CN110594105B - Aerodynamic characteristics measurement device of small power wind turbine suitable for wind tunnel test - Google Patents

Abstract

The invention relates to a low-power wind turbine aerodynamic characteristic measuring device suitable for a wind tunnel test, wherein a wind turbine comprises a hub arranged at the front end of a fan shaft, blades are arranged on the circumference of the hub, the fan shaft and the wind tunnel are coaxial, the middle section of the fan shaft is arranged in a bearing seat, the rear end of the fan shaft is connected with one end of a torquer through a first coupling, and the other end of the torquer is connected with a rotor shaft of a three-phase asynchronous generator through a second coupling; the bearing seat and the torquemeter are installed on the wind turbine base, the wind turbine base and the three-phase asynchronous generator are fixed on a common base, the gravity center point of the common base is arranged on the six-component balance, and the six-component balance is fixed on the top of the wind turbine support. The output end of the generator is connected with the input end of the three-phase full-bridge rectifying circuit through the air switch and the fuse, and the output end of the three-phase full-bridge rectifying circuit is connected with the main loop filter capacitor bank and is connected with the load through the solid-state relay. The device can accurately measure the pneumatic performance parameters of the wind turbine when the rotating speed is stable.

Description

Aerodynamic characteristics measurement device of small power wind turbine suitable for wind tunnel test

technical field

The invention relates to a wind tunnel test device, in particular to a low-power wind turbine aerodynamic characteristic measurement device suitable for wind tunnel test, belonging to the technical field of wind turbine measurement.

Background technique

A wind tunnel is a kind of pipe shape experimental equipment that can artificially generate and control airflow to simulate the flow of gas around an aircraft or an object, measure the effect of airflow on an object, and observe physical phenomena. effective tool.

In the existing wind turbine testing technology, a dual-drive parallel PWM back-to-back wind power converter is often used for wind turbine control, which has high power and high cost. Considering that in the permanent magnet direct-drive wind power generation system, the full-power converter needs to carry all the power generated by the generator, and the capacity of the converter needs to be selected according to 100% of the power. In the wind tunnel aerodynamic characteristics test with power and small cross-section. Moreover, in order to measure the aerodynamic characteristics of wind turbines in wind tunnels, it is necessary to precisely control the rotational speed of the wind turbines within a certain range under different inflow conditions, which is inconsistent with the existing mature wind turbine control strategies on the market. Some wind turbine control strategies are mostly to ensure that the wind turbine runs at the maximum output power position, and the control of the low-power wind turbine model is difficult. Within the rotational speed range, stall is likely to occur. So far, there is no mature, reliable and low-cost wind turbine rotational speed control device suitable for the measurement of aerodynamic characteristics of low-power wind turbines.

For this reason, the current wind tunnel test on the aerodynamic characteristics of wind turbines urgently needs a set of low-power wind turbine speed control devices with high reliability, maturity, strong fault tolerance and safety. On the basis of the measures, under different working conditions, the rotational speed of the wind turbine during the wind tunnel experiment can be monitored in real time, and the experiment can be visualized and real-time, and accurate measurement data of the aerodynamic characteristics of the wind turbine can be obtained.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the problems existing in the prior art, and to provide a low-power wind turbine aerodynamic characteristic measurement device suitable for wind tunnel tests, which can accurately collect six loads of wind turbines under various wind speeds and rotational speeds of the wind turbine. Performance parameters such as weight and torque.

In order to solve the above technical problems, a low-power wind turbine aerodynamic characteristic measurement device suitable for wind tunnel tests of the present invention includes a wind tunnel and a wind turbine located in the wind tunnel, and the wind turbine includes a hub installed at the front end of the fan shaft. , blades are installed on the circumference of the hub, the fan shaft is coaxial with the wind tunnel, the middle section of the fan shaft is installed in the bearing seat, and the rear end of the fan shaft passes through the coupling one and one end of the torque meter Connected, the other end of the torque meter is connected with the rotor shaft of the three-phase asynchronous generator through the second coupling; the bearing seat and the torque meter are installed on the base of the wind turbine, and the base of the wind turbine and the three-phase asynchronous generator are both connected. It is fixed on a common base, the center of gravity of the common base is placed on a six-component balance, and the six-component balance is fixed on the top of the wind turbine bracket.

Compared with the prior art, the present invention achieves the following beneficial effects: the gravity of the bearing seat and the torque meter is located on the base of the wind turbine, the weight of the base of the wind turbine and the weight of the three-phase asynchronous generator are both carried on the common base, and the common base The center of gravity is placed on the six-component balance, so that the six-component balance is in the zero position before the wind turbine runs, making the test data more accurate. Set the wind speed of the wind tunnel and blow it to the wind turbine. The fan blades continue to rotate under the blowing of the incoming flow, and the fan shaft is driven to rotate through the hub. The fan shaft drives the torque meter through the first coupling, and the torque meter is driven through the second coupling. The rotor shaft of the three-phase asynchronous generator rotates, and the stator of the three-phase asynchronous generator outputs three-phase alternating current. The middle section of the fan shaft is installed in the bearing seat, the hub is installed at one end, and the torque meter is connected at the other end, which can change the single-end cantilever state of the fan shaft, improve the stress state of the fan shaft and the bearing seat, prolong the service life of the bearing, and make the wind turbine The operation is more stable and balanced. The torque meter can measure the torque and mechanical power of the wind turbine at different incoming wind speeds and different rotational speeds of the wind turbine; the six-component balance can simultaneously measure six load components under different incoming wind speeds and different rotational speeds of the wind turbine, including the normal direction Force, pitch moment, side force, yaw moment, axial force and roll moment.

As an improvement of the present invention, the three-phase output end of the three-phase asynchronous generator is connected with the input end of the three-phase full-bridge rectifier circuit through the air switch and the fuse, and the output end of the three-phase full-bridge rectifier circuit is connected with the main loop filter The capacitor bank is connected to the load through a solid state relay. The three-phase AC power output by the three-phase asynchronous generator is rectified into DC power by the three-phase full-bridge rectifier circuit. After being filtered by the main circuit filter capacitor group, the voltage is more stable. The main circuit filter capacitor group can stabilize the DC side voltage after the three-phase full-bridge rectifier circuit. , while buffering the energy exchange between the AC side and the DC side load to suppress harmonics; considering that there are few electrolytic capacitors with large capacity and high withstand voltage on the market and are easily damaged, multiple capacitors of the same type are used in series. . When the contacts of the solid state relay 1 are closed, the load is connected to the DC circuit, which is convenient for measuring the voltage and current of the output terminal of the three-phase asynchronous generator and calculating its output electric power.

As a further improvement of the present invention, each blade is respectively provided with a blade inner hole extending along its own length direction, a certain blade is selected as a pressure measuring blade, and a pressure measuring section is selected on the pressure measuring blade, and the pressure measuring section is away from the axis of the fan shaft The distance is L, L=0.5～0.7R, where R is the radius of gyration of the blade; the suction surface and the pressure surface of the pressure measuring blade are provided with a plurality of pressure measuring holes correspondingly, and the leading edge point where the suction surface and the pressure surface meet There are also pressure measuring holes, the axis of each pressure measuring hole is located on the pressure measuring section, and a thin film pressure sensor is embedded in each pressure measuring hole; a pressure data collector is fixed on the front end surface of the hub, and pressure data collection A wireless communication device is fixed on the front end of the device; the signal lines of each film pressure sensor pass through the inner hole of the blade to the inner cavity of the hub and are respectively connected with the signal input ends of the pressure data collector. The pressure value of the point is sent to the upper computer through the wireless communication device. A plurality of pressure measuring holes are arranged on the suction and pressure surfaces of the pressure measuring blade and a membrane pressure sensor is embedded. The outer surface of the membrane pressure sensor is flush with the outer surface of the blade, so that each measuring point on the suction and pressure surfaces of the blade can be accurately measured. After the signal lines of each film pressure sensor are bundled into a bundle, they pass from the inner hole of the blade to the hub and are connected to the pressure data collector, so as not to interfere with the flow of the airflow and the wind condition of the wind turbine. The pressure data collector communicates wirelessly with the upper computer through the wireless communication device, and the upper computer can display the pressure value of each measuring point through the touch screen.

