A temporal and spatial co-location measurement method for temperature and wall shear stress

Abstract

The present invention provides a method for the simultaneous, spatiotemporal measurement of temperature and wall shear stress, relating to the field of intelligent sensing and measurement technology. The method comprises steps S1: calibrating the resistance temperature coefficient of a multilayer composite thermal film sensor to obtain the resistance temperature coefficients of the upper thermal temperature measurement unit and the lower wall shear stress thermal unit; S2: placing the multilayer composite thermal film sensor in a flat channel; S3: measuring the working resistance and working voltage according to a preset process and conducting a test; and S4: adjusting the temperature and wall shear stress of the fluid in the flat channel to obtain data on the fluid temperature, wall shear stress, the measured temperature of the upper thermal temperature measurement unit, and the output voltage of the lower wall shear stress thermal unit. This method enables the flexible thermal sensor to accurately measure temperature and fluid wall shear stress simultaneously and spatiotemporally.

Description

Technical Field

[0001] The present invention relates to the field of intelligent sensing measurement technology, and in particular to a method for measuring temperature and wall shear stress at the same point in time and space. Background Art

[0002] Temperature and wall shear stress are two important parameters in fluid dynamics measurement. In scientific research and engineering practice, both temperature and wall shear stress can be measured using hot-film sensors. This measurement is achieved by coupling the resistance-temperature characteristics of the hot-film sensor's sensitive unit in its non-heating state with the wall shear stress characteristics of forced convection heat transfer in its heating state. However, due to the temperature sensitivity of hot-film sensors, they are highly susceptible to temperature fluctuations when measuring wall shear stress, severely reducing the measurement accuracy of these sensors and hindering their widespread application.

[0003] Temperature compensation for flexible thermistors requires placing temperature sensors in the measured flow field to monitor the temperature of the fluid flowing through the heat-sensitive unit in real time. A temperature compensation algorithm then applies compensation based on the temperature-dependent changes in the sensor's output signal. To ensure the sensor's spatial resolution and accurate flow temperature measurement, the temperature sensor and the heat-sensitive unit must be kept very close. However, this close distance can affect the temperature sensor's measurement results due to the temperature of the heat-sensitive unit. Summary of the Invention

[0004] The problem solved by the present invention is how to realize the simultaneous and accurate measurement of temperature and fluid wall shear stress by a flexible thermal sensor.

[0005] To solve the above problems, the present invention provides a method for measuring temperature and wall shear stress at the same point in time and space, comprising the following steps:

[0006] S1: Calibrate the resistance temperature coefficient of the multi-layer composite thermal film sensor to obtain the resistance temperature coefficient of the upper thermal temperature measurement unit and the lower wall shear stress thermal unit respectively;

[0007] S2: placing the multi-layer composite thermal film sensor in the flat groove;

[0008] S3: Measure the working resistance and working voltage through the preset process and perform the test;

[0009] S4: By adjusting the temperature and wall shear stress of the fluid in the flat channel, data information of the fluid temperature, wall shear stress, the temperature measured by the upper thermal sensing unit, and the output voltage of the lower wall shear stress thermal sensing unit is obtained;

[0010] S5: Importing data information into an artificial neural network multilayer perceptron for training, and establishing a coupling relationship model among fluid temperature, wall shear stress, the temperature measured by the upper thermal sensing unit, and the output voltage of the lower wall shear stress thermal sensing unit;

[0011] S6: Import the coupling relationship model into the signal conditioning FPGA module and connect it to the test data acquisition card of the multi-layer composite thermal film sensor. Drive the multi-layer composite thermal film sensor according to step S3 to perform spatiotemporal co-location measurement of temperature and wall shear stress.

[0012] In this method, a multilayer composite thermal sensor is used to simulate the collaborative sensing mechanism of human skin. A coupled sensing signal is obtained by spatially stacking the temperature-sensitive and wall-shear-stress-sensitive units of the multilayer composite thermal sensor. A neural network algorithm is then used to decouple the two physical quantities. By integrating and applying multifunctional, co-located stacking of multilayer composite thermal film sensors under a constant temperature regime, the flexible thermal sensor achieves accurate simultaneous and spatial measurement of temperature and fluid wall shear stress.

