Gust flow field calibration method based on hot-wire probe

Abstract

The invention discloses a gust flow field calibration method based on a hot-wire probe, relates to the technical field of intelligent sensors, and solves the technical problem that a traditional gust flow field calibration method is low in frequency response, poor in precision and large in probe size, so that flow field interference is remarkable. The probe is subjected to calibration, data decomposition and error analysis, and finally gust amplitude data is obtained. According to the test method disclosed by the invention, the geometric dimension of the adopted probe is small, the interference on a space flow field is small, the spatial resolution is high, and the calibration accuracy and the frequency response range are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of intelligent sensors, and in particular to a gust flow field calibration method based on a hot wire probe. Background Art

[0002] Gusts are strong, deterministic wind disturbances in the atmosphere. When an aircraft encounters a gust, the airframe generates additional unsteady aerodynamic forces and moments, which adversely affect the aircraft's flight performance. Modern civil aircraft, such as large passenger aircraft, emphasize economy, comfort, safety, and reliability, requiring high aerodynamic efficiency and low structural weight. They typically employ high-aspect-ratio wings and extensive use of composite materials. The wings are also highly flexible, making them more sensitive to gusts. Gust loads, especially vertical discrete gust loads, often become the most severe flight loads. When an aircraft encounters unsteady aerodynamic loads from low to medium-intensity gusts, it can cause turbulence, create tension for passengers, reduce comfort, and even cause personal injury. When an aircraft encounters high-intensity unsteady aerodynamic loads, the aircraft's local overload can reach over 2.5g, which can damage the aircraft structure or cause fatigue cracks, shortening the aircraft's service life and significantly impacting its safety and reliability. Civil aircraft are extremely sensitive to fatigue damage caused by gust loads, and the gust load spectrum is an important scientific basis for the design of aircraft structural life reliability. Due to gust load issues, to ensure aircraft strength, the aircraft structure needs to be strengthened, resulting in increased aircraft weight and, in turn, impacting the aircraft's economic efficiency.

[0003] Domestic and international civil aircraft airworthiness regulations clearly define gust loads. Both China's transport aircraft airworthiness standards (CCAR-25-R4) and the US Aviation Administration regulations (FAR-25) provide specific guidelines for gust load design. Accurately predicting gust loads is a crucial task during the aircraft design phase.

[0004] Experimental research on gust load mitigation is mainly carried out in wind tunnels, which requires calibration of the gust flow field formed in the wind tunnel in order to understand the amplitude and frequency characteristics of the gust flow field.

[0005] At present, due to the increasing aspect ratio of aircraft and the extensive application of composite materials, the gust flow field frequency and incoming wind speed that need to be measured are both relatively high. Five-hole probes, laser Doppler velocimeters, particle imaging velocimetry, etc. are often used in wind tunnels to calibrate the gust flow field. These measurement methods have complex systems, low measurement accuracy, and low frequency response, and are difficult to meet the requirements. In addition, in order to obtain the distribution of newly developed gust generators along the span direction of the wind tunnel, multiple measurement sensors need to be used simultaneously for gust field calibration. If a five-hole probe is used for calibration, due to its complex system and large size, it will affect the measurement results of the gust flow field. Summary of the Invention

[0006] To address the technical issues of low frequency response, poor accuracy, and significant flow field interference caused by large probe volume in conventional gust flow field calibration methods, the present invention provides a gust flow field calibration method based on a hot wire probe, comprising:

[0007] S1: Install the X-shaped hot wire probe on the support frame and place it in the wind tunnel measurement position. Adjust the probe pitch and sideslip angles to be less than 5'. Set the superheat ratio parameters and perform bridge leveling.

[0008] S2: Based on the probe state set in S1, with the gust generator blades in the horizontal state, the probe support is rotated ±45° to make the single tungsten wire perpendicular to the incoming flow direction, the incoming flow velocity is adjusted, the calibration point data is collected, and the calibration curve is fitted;

[0009] S3: Perform data acquisition and apply the calibration curve of S2 to resolve the real-time output voltage into axial velocity and vertical velocity;

[0010] S4: Perform error analysis on the axial velocity and vertical velocity of S3. If the data passes the error analysis, it is marked as valid data and enters S5. If the error analysis fails, return to the wind tunnel flow field generation link to reset the gust generator parameters and re-execute S3.