As a further improvement of the present invention, a square window is respectively opened on the suction surface and the pressure surface of the pressure measuring blade with the pressure measuring section as the center, the square window is covered with a square window plate, and the bottom of the square window plate is respectively passed through the glass glue It is bonded to the blade body, the outer surface of the square window panel is consistent with the shape of the blade in this area, and the joints around the square window panel are filled with glass glue to be smooth with the blade surface; a plurality of the pressure measuring holes are distributed in on the centerline of the square window panel. The thin film pressure sensor is relatively expensive and small in size, the signal line is very thin, and frequent pulling is prone to breakage; the present invention adopts a square window on the surface of the blade, and then covers it with a square window plate, which is convenient for processing each pressure measuring hole, It is also easy to install the film pressure sensor, and the signal lines of each film pressure sensor are easy to organize and bundle into bundles, which greatly reduces the difficulty of passing through the inner hole of the blade, and at the same time greatly reduces the installation damage rate of the film pressure sensor. Save test costs. By replacing the square window plate, the position of the pressure measuring hole can be changed to obtain the pressure value of different measuring points, avoiding the replacement of the entire blade.

As a further improvement of the present invention, the square window panel is formed by splicing two large and small pieces in the direction of its own length, and the splicing seam between the two pieces is parallel to the short side of the square window. The length is 1/12~1/8 of the length of the large window panel. When the small window plate is located on the upper side of the large window plate, the pressure data of a group of measuring points can be measured. After the test, the small window plate can be removed, the large window plate can be pushed up in place, and the small window plate can be replaced with the large window plate. The lower side is glued with glass glue again. At this time, the position of each measuring point on the large window panel has a certain deviation from the original measuring point position, so that the pressure data of another set of measuring points can be obtained. In this way, there is no need to replace the square window plate, re-drilling holes, or plug and unplug a large number of membrane pressure sensors. The same set of window plates can be used to measure two sets of pressure data, which improves the test efficiency and reduces the damage probability of the membrane pressure sensor.

As a further improvement of the present invention, a static pressure probe and a total pressure probe are installed in the wind tunnel 0.5 meters in front of the wind turbine inflow direction, and the signal output ends of the static pressure probe and the total pressure probe are respectively connected to the electronic pressure probe. The air pressure signal input end of the scanning valve is connected, and the air pressure signal output end of the electronic pressure scanning valve is connected with the air pressure signal input end of the control system CPU. The electronic pressure scanning valve corresponds to a pressure sensor interface for each pressure to be measured. Using electronic scanning technology, it has a faster acquisition speed and an accuracy of 0.5%. The electronic pressure scanning valve sends the static pressure and total pressure signals of the wind tunnel to Into the CPU, the test results and the experimental state of the wind tunnel can be kept in real time, and the data is more accurate and reliable. The CPU can calculate the dynamic pressure generated when the air flows in the wind tunnel according to the difference between the static pressure and the total pressure data of the wind tunnel, and use the dynamic pressure calculation formula to calculate the real-time incoming wind speed of the wind turbine.

As a further improvement of the present invention, the signal output end of the torque meter is connected with the torque signal input end of the CPU through the torque signal communication circuit; the signal output end of the six-component balance is connected with the data signal input end of the CPU; the three The output end of the phase full-bridge rectifier circuit is provided with a current signal conditioning circuit, and the current signal output end of the current signal conditioning circuit is connected with the current signal input end of the CPU; the rotor shaft end of the three-phase asynchronous generator is installed with a photoelectric encoder The signal output end of the photoelectric encoder is connected with the input end of the rotational speed signal conditioning circuit, and the output end of the rotational speed signal conditioning circuit is connected with the rotational speed signal input end of the CPU; the pulse width modulation signal output end of the CPU is driven by a PWM drive circuit. Control the on-off of solid-state relay 1; CPU and the upper computer carry out two-way communication. The torque meter provides the torque signal of the fan shaft to the CPU, and the six-component balance provides the six load components to the CPU; the photoelectric encoder measures the speed signal of the three-phase asynchronous generator, and provides it to the CPU through the speed signal conditioning circuit, and the CPU calculates the three The rotational speed of the phase asynchronous generator; the current signal conditioning circuit provides the current signal at the output end of the three-phase full-bridge rectifier circuit to the CPU. The CPU performs real-time PID operation according to the collected blade speed and load current, obtains the desired output PWM signal, and controls the on-off of the solid-state relay 1 through the PWM drive circuit, so as to control the current amplitude of the load and the speed of the wind turbine. The host computer can perform human-computer interaction through the touch screen. For example, the speed of the wind turbine can be set through the touch screen, which is sent to the CPU by the host computer. The fixed speed is the same to achieve the purpose of precise control of the speed. At the same time, the CPU transmits real-time load current, torque, incoming wind speed, wind turbine speed, six load components, PWM output duty cycle and other signals to the host computer, and displays them on the touch screen.

As a further improvement of the present invention, the CPU adopts the STM32F103ZET6 module, the total pressure signal output end of the electronic pressure scanning valve is connected with the PC4 port of the CPU, and the static pressure signal output end of the electronic pressure scanning valve is connected with the PC5 port of the CPU; The current signal conditioning circuit includes a sampling resistor R59 connected in series in the load loop, the two ends of the sampling resistor R59 are respectively connected with the two input ends of the operational amplifier U1D, and the output end of the operational amplifier U1D is connected with the resistor R61 and the resistor R62 in series with each other. The non-inverting input terminal of the operational amplifier U1B is connected, the capacitor C29 is connected between the resistor R62 and the analog ground VSSA, the capacitor C30 is connected between the resistor R61 and the output terminal of the operational amplifier U1B, and the output terminal of the operational amplifier U1B is connected to the non-inverting terminal of the operational amplifier U1A. The input end is connected, and the output end AOUT0 of the operational amplifier U1A is connected with the PA0 port of the CPU. The CPU is developed by STMicroelectronics STM32 programming, and the Keilv5 software is used for programming combined with the aerodynamic theory of the horizontal axis wind turbine and the principle of motor control. The electronic pressure scanning valve sends the total pressure signal of the wind tunnel directly to the PC4 port of the CPU, and sends the static pressure signal of the wind tunnel directly to the PC5 port of the CPU. The CPU calculates the difference between the total pressure value and the static pressure value of the wind tunnel. The dynamic pressure generated when the air flows in the wind tunnel is used to calculate the real-time incoming wind speed of the wind turbine by using the calculation formula of dynamic pressure. The sampling resistor R59 obtains a weak voltage signal from the load circuit, and the operational amplifier U1D is used as the first-stage reverse amplifier operational amplifier circuit, and the voltage signal is amplified by -6 times; the resistor R61 and the capacitor C30, and the resistor R62 and the capacitor C29 are enough to form two The second-order Butterworth low-pass filter circuit is formed by combining with the operational amplifier U1B; the operational amplifier U1A is used as the second-stage reverse amplification operational amplifier circuit, the voltage signal is amplified by -5 times, and the output terminal of the operational amplifier U1A AOUT0 transmits the analog voltage signal to the PA0 port of the CPU and converts it into a digital signal. Considering that the sampling accuracy directly affects the control performance of the entire system, the operational amplifier U1D, operational amplifier U1B and operational amplifier U1A all use LF347BN, and each resistor in the conditioning circuit uses precision resistors with an error within 1%. The selection of two-stage amplification for the current conditioning circuit can eliminate the multiple limit of single-stage amplification, increase the ability to suppress common mode signals, and avoid the circuit from falling into a series of problems such as self-excitation, high noise, and poor frequency response. The design range of the current signal conditioning circuit is 0-10A, and the voltage of the electrical connection with the CPU should be less than the maximum allowable voltage of the chip 3.3V. At the same time, considering the need to leave a margin, the sampling resistor R59 takes the value of 0.01 ohm, after two-stage amplification The amplitude of the analog voltage signal transmitted to the CPU is 3V. Compared with the current Hall sensor circuit, the current signal conditioning circuit of the present invention has a lower price and meets the accuracy requirements.

