Method for measuring time constant of airflow temperature sensor based on laser positive step excitation

Abstract

The application discloses a kind of airflow temperature sensor time constant measurement method based on laser positive step excitation, belong to airflow temperature measurement field.The application implementation method is: in wind tunnel constructs normal temperature airflow under thermal equilibrium;Keep the airflow temperature sensor to be measured in the normal temperature airflow of fluid parameter that has been set reaches thermal equilibrium state, open laser, under normal temperature airflow, using continuous laser irradiation airflow temperature sensor's sensitive part, so that the airflow temperature sensor to be measured reaches new thermal equilibrium state, using data acquisition equipment collects the temperature-time response curve of airflow temperature sensor to be measured under laser positive step excitation;Equivalent airflow temperature model is constructed, and the airflow temperature sensor time constant under high-temperature airflow is obtained using the equivalent airflow temperature model, realizes the airflow temperature sensor time constant measurement under laser positive step excitation.The application does not need to heat flow field to high-temperature state, can reduce airflow temperature sensor time constant measurement cost.

Description

TECHNICAL FIELD

[0001] The application relates to a kind of airflow temperature sensor time constant measurement methods based on laser positive step excitation, belong to airflow temperature measurement technical field. BACKGROUND

[0002] In the aerospace industry, airflow temperature sensor is an important sensor, which is widely used in wind tunnel flow field test, aircraft engine performance evaluation and other fields. These measurement occasions often have high requirements for the dynamic characteristics of airflow sensor. Time constant is an important indicator to measure the dynamic characteristics of airflow temperature sensor.

[0003] When measuring the time constant of airflow temperature sensor, a dynamic temperature excitation needs to be provided for the sensor. According to the current "JJF 1049-1995 Temperature Sensor Dynamic Response Calibration" and "JJG (Military) 181-2019 Airflow Temperature Sensor (Dynamic)", the dynamic excitation source of ejection type can provide dynamic temperature excitation for airflow temperature sensor with time constant of 30 ms or more. When facing airflow temperature sensor with smaller time constant, the time constant measurement method using pulsed laser as excitation source is still in the laboratory research stage, and there is no unified standard in China. In the airflow environment, when the airflow temperature sensor is suddenly irradiated by pulsed laser, the sensor is affected by airflow heat and laser heating at the same time, and the rising edge of the temperature-time response curve cannot be directly fitted with the ideal first-order response curve to measure the time constant. Therefore, when using pulsed laser as excitation source in the laboratory, pulsed laser is usually used to irradiate the airflow temperature sensor to make it warm up, and then the time constant of the airflow temperature sensor is measured on the falling edge of the temperature-time response curve after the pulsed laser. However, this measurement method is based on negative step excitation of pulsed laser, and cannot completely reflect the dynamic characteristics of airflow temperature sensor, missing the time constant under positive step excitation.

[0004] In addition, the measurement of time constant of airflow temperature sensor needs to be carried out in high-speed and high-temperature airflow environment, which often requires huge investment to build a large hot wind tunnel, and also consumes a large amount of fuel and electricity, with high test cost. Especially when measuring the time constant under the condition of 2000K high temperature airflow, the technical difficulty and operating cost of the test make it difficult for researchers to accept.

[0005] In summary, whether to meet the complete evaluation requirements of the dynamic characteristics of airflow temperature sensor or to reduce the technical difficulty and operating cost of measurement, it is necessary to develop a new time constant measurement method. SUMMARY

[0006] In order to solve the problem that the time constant under the positive step excitation cannot be obtained in the prior art, the main purpose of the present application is to provide a gas flow temperature sensor time constant measurement method based on laser positive step excitation, high temperature state of the gas flow temperature sensor is realized through laser positive step excitation, the flow field does not need to be heated to the high temperature state, the gas flow temperature sensor is continuously irradiated by laser under the normal temperature gas flow, the equivalent time constant is measured through the rising edge of the temperature-time response curve, the equivalent temperature is obtained to obtain the gas flow temperature sensor time constant under the high temperature gas flow, the gas flow temperature sensor time constant measurement under the laser positive step excitation is realized, and the gas flow temperature sensor time constant measurement cost can be reduced.

[0007] The purpose of the present application is realized by the following technical solutions:

[0008] The gas flow temperature sensor time constant measurement method based on laser positive step excitation of the present application comprises the following steps:

[0009] Step one: build thermal equilibrium under normal temperature gas flow.