[0011] S5: Calculate the gust speed amplitude based on the valid data of S4.

[0012] Furthermore, in S1, the superheat ratio parameters are set and the bridge leveling is performed as follows:

[0013] S1.1: Control the hot wire operating temperature by setting the hot wire probe and the resistance temperature coefficient of the hot wire probe. The hot wire operating temperature is controlled by:

[0014]

[0015] Obtain, among which, is the hot wire working temperature, the hot wire probe overheat ratio The resistance temperature coefficient of the hot wire probe is 1.4. is 0.00482;

[0016] S1.2: Place the hot wire probe in the maximum wind speed environment of the calibration device and confirm that the output voltage does not exceed the limit;

[0017] S1.3: Start the simulated turbulence signal device and apply a 500 Hz square wave signal to the top of the bridge;

[0018] S1.4: Adjust the bridge balance value and observe the oscilloscope output simultaneously. When the output waveform matches the square wave signal and the oscillation recovery after the disturbance is ≤2 times, the leveling is determined to be complete.

[0019] S1.5: Turn off the simulated turbulence signal and lock the balance parameters.

[0020] Furthermore, in S2, the calibration curve is obtained by:

[0021]

[0022] obtain, among which is the actual wind speed, is the output voltage of the hot wire anemometer, is the correction coefficient, which is set to 1 during calibration. is the calibration coefficient of the quartic curve.

[0023] Furthermore, in S3, the calibration curve of S2 is applied to resolve the real-time output voltage into axial velocity and vertical velocity as follows:

[0024] S3.1: Calculate the speed corresponding to the output voltage of the two tungsten filaments;

[0025] The speed sensed by tungsten filament 1 is:

[0026] ]

[0027] Obtain, among which, is the velocity sensed by the tungsten wire 1, k is the sensitivity of the tungsten wire to the flow parallel to the tungsten wire, is the angle between the incoming flow and the tungsten wire 1;

[0028] Tungsten 2 senses the speed through

[0029] ]

[0030] Obtain, among which, is the speed sensed by tungsten wire 2, is the angle between tungsten wire 1 and tungsten wire 2 in the XY plane;

[0031] S3.2: Calculate the velocity components to obtain the velocity components of tungsten wire 1 and tungsten wire 2;

[0032] The velocity component of tungsten wire 1 is:

[0033]

[0034] Obtain, among which, is the velocity component of tungsten wire 1;

[0035] The velocity component of tungsten wire 2 is given by:

[0036]

[0037] Obtain, among which is the velocity component of tungsten wire 2;

[0038] S3.3: Calculate the axial velocity and vertical velocity. The axial velocity is calculated by:

[0039]

[0040] Obtain, among which is the axial velocity;

[0041] Verticality via:

[0042]

[0043] Obtain, among which, is the vertical speed.

[0044] Furthermore, it is characterized in that, in S4, the error analysis includes: analytical error determination, statistical error control and condition change error suppression.

[0045] Furthermore, in S5, the gust velocity amplitude is calculated by:

[0046]

[0047]

[0048] Obtain, among which, is the blade swing amplitude, is the maximum swing amplitude of the blade, is the blade swing frequency, is the vertical velocity of each point in the gust flow field, is the gust speed amplitude, is the gust frequency.

[0049] Beneficial effects of the present invention: The present invention significantly improves the accuracy and frequency response range of gust flow field calibration by optimizing the high-frequency response capability of the hot wire probe, innovating the dual-wire calibration and decoupling algorithm, reducing the probe volume to reduce flow field interference, and establishing a closed-loop error control mechanism, thereby providing high-reliability data support for the airworthiness certification of aircraft gust loads. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 It is a schematic diagram of the overall process of the present invention.

[0051] Figure 2 Data calibration curve.

[0052] Figure 3 The angle between the hot wire probe and the incoming flow.

[0053] Figure 4 The angle between the tungsten wire and the incoming flow.

[0054] Figure 5 The curve of tungsten filament output voltage changing with the angle between the incoming current and the probe.