As a further improvement of the present invention, the photoelectric encoder is an ERN1387 photoelectric encoder, the rotational speed signal conditioning circuit includes an incremental signal conditioning circuit and an index signal conditioning circuit, the sine wave signal of the photoelectric encoder and the A+, The A- port is connected, an impedance matching resistor R103 is connected between the A+ and A- ports, the two ends of the impedance matching resistor R103 are connected to the two input terminals of the operational amplifier U4A, the resistor R101 and the capacitor C56 are connected in parallel with each other and then connected to the operational amplifier U4A Between the inverting input terminal and the output terminal, the output terminal of the operational amplifier U4A is connected to the non-inverting input terminal of the operational amplifier U5A, and the output terminal A of the operational amplifier U5A is connected to the PB1 port of the CPU; the index signal of the photoelectric encoder and the index signal conditioning The R+ and R- ports of the circuit are connected, and an impedance matching resistor R109 is connected between the R+ and R- ports. The two ends of the impedance matching resistor R109 are connected to the two input terminals of the operational amplifier U4C. The resistor R107 and the capacitor C61 are connected in parallel with each other. Between the inverting input terminal and the output terminal of the operational amplifier U4C, the output terminal of the operational amplifier U4C is connected to the non-inverting input terminal of the operational amplifier U5C, and the output terminal R of the operational amplifier U5C is connected to the PC1 port of the CPU. Since the incoming flow direction of the wind turbine is always the same, the rotation direction of the blade remains unchanged under the incoming flow blowing, and there is no problem of judging the forward and reverse rotation. Therefore, the photoelectric encoder of the present invention takes the A-phase sine wave signal to send Enter the A+ and A- ports of the incremental signal conditioning circuit. Since the output signal of the photoelectric encoder is a sinusoidal differential signal, the sinusoidal differential signal must be de-differentiated first. The operational amplifier U4A is used to form a differential conditioning circuit. Resistor R101 and capacitor C56 As the feedback bridge arm of the differential circuit. A 120 ohm impedance matching resistor R103 needs to be connected between the A+ and A- ports to balance the signal voltage difference between A+ and A- during transmission; and then pass the RC low-pass filter composed of the resistor R104 and the capacitor C58 to the signal. Filter processing to remove high-frequency noise, and the sine wave signal range obtained after filtering processing is -1.5V to 1.5V. Since the control chip cannot identify negative signals, it is necessary to perform voltage offset processing on the signal, and in order to facilitate the processing of the signal by the CPU, the level of the sine wave signal needs to be adjusted; the output terminal of the operational amplifier U4A is connected to the non-inverting input terminal of the operational amplifier U5A. , use the operational amplifier U5A to form a comparison circuit, and process the positive offset of the voltage signal. The sine wave signal is compared with the +1.5V voltage signal through the operational amplifier U5A. When the voltage signal at the positive input terminal of U5A is greater than 1.5V, the output terminal of U5A outputs a high level of 3.3V, and the PB1 port of the CPU is at a high level. When the voltage signal of the positive input terminal of U5A is less than 1.5V, the output terminal of U5A outputs a low level of 0V, and the PB1 port of the CPU is at a low level. In the same way, when the output terminal R of the operational amplifier U5C outputs a high level to the PC1 port of the CPU, the index signal is triggered, so that the external interrupt input of the CPU connected to it triggers the reset of the counter. By calculating the pulse number of the incremental signal for one index signal period , calculate the real-time rotational speed of the wind turbine, and the CPU counts again to calculate the rotational speed of the wind turbine at the next moment.

As a further improvement of the present invention, the PA11 port of the CPU is connected to the input terminal PWM-IN of the PWM drive circuit, the resistor R86 and the capacitor C54 are connected in parallel between the PWM-IN port and the base of the transistor Q1, and the resistor R84 is connected to the capacitor C53 After parallel connection, it is connected between the collector of the transistor Q1 and the base of the transistor Q2. The collector of the transistor Q2 is connected to the base of the input push-pull circuit, and the emitter of the input push-pull circuit is connected to the transformer T1 through the DC blocking capacitor C52. The primary side of the transformer T1 is connected to the base of the output push-pull circuit through the displacement capacitor C51, and the emitter of the output push-pull circuit is connected to a control terminal of the solid state relay. In order to prevent oscillation and interference, the PWM signal output by the CPU needs to be transmitted in parallel through the resistor R86 and the capacitor C54, and the base voltage of the transistor Q2 is adjusted by the transistor Q1; similarly, the resistor R84 and the capacitor C53 are connected in parallel to further prevent oscillation and interference. The way can make the PWM output signal and the drive signal in phase. The push-pull circuit at the input end consists of a transistor Q3 and a transistor Q4, which are turned on and off alternately; the DC blocking capacitor C52 on the primary side of the transformer T1 can filter out the DC component in the signal. The energy is transferred to the secondary side of the transformer T1, and the displacement capacitor C51 on the secondary side of the transformer T1 is used to maintain the reset of the magnetic flux and maintain the volt-second balance, thereby achieving the purpose of demagnetization. The transistor Q5 and the transistor Q6 form a push-pull circuit at the output end. The emitters of the transistor Q5 and the transistor Q6 are connected to the positive pole of the first control terminal of the solid state relay through the G+ port, and the collector of the transistor Q6 is connected to the negative pole of the first control terminal of the solid state relay through the G- port. When the PWM signal is at a high level, the control terminal of the solid-state relay 1 is energized, the main contact is closed, and the load circuit is connected; when the PWM signal is at a low level, the control terminal of the solid-state relay 1 is de-energized, the main contact is disconnected, and the load circuit is turned on. disconnect. At the same time, due to the inevitable existence of parasitic distributed inductance in the signal circuit, the voltage and current of the relay contacts cannot be changed abruptly at the moment of turn-on or turn-off, and the reverse recovery time is long under high-frequency operation, resulting in high voltage and high voltage. For the short-term overlap of current, four diodes D1, D2, D3, D4 are added to the secondary circuit of the transformer, that is, diodes are connected in series between the bases and collectors of the transistors Q5 and Q6 and the displacement capacitor C51 respectively to prevent switching. The signal malfunctions and damages the power device. The PWM drive circuit of the invention has less interference, less high-frequency noise, short switching time, low input power consumption, transformer isolation between the input circuit and the output circuit, and has the protection function and strong load capacity.

As a further improvement of the present invention, the torque signal communication circuit includes a MAX3232C module and a MAX3485 module, the signal output end of the torque meter is connected to the MAX3232C module and the MAX3485 module through a nine-pin serial port connector (DB1), and the R1OUT port of the MAX3232C module and the MAX3485 module The RO port is connected to the PA10 port of the CPU together, and the T1IN port of the MAX3232C module and the DI port of the MAX3485 module are connected to the PA9 port of the CPU. The USB interface of the host computer is electrically connected to the PD5 port and the PD6 port of the CPU. The torque meter is reserved with a nine-pin serial port connector, and communicates through the RS232 (short distance) or RS485 (long distance) protocol. Considering that in the actual wind turbine test application, the situation of the serial interface of the torque meter on site cannot be determined, so the communication circuit required to be designed has the functions of both RS232 and RS485 interfaces. The torque signal communication circuit of the present invention is compatible with two protocols, does not require an additional communication protocol conversion circuit, saves space and cost, and can realize real-time monitoring and display of the torque parameters of the wind turbine.

As a further improvement of the present invention, the output end of the three-phase full-bridge rectifier circuit is connected to the braking resistor through the second solid state relay, and an emergency braking button is connected in series in the control loop of the second solid state relay. The braking resistor adopts cement resistor with good heat dissipation effect and high power. When the test is completed, or the wind tunnel test has an accident or the power supply is suddenly interrupted, press the emergency braking button, and the braking resistor will be connected to the three-phase asynchronous generator. The braking resistor directly converts the regenerative electric energy during the rapid braking process of the wind turbine into thermal energy, so that the electric energy will not be fed back to the AC measurement, causing the DC voltage to fluctuate. Lead to mechanical damage, overcurrent damage to the power supply circuit, and overload damage to the torque meter and six-component balance used in the test, which can ensure the safety of the entire test.

