind turbine electrical conversion efficiency; h is the Gurney flap height; R is the rotor radius. 1 (ω r ), K 2 (ω r ), and For r , The related polynomial is used to represent the wind wheel speed value ω r and The wind energy utilization rate at that time.

[0081] In this case, K 1 (ω r ), K 2 (ω r ), and The expression is shown in formula (1-2), then the above expression can be rewritten as:

[0082]

[0083] As shown in formula (4-1), at this time, within the speed range of the model wind turbine (60rad / s to 220rad / s), D≈22.21, K r = 0.1, for Gurney flaps with 1.5% and 3% chord height, due to e 1 The actual wind rotor speed obtained by the Hall sensor measuring the speed is subtracted from the expected wind rotor speed. Due to the problem of sensor accuracy, e 1 The absolute value of cannot be too small. Then the Gurney flap designed in this embodiment satisfies formula (4-1) when h is in the range of 0% to 3%, and the unsteady blade element momentum theory is combined to verify that the model wind turbine equipped with the Gurney flap can operate stably.

[0084] The following simulation of unsteady blade element momentum theory verifies that the wind turbine equipped with Gurney flaps can operate stably under different working conditions. Figure 6 The wind turbine with Gurney flaps designed by the method of the present invention is a graph showing the relationship between the incoming wind speed and the shaft power in working condition 1. The simulated wind turbine and operating conditions are consistent with the model wind turbine and operating conditions used in the test. The incoming wind speed is 7.12 m / s, the tip speed ratio is 4.46, the corresponding expected speed of the wind rotor is 158.77 rad / s, and the Gurney flap height is 1.5% of the relative chord length. Figure 7The relationship curve between the incoming wind speed and the shaft power of the wind turbine equipped with a Gurney flap designed by the method of the present invention in working condition 2. The wind turbine and operating conditions simulated at this time are consistent with the model wind turbine and working conditions used in the test. The incoming wind speed is 7.12m / s, the tip speed ratio is 5.70, the corresponding expected speed of the wind rotor is 202.92rad / s, and the height of the Gurney flap is 3% of the relative chord length. The simulation time for the two working conditions is 2s, and the time step is 0.001s. At 1s, the Gurney flap starts to work. It can be seen that in both working conditions, with the pulsation of the incoming wind speed, the model wind turbine equipped with a Gurney flap can operate stably. Figure 6 and Figure 7 The partial enlarged image shows the additional power output of the model wind turbine after the Gurney flap is installed. At this time, within the range of simulated operating conditions, the additional power output Δ is positive. Comparing the average increase, the two operating conditions are 5.55% and 8.35% respectively. This verifies that the designed model wind turbine with Gurney flap can operate stably and optimally.

[0085] Step 6) Install a Gurney flap on the model wind turbine; the Gurney flap uses a photocuring 3D printing technology to solidify the photosensitive resin raw material into a rectangular strip, and is vertically fixed to the trailing edge of the pressure surface of the model wind turbine rotor by epoxy resin glue (installation angle 90°); affected by the three-dimensional rotation effect, the radial installation position of the flap is at 30% to 65% of the relative radius of the middle section of the blade, and the flap height is 1.5% of the relative chord length. Figure 8 shown.

[0086] Step 7) Repeat step 3, open the wind tunnel, adjust the control cabinet frequency to obtain a set wind speed of 7.12 m / s; obtain the shaft power of the model wind turbine with Gurney flaps installed at the expected speed, and close the wind tunnel;

[0087] Step 8) data processing and comparison; Fig. 9 The shaft power comparison curve of the model wind turbine of the method of the present invention in the baseline working condition and the model wind turbine equipped with Gurney flaps is shown. The figure illustrates the changes in the power coefficient under the baseline working condition and the working condition with Gurney flaps installed under the conditions of 0° yaw and 0° pitch angle. In order to more accurately measure the impact of installing Gurney flaps on the power coefficient, the standard deviation of the time-averaged power coefficient in the figure is marked in the form of a shaded area. From the analysis of the figure, it can be seen that the power coefficients of the two are quite different during the high tip speed ratio period, while during the low tip speed ratio period, the impact of installing flaps on the power coefficient of the wind turbine is not obvious, and the two show similarities in power coefficient and change slope. This is because at low tip speed ratios, there is a large range of flow separation on the suction surface of the blade. For the DTU-LN221 airfoil with Gurney flaps, the lift-drag efficiency after flow stall is not as significant as in the linear region. Therefore, during the low tip speed ratio period, the difference between the two is relatively small.

