Testing device and testing method for measuring critical freezing total temperature of freezing wind tunnel

Abstract

The invention belongs to the technical field of airplane anti-icing and deicing tests, and relates to a test device and a test method for measuring the critical freezing total temperature of an icing wind tunnel. According to the device, firstly, an icing detector is installed on a displacement adjusting device through a switching clamp, and a signal line is connected to an upper computer. And the probe of the icing detector is adjusted to a to-be-detected position through the displacement adjusting device. Starting a power system and a spraying system of the icing wind tunnel, adjusting parameters such as wind speed and spraying rake water pressure to be stable, starting a refrigerating system, reducing the total temperature of the icing wind tunnel, and recording a curve graph of total temperature time and frequency time; when the frequency value obviously changes, the total temperature at the corresponding moment is recorded; and removing accumulated ice on the probe, recovering the static temperature of the wind tunnel to be above 0 DEG C, repeating the test for three times, and taking an average value, namely the critical icing total temperature of the icing wind tunnel at the position. The device is reasonable in configuration, the detection method is easy and convenient to operate, the to-be-detected position can be accurately adjusted, the critical freezing total temperature is accurately obtained according to the test method, and the result is effective and reliable.

Description

Technical Field

[0001] This invention belongs to the field of aircraft anti-icing and de-icing test technology, and relates to a test device and test method for measuring the critical total icing temperature in an icing wind tunnel. Background Technology

[0002] Ice wind tunnel testing is a ground-based simulation test used to test icing and de-icing of aircraft flying in high-altitude icing environments. In ice wind tunnel icing tests, the total airflow temperature remains relatively constant from the stable section through the contraction section to the test section, but the static airflow temperature decreases with increasing wind speed. In the stable section, sprayed water droplets rapidly cool to the airflow temperature; in the middle of the contraction section, the decrease in airflow temperature causes a decrease in water droplet temperature, but due to the higher specific heat capacity of water droplets, the rate of temperature drop is less than that of air, and the temperature difference gradually increases with increasing distance; in the test section, the water droplet temperature further decreases, gradually approaching the airflow temperature, but a certain temperature difference still exists. Furthermore, at a constant wind speed, the maximum total temperature required for icing to occur at the icing site of the test specimen varies depending on its installation location and size / shape. Summary of the Invention

[0003] The purpose of this invention is to determine the total temperature at which water droplets in a test section are in a critical freezing state under certain wind speeds and icing locations during an icing wind tunnel test. Therefore, a test device and test method for measuring the critical freezing total temperature of an icing wind tunnel are proposed, providing a reference for the selection of test state points in an icing wind tunnel.

[0004] To solve this technical problem, the technical solution of the present invention is as follows: A test apparatus for measuring the critical total freezing temperature of an icing wind tunnel, comprising: The displacement adjustment device is installed on the Z-axis motion mechanism in the icing wind tunnel test section; The icing detector is mounted on the displacement adjustment device via an adapter clamp; The displacement adjustment device is used to drive the icing detector to move in the X / Y directions; The total temperature sensor is installed on the inner wall of the icing wind tunnel test section; The inner wall of the icing wind tunnel test section is equipped with wiring holes; the total temperature sensor and the icing detector are connected to the host computer through the wiring holes via wires.

[0005] A test method for measuring the critical total freezing temperature of an icing wind tunnel. Step 1: Adjust the icing detector to the position to be measured; Step 2: Set the icing wind tunnel test state point, turn on the power system and spray system to make the icing wind tunnel test section reach the test state point and stabilize; Step 3: Turn on the cooling system to lower the total temperature of the test section; record the total temperature over time curve on the host computer. Step 4: Record the frequency value output by the icing detector on the host computer and record the frequency-time curve. Step 5: When obvious icing appears on the icing detector or the frequency value output from the icing detector changes significantly, record the corresponding time t; Step 6: Find the total temperature W corresponding to time t on the total temperature-time curve; Step 7: Remove the ice buildup on the icing detector, restore the static temperature of the icing wind tunnel to above zero, repeat steps 3 to 6, and take the average value at least three times as the critical total icing temperature of the icing wind tunnel at the current test location and test point. Step 8: Repeat steps 1 to 7 to obtain the critical total icing temperature of the icing wind tunnel at different test locations and test conditions.

[0006] Furthermore, based on the range of the test position adjusted by the displacement adjustment device, four types of commonly used test positions can be measured: the first type is the typical icing position of the detector-type test piece (0mm, 240mm, 400mm); the second type is the typical icing position of the sidewall airfoil test piece (0mm, 240mm, 400mm); the third type is the typical icing position of the bottom detector test piece (100mm, 0mm, 200mm); and the fourth type is the typical icing position of the bottom airfoil test piece (100mm, 0mm, 200mm).

[0007] Furthermore, each test state point includes wind speed, liquid water content, and median particle diameter.