As a further improvement of the present invention, the outer periphery of the wireless communication device and the pressure data collector is covered with an elliptical shroud, and the root of the elliptical shroud is fixed on the front end surface of the wheel hub; the rear end surface of the wheel hub The outer periphery is connected with a cylindrical shield, the cylindrical shield is coaxial with the fan shaft, the coupling, the torque meter and the three-phase asynchronous generator are all located in the inner cavity of the cylindrical shield; the bearing seat is provided with The oil bath cavity, the front and rear ends of the oil bath cavity are respectively provided with bearings for supporting the fan shaft, and the outer sides of the two bearings are respectively provided with shaft seals. The oval shroud has a three-dimensional streamlined body surface shape, so that the oval shroud can smoothly guide the airflow from the front of the wind turbine to the top and sides, reducing the impact of the airflow on the fan head, thereby improving airflow. The field structure can reduce the resistance to the incoming flow and avoid the formation of eddy currents in front of the blades. The cylindrical shield is used to cover the coupling, torque meter and three-phase asynchronous generator, which can improve the airflow state behind the blades and increase the number of wind turbines. Stability during high-speed operation, improve the accuracy of wind turbine aerodynamic characteristics test. Improve the operating efficiency of the wind turbine, improve the inflow speed of the impeller rotating plane, and make the plane wind pressure distribution more uniform. The bearing seat is supported by bearings at both ends, and the oil bath in the middle is lubricated, which not only has a good stress state, but also can lubricate and cool the bearing. The bearing and the fan shaft run smoothly and have a long service life.

Description of drawings

The present invention will be described in further detail below with reference to the accompanying drawings and specific embodiments. The accompanying drawings are only for reference and illustration purposes, and are not intended to limit the present invention.

FIG. 1 is a schematic structural diagram of a wind tunnel device in the present invention.

FIG. 2 is an enlarged view of the test equipment in the wind tunnel of FIG. 1 .

FIG. 3 is an enlarged view of Embodiment 1 of the pressure measuring blade in FIG. 2 .

FIG. 4 is a diagram of two working states of the second embodiment of the pressure measuring blade in FIG. 2 .

Figure 5 is the distribution diagram of each measuring point on the pressure measuring blade.

FIG. 6 is a control principle diagram of the wind turbine aerodynamic characteristic measuring device in the present invention.

FIG. 7 is a diagram of the CPU and its peripheral circuits in FIG. 6 .

FIG. 8 is a schematic diagram of the torque signal communication circuit in FIG. 6 .

FIG. 9 is a schematic diagram of the rotational speed signal conditioning circuit in FIG. 6 .

FIG. 10 is a schematic diagram of the current signal conditioning circuit in FIG. 6 .

FIG. 11 is a schematic diagram of the PWM drive circuit in FIG. 6 .

FIG. 12 is a comparison diagram of experimental data of the surface pressure coefficient of the blade at the 0° position and the calculated data of the simulation software in the present invention.

FIG. 13 is a comparison diagram of the experimental data of the torque of the wind turbine and the calculation data of the simulation software according to the present invention.

In the figure: 1. Wind turbine; 1a. Blade; 1a1. Inner channel of blade; 1b. Square window plate; 1b1. Large window plate; 1b2. Small window plate; 1c. Wheel hub; 1d. Fan shaft; 1e. Bearing seat; 1f. Oval shroud; 1g. Cylindrical shield; 2. Coupling 1; 3. Torque meter; 4. Coupling 2; 5. Three-phase asynchronous generator; 5a. Photoelectric encoder; 6. Wind turbine base; 7. Common base; 8. Six-component balance; 9. Wind turbine bracket; 10. Pressure data collector; 11. Wind tunnel; 12. Three-phase full-bridge rectifier circuit; HK. Air switch; RX. C0. Main circuit filter capacitor group; J1. Solid state relay 1; J2. Solid state relay 2; FX1. Load; FX2. Braking resistor; SA. Emergency brake button.

Detailed ways

As shown in FIG. 1 to FIG. 5 , the aerodynamic characteristic measuring device of the low-power wind turbine suitable for the wind tunnel test of the present invention includes a wind tunnel 11 and a wind turbine 1 located in the wind tunnel 11 , and the wind turbine 1 includes a front end of the fan shaft 1d installed The hub 1c, the blade 1a is installed on the circumference of the hub 1c, the fan shaft 1d is coaxial with the wind tunnel 11, the middle section of the fan shaft 1d is installed in the bearing seat 1e, the bearing seat 1e is provided with an oil bath cavity, the front and rear of the oil bath cavity The two ends are respectively provided with bearings for supporting the fan shaft 1d, and the outer sides of the two bearings are respectively provided with shaft seals. The rear end of the fan shaft 1d is connected with one end of the torque meter 3 through the coupling one 2, and the other end of the torque meter 3 is connected with the rotor shaft of the three-phase asynchronous generator 5 through the coupling two 4; the bearing seat 1e and the torque The instrument 3 is installed on the wind turbine base 6, the wind turbine base 6 and the three-phase asynchronous generator 5 are fixed on the common base 7, the center of gravity of the common base 7 is placed on the six-component balance 8, and the six-component balance 8 is fixed on the wind power. the top of the machine bracket 9.

The gravity of the bearing seat 1e and the torque meter 3 is located on the wind turbine base 6, the weight of the wind turbine base 6 and the weight of the three-phase asynchronous generator 5 are both carried on the common base 7, and the center of gravity of the common base 7 is placed on the six-component On the balance 8, before the wind turbine 1 is running, the six-component balance 8 is in a zero position state, so that the test data is more accurate. Set the wind speed of the wind tunnel 11 and blow it to the wind turbine 1, the fan blades continue to rotate under the blowing of the incoming flow, the fan shaft 1d is driven to rotate through the hub 1c, and the fan shaft 1d drives the torque meter 3 to rotate through the coupling 1 2, and the torque The instrument 3 drives the rotor shaft of the three-phase asynchronous generator 5 to rotate through the second coupling 4, and the stator of the three-phase asynchronous generator 5 outputs three-phase alternating current. The middle section of the fan shaft 1d is installed in the bearing seat 1e, one end is installed with the hub 1c, and the other end is connected with the torque meter 3, which can change the single-end cantilever state of the fan shaft 1d, improve the force state of the fan shaft 1d and the bearing seat 1e, and extend the bearing service life, and make the operation of the wind turbine 1 more stable and balanced. The torque meter 3 can measure the torque and mechanical power of the wind turbine 1 under different incoming wind speeds and different rotational speeds of the wind turbine; the six-component balance 8 can simultaneously measure six load components under different incoming wind speeds and different rotational speeds of the wind turbine, Including normal force, pitch moment, side force, yaw moment, axial force and roll moment.

The outer periphery of the wireless communication device and the pressure data collector 10 is covered with an elliptical shroud 1f to reduce the resistance to the incoming flow and avoid the formation of eddy currents in front of the blades 1a, and the root of the elliptical shroud 1f is fixed to the front end of the hub 1c face.

A cylindrical shield 1g is connected to the outer periphery of the rear end surface of the hub 1c. The cylindrical shield 1g is coaxial with the fan shaft 1d. The coupling, the torque meter 3 and the three-phase asynchronous generator 5 are all located in the inner cavity of the cylindrical shield 1g. , in order to improve the airflow state behind the fan blade and improve the accuracy of the wind turbine aerodynamic characteristics test. Improve the operating efficiency of the wind turbine, improve the inflow speed of the impeller rotating plane, and make the plane wind pressure distribution more uniform.