[0013] Furthermore, step S3 includes:

[0014] S31: Connect the upper thermal temperature measuring unit to a digital desktop multimeter using a four-wire method to measure the working resistance;

[0015] S32: driving the lower wall shear stress thermosensitive unit using a constant temperature circuit and collecting the working voltage through a data acquisition card;

[0016] S33: The digital desktop multimeter and the data acquisition card are controlled by the synchronous trigger controller to perform synchronous testing.

[0017] Furthermore, the output temperature of the upper thermal sensitive temperature measuring unit in step S3 is:

[0018]

[0019] Among them, R wu Expressed as working resistance; R 20 Expressed as the resistance value of the thermal unit at 20°C; α 20 Expressed as the resistance temperature coefficient of the thermistor unit at 20°C.

[0020] Furthermore, in step S4, the fluid temperature and the fluid wall shear stress are transformed in the flat channel, and the test fluid temperature is measured by a platinum resistor; the along-line pressure of the channel test section is obtained by a pressure scanning valve and the along-line pressure gradient is calculated.

[0021] Furthermore, the wall shear stress is expressed as:

[0022]

[0023] Wherein, h represents the height of the flat channel; dp / dx represents the pressure gradient along the flat channel measured by the pressure scanning valve.

[0024] Furthermore, the upper thermal temperature measuring unit and the lower wall shear stress thermal measuring unit are spatially stacked.

[0025] The present invention adopts the above technical solution to achieve the following beneficial effects:

[0026] The present invention uses a method for measuring temperature and wall shear stress in the same time and space to train the output signals of the upper thermal temperature measurement unit and the lower wall shear stress thermal unit, along with the corresponding environmental parameters, to achieve spatiotemporal decoupling of the temperature and wall shear stress signals. This spatiotemporal co-location measurement method utilizes multi-layer composite thermal sensors to simulate the collaborative sensing mechanism of human skin. Through the co-location, multi-functional stacking and integration of multi-layer composite thermal film sensors under a constant temperature mechanism, the flexible thermal sensor can accurately measure temperature and fluid wall shear stress in both space and time. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 The process of the method for measuring the temperature and wall shear stress at the same time and space provided by the embodiment of the present invention Figure 1 ;

[0028] Figure 2 The process of the method for measuring the temperature and wall shear stress at the same time and space provided by the embodiment of the present invention Figure 2 ;

[0029] Figure 3 A schematic diagram of the structure of a multi-layer composite hot film sensor in the method for measuring temperature and wall shear stress at the same point in time and space provided by an embodiment of the present invention;

[0030] Figure 4 A schematic diagram of the system structure for performing spatiotemporal co-location measurement of local wall shear stress and fluid temperature in a flat channel flow using a multi-layer composite hot film sensor in the spatiotemporal co-location measurement method of temperature and wall shear stress provided by an embodiment of the present invention;

[0031] Figure 5 A schematic diagram of the structure of an artificial neural network multilayer perceptron in the temporal and spatial co-point measurement method of temperature and wall shear stress provided by an embodiment of the present invention;

[0032] Figure 6 A schematic diagram of the measurement results of the temperature at the same point in time and space in the method for measuring the temperature and wall shear stress at the same point in time and space provided by an embodiment of the present invention;

[0033] Figure 7A schematic diagram of the measurement results of the wall shear stress at the same time and space position in the method for measuring the temperature and wall shear stress at the same time and space position provided by an embodiment of the present invention; Description of the drawings:

[0035] 1-upper layer thermistor temperature measuring unit, 2-upper layer lead unit, 3-polyimide insulation layer, 4-lower layer wall shear stress thermistor unit, 5-lower layer lead unit, 6-polyimide substrate, 7-high pressure gas pipe, 8-air heater, 9-flow control valve, 10-flat channel inlet, 11-flat channel, 12-pressure scanning valve, 13-flat channel outlet, 14-digital desktop multimeter, 15-synchronous trigger controller, 16-data acquisition card, 17-FPGA module. DETAILED DESCRIPTION

[0036] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0037] The following are specific embodiments of the present invention and the accompanying drawings to further describe the technical solutions of the present invention, but the present invention is not limited to these embodiments.

