Airflow small temperature rise high-precision receiving part calibration device

Abstract

The application discloses a kind of airflow small temperature rise high-precision receiving part calibration device, belong to airflow temperature measurement field.The application includes heating section, rectifier section, stable section, convergent section, test section;Each part is sequentially connected in head-to-tail to form wind tunnel, and outer surface is applied with heat preservation layer;Reference airflow temperature sensor is placed in stable section, and the temperature field and velocity field in stable section are uniform and stable, provide favorable conditions for high-precision temperature measurement of reference airflow temperature sensor, and then improve the calibration accuracy of receiving part;Calibration airflow temperature sensor is placed in test section;Total pressure sensor, atmospheric pressure sensor are connected with pressure detector;By setting surface temperature sensor and atmospheric temperature sensor, the airflow temperature drop value caused by heat dissipation is monitored and compensated, the airflow temperature standard value is obtained after removing the airflow temperature drop value caused by heat dissipation, and is used for temperature deviation calibration of calibration airflow temperature sensor.The application has the advantages of small calibration uncertainty.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of airflow temperature measurement, and relates to a calibration device for an airflow temperature sensor. BACKGROUND

[0002] In the fields of national defense science and technology such as aviation, aerospace, weapons and ships, airflow temperature is an important test parameter for measuring the performance of whole machines or components such as aero-engines and gas turbines. In order to ensure the accuracy of the airflow temperature sensor, it is usually necessary to calibrate it. At present, according to the "JJF (military) 73-2014 Airflow Temperature Sensor Steady-state Calibration Specification", when calibrating the temperature measurement deviation of the airflow temperature sensor, the reference airflow temperature sensor and the calibrated airflow temperature sensor need to be placed in the test section of the hot wind tunnel at the same time, and the temperature measurement deviation of the calibrated airflow temperature sensor is calibrated by the reference airflow temperature sensor in the high-speed and high-temperature airflow environment. The airflow environment required for calibration is selected according to the required temperature and Mach number.

[0003] Due to the influence of the recovery characteristics of the airflow temperature sensor, when in a high-speed airflow environment, both the reference airflow temperature sensor and the calibrated airflow temperature sensor always have a speed error of more than 1℃, thereby introducing uncertainty to the calibration. When the airflow temperature is high, the relative uncertainty introduced by the speed error is within an acceptable range. When the airflow temperature is low, i.e. in a small temperature rise state with a temperature rise of no more than 100℃ above normal temperature, the relative uncertainty introduced by the speed error will increase significantly, and it will not be able to meet the calibration requirements of the small temperature rise high-precision sensing part of the aero-engine compressor test airflow. Therefore, it is necessary to study a new calibration device for calibrating the high-precision sensing part of the airflow temperature sensor under the condition of small temperature rise of airflow, so as to reduce the calibration uncertainty. SUMMARY

[0004] In order to solve the problem of excessive uncertainty of the existing airflow temperature sensor temperature measurement deviation calibration technology under the condition of small temperature rise, the main purpose of the present application is to provide an airflow small temperature rise high-precision sensing part calibration device, which can calibrate the high-precision sensing part of the airflow temperature sensor under the condition of small temperature rise of airflow, and improve the calibration precision.

[0005] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows:

[0006] The application discloses a kind of airflow small temperature rise high-precision sensing part calibration device, including heating section, rectifier section, stable section, convergent section, test section.Each part is sequentially connected head to tail to form wind tunnel;Heater is placed in heating section;Rectifier is placed in rectifier section;Reference airflow temperature sensor, total pressure sensor are placed in stable section;Calibration airflow temperature sensor is placed in test section;The outer surface of heating section, rectifier section, stable section, convergent section, test section is applied with heat preservation layer;Surface temperature sensor is placed on the outer surface of heat preservation layer;Atmospheric pressure sensor, atmospheric temperature sensor are placed in the environment around test section;Reference airflow temperature sensor, calibration airflow temperature sensor, surface temperature sensor, atmospheric temperature sensor are connected with temperature detector;Total pressure sensor, atmospheric pressure sensor are connected with pressure detector.