The three-phase output end of the three-phase asynchronous generator 5 is connected with the input end of the three-phase full-bridge rectifier circuit 12 through the air switch HK and the fuse RX, and the output end of the three-phase full-bridge rectifier circuit 12 is connected with the main circuit filter capacitor group C0 And it is connected with the load FX1 through a solid state relay-J1. The three-phase AC power output by the three-phase asynchronous generator 5 is rectified into DC power by the three-phase full-bridge rectifier circuit 12, and the voltage is more stable after being filtered by the main circuit filter capacitor group C0. The main circuit filter capacitor group C0 can stabilize the three-phase full-bridge rectifier circuit. After the DC side voltage, the energy exchange between the AC side and the DC side load is buffered to suppress harmonics; considering that there are few large-capacity, high-voltage electrolytic capacitors on the market, and they are easily damaged, multiple Capacitors are used in series. When the contacts of the solid-state relay-J1 are closed, the load FX1 is connected to the DC circuit, which is convenient for measuring the voltage and current of the output terminal of the three-phase asynchronous generator 5 and calculating its output electric power.

Each blade 1a is respectively provided with a blade inner hole 1a1 extending along its own length direction, select a certain blade as a pressure measuring blade, select a pressure measuring section on the pressure measuring blade, and the distance between the pressure measuring section and the axis of the fan shaft is L, L= 0.5～0.7R, where R is the radius of gyration of the blade; there are multiple pressure measuring holes on the suction surface and pressure surface of the pressure measuring blade, and pressure measuring holes are also set at the leading edge point where the suction surface and the pressure surface meet, The axis of each pressure measuring hole is located on the pressure measuring section, and each pressure measuring hole is respectively embedded with a thin film pressure sensor; the front end surface of the hub 1c is fixed with a pressure data collector 10, and the front end surface of the pressure data collector 10 is fixed with a wireless communication device The signal line of each film pressure sensor runs along the inner hole 1a1 of the blade to the inner cavity of the hub and is respectively connected with the signal input end of the pressure data collector 10, and the pressure value of each measuring point collected by the pressure data collector 10 is through wireless communication. The device is sent to the upper computer.

A plurality of pressure measuring holes are arranged on the suction and pressure surfaces of the pressure measuring blade and a membrane pressure sensor is embedded. The outer surface of the membrane pressure sensor is flush with the outer surface of the blade, so that each measuring point on the suction and pressure surfaces of the blade can be accurately measured. After the signal lines of each film pressure sensor are bundled into a bundle, they pass from the inner hole 1a1 of the blade to the hub and are connected to the pressure data collector 10, without disturbing the flow of the airflow and the wind state of the wind turbine. The pressure data collector 10 performs wireless communication with the upper computer through the wireless communication device, and the upper computer can display the pressure value of each measuring point through the touch screen.

As shown in Figure 3, with the pressure measuring section as the center, square windows are opened on the suction surface and pressure surface of the pressure measuring blade, respectively, and the square windows are covered with a square window plate 1b, and the bottom of the square window plate 1b passes through glass. Glue is adhered to the blade body, the outer surface of the square window panel 1b is consistent with the shape of the blade in this area, and the seams around the square window panel 1b are filled with glass glue until it is smooth with the blade surface; multiple pressure measuring holes are distributed in the square. On the midline of the window panel 1b. The thin film pressure sensor is relatively expensive and small in size, the signal line is extremely thin, and the strands are easily broken by frequent pulling; the present invention adopts a square window on the surface of the blade, and then covers it with a square window plate 1b, which is convenient for processing each pressure measurement on the square window plate 1b. It is also easy to install the membrane pressure sensor. The signal lines of each membrane pressure sensor are easy to organize and bind into bundles, which greatly reduces the difficulty of passing through the inner hole 1a1 of the blade, and at the same time greatly reduces the installation damage rate of the membrane pressure sensor. The test is difficult and the test cost is saved. By replacing the square window plate 1b, the position of the pressure measuring hole can be changed to obtain the pressure value of different measuring points, so as to avoid replacing the entire blade.

As shown in Figure 4, the square window panel 1b is formed by splicing two large and small pieces in the direction of its own length, and the splicing seam between the two pieces is parallel to the short side of the square window. 1/12~1/8 of the length of the window panel 1b1. When the small window plate 1b2 is located on the upper side of the large window plate 1b1, the pressure data of a group of measuring points can be measured. After the test is completed, the small window plate 1b2 can be removed, the large window plate 1b1 can be pushed up in place, and the small window plate 1b2 can be removed. Change to the lower side of the large window panel 1b1, and re-bond it with glass glue. At this time, the position of each measuring point on the large window panel 1b1 has a certain deviation from the original measuring point position, so that another set of measuring points can be obtained. pressure data. In this way, there is no need to replace the square window plate 1b, no need to re-drill holes, and no need to plug and unplug a large number of membrane pressure sensors. The same set of window plates can be used to measure two sets of pressure data, which improves the test efficiency and reduces the damage probability of the membrane pressure sensor.

As shown in Figures 5 to 11, a static pressure probe and a total pressure probe are installed in the wind tunnel 11 at 0.5 meters in front of the wind turbine's incoming flow direction. The signal output ends of the static pressure probe and the total pressure probe are respectively connected with the electronic pressure scanning The air pressure signal input end of the valve is connected, and the air pressure signal output end of the electronic pressure scanning valve is connected with the air pressure signal input end of the control system CPU. The electronic pressure scanning valve corresponds to a pressure sensor interface for each pressure to be measured. Using electronic scanning technology, it has a faster acquisition speed and an accuracy of 0.5%. The electronic pressure scanning valve sends the static pressure and total pressure signals of the wind tunnel to Into the CPU, the test results and the experimental state of the wind tunnel can be kept in real time, and the data is more accurate and reliable. The CPU can calculate the dynamic pressure generated when the air flows in the wind tunnel according to the difference between the static pressure and the total pressure data of the wind tunnel, and use the dynamic pressure calculation formula to calculate the real-time incoming wind speed of the wind turbine.

The signal output end of the torque meter 3 is connected with the torque signal input end of the CPU through the torque signal communication circuit, and the torque meter 3 provides the torque signal of the fan shaft 1d to the CPU. The signal output end of the six-component balance 8 is connected with the data signal input end of the CPU, and the six-component balance provides six load components to the CPU. The output end of the three-phase full-bridge rectifier circuit 12 is provided with a current signal conditioning circuit, the current signal output end of the current signal conditioning circuit is connected with the current signal input end of the CPU, and the current signal conditioning circuit converts the current at the output end of the three-phase full-bridge rectifier circuit 12 Signals are provided to the CPU. A photoelectric encoder 5a is installed at the end of the rotor shaft of the three-phase asynchronous generator 5. The signal output end of the photoelectric encoder 5a is connected to the input end of the rotational speed signal conditioning circuit, and the output end of the rotational speed signal conditioning circuit is connected to the rotational speed signal input end of the CPU. connected. The photoelectric encoder 5a measures the rotational speed signal of the three-phase asynchronous generator 5, and provides it to the CPU through the rotational speed signal conditioning circuit, and the CPU calculates the rotational speed of the three-phase asynchronous generator 5.

The output terminal of the pulse width modulation signal of the CPU controls the on-off of the solid-state relay-J1 through the PWM drive circuit; the CPU and the host computer carry out two-way communication. The CPU performs real-time PID operation according to the collected blade speed and load current, obtains the desired output PWM signal, and controls the on-off of the solid-state relay-J1 through the PWM drive circuit, so as to control the current amplitude of the load FX1 and the speed of the wind turbine. The host computer can carry out human-computer interaction through the touch screen. For example, the speed of the wind turbine can be set through the touch screen, which is sent to the CPU by the host computer. The set speed is the same to achieve the purpose of precise control of the speed. At the same time, the CPU transmits real-time load current, torque, incoming wind speed, wind turbine speed, six load components, PWM output duty cycle and other signals to the host computer, and displays them on the touch screen.

As shown in Figure 7, the CPU adopts the STM32F103ZET6 module, the CPU is developed by STMicroelectronics STM32 programming, and the Keilv5 software is used for programming combined with the aerodynamic theory of the horizontal axis wind turbine and the principle of motor control.