[0038] Example

[0039] This embodiment provides a method for measuring temperature and wall shear stress at the same point in time and space, such as Figure 1 As shown, the method includes the steps of:

[0040] S1: Calibrate the resistance temperature coefficient of the multi-layer composite thermal film sensor to obtain the resistance temperature coefficient of the upper thermal temperature measurement unit and the lower wall shear stress thermal unit respectively;

[0041] S2: placing the multi-layer composite thermal film sensor in the flat groove;

[0042] S3: Measure the working resistance and working voltage through the preset process and perform the test;

[0043] S4: By adjusting the temperature and wall shear stress of the fluid in the flat channel, data information of the fluid temperature, wall shear stress, the temperature measured by the upper thermal sensing unit, and the output voltage of the lower wall shear stress thermal sensing unit is obtained;

[0044] S5: Importing data information into an artificial neural network multilayer perceptron for training, and establishing a coupling relationship model among fluid temperature, wall shear stress, the temperature measured by the upper thermal sensing unit, and the output voltage of the lower wall shear stress thermal sensing unit;

[0045] S6: Import the coupling relationship model into the signal conditioning FPGA module and connect it to the test data acquisition card of the multi-layer composite thermal film sensor. Drive the multi-layer composite thermal film sensor according to step S3 to perform spatiotemporal co-location measurement of temperature and wall shear stress.

[0046] See Figure 3 Specifically, the measuring device is a multi-layer composite thermal film sensor, which is manufactured using a micro-electromechanical system process and includes an upper thermal-sensitive temperature measurement unit 1, an upper lead unit 2, a polyimide insulating layer 3, a lower wall shear stress thermal-sensitive unit 4, a lower lead unit 5, and a polyimide substrate 6. The polyimide insulating layer 3 is provided on the polyimide substrate 6, and the upper thermal-sensitive temperature measurement unit 1, the upper lead unit 2, the lower wall shear stress thermal-sensitive unit 4, and the lower lead unit 5 are provided on the polyimide insulating layer 3. The upper thermal-sensitive temperature measurement unit 1 and the lower wall shear stress thermal-sensitive unit 4 are designed to be vertically stacked, and the upper lead unit 2 and the lower lead unit 5 are also designed to be stacked. The resistance values ​​of the upper thermal-sensitive temperature measurement unit 1 and the lower wall shear stress thermal-sensitive unit 4 change with temperature, and have the relationship: R = R 20 [1+α 20 (T-20)]; where R is the resistance value of the thermal unit at temperature T, R 20 is the resistance value of the thermal unit at 20°C, α 20 is the temperature coefficient of resistance (TCR) of the thermal unit at 20°C.

[0047] Specifically, during the measurement process, the upper thermal temperature measuring unit 1 is not driven to generate heat, and the lower wall shear stress thermal unit 4 is driven to control a constant temperature by a constant temperature circuit (CTA); the working resistance R wu The values ​​are collected, and the synchronous trigger controller 15 is used to control the output voltage collection of the lower wall shear stress thermistor unit 4, so as to achieve the time synchronization of the temperature and wall shear stress signals. At the same time, since the upper thermal temperature measuring unit 1 and the lower wall shear stress thermistor unit 4 are stacked in space, the synchronous measurement of the relevant physical quantities in space is also guaranteed.

[0048] Specifically, the spatially overlapping arrangement of measurement points results in a complex coupling relationship between the output signals of the upper thermal temperature measurement unit 1 and the lower wall shear stress thermal unit 4 and the measured physical quantity. Specifically, the lower constant-temperature wall shear stress thermal unit 4 transfers heat to the polyimide insulation layer 3 and the upper thermal temperature measurement unit 1, which is ultimately carried away by the fluid. This heat loss is related to the incoming flow temperature and the incoming flow wall shear stress. The upper thermal temperature measurement unit 1 itself does not generate heat, but instead senses the temperature transmitted from the lower wall shear stress thermal unit 4 and the incoming flow temperature. The output signals of both units are affected by the coupling of the incoming flow temperature and the fluid wall shear stress. An artificial intelligence learning method is used to train the output signals of the upper thermal temperature measurement unit 1 and the lower wall shear stress thermal unit 4, along with the corresponding environmental parameters, to simulate the working mechanism of human skin and achieve temporal and spatial co-location decoupling of the temperature and wall shear stress signals.