[0007] Further, the reference airflow temperature sensor is a two-grade standard platinum resistance.

[0008] Further, the reference airflow temperature sensor is a one-grade standard platinum resistance.

[0009] Further, the surface temperature sensor is placed on the outer surface of heat preservation layer between reference airflow temperature sensor and calibration airflow temperature sensor.

[0010] Further, the non-uniformity of the temperature field of stable section is not more than 0.05 DEG C, and the instability is not more than 0.02 DEG C.

[0011] Further, the temperature of the outer surface of heat preservation layer is not higher than ambient temperature by 10 DEG C.

[0012] Further, the heating temperature rise of heating section to airflow is not higher than ambient temperature by 100 DEG C.

[0013] Further, the heater is an electric heater.

[0014] The working method of the airflow small temperature rise high-precision sensing part calibration device disclosed by the application is as follows:

[0015] When the application is applied to calibrate temperature deviation of calibration airflow temperature sensor, airflow flows through heating section, rectifier section, stable section, convergent section and test section in sequence.Heater heats airflow to a small temperature rise state required for calibration.After airflow is rectified by rectifier, uniform and stable temperature field and velocity field are formed in stable section.Convergent section accelerates airflow to Mach number required for calibration of test section, and the Mach number of airflow in test section can be accurately calculated according to measurement results of total pressure sensor and atmospheric pressure sensor.

[0016] The reference air flow temperature sensor is used to accurately measure the air flow temperature T0 in the stable section. The surface temperature sensor is used to measure the outer surface temperature of the heat preservation layer between the reference air flow temperature sensor and the calibrated air flow temperature sensor, and the atmospheric temperature sensor is used to measure the atmospheric temperature; according to the outer surface temperature of the heat preservation layer and the atmospheric temperature, the air flow temperature drop value T caused by heat dissipation of the calibration device to the surrounding environment when the air flow flows through the distance between the reference air flow temperature sensor and the calibrated air flow temperature sensor in turn can be calculated. loss The air flow temperature value measured by the calibrated air flow temperature sensor is T j The temperature measurement deviation calibration value of the calibrated air flow temperature sensor is calculated according to the following formula:

[0017] ΔT=T0-T loss -T j

[0018] Advantages:

[0019] 1. The air flow small temperature rise high-precision sensing part calibration device disclosed by the application changes the method of installing a reference air flow temperature sensor in a test section in the existing air flow temperature sensor temperature measurement deviation calibration technology, and places the reference air flow temperature sensor in a stable section. The flow speed of the stable section is extremely low, the speed error of the reference air flow temperature sensor is zero, and the structure strength of the sensor itself does not need to be considered, so a second or first standard platinum resistance with extremely high temperature measurement precision can be selected as the reference air flow temperature sensor. In addition, the core area of the stable section is much larger than that of the test section, the temperature field and the speed field are uniform and stable, which provides very favorable conditions for high-precision temperature measurement of the reference air flow temperature sensor, and further improves the calibration precision of the sensing part.

[0020] 2. Influenced by heat dissipation of the calibrated device to the surrounding environment, the air flow temperature continuously decreases during the process that the air flow flows from the stable section to the test section. The air flow small temperature rise high-precision sensing part calibration device disclosed by the application moves the reference air flow temperature sensor from the test section to the stable section, which may cause that the air flow temperatures measured by the reference air flow temperature sensor and the calibrated air flow temperature sensor are not exactly the same. The application monitors and compensates the air flow temperature drop value caused by heat dissipation through the surface temperature sensor and the atmospheric temperature sensor, so as to reduce the calibration uncertainty and further improve the calibration precision of the sensing part.