The total pressure signal output end of the electronic pressure scan valve is connected to the PC4 port of the CPU, and the static pressure signal output end of the electronic pressure scan valve is connected to the PC5 port of the CPU; the electronic pressure scan valve sends the total pressure signal of the wind tunnel 11 directly to the CPU The PC4 port of the wind tunnel 11 directly sends the static pressure signal of the wind tunnel 11 to the PC5 port of the CPU. The CPU calculates the dynamic pressure generated when the air flows in the wind tunnel according to the difference between the total pressure value of the wind tunnel 11 and the static pressure value. The dynamic pressure calculation formula calculates the real-time incoming wind speed of the wind turbine.

As shown in Figure 8, the torque signal communication circuit includes the MAX3232C module and the MAX3485 module. The signal output end of the torque meter 3 is connected to the MAX3232C module and the MAX3485 module through the nine-pin serial port connector (DB1). The R1OUT port of the MAX3232C module and the RO of the MAX3485 module The ports are connected to the PA10 port of the CPU, the T1IN port of the MAX3232C module and the DI port of the MAX3485 module are connected to the PA9 port of the CPU; the host computer and the CPU are electrically connected by a USB to TTL serial port module based on the PL2303HX chip, and the USB interface of the host computer It is electrically connected to the PD5 port and PD6 port of the CPU. The torque meter 3 is reserved with a nine-pin serial port connector, and communicates through the RS232 (short distance) or RS485 (long distance) protocol. Considering that in the actual wind turbine test application, the situation of the serial interface of the torque meter on site cannot be determined, so the communication circuit required to be designed has the functions of both RS232 and RS485 interfaces. The torque signal communication circuit of the present invention is compatible with two protocols, does not require an additional communication protocol conversion circuit, saves space and cost, and can realize real-time monitoring and display of the torque parameters of the wind turbine.

As shown in Figure 9, the photoelectric encoder 5a is an ERN1387 photoelectric encoder. The rotational speed signal conditioning circuit includes an incremental signal conditioning circuit and an index signal conditioning circuit. The sine wave signal of the photoelectric encoder 5a and the incremental signal conditioning circuit A+, A - port is connected, impedance matching resistor R103 is connected between A+ and A- ports, both ends of impedance matching resistor R103 are connected to the two input terminals of operational amplifier U4A, resistor R101 and capacitor C56 are connected in parallel with each other and then connected to the inverse of operational amplifier U4A Between the phase input terminal and the output terminal, the output terminal of the operational amplifier U4A is connected to the non-inverting input terminal of the operational amplifier U5A, and the output terminal A of the operational amplifier U5A is connected to the PB1 port of the CPU; the index signal of the photoelectric encoder 5a is conditioned with the index signal The R+ and R- ports of the circuit are connected, and an impedance matching resistor R109 is connected between the R+ and R- ports. The two ends of the impedance matching resistor R109 are connected to the two input terminals of the operational amplifier U4C. The resistor R107 and the capacitor C61 are connected in parallel with each other. Between the inverting input terminal and the output terminal of the operational amplifier U4C, the output terminal of the operational amplifier U4C is connected to the non-inverting input terminal of the operational amplifier U5C, and the output terminal R of the operational amplifier U5C is connected to the PC1 port of the CPU.

Since the incoming flow direction of the wind turbine is always the same, the rotation direction of the blade remains unchanged under the incoming flow blowing, and there is no problem of judging forward and reverse rotation. Therefore, the photoelectric encoder 5a of the present invention takes the sine wave signal of phase A It is sent to the A+ and A- ports of the incremental signal conditioning circuit. Since the output signal of the photoelectric encoder is a sinusoidal differential signal, the sinusoidal differential signal must be de-differentiated first. The operational amplifier U4A is used to form a differential conditioning circuit. Resistor R101 and capacitor C56 is used as the feedback bridge arm of the differential circuit. A 120 ohm impedance matching resistor R103 needs to be connected between the A+ and A- ports to balance the signal voltage difference between A+ and A- during transmission; and then pass the RC low-pass filter composed of the resistor R104 and the capacitor C58 to the signal. Filter processing to remove high-frequency noise, and the sine wave signal range obtained after filtering processing is -1.5V to 1.5V. Since the control chip cannot identify negative signals, it is necessary to perform voltage offset processing on the signal, and in order to facilitate the processing of the signal by the CPU, the level of the sine wave signal needs to be adjusted; the output terminal of the operational amplifier U4A is connected to the non-inverting input terminal of the operational amplifier U5A. , use the operational amplifier U5A to form a comparison circuit, and process the positive offset of the voltage signal. The sine wave signal is compared with the +1.5V voltage signal through the operational amplifier U5A. When the voltage signal at the positive input terminal of U5A is greater than 1.5V, the output terminal of U5A outputs a high level of 3.3V, and the PB1 port of the CPU is at a high level. When the voltage signal of the positive input terminal of U5A is less than 1.5V, the output terminal of U5A outputs a low level of 0V, and the PB1 port of the CPU is at a low level. In the same way, when the output terminal R of the operational amplifier U5C outputs a high level to the PC1 port of the CPU, the index signal is triggered, so that the external interrupt input of the CPU connected to it triggers the reset of the counter. By calculating the pulse number of the incremental signal for one index signal period , calculate the real-time rotational speed of the wind turbine, and the CPU counts again to calculate the rotational speed of the wind turbine at the next moment.

As shown in Figure 10, the current signal conditioning circuit includes a sampling resistor R59 connected in series in the load loop. Both ends of the sampling resistor R59 are connected to the two input ends of the operational amplifier U1D respectively. The resistor R62 is connected to the non-inverting input terminal of the operational amplifier U1B, the capacitor C29 is connected between the resistor R62 and the analog ground VSSA, the capacitor C30 is connected between the resistor R61 and the output terminal of the operational amplifier U1B, and the output terminal of the operational amplifier U1B is connected to the operational amplifier U1B. The non-inverting input terminal of the amplifier U1A is connected, and the output terminal AOUT0 of the operational amplifier U1A is connected to the PA0 port of the CPU.

The sampling resistor R59 obtains a weak voltage signal from the load circuit, and the operational amplifier U1D is used as the first-stage reverse amplifier operational amplifier circuit, and the voltage signal is amplified by -6 times; the resistor R61 and the capacitor C30, and the resistor R62 and the capacitor C29 are enough to form two The second-order Butterworth low-pass filter circuit is formed by combining with the operational amplifier U1B; the operational amplifier U1A is used as the second-stage reverse amplification operational amplifier circuit, the voltage signal is amplified by -5 times, and the output terminal of the operational amplifier U1A AOUT0 transmits the analog voltage signal to the PA0 port of the CPU and converts it into a digital signal. Considering that the sampling accuracy directly affects the control performance of the entire system, the operational amplifier U1D, operational amplifier U1B and operational amplifier U1A all use LF347BN, and each resistor in the conditioning circuit uses precision resistors with an error within 1%. The selection of two-stage amplification for the current conditioning circuit can eliminate the multiple limit of single-stage amplification, increase the ability to suppress common mode signals, and avoid the circuit from falling into a series of problems such as self-excitation, high noise, and poor frequency response. The design range of the current signal conditioning circuit is 0-10A, and the voltage of the electrical connection with the CPU should be less than the maximum allowable voltage of the chip 3.3V. At the same time, considering the need to leave a margin, the sampling resistor R59 takes the value of 0.01 ohm, after two-stage amplification The amplitude of the analog voltage signal transmitted to the CPU is 3V. Compared with the current Hall sensor circuit, the current signal conditioning circuit of the present invention has a lower price and meets the accuracy requirements.

As shown in Figure 11, the PA11 port of the CPU is connected to the input terminal PWM-IN of the PWM drive circuit, the resistor R86 is connected in parallel with the capacitor C54 and then connected between the PWM-IN port and the base of the transistor Q1, and the resistor R84 is connected in parallel with the capacitor C53. It is then connected between the collector of the transistor Q1 and the base of the transistor Q2, the collector of the transistor Q2 is connected to the base of the input push-pull circuit, and the emitter of the input push-pull circuit is connected to the transformer T1 through the DC blocking capacitor C52. The primary side is connected, the secondary side of the transformer T1 is connected with the base of the output push-pull circuit through the displacement capacitor C51, and the emitter of the output push-pull circuit is connected with the solid-state relay-J1 control end.