[0010] The to-be-measured gas flow temperature sensor is fixed on the test section of the wind tunnel, the sensing part is in the core area of the wind tunnel flow field, the wind tunnel is started, and the to-be-measured gas flow temperature sensor reaches the thermal equilibrium state in the normal temperature gas flow with the set fluid parameters.

[0011] Step two: continuous laser irradiation.

[0012] The to-be-measured gas flow temperature sensor is kept in the thermal equilibrium state in the normal temperature gas flow with the set fluid parameters in step one, the laser is started, the sensing part of the gas flow temperature sensor is irradiated by continuous laser, the to-be-measured gas flow temperature sensor reaches a new thermal equilibrium state, and the temperature-time response curve of the to-be-measured gas flow temperature sensor under the laser positive step excitation is collected by using the data acquisition equipment.

[0013] Step three: measure the equivalent time constant.

[0014] Based on the temperature-time response curve of the to-be-measured gas flow temperature sensor under the laser positive step excitation obtained in step two, the equivalent time constant τ of the to-be-measured gas flow temperature sensor is measured through the rising edge. e .

[0015] Step four: determine the equivalent temperature.

[0016] The equivalent gas flow temperature T of the to-be-measured gas flow temperature sensor is determined. g,e As shown in formula (1):

[0017]

[0018] In the formula, T gdenoted as the total temperature at which the airflow reaches thermal equilibrium, P is the power of the laser input to the sensing element of the airflow temperature sensor, h is the convective heat transfer coefficient between the sensing element of the airflow temperature sensor and the airflow at room temperature, and A is the surface area of ​​the sensing element of the airflow temperature sensor.

[0019] Step 5: Measure the time constant under high-temperature airflow.

[0020] The equivalent time constant τ obtained in step three e As a temperature sensor for the airflow to be measured, it is used in Mach number Ma and total temperature T. g,e The time constant τ in the high-temperature airflow is used to determine the time constant of the temperature sensor for the airflow to be measured.

[0021] Beneficial effects:

[0022] 1. The present invention provides a method for measuring the time constant of a gas flow temperature sensor based on laser positive step excitation, wherein an equivalent gas flow temperature model is constructed as shown in formula (1), and the time constant of the gas flow temperature sensor under laser positive step excitation is measured using the equivalent gas flow temperature model.

[0023] 2. The method for measuring the time constant of an airflow temperature sensor based on laser positive step excitation of the present invention achieves the high-temperature state of the airflow temperature sensor through laser positive step excitation. It can obtain the equivalent time constant of the airflow temperature sensor in high-temperature airflow without heating the flow field to a high temperature state, thereby significantly reducing the construction cost and operating expenses of wind tunnels and reducing the technical difficulty of research and development and measurement work. Attached Figure Description

[0024] Figure 1 This is a flowchart of the time constant measurement method for airflow temperature sensor based on laser positive step excitation of the present invention;

[0025] Figure 2 This is a schematic diagram of the measurement system structure of the airflow temperature sensor time constant measurement method based on laser positive step excitation of the present invention;

[0026] Among them: 1-wind tunnel, 2-temperature sensor of the airflow to be measured, 3-sensor, 4-laser, 5-test section, 6-data acquisition equipment. Detailed Implementation

[0027] To better illustrate the purpose and advantages of the present invention, the invention will be further described below in conjunction with the accompanying drawings and examples.

[0028] Example 1:

[0029] like Figure 1 As shown in the figure, this embodiment discloses a method for measuring the time constant of an airflow temperature sensor based on laser positive step excitation, which includes the following steps:

[0030] Step one: build the heat balance under normal temperature airflow.

[0031] The application background of this embodiment refers to JJF 1049-1995 Temperature Sensor Dynamic Response Calibration and JJG (Military) 181-2019 Airflow Temperature Sensor (Dynamic), as shown in Figure 2 The measured airflow temperature sensor 2 is fixed on the test section 5 of the wind tunnel 1, so that the sensing part 3 of the measured airflow temperature sensor 2 is in the core area of the wind tunnel flow field, the data acquisition equipment 6 is used to collect the output signal of the measured airflow temperature sensor 2, and the laser 4 aims at the sensing part 3 of the airflow temperature sensor 2.

[0032] Turn on the wind tunnel 1, and adjust the airflow of the test section 5 to Mach number Ma, total temperature T g .

[0033] The measured airflow temperature sensor 2 reaches a heat balance state after being placed in the normal temperature airflow of the wind tunnel 2 with Mach number Ma and total temperature T g for a period of time.

[0034] Step two: continuous laser irradiation.