[0021] 3. The present invention discloses a calibration device for a small temperature rise accuracy sensing element of airflow. Through extensive innovative analysis and experimentation, it was found that the uncertainty of the temperature measurement deviation of the calibration device under small temperature rise conditions can be reduced from about 1℃ in the prior art to below 0.1℃ when the following conditions are met: the non-uniformity of the temperature field in the stable section is not greater than 0.05℃, and the instability is not greater than 0.02℃; the temperature of the outer surface of the insulation layer is not higher than the ambient temperature by 10℃; and the temperature rise of the airflow by the heating section is not higher than 100℃ of the ambient temperature. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of a small temperature rise accuracy sensing element calibration device for airflow according to the present invention.

[0023] In the diagram: 1—Heating section, 2—Rectifying section, 3—Stabilizing section, 4—Converging section, 5—Test section, 6—Insulation layer, 7—Heater, 8—Rectifier, 9—Ambient temperature sensor, 10—Total pressure sensor, 11—Pressure detector, 12—Reference airflow temperature sensor, 13—Surface temperature sensor, 14—Temperature detector, 15—Calibrated airflow temperature sensor, 16—Ambient temperature sensor. Detailed Implementation

[0024] The principles and features of the present invention are described below with reference to the accompanying drawings. The embodiments described are only for explaining the present invention and are not intended to limit the scope of the present invention.

[0025] Example 1:

[0026] like Figure 1 As shown in the figure, this embodiment discloses a device for calibrating the accuracy of airflow temperature rise sensing element, comprising a thin-walled cylinder consisting of a heating section 1, a rectifying section 2, a stabilizing section 3, a converging section 4, and a test section 5. These sections are connected end-to-end, with their axes at the same horizontal level, forming a wind tunnel. When the wind tunnel is running, airflow enters from the heating section 1, passes sequentially through the rectifying section 2, the stabilizing section 3, and the converging section 4, and then exits from the test section 5.

[0027] The outer surfaces of heating section 1, rectification section 2, stabilization section 3, convergence section 4, and test section 5 are all covered with a heat insulation layer 6.

[0028] Heater 7 is installed inside heating section 1 and can heat the airflow to the temperature required for calibration.

[0029] The rectifier 8 is installed inside the rectification section 2 and has a honeycomb structure. The length of the stabilization section 3 should meet the requirements for sufficient airflow development. After the airflow is rectified by the rectifier 8, a uniform and stable temperature and velocity field will be formed within the stabilization section 3.

[0030] The converging section 4 accelerates the airflow to the required Mach number in the test section 5 by the contraction of the flow passage. The total pressure sensor 10 and the atmospheric pressure sensor 9 are connected to the pressure detector 11; the total pressure sensor 10 is installed in the stable section 3 to measure the total pressure of the airflow; the atmospheric pressure sensor 9 is installed in the atmospheric environment around the test section 5 to measure the atmospheric pressure. The Mach number of the airflow in the test section 5 can be accurately calculated according to the measurement results of the total pressure sensor 10 and the atmospheric pressure sensor 9.

[0031] The reference airflow temperature sensor 12 is installed in the stable section 3 to measure the temperature of the airflow in the stable section 3. The flow velocity in the stable section 3 is extremely low, the speed error of the reference airflow temperature sensor 12 is zero, and the structural strength of the sensor itself does not need to be considered. In this embodiment, a secondary standard platinum resistance is selected as the reference airflow temperature sensor 12, which is a sensor with very low structural strength, and the measurement uncertainty of the static temperature is less than 0.015℃ under the condition that the temperature is not higher than 100℃ of the ambient temperature. In the prior art, the reference airflow temperature sensor needs to be installed in the test section, and the reference airflow sensor itself must have a certain structural strength to withstand the impact of high-speed airflow.

[0032] The core area of the stable section 3 is much larger than that of the test section 5, and the temperature field and velocity field are uniformly stable, providing a measurement environment similar to a static temperature calibration furnace for the high-precision temperature measurement of the reference airflow temperature sensor 12, so that a standard platinum resistance with extremely high temperature measurement accuracy can be selected as the reference airflow temperature sensor 12 operating in the stable section 3. In this embodiment, the non-uniformity of the temperature field in the stable section 3 is not greater than 0.05℃, and the instability is not greater than 0.02℃, which is the minimum requirement for achieving the beneficial effects of this embodiment, and a person skilled in the art can achieve this requirement by selecting a stable section 3 with appropriate size and length.