[0055] Figure 6 Regional distribution of data analysis errors.

[0056] Figure 7 Time domain curve of gust flow field.

[0057] Figure 8 Frequency domain curve of gust flow field. DETAILED DESCRIPTION

[0058] The technical solution of the present invention is further described below with reference to the embodiments, but is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention shall be included in the scope of protection of the present invention. The process equipment or devices not specifically noted in the following examples are all conventional equipment or devices in the art. Unless otherwise specified, the raw materials used in the examples of the present invention can be obtained commercially; unless otherwise specified, the technical means used in the examples of the present invention are all conventional means well known to those skilled in the art.

[0059] Example 1, a gust flow field calibration method based on a hot wire probe, comprising:

[0060] S1: Install the X-shaped hot wire probe on the support frame and place it in the wind tunnel measurement position. Adjust the probe's pitch and sideslip angles to be less than 5'. Set the superheat ratio parameters and perform bridge leveling.

[0061] S2: Based on the probe state set in S1, with the gust generator blades in the horizontal state, the probe support is rotated ±45° to make the single tungsten wire perpendicular to the incoming flow direction, the incoming flow velocity is adjusted, the calibration point data is collected, and the calibration curve is fitted;

[0062] S3: Perform data acquisition and apply the calibration curve of S2 to resolve the real-time output voltage into axial velocity and vertical velocity;

[0063] S4: Perform error analysis on the axial velocity and vertical velocity of S3. If the data passes the error analysis, it is marked as valid data and enters S5. If the error analysis fails, return to the wind tunnel flow field generation link to reset the gust generator parameters and re-execute S3.

[0064] S5: Calculate the gust speed amplitude based on the valid data of S4.

[0065] Specific, combined Figure 1It can be seen that the present invention is based on the high-frequency response characteristics of the X-type hot wire probe, establishes a wind speed-voltage mapping relationship through bridge leveling and orthogonal calibration, analyzes the axial and vertical velocity components in real time, and dynamically verifies the data based on the error control mechanism, ultimately ensuring the gust speed amplitude and providing core data support for the airworthiness certification of aircraft gust loads.

[0066] In S1, set the superheat ratio parameters and perform bridge leveling as follows:

[0067] S1.1: Control the hot wire operating temperature by setting the hot wire probe and the resistance temperature coefficient of the hot wire probe. The hot wire operating temperature is controlled by:

[0068]

[0069] Obtain, among which, is the hot wire working temperature, the hot wire probe overheat ratio The resistance temperature coefficient of the hot wire probe is 1.4. is 0.00482;

[0070] S1.2: Place the hot wire probe in the maximum wind speed environment of the calibration device and confirm that the output voltage does not exceed the limit;

[0071] S1.3: Start the simulated turbulence signal device and apply a 500 Hz square wave signal to the top of the bridge;

[0072] S1.4: Adjust the bridge balance value and observe the oscilloscope output simultaneously. When the output waveform matches the square wave signal and the oscillation recovery after the disturbance is ≤2 times, the leveling is determined to be complete.

[0073] S1.5: Turn off the simulated turbulence signal and lock the balance parameters.

[0074] In S2, the calibration curve is obtained by:

[0075]

[0076] obtain, among which is the actual wind speed, is the output voltage of the hot wire anemometer, is the correction coefficient, which is set to 1 during calibration. is the calibration coefficient of the quartic curve.

[0077] Specifically, Figure 2 Display the calibration curve by Figure 2 It can be seen that the fourth-order polynomial fitting relationship between the hot wire voltage (horizontal axis) and the actual wind speed (vertical axis) provides a benchmark mapping for speed analysis.

[0078] Figure 3The angle φ formed by the horizontal flow and the probe support after rotating ±45° is shown, visualizing the positioning principle of a single tungsten wire perpendicular to the flow.