In order to prevent oscillation and interference, the PWM signal output by the CPU needs to be transmitted in parallel through the resistor R86 and the capacitor C54, and the base voltage of the transistor Q2 is adjusted by the transistor Q1; similarly, the resistor R84 and the capacitor C53 are connected in parallel to further prevent oscillation and interference. The way can make the PWM output signal and the drive signal in phase. The push-pull circuit at the input end consists of a transistor Q3 and a transistor Q4, which are turned on and off alternately; the DC blocking capacitor C52 on the primary side of the transformer T1 can filter out the DC component in the signal. The energy is transferred to the secondary side of the transformer T1, and the displacement capacitor C51 on the secondary side of the transformer T1 is used to maintain the reset of the magnetic flux and maintain the volt-second balance, thereby achieving the purpose of demagnetization. Transistor Q5 and transistor Q6 form a push-pull circuit at the output end. The emitters of transistor Q5 and transistor Q6 are connected to the positive pole of the control terminal of solid state relay-J1 through the G+ port, and the collector of the transistor Q6 is connected to the negative pole of the control terminal of solid-state relay-J1 through the G- port. connect. When the PWM signal is at a high level, the control terminal of the solid-state relay-J1 is energized, the main contact is closed, and the load circuit is connected; when the PWM signal is at a low level, the control terminal of the solid-state relay-J1 is de-energized, and the main contact is disconnected. The load circuit is disconnected. At the same time, due to the inevitable existence of parasitic distributed inductance in the signal circuit, the voltage and current of the relay contacts cannot be changed abruptly at the moment of turn-on or turn-off, and the reverse recovery time is long under high-frequency operation, resulting in high voltage and high voltage. For the short-term overlap of current, four diodes D1, D2, D3, D4 are added to the secondary circuit of the transformer, that is, diodes are connected in series between the bases and collectors of the transistors Q5 and Q6 and the displacement capacitor C51 respectively to prevent switching. The signal malfunctions and damages the power device. The PWM drive circuit of the invention has less interference, less high-frequency noise, short switching time, low input power consumption, transformer isolation between the input circuit and the output circuit, and has the protection function and strong load capacity.

The output end of the three-phase full-bridge rectifier circuit 12 is connected to the braking resistor FX2 through the second solid-state relay J2, and an emergency braking button SA is connected in series with the control loop of the second solid-state relay J2. The braking resistor adopts cement resistor with good heat dissipation effect and high power. When the test is completed, or an accident occurs in the wind tunnel test or the power supply is suddenly interrupted, press the emergency braking button SA, and the braking resistor FX2 is connected to the three-phase asynchronous In the output circuit of generator 5, the braking resistor directly converts the regenerative electric energy during the rapid braking of the wind turbine into thermal energy, so that the electric energy will not be fed back to the AC measurement, causing the DC voltage to fluctuate, and at the same time, the wind turbine will be stopped suddenly, preventing The speed of the wind turbine causes mechanical damage, overcurrent damage to the power supply circuit, and overload damage to the torque meter and six-component balance used for the test, which can ensure the safety of the entire test.

The blade airfoil adopts the DTU-LN221 airfoil developed by the Technical University of Denmark. The number of blades is 3 and the chord length is 0.75m. 11 pressure measuring holes are arranged on the suction surface and the pressure surface at 60% of the spanwise length of the pressure measuring blade, and the coordinates of the leading edge point are defined as (0, 0). The distribution of each measuring point on the pressure measuring blade is shown in Figure 5. The coordinates of each measuring point are shown in Table 1:

After obtaining the pressure value of each measuring point, calculate the surface pressure coefficient of the wind turbine blade at different positions according to formula (a);

In formula (a), Num is the number of rotations of the wind turbine during the measurement, and an array Pul is defined. Pul(Num) is used to represent the starting position of the pressure data sequence of the Num-th circle of the wind turbine, and PD(i) is the wind turbine in the i-th cycle. The number of pressure data occupied by one revolution, the total number of revolutions of the wind turbine during measurement is recorded as NumEnd; b1Angle is the angle in the initial state of the blade, which is a positive value; qi is the incoming flow pressure, and int is a numerical value A function of rounding down, j is a positive integer from 1 to 23, representing 23 pressure taps, 1 to 11 represents 11 pressure taps on the suction surface, 12 represents a leading edge point, and a positive value from 13 to 23 Integer, indicating 11 pressure measuring holes on the pressure surface; p ₀ (j) is the zero-point pressure data of No. j under the condition that the wind turbine speed is zero and the wind speed is zero; k is a positive integer from 1 to 360, indicating In the 360-degree space direction in the plane, k takes the value of 0 in the vertical upward direction of the horizontal plane, and increases in turn clockwise; p(k,j) is the static pressure of the j pressure hole on the blade surface at the k position; Cp( k,j) is the pressure coefficient of the j pressure measuring hole on the blade surface at the k position.

FIG. 12 is a comparison diagram of experimental data of the surface pressure coefficient of the blade at the 0° position and the calculated data of the simulation software in the present invention. The wind turbine used in the experiment and numerical simulation has a chord length of 0.75m, a running speed of 800R/min, a forward wind speed of 8m/s, a dynamic pressure sensor sampling frequency of 5kHz, and an angle b1Angle of 169.7° in the initial state of the blade. During the actual measurement, the sampling time is 4s, and the wind turbine rotates 54 times. The ordinate is the pressure coefficient, and the abscissa is the percentage of the chord length of the measuring point to the total chord length. It can be seen from Figure 12 that the data obtained by using the measuring device of the present invention and the data obtained by using the Fluent numerical simulation software are relatively close.

FIG. 13 is a comparison diagram of the experimental data of the torque of the wind turbine and the calculation data of the simulation software according to the present invention. The test incoming wind speed is 8m/s, and the rotating speed is from 200r/min to 700r/min, and is measured once every 100r/min. As can be seen from Figure 6, the data obtained by the measuring device of the present invention and the calculation obtained by the Fluent numerical simulation software The data are relatively close.

The above descriptions are only preferred feasible embodiments of the present invention, and are not intended to limit the scope of the patent protection of the present invention. In addition to the above-described embodiments, the present invention may also have other embodiments. All technical solutions formed by equivalent replacement or equivalent transformation fall within the protection scope required by the present invention. The undescribed technical features of the present invention can be realized by or using the prior art, and are not repeated here.

Claims (9)