[0008] Furthermore, the test state points include:

[0009] These state points are derived from the aviation industry standard HB 20530-2018 "Airborne Aerodynamic Instrument Ice Wind Tunnel Test Method", and can be used for de-icing tests, anti-icing tests, sensitivity limit tests, continuous de-icing tests, and icing rate tests.

[0010] The remarks indicate the state point category, which is divided into the maximum continuous intensity and the maximum discontinuous intensity of atmospheric icing. The judgment criteria are derived from Appendix C of the CCAR-25-R4 transport category aircraft airworthiness standard.

[0011] Furthermore, the total temperature-time curve and the frequency-time curve are measured at intervals of Δt, with Δt ranging from less than or equal to 1000 ms, to ensure that the temperature acquisition interval is small enough to reflect temperature changes in real time.

[0012] Furthermore, the external circulating water temperature of the refrigeration system is set not lower than -10℃, the load of the refrigeration system cannot exceed 20%, the total temperature cooling rate v of the icing wind tunnel does not exceed 0.6℃ / min, which is equivalent to 0.01℃ / s, and the accuracy of the total temperature sensor is 0.01℃. 0.01℃ / s×1000ms≤0.01℃, that is, the actual temperature change per second is less than or equal to the temperature accuracy of the total temperature sensor.

[0013] Furthermore, when the icing wind tunnel test section is in a critical freezing state, the icing type is clear ice with a high degree of transparency. When the icing thickness on the icing detector exceeds 0.3 mm, the icing effect is more obvious and easy to distinguish. The frequency value output by the icing detector when it is not icing varies within the range of 40000±20Hz. If the frequency value exceeds this range, it indicates that icing has formed on the icing detector.

[0014] The beneficial effects of this invention are: Since the temperature change of water droplets in the contraction section lags behind that of the airflow, under conditions of high total temperature, water droplets may not be cooled enough near the contraction section of the test section. In order to determine the critical total temperature for icing of the test piece at different locations in the test section, the device and method of this invention can confirm the critical total temperature for icing at different locations in the wind tunnel test section. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the experimental setup for measuring the critical total icing temperature of an icing wind tunnel.

[0016] Figure 2 This is a schematic diagram of the experimental setup for measuring the critical total icing temperature in an icing wind tunnel.

[0017] Figure 3 This is a flowchart of measuring the critical total icing temperature using an experimental setup for a wind tunnel with a critical total icing temperature.

[0018] It includes a total temperature sensor 1, the inner wall of the test section tunnel 2, a displacement adjustment device 3, a transition plate 4, a mounting clamp 5, an icing detector transition plate 6, an icing detector 7, a waterproof signal line 8, and a host computer 9. The transition plate 4, the mounting clamp 5, and the icing detector transition plate 6 together form the adapter clamp. Detailed Implementation

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments: A test device for measuring the critical total freezing temperature of an icing wind tunnel consists of a total temperature sensor 1, the inner wall of the test section of the tunnel 2, a displacement adjustment device 3, a transition plate 4, a mounting fixture 5, an icing detector transition plate 6, an icing detector 7, a waterproof signal line 8, and a host computer 9.

[0020] The displacement adjustment device 3 consists of a dual-axis ball screw, a motor and its drive control system, a motor flange, a coupling, a slider panel, and a slide base plate. It can move in both the x and y axes. The motor is IP68 waterproof, completely preventing water ingress or long-term submersion. The slide base plate has two round countersunk holes for bolt fixing to two round-hole columns at the bottom of the inner wall 2 of the test section. The round-hole columns can adjust the z-axis displacement. The slider panel has four threaded holes for fixing the transition plate 4.

[0021] The transition plate 4 has four countersunk through holes, which are fixed to the slide base plate of the displacement adjustment device 3 by bolts. The transition plate 4 also has four threaded holes for connecting the mounting fixture 5. The four through holes at the bottom of the mounting fixture 5 are used to fix it on the transition plate 4. The top of the mounting fixture 5 has eight threaded holes, which are matched with the eight through holes on the icing detector transition plate 6 to install the icing detector transition plate 6 onto the mounting fixture 5. The icing detector transition plate 6 also has eight threaded holes, which are matched with the eight through holes on the icing detector 7 to install the icing detector 7 onto the icing detector transition plate 6.

[0022] The internal space of the mounting fixture 5 is used to accommodate and protect the connector of the waterproof signal line 8. The waterproof signal line 8 passes through the hole in the side wall of the mounting fixture 5, passes through the side wall of the inner wall 2 of the test section, and connects to the host computer 9.

[0023] The motor wire of the displacement adjustment device 3 passes through the inner wall 2 of the test section tunnel and is connected to the motor drive control system.

[0024] The host computer 9 determines whether the current position of the icing detector probe is under critical freezing conditions by receiving the frequency value measured in real time by the icing detector 7. This critical freezing condition can be determined by the icing frequency value.