[0079] In S3, the calibration curve of S2 is applied to resolve the real-time output voltage into axial velocity and vertical velocity:

[0080] S3.1: Calculate the speed corresponding to the output voltage of the two tungsten filaments;

[0081] The speed sensed by tungsten filament 1 is:

[0082] ]

[0083] Obtain, among which, is the velocity sensed by the tungsten wire 1, k is the sensitivity of the tungsten wire to the flow parallel to the tungsten wire, is the angle between the incoming flow and the tungsten wire 1;

[0084] Tungsten 2 senses the speed through

[0085] ]

[0086] Obtain, among which, is the speed sensed by tungsten wire 2, is the angle between tungsten wire 1 and tungsten wire 2 in the XY plane;

[0087] S3.2: Calculate the velocity components to obtain the velocity components of tungsten wire 1 and tungsten wire 2;

[0088] The velocity component of tungsten wire 1 is:

[0089]

[0090] Obtain, among which, is the velocity component of tungsten wire 1;

[0091] The velocity component of tungsten wire 2 is given by:

[0092]

[0093] Obtain, among which is the velocity component of tungsten wire 2;

[0094] S3.3: Calculate the axial velocity and vertical velocity. The axial velocity is calculated by:

[0095]

[0096] Obtain, among which is the axial velocity;

[0097] Vertical speed via:

[0098]

[0099] Obtain, among which, is the vertical speed.

[0100] Specifically, Figure 4 Shows two orthogonal tungsten wires and their angle , showing the spatial relationship between the incoming flow direction and the probe.

[0101] Figure 5 The voltage-angle response curve shows the change of the dual-wire voltage with the rotation angle of the probe.

[0102] It is characterized in that, in S4, the error analysis includes: analytical error determination, statistical error control and condition change error suppression.

[0103] Specifically, 1. Analytical error. Any calibration method will have errors. When using hot wires to measure gust flow fields, various influences will form errors in the results. Therefore, the size of the error can be estimated through principles and empirical formulas, and the results that produce errors can be corrected. Because the turbulence of the gust flow field after the blades swing when the generator is working is very large, the incoming flow direction may not be within the angle between the two tungsten wires when using hot wires to measure the gust flow field. At this time, the output result of the hot wire will have a large deviation, which is usually called analytical error. It is necessary to estimate the size of the analytical error that may occur during the experiment. The measured results will be plotted and A distribution graph is created, and an acceptable region is plotted within the graph, defined as the area between the two lines shown below. If a significant portion of the measurement points fall outside the acceptable region, the measurement contains a significant amount of data that cannot be correctly interpreted by the "X" hotline, resulting in a large interpretation error. If the vast majority of the measurement points fall within the acceptable region, the interpretation error is minimal and can be ignored.

[0104]

[0105]

[0106] For example, in a test of measuring gust flow fields, the streamwise velocity is much greater than the vertical velocity, so all the data are within the acceptable range. It can be considered that there is no analytical error problem in the gust field measured this time.

[0107] 2. Statistical Error

[0108] Since the turbulence in the gust flow field changes greatly with time, statistical errors will occur when the total measurement time T is short and the number of sampling points is small. Generally, the measurement time is set to more than 100s, the sampling frequency is 100Hz, and the total number of sampling points N is greater than 10000. Therefore, the statistical error ε can be estimated as ε≈1 / <0.01, that is, the error caused by the total measurement time is less than 1%, which meets the measurement and use requirements.

[0109] 3. Condition change error

[0110] When actual measurement conditions differ from those used during calibration, significant measurement errors can occur. Conditions that can affect measurement results include fluid conditions (temperature, density, humidity, etc.) and the degree of surface oxidation on the hot-wire probe itself. Therefore, hot-wire measurements generally require careful observation and waiting for stable results, or minimizing the time between calibration and measurement to minimize the amount of variation in conditions.

[0111] Figure 6 pass - The scatter distribution verifies the S4 analytical error criterion. The measured data points are concentrated in the diamond area surrounded by two straight lines, proving that when the dual-channel voltage signal meets the geometric constraint, the velocity analytical error can be ignored.

[0112] In S5, the gust velocity amplitude is calculated by:

[0113]

[0114]

[0115] Obtain, among which, is the blade swing amplitude, is the maximum swing amplitude of the blade, is the blade swing frequency, is the vertical velocity of each point in the gust flow field, is the gust speed amplitude, is the gust frequency.

[0116] Specifically, Figure 7 The periodic time-domain fluctuations of the vertical velocity are demonstrated, directly proving the calculation logic of the gust amplitude. Figure 8 This reflects the core method for extracting the gust frequency f and highlights the frequency band where energy is concentrated.