[0035] Keep the airflow of the test section 5 at Mach number Ma and total temperature T g unchanged, turn on the laser 4, and use continuous laser irradiation on the sensing part 3 of the measured airflow temperature sensor 2. After a period of laser irradiation, the measured airflow temperature sensor 2 reaches a new heat balance state, and the temperature-time response curve of the measured airflow temperature sensor 2 under laser positive step excitation is collected using the data acquisition equipment 6.

[0036] Step three: measure the equivalent time constant.

[0037] Based on the temperature-time response curve of the measured airflow temperature sensor 2 under laser positive step excitation obtained in step two, the equivalent time constant τ e of the measured airflow temperature sensor 2 is measured by the rising edge.

[0038] Step four: determine the equivalent temperature.

[0039] The equivalent airflow temperature T g,e of the measured airflow temperature sensor is as shown in formula (1):

[0040]

[0041] In the formula, T gT is the total temperature of the normal temperature airflow reaching a thermal equilibrium state, P is the power of the laser input to the sensing part 3 of the airflow temperature sensor 2 to be measured, h is the convective heat transfer coefficient between the sensing part 3 of the airflow temperature sensor 2 to be measured and the normal temperature airflow, and A is the surface area of the sensing part 3 of the airflow temperature sensor 2 to be measured.

[0042] Step five: measure the time constant under the high temperature airflow.

[0043] The equivalent time constant τ obtained in step three is used to determine the time constant of the airflow temperature sensor 2 to be measured. e The time constant τ of the airflow temperature sensor 2 to be measured is determined as the time constant of the airflow temperature sensor 2 to be measured under the Mach number Ma, the total temperature T g,e of the high temperature airflow.

[0044] The airflow temperature sensor time constant measurement method based on the laser positive step excitation disclosed in the embodiment uses the equivalent temperature model, and the wind tunnel 1 only needs to provide a normal temperature airflow with a temperature of about 300K. g By adjusting the values of P, h and A, the equivalent temperature T g,e is equal to 2000K, and the time constant of the airflow temperature sensor 2 under the condition of a high temperature airflow of 2000K is measured, thereby greatly reducing the construction cost and operation cost of the wind tunnel 1 and reducing the technical difficulty of research and measurement work.

[0045] The above specific description further details the purpose, technical solution and beneficial effects of the application. It should be understood that the above description is only a specific embodiment of the application and is not used to limit the protection scope of the application. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the application should be included in the protection scope of the application.

Claims

1. A method for measuring the time constant of an airflow temperature sensor based on laser positive step excitation, characterized in that: Includes the following steps, Step 1: Establish thermal equilibrium under ambient temperature airflow; The airflow temperature sensor to be measured is fixed on the test section of the wind tunnel, with its sensing part located in the core region of the wind tunnel flow field. The wind tunnel is then turned on, and the airflow temperature sensor is subjected to Mach number Ma and total temperature T. g Achieving thermal equilibrium in a normal temperature airflow; Step 2: Irradiate with continuous laser light; Keep the airflow temperature sensor under test in a normal temperature airflow with the fluid parameters set in step one to reach thermal equilibrium. Turn on the laser and use continuous laser to irradiate the sensing part of the airflow temperature sensor to make the airflow temperature sensor under test reach a new thermal equilibrium state. Use data acquisition equipment to collect the temperature-time response curve of the airflow temperature sensor under test under laser positive step excitation. Step 3: Measure the equivalent time constant; Based on the temperature-time response curve of the airflow temperature sensor under laser positive step excitation obtained in step two, the equivalent time constant τ of the airflow temperature sensor is measured by measuring the rising edge. e ; Step 4: Determine the equivalent temperature; The equivalent airflow temperature T of the airflow temperature sensor to be measured g,e As shown in equation (1): In the formula, T g , where is the total temperature in the ambient airflow that reaches thermal equilibrium, P is the power of the laser input to the sensing part of the temperature sensor of the airflow under test, h is the convective heat transfer coefficient between the sensing part of the temperature sensor of the airflow under test and the ambient airflow, and A is the surface area of ​​the sensing part of the temperature sensor of the airflow under test. Step 5: Measure the time constant under high-temperature airflow; The equivalent time constant τ obtained in step three e As a temperature sensor for the airflow to be measured, it is used in Mach number Ma and total temperature T. g,e The time constant τ in the high-temperature airflow is used to determine the time constant of the airflow temperature sensor, thus realizing the measurement of the airflow temperature sensor time constant under laser positive step excitation.

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