[0049] See Figure 2 , wherein step S3 includes:

[0050] S31: Connect the upper thermal temperature measuring unit to a digital desktop multimeter using a four-wire method to measure the working resistance;

[0051] S32: driving the lower wall shear stress thermosensitive unit using a constant temperature circuit and collecting the working voltage through a data acquisition card;

[0052] S33: The digital desktop multimeter and the data acquisition card are controlled by the synchronous trigger controller to perform synchronous testing.

[0053] See Figure 4 Specifically, the temperature coefficient of resistance (TCR) of the multi-layer composite thermal film sensor is calibrated, and the temperature coefficients of resistance of the upper thermal temperature measuring unit 1 and the lower wall shear stress thermal unit 4 are collected respectively. In this embodiment, the temperature coefficient of resistance of the upper thermal temperature measuring unit 1 at 20°C is 4564ppm / °C, and the temperature coefficient of resistance of the lower wall shear stress thermal unit at 20°C is 3614ppm / °C. The multi-layer composite thermal film sensor is attached flush to the wall of the flat groove 11 to be measured. The upper thermal temperature measuring unit 1 is connected to the digital desktop multimeter 14 according to the four-wire method to measure the working resistance R wu The lower wall shear stress thermistor unit 4 uses a constant temperature drive circuit to control the working heating temperature of 35 ℃ and is connected to the data acquisition card 16 to achieve the working voltage U wl using a synchronous trigger controller 15 to control the digital desktop multimeter 14 and the data acquisition card 16 to achieve synchronous testing.

[0054] Specifically, the high-pressure air pipe 7 is fed into the air heater 8, and the air heater 8 and the flow control valve 9 at the flat channel inlet 10 are adjusted to adjust the fluid temperature and fluid wall shear stress in the test section of the flat channel 11, and the excess air is discharged from the flat channel outlet 13. A platinum resistor is used to measure the temperature of the test fluid; a pressure scanning valve 12 is used to obtain the pressure along the test section of the flat channel 11 and calculate the pressure gradient along the process. By continuously changing the temperature of the fluid in the flat channel 11 and the inlet flow control valve 9, 1012 sets of fluid temperatures T are obtained. f , wall shear stress τ, upper thermal temperature measurement unit measured temperature T wu and the output voltage U of the lower wall shear stress thermal sensing unit 4 wl .

[0055] See Figure 5 , the collected data is imported into the artificial neural network multilayer perceptron (MLP) for training, and the fluid temperature T is established f , wall shear stress τ, upper thermal temperature measurement unit measured temperature T wu and the output voltage U of the lower wall shear stress thermal sensing unit 4 wl The coupling relationship model between them. In this embodiment, all measurement data are divided into a training set consisting of 700 samples and a test set consisting of 312 samples; MLP designs 3 hidden layers, with 8, 16 and 8 neurons respectively; the Relu function is used as the activation function, and the mean absolute error (MAE) is used as the loss function; and the Adam optimizer is used for training, wherein the hidden layer includes an input layer and an output layer, and the input layer and the output layer respectively include multiple neurons. The MLP training model is imported into the designed FPGA module 17 of the signal conditioning circuit. The FPGA module 17 of the signal conditioning circuit is connected to the test data acquisition card 16 of the multi-layer composite thermal film sensor, and the multi-layer composite thermal film sensor is driven again according to step S3 to realize the time-space co-point measurement of temperature and wall shear stress.

[0056] The output temperature of the upper thermal sensitive temperature measuring unit in step S3 is:

[0057]

[0058] Among them, R wu Expressed as working resistance; R 20 Expressed as the resistance value of the thermal unit at 20°C; α 20 Expressed as the resistance temperature coefficient of the thermistor unit at 20°C.

[0059] Among them, in step S4, the transformation of fluid temperature and fluid wall shear stress occurs in the flat channel, and the test fluid temperature is measured by a platinum resistor; the along-the-line pressure of the channel test section is obtained by a pressure scanning valve and the along-the-line pressure gradient is calculated.

[0060] The wall shear stress is expressed as:

[0061]

[0062] Wherein, h represents the height of the flat channel; dp / dx represents the pressure gradient along the flat channel measured by the pressure scanning valve.