[0025] During installation, first install the displacement adjustment device 3 on the circular column of the inner wall 2 of the test section tunnel. Install the transition plate 4 on the slider panel of the displacement adjustment device 3. Install the mounting clamp 5 on the transition plate 4. Install the icing detector transition plate 6 on the mounting clamp 5. Install the icing detector 7 on the icing detector transition plate 6. The waterproof signal line 8 and the signal line of the displacement adjustment device 3 pass through the side hole of the inner wall 2 of the test section tunnel. The waterproof signal line 8 is connected to the host computer 9 to ensure normal communication. The motor wire is connected to the host computer. Taking the bottom center of the test section as the origin, the position in the x and y directions is adjusted by the motor of the displacement adjustment device 3. The position in the z direction is adjusted by the lifting mechanism of the inner wall 2 of the test section tunnel. The probe of the icing detector 7 is adjusted to the first type of test position. The typical icing position of the detector-type test piece is (0mm, 240mm, 400mm).

[0026] The specific implementation steps for measuring the critical freezing point of this invention are as follows: Step 1: First, turn on the power system and spray system of the icing wind tunnel, and adjust the wind speed and spray rake water pressure to a stable level. The wind speed in the test section is set to 56.5 m / s, and the liquid water content and median particle diameter are 0.8 g / m. 3 And 12μm, then turn on the cooling system, set the external circulating water temperature of the cooling system to -10℃, reduce the total temperature of the icing wind tunnel at a rate of 0.6℃ per minute, so that the probe surface is as close to thermal equilibrium as possible, and record the curve of total temperature over time. Step 2: Simultaneously record the frequency value returned by the icing detector on the host computer. The initial frequency of the probe is 39998Hz. Observe the icing situation on the icing detector probe and record the corresponding frequency-time curve. Step 3: When the frequency value of the icing detector changes to 39975Hz, record the corresponding time 605s; Step 4: Use this moment to find the total temperature of 4.32℃ corresponding to the total temperature-time curve; Step 5: Remove the ice buildup on the probe, restore the wind tunnel static temperature to above zero, and repeat steps 1-4 to obtain the remaining total temperatures as 4.28℃ (39974Hz, 612s) and 4.23℃ (39972Hz, 602s). Take the average of the three total temperatures, 4.28℃, as the critical total icing temperature of the wind tunnel at this location.

Claims

1. A test apparatus for measuring the critical total freezing temperature of an icing wind tunnel, characterized in that: include: The displacement adjustment device is installed on the Z-axis motion mechanism in the icing wind tunnel test section; The icing detector is mounted on the displacement adjustment device via an adapter clamp; The displacement adjustment device is used to drive the icing detector to move in the X / Y directions; The total temperature sensor is installed on the inner wall of the icing wind tunnel test section; The inner wall of the icing wind tunnel test section is equipped with wiring holes; the total temperature sensor and the icing detector are connected to the host computer through the wiring holes via wires.

2. A test method for measuring the critical total freezing temperature of an icing wind tunnel, implemented based on the test apparatus described in claim 1; characterized in that: Step 1: Adjust the icing detector to the position to be measured; Step 2: Set the icing wind tunnel test state point, turn on the power system and spray system to make the icing wind tunnel test section reach the test state point and stabilize; Step 3: Turn on the cooling system to lower the total temperature of the test section; record the total temperature over time curve. Step 4: Record the frequency value output by the icing detector on the host computer and record the frequency-time curve. Step 5: When obvious icing appears on the icing detector or the frequency value output from the icing detector changes significantly, record the corresponding time t; Step 6: Find the total temperature W corresponding to time t on the total temperature-time curve; Step 7: Remove the ice buildup on the icing detector, restore the static temperature of the icing wind tunnel to above zero, repeat steps 3 to 6, and take the average value at least three times as the critical total icing temperature of the icing wind tunnel at the current test location and current test state point; Step 8: Repeat steps 1 to 7 to obtain the critical total icing temperature of the icing wind tunnel at different test locations and test conditions.

3. The method according to claim 2, characterized in that: With the center of the bottom of the test section as the origin and the windward direction as the positive x-axis, a right-hand rectangular coordinate system is established. The range of the test position to be adjusted by the displacement adjustment device is a cubic space range with x from -200mm to 400mm, y from -150mm to 250mm, and z from 150mm to 500mm.

4. The method according to claim 2, characterized in that: Each test state point includes wind speed, liquid water content, and median particle diameter.

5. The method according to claim 4, characterized in that: The test state points include: 。 6. The method according to claim 2, characterized in that: The total temperature-time curve and the frequency-time curve are measured at intervals of Δt, with Δt ranging from less than or equal to 1000 ms, to ensure that the temperature acquisition interval is small enough to reflect temperature changes in real time.

7. The method according to claim 2, characterized in that: The external circulating water temperature of the refrigeration system shall be set not lower than -10℃, the load of the refrigeration system shall not exceed 20%, and the total temperature drop rate of the icing wind tunnel shall not exceed 0.6℃ / min, which is equivalent to 0.01℃ / s.

8. The method according to claim 2, characterized in that: When the ice thickness on the icing detector exceeds 0.3 mm, it is considered significant icing; when the frequency value output by the icing detector changes by more than 20 Hz, it is considered a significant change.

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