1. The utility model provides a miniwatt wind turbine aerodynamic characteristics measuring device suitable for wind tunnel test, includes the wind tunnel and is located the wind turbine in the wind tunnel, the wind turbine is including installing the wheel hub at fan shaft front end, install the blade on wheel hub's the circumference, fan shaft and wind tunnel coaxial line, its characterized in that: the middle section of the fan shaft is arranged in the bearing seat, the rear end of the fan shaft is connected with one end of a torquer through a first coupler, and the other end of the torquer is connected with a rotor shaft of the three-phase asynchronous generator through a second coupler; the bearing seat and the torquemeter are installed on a wind turbine base, the wind turbine base and the three-phase asynchronous generator are fixed on a common base, a gravity center point of the common base is arranged on a six-component balance, and the six-component balance is fixed at the top of a wind turbine support; the three-phase output end of the three-phase asynchronous generator is connected with the input end of a three-phase full-bridge rectifying circuit through an air switch and a fuse, and the output end of the three-phase full-bridge rectifying circuit is connected with a main loop filter capacitor bank and is connected with a load through a first solid-state relay; each blade is provided with a blade inner pore channel extending along the length direction of the blade, a certain blade is selected as a pressure measuring blade, a pressure measuring section is selected from the pressure measuring blade, the distance between the pressure measuring section and the axis of the fan shaft is L, L is 0.5-0.7R, and R is the turning radius of the blade; a plurality of pressure measuring holes are correspondingly arranged on the suction surface and the pressure surface of the pressure measuring blade, pressure measuring holes are also arranged at the front edge point of the junction of the suction surface and the pressure surface, the axis of each pressure measuring hole is positioned on the pressure measuring section, and a film pressure sensor is respectively embedded in each pressure measuring hole; a pressure data collector is fixed on the front end face of the hub, and a wireless communication device is fixed on the front end face of the pressure data collector; the signal wire of each film pressure sensor passes through the inner cavity of the hub along the inner pore canal of the blade and is respectively connected with the signal input end of a pressure data collector, and the pressure value of each measuring point collected by the pressure data collector is sent to an upper computer through the wireless communication device; square windows are respectively arranged on the suction surface and the pressure surface of the pressure measuring blade by taking the pressure measuring section as the center, square window plates are respectively covered in the square windows, the bottoms of the square window plates are respectively bonded on the blade body through glass cement, the outer surfaces of the square window plates are consistent with the shape of the blade in the area where the square window plates are located, and the abutted seams around the square window plates are filled by the glass cement until the surfaces of the square window plates are smooth; the pressure measuring holes are distributed on the center line of the square window plate; square luffer boards are formed by two big one little splices at self length direction, and the concatenation seam between two is on a parallel with square window's minor face, the length of little luffer boards is 1/12 ~ 1/8 of big luffer boards length.

2. The aerodynamic characteristic measurement device of the low-power wind turbine applicable to the wind tunnel test as claimed in claim 1, wherein: and a static pressure probe and a total pressure probe are arranged at a position 0.5 meter in front of the incoming flow direction of the wind turbine in the wind tunnel, the signal output ends of the static pressure probe and the total pressure probe are respectively connected with the wind pressure signal input end of an electronic pressure scanning valve, and the wind pressure signal output end of the electronic pressure scanning valve is connected with the wind pressure signal input end of a control system CPU.

3. The aerodynamic characteristic measurement device of the low-power wind turbine applicable to the wind tunnel test as claimed in claim 2, wherein: the signal output end of the torque meter is connected with the torque signal input end of the CPU through a torque signal communication circuit; the signal output end of the six-component balance is connected with the data signal input end of the CPU; the output end of the three-phase full-bridge rectifying circuit is provided with a current signal conditioning circuit, and the current signal output end of the current signal conditioning circuit is connected with the current signal input end of the CPU; the tail end of a rotor shaft of the three-phase asynchronous generator is provided with a photoelectric encoder, the signal output end of the photoelectric encoder is connected with the input end of a rotating speed signal conditioning circuit, and the output end of the rotating speed signal conditioning circuit is connected with the rotating speed signal input end of a CPU; the pulse width modulation signal output end of the CPU controls the on-off of the first solid-state relay through the PWM driving circuit; and the CPU is in bidirectional communication with the upper computer.

4. The aerodynamic characteristic measurement device of the low-power wind turbine applicable to the wind tunnel test as claimed in claim 3, wherein: the CPU adopts an STM32F103ZET6 module, a total pressure signal output end of the electronic pressure scanning valve is connected with a PC4 port of the CPU, and a static pressure signal output end of the electronic pressure scanning valve is connected with a PC5 port of the CPU; the current signal conditioning circuit comprises a sampling resistor R59 connected in series in a load circuit, two ends of the sampling resistor R59 are respectively connected with two input ends of an operational amplifier U1D, an output end of the operational amplifier U1D is connected with a non-inverting input end of an operational amplifier U1B through a resistor R61 and a resistor R62 which are mutually connected in series, a capacitor C29 is connected between the resistor R62 and an analog ground VSSA, a capacitor C30 is connected between the resistor R61 and an output end of the operational amplifier U1B, an output end of the operational amplifier U1B is connected with the non-inverting input end of the operational amplifier U1A, and an output end AOUT0 of the operational amplifier U1A is connected with a PA0 port of a CPU.

5. The aerodynamic characteristic measurement device of the low-power wind turbine applicable to the wind tunnel test as claimed in claim 4, wherein: the photoelectric encoder is an ERN1387 photoelectric encoder, the rotating speed signal conditioning circuit comprises an incremental signal conditioning circuit and an index signal conditioning circuit, sine wave signals of the photoelectric encoder are connected with A + and A-ports of the incremental signal conditioning circuit, an impedance matching resistor R103 is connected between the A + and A-ports, two ends of the impedance matching resistor R103 are connected with two input ends of an operational amplifier U4A, a resistor R101 and a capacitor C56 are connected between an inverting input end and an output end of the operational amplifier U4A after being connected in parallel, the output end of the operational amplifier U4A is connected with an inverting input end of the operational amplifier U5A, and the output end A of the operational amplifier U5A is connected with a PB1 port of the CPU; an index signal of the photoelectric encoder is connected with R + and R-ports of an index signal conditioning circuit, an impedance matching resistor R109 is connected between the R + and R-ports, two ends of the impedance matching resistor R109 are connected with two input ends of an operational amplifier U4C, a resistor R107 and a capacitor C61 are connected between an inverting input end and an output end of the operational amplifier U4C after being connected in parallel, an output end of the operational amplifier U4C is connected with a non-inverting input end of the operational amplifier U5C, and an output end R of the operational amplifier U5C is connected with a PC1 port of a CPU.

6. The aerodynamic characteristic measurement device of the low-power wind turbine applicable to the wind tunnel test as claimed in claim 4, wherein: the port PA11 of the CPU is connected with the input end PWN-IN of the PWM driving circuit, the resistor R86 is connected between the port PWN-IN and the base electrode of the triode Q1 after being connected with the capacitor C54 IN parallel, the resistor R84 is connected between the collector electrode of the triode Q1 and the base electrode of the triode Q2 after being connected with the capacitor C53 IN parallel, the collector electrode of the triode Q2 is connected with the base electrode of the input end push-pull circuit, the emitter electrode of the input end push-pull circuit is connected with the primary side of the transformer T1 through the blocking capacitor C52, the secondary side of the transformer T1 is connected with the base electrode of the output end push-pull circuit through the displacement capacitor C51, and the emitter electrode of the output.

7. The aerodynamic characteristic measurement device of the low-power wind turbine applicable to the wind tunnel test as claimed in claim 4, wherein: the torque signal communication circuit comprises a MAX3232C module and a MAX3485 module, wherein a signal output end of the torque meter is connected with the MAX3232C module and the MAX3485 module through a nine-pin serial port connector (DB1), an R1OUT port of the MAX3232C module and an RO port of the MAX3485 module are connected with a PA10 port of a CPU together, and a T1IN port of the MAX3232C module and a DI port of the MAX3485 module are connected with a PA9 port of the CPU together; the upper computer is electrically connected with the CPU by adopting a USB-to-TTL serial port module based on a PL2303HX chip, and a USB interface of the upper computer is electrically connected with a PD5 port and a PD6 port of the CPU.

8. The aerodynamic characteristic measurement device of the low-power wind turbine applicable to the wind tunnel test as claimed in claim 1, wherein: the output end of the three-phase full-bridge rectifying circuit is connected with a brake resistor through a second solid-state relay, and an emergency brake button is connected in series in a control loop of the second solid-state relay.

9. The aerodynamic characteristic measurement device of the low-power wind turbine suitable for the wind tunnel test according to any one of claims 1 to 8, wherein: the peripheries of the wireless communication device and the pressure data acquisition unit are covered with an oval air guide sleeve, and the root of the oval air guide sleeve is fixed on the front end face of the hub; the periphery of the rear end face of the hub is connected with a cylindrical shield, the cylindrical shield and the fan shaft are coaxial, and the coupler, the torque meter and the three-phase asynchronous generator are all positioned in an inner cavity of the cylindrical shield; the bearing pedestal is provided with an oil bath cavity, bearings for supporting the fan shaft are arranged at the front end and the rear end of the oil bath cavity respectively, and shaft seals are arranged on the outer sides of the two bearings respectively.

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