[0088] Step 10) Estimate the aerodynamic efficiency of the actual full-scale wind turbine after aerodynamic optimization. The expression for estimating the aerodynamic efficiency of the actual full-scale wind turbine after aerodynamic optimization is shown in formula (5);

[0089]

[0090] In the formula, C p The wind energy utilization rate of the model wind turbine equipped with Gurney flap; C p_full Wind energy utilization rate of full-size wind turbine equipped with Gurney flap; Re _full is the Reynolds number corresponding to the estimated full-size wind turbine rotor diameter as the characteristic length; Re _model is the Reynolds number corresponding to the characteristic length of the rotor diameter of the model wind turbine used in the test; n 1 、n 2 The power factor is obtained by calculating the power factor of the full-scale wind turbine without Gurney flaps at the same tip speed ratio and the power factor of the model wind turbine under the reference condition obtained by the wind tunnel test. Fig.10 As shown, Fig.10 The following is a relationship diagram of the expression for estimating the aerodynamic efficiency of an actual full-size wind turbine using the method of the present invention. Wind rotors of the same shape are selected for comparison. The black dots in the figure represent the result values ​​of the comparison between wind rotors with diameters of 0.4m, 1.5m, 13.75m and 20m, respectively. The wind energy utilization results of wind rotors with diameters of 0.4m and 1.5m are from the wind tunnel test results of Yangzhou University; the wind energy utilization results of wind rotors with diameters of 13.75m and 20m are from the unsteady blade momentum theory simulation. From the results, it can be seen that in this embodiment, the expression for estimating the aerodynamic efficiency of an actual full-size wind turbine after aerodynamic optimization is as shown in formula (5-1), so that the wind energy utilization of the wind turbine with Gurney flaps installed at the desired Reynolds number can be obtained.

[0091]

[0092] In addition, in order to ensure the safety of wind tunnel tests, the model wind turbine test platform is installed inside the wind tunnel test section, and a 10W 1kΩ power resistor and a button switch are connected in parallel to the model wind turbine control circuit. The switch adopts a two-pin two-gear form. During normal operation, the button switch is in the normally open state. When an accident occurs in the test, the button switch is pressed urgently to reduce the wind speed and reduce the loss. Fig.11 This is a trend diagram of the wind turbine speed change when the emergency button is pressed in the method of the present invention. It can be seen that after pressing the emergency button, the speed of the high-speed wind turbine drops rapidly to a lower speed area within 0.8s, and it is obvious that the test platform has the characteristics of high safety.

[0093] The present invention is applicable to a flow control method for a wind turbine equipped with a Gurney flap. The method has the characteristics of simple design, good reliability and high safety. By means of wind tunnel measurement, the aerodynamic changes of a model wind turbine equipped with a Gurney flap under expected working conditions can be accurately obtained. At the same time, the present invention takes into account the influence of the Reynolds number, so that the aerodynamic changes of an actual full-size wind turbine after the Gurney flap is installed can be estimated, which has important engineering significance for the aerodynamic optimization of existing full-size wind turbines.

[0094] The present invention is not limited to the above-mentioned embodiments. On the basis of the technical solution disclosed in the present invention, technicians in this field can make some substitutions and deformations to some technical features therein according to the disclosed technical content without creative labor, and these substitutions and deformations are all within the protection scope of the present invention.