[0063] Among them, the upper thermal temperature measuring unit and the lower wall shear stress thermal measuring unit are stacked in space.

[0064] See Figure 6 and Figure 7 Specifically, for a range of flat channel test conditions for ambient temperature and wall shear stress, the measurement results obtained under different test conditions using the above method steps show that the measurement errors of fluid temperature and wall shear stress in this embodiment are relatively small, both within 6%. Therefore, it can be seen that the method proposed in this method provides an effective means for the spatiotemporal co-location measurement of temperature and wall shear stress.

[0065] This method uses a spatiotemporal co-location measurement method for temperature and wall shear stress to train the output signals and corresponding environmental parameters of the upper thermal temperature measurement unit and the lower wall shear stress thermal unit to simulate the working mechanism of human skin and achieve spatiotemporal co-location decoupling of temperature and wall shear stress signals. This spatiotemporal co-location measurement method utilizes a multilayer composite thermal sensor to simulate the collaborative sensing mechanism of human skin. Coupled sensing signals are obtained by spatially stacking the temperature and wall shear stress sensing units of the multilayer composite thermal sensor, and a neural network is used to decouple the two physical quantities.

[0066] Although the present disclosure is disclosed as above, the protection scope of the present disclosure is not limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the present disclosure, and these changes and modifications will fall within the protection scope of the present invention.

Claims

1. A method for measuring temperature and wall shear stress at the same point in time and space, characterized in that: Including steps: S1: Calibrate the resistance temperature coefficient of the multi-layer composite thermal film sensor to obtain the resistance temperature coefficient of the upper thermal temperature measurement unit and the lower wall shear stress thermal unit respectively; S2: placing the multi-layer composite thermal film sensor in the flat groove; S3: Measure the working resistance and working voltage through the preset process and perform tests; including: S31: Connect the upper thermal temperature measuring unit to a digital desktop multimeter using a four-wire method to measure the working resistance; S32: driving the lower wall shear stress thermosensitive unit using a constant temperature circuit and collecting the working voltage through a data acquisition card; S33: Control the digital desktop multimeter and data acquisition card to perform synchronous testing through the synchronous trigger controller; S4: By adjusting the temperature and wall shear stress of the fluid in the flat channel, data information of the fluid temperature, wall shear stress, the temperature measured by the upper thermal sensing unit, and the output voltage of the lower wall shear stress thermal sensing unit is obtained; S5: Importing data information into an artificial neural network multilayer perceptron for training, and establishing a coupling relationship model among fluid temperature, wall shear stress, the temperature measured by the upper thermal sensing unit, and the output voltage of the lower wall shear stress thermal sensing unit; S6: Import the coupling relationship model into the signal conditioning FPGA module and connect it to the test data acquisition card of the multi-layer composite thermal film sensor. Drive the multi-layer composite thermal film sensor according to step S3 to perform spatiotemporal co-location measurement of temperature and wall shear stress.

2. The method for measuring temperature and wall shear stress at the same time and space position according to claim 1, characterized in that: The output temperature of the upper thermal sensitive temperature measuring unit in step S3 is: ； in, R wu Expressed as working resistance; R 20 Expressed as the resistance value of the thermal unit at 20°C; α 20 Expressed as the resistance temperature coefficient of the thermistor unit at 20°C.

3. The method for measuring temperature and wall shear stress at the same time and space position according to claim 1, characterized in that: In step S4, the fluid temperature and the fluid wall shear stress in the flat channel are transformed, and the test fluid temperature is measured by a platinum resistor; the pressure along the channel test section is obtained by a pressure scanning valve and the pressure gradient along the channel is calculated.

4. The method for measuring temperature and wall shear stress at the same time and space position according to claim 3, characterized in that: The wall shear stress is expressed as: ； in, h Expressed as the height of the flat channel; dp / dx It represents the pressure gradient along the flat channel measured by the pressure scanning valve.

5. The method for measuring temperature and wall shear stress at the same time and space position according to claim 1, characterized in that: The upper layer thermal sensitive temperature measuring unit and the lower layer wall shear stress thermal sensitive unit are spatially stacked.

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