Claims

1. A gust flow field calibration method based on a hot wire probe, characterized in that: include: S1: Install the X-shaped hot wire probe on the support frame and place it in the wind tunnel measurement position. Adjust the probe pitch and sideslip angles to be less than 5'. Set the superheat ratio parameters and perform bridge leveling. S2: Based on the probe state set in S1, with the gust generator blades in the horizontal state, the probe support is rotated ±45° to make the single tungsten wire perpendicular to the incoming flow direction, the incoming flow velocity is adjusted, the calibration point data is collected, and the calibration curve is fitted; S3: Perform data acquisition and apply the calibration curve of S2 to resolve the real-time output voltage into axial velocity and vertical velocity; S4: Perform error analysis on the axial velocity and vertical velocity of S3. If the data passes the error analysis, it is marked as valid data and enters S5. If the error analysis fails, return to the wind tunnel flow field generation link to reset the gust generator parameters and re-execute S3. S5: Calculate the gust speed amplitude based on the valid data of S4.

2. The gust flow field calibration method based on a hot wire probe according to claim 1, characterized in that: In S1, set the superheat ratio parameters and perform bridge leveling as follows: S1.1: Control the hot wire operating temperature by setting the hot wire probe and the resistance temperature coefficient of the hot wire probe. The hot wire operating temperature is controlled by: Obtain, among which, is the hot wire working temperature, the hot wire probe overheat ratio The resistance temperature coefficient of the hot wire probe is 1.

4. is 0.00482; S1.2: Place the hot wire probe in the maximum wind speed environment of the calibration device and confirm that the output voltage does not exceed the limit; S1.3: Start the simulated turbulence signal device and apply a 500 Hz square wave signal to the top of the bridge; S1.4: Adjust the bridge balance value and observe the oscilloscope output simultaneously. When the output waveform matches the square wave signal and the oscillation recovery after the disturbance is ≤2 times, the leveling is determined to be complete. S1.5: Turn off the simulated turbulence signal and lock the balance parameters.

3. The method for calibrating gust flow field based on a hot wire probe according to claim 1, characterized in that: In S2, the calibration curve is obtained by: obtain, among which is the actual wind speed, is the output voltage of the hot wire anemometer, is the correction coefficient, which is set to 1 during calibration. is the calibration coefficient of the quartic curve.

4. The method for calibrating gust flow field based on a hot wire probe according to claim 1, characterized in that: In S3, the calibration curve of S2 is applied to resolve the real-time output voltage into axial velocity and vertical velocity: S3.1: Calculate the speed corresponding to the output voltage of the two tungsten filaments; The speed sensed by tungsten filament 1 is: ] Obtain, among which, is the velocity sensed by the tungsten wire 1, k is the sensitivity of the tungsten wire to the flow parallel to the tungsten wire, is the angle between the incoming flow and the tungsten wire 1; Tungsten 2 senses the speed through ] Obtain, among which, is the speed sensed by tungsten wire 2, is the angle between tungsten wire 1 and tungsten wire 2 in the XY plane; S3.2: Calculate the velocity components to obtain the velocity components of tungsten wire 1 and tungsten wire 2; The velocity component of tungsten wire 1 is: Obtain, among which, is the velocity component of tungsten wire 1; The velocity component of tungsten wire 2 is given by: Obtain, among which is the velocity component of tungsten wire 2; S3.3: Calculate the axial velocity and vertical velocity. The axial velocity is calculated by: Obtain, among which is the axial velocity; Vertical speed via: Obtain, among which, is the vertical speed.

5. The method for calibrating gust flow field based on a hot wire probe according to claim 1, characterized in that: In S4, error analysis includes: analytical error determination, statistical error control and condition change error suppression.

6. The method for calibrating gust flow field based on a hot wire probe according to claim 1, characterized in that: In S5, the gust velocity amplitude is calculated by: Obtain, among which, is the blade swing amplitude, is the maximum swing amplitude of the blade, is the blade swing frequency, is the vertical velocity of each point in the gust flow field, is the gust speed amplitude, is the gust frequency.

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