Claims

1. A method for aerodynamic optimization design of a wind turbine with a Gurney flap installed in a wind tunnel experiment, characterized in that: The following steps are involved: Step 1) Using 3D modeling software to model and 3D print various components of the model wind turbine, and building a model wind turbine test platform for wind tunnel experiments; Step 2) Check the safety of equipment and experimental environment, including: whether the connection fasteners are loose; whether the wind turbine is fixedly installed; whether the signal acquisition circuit is correctly connected and operating normally, and ensure that the inside of the wind tunnel is clean; Step 3) opening the wind tunnel to obtain a set wind speed; obtaining the shaft power of the model wind turbine under the reference working condition at the expected speed, and closing the wind tunnel; Step 4) Design a Gurney flap, establish an aerodynamic model of a model wind turbine equipped with a Gurney flap, preliminarily obtain the relationship between the power coefficient and the flap height of the model wind turbine equipped with a Gurney flap, and use formula (1) combined with blade element momentum theory to preliminarily obtain the relationship between the power coefficient and the flap height of the model wind turbine equipped with a Gurney flap; and use formula (2) to establish an aerodynamic model of a model wind turbine equipped with a Gurney flap. C p =K1(ω r )+K2(ω r )h (1) Where, J is the moment of inertia; K r is the viscous friction coefficient; ρ is the air density; ω r is the actual wind rotor speed; U0 is the incoming flow velocity; η is the wind turbine electrical conversion efficiency, h is the Gurney flap height; R is the wind rotor radius; C p is the wind energy utilization rate of the model wind turbine equipped with Gurney flap; K1(ω r ) and K2(ω r ) is the same as ω r The related polynomial is used to fit the wind wheel speed ω r Wind energy utilization rate at 1000 s; Step 5) constructing a Lyapunov function using the difference between the actual speed and the expected speed, and determining whether the derivative of the function is negative, to determine whether the designed model wind turbine with the Gurney flap installed can operate stably; Step 6) installing a Gurney flap on the model wind turbine; Step 7) repeating step 3) to obtain the shaft power of the model wind turbine with the Gurney flap installed at the desired speed, and closing the wind tunnel; Step 8) data processing and comparison; Step 9) Estimate the aerodynamic efficiency of the actual full-scale wind turbine after aerodynamic optimization.

2. The aerodynamic optimization design method for a wind turbine equipped with a Gurney flap for wind tunnel experiment according to claim 1 is characterized in that: In step 5), the difference between the actual speed and the expected speed is used to construct the Lyapunov function V1; In the formula, e1 is the state variable, that is, the difference between the actual speed and the expected speed; is the expected wind rotor speed; ω r is the actual wind wheel speed.

3. The aerodynamic optimization design method for a wind turbine equipped with a Gurney flap for a wind tunnel experiment according to claim 1, characterized in that: In step 5), the model wind turbine with Gurney flaps installed can be verified to operate stably by combining formula (4) with blade element momentum theory; Where: K r is the viscous friction coefficient; ρ is the air density; U0 is the incoming flow velocity; η is the wind turbine electrical conversion efficiency, h is the Gurney flap height; R is the rotor radius; K1(ω r )、K2(ω r ), and For r , The related polynomial is used to represent the wind wheel speed value ω r and The utilization rate of wind energy at that time.

4. The aerodynamic optimization design method for a wind turbine equipped with a Gurney flap for a wind tunnel experiment according to claim 1, characterized in that: The Gurney flap in step 6) uses photocuring 3D printing technology to cure the photosensitive resin raw material into a rectangular strip, and vertically fix it to the trailing edge of the pressure surface of the model wind turbine rotor through epoxy resin glue. The radial installation position of the Gurney flap is at the middle section of the rotor blade.

5. The aerodynamic optimization design method for a wind turbine equipped with a Gurney flap for wind tunnel experiment according to claim 1, characterized in that: The shaft power in step 3) and step 7) is measured indirectly: the shaft power is fitted by measuring the actual rotational speed and output current, and the output current is accurately obtained through a zero-phase digital filter, and the passband boundary frequency and stopband boundary frequency of the filter are 1 times and 2 times the wind wheel rotation frequency respectively.

6. The aerodynamic optimization design method for a wind turbine equipped with a Gurney flap for wind tunnel experiment according to claim 1, characterized in that: The expression for estimating the aerodynamic efficiency of the actual full-scale wind turbine after aerodynamic optimization in step 9) is shown in formula (5); In the formula, C p The wind energy utilization rate of the model wind turbine equipped with Gurney flap; C p_full Wind energy utilization rate of full-size wind turbine equipped with Gurney flap; Re _full is the Reynolds number corresponding to the estimated full-size wind turbine rotor diameter as the characteristic length; Re _model is the Reynolds number corresponding to the characteristic length of the rotor diameter of the model wind turbine used in the test; n1 and n2 are power factors, which are obtained by calculating the power coefficient of the full-size wind turbine without Gurney flaps at the same tip speed ratio and the power coefficient of the model wind turbine under the benchmark conditions obtained by the wind tunnel test.

7. The aerodynamic optimization design method for a wind turbine equipped with a Gurney flap for wind tunnel experiment according to claim 1, characterized in that: The model wind turbine test platform is installed inside the wind tunnel test section, and a 10W 1kΩ power resistor and a button switch are connected in parallel to the model wind turbine control circuit. The button switch adopts a two-pin two-gear form. When the model wind turbine is operating normally, The button switch is in the normally open state. If an accident occurs during the test, press the button switch and reduce the wind speed. Thereby reducing losses.

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