[0033] The calibrated airflow temperature sensor 15 is installed in the test section 5. The atmospheric temperature sensor 16 is installed in the atmospheric environment around the test section 5 to measure the atmospheric temperature.

[0034] The surface temperature sensor 13 is installed on the outer surface of the heat preservation layer 6 between the reference airflow temperature sensor 12 and the calibrated airflow temperature sensor 15 to measure the temperature of the outer surface of the heat preservation layer 6. In this embodiment, four measurement sections are selected on the outer surface of the heat preservation layer 6 to install the surface temperature sensor 13, and four surface temperature sensors 13 are installed on each section, a total of 16.

[0035] The reference airflow temperature sensor 12, the calibrated airflow temperature sensor 15, the surface temperature sensor 13, and the atmospheric temperature sensor 16 are connected to the temperature detector 14.

[0036] When calibrating the calibrated gas temperature sensor 15 with the reference gas temperature sensor 12, it is necessary to ensure that the gas temperature measured by both sensors is the same. Due to the heat dissipation of the calibrating device to the ambient environment, the gas temperature continuously decreases during the process of the gas flowing from the stable section 3 to the test section 5. In the embodiment, the temperature of the outer surface of the heat preservation layer 6 is not more than ±10℃ of the ambient temperature, so that the decrease of the gas temperature caused by the heat dissipation is controlled within 0.4℃, which is the minimum requirement for achieving the beneficial effects of the embodiment. The person skilled in the art can achieve this requirement by selecting the material and thickness of the heat preservation layer 6.

[0037] In the embodiment, the heating section 1 heats the gas to a temperature that is not more than 100℃ higher than the ambient temperature, so that the working range of the calibrating device provided by the embodiment is limited to the condition of small temperature rise of the gas. If the temperature of the gas is higher than 100℃, the heat dissipation will greatly increase the uncertainty of the calibrating device, so that the beneficial effects of the embodiment cannot be achieved. In the embodiment, the heater 7 is an electric heater. Compared with combustion heating, the power input by the electric heater 7 to the gas is more stable, so that the temperature of the gas will not fluctuate due to the instability of the heating power.

[0038] The reference gas temperature sensor 12 and the calibrated gas temperature sensor 15 are not in the same gas temperature, so the measurement result of the reference gas temperature sensor 12 cannot be directly used. According to the measurement results of the surface temperature sensor 13 and the atmospheric temperature sensor 16, the decrease of the gas temperature caused by the heat dissipation can be calculated according to the method described in GB-T 17357-2008 “Determination of heat loss on the surface of equipment and pipeline insulation layer by heat flow meter method and surface temperature method”. After removing the decrease of the gas temperature caused by the heat dissipation from the measurement result of the reference gas temperature sensor 12, the standard value of the gas temperature can be obtained, and then the temperature measurement deviation of the calibrated gas temperature sensor 15 can be calibrated according to the following formula:

[0039] ΔT = T0 - T loss - T j (1)

[0040] In formula (1), ΔT is the temperature measurement deviation of the calibrated gas temperature sensor 15, T0 is the measurement result of the reference gas temperature sensor 12, T loss is the decrease of the gas temperature caused by the heat dissipation, and T j is the measurement result of the calibrated gas temperature sensor 15.

[0041] In the embodiment, the selection of the reference airflow temperature sensor 12, the non-uniformity and instability of the temperature field in the stable section 3, the temperature of the outer surface of the heat preservation layer 6, and the heating temperature rise of the airflow in the heating section 1 are limited, which are all influencing factors of the uncertainty of the calibration device. According to the limitations, the measurement uncertainty introduced by the reference airflow temperature sensor 12 is u1=0.015℃; the measurement uncertainty introduced by the flow field non-uniformity is u2= The measurement uncertainty introduced by the flow field instability is u3= The measurement uncertainty introduced by the heat dissipation is u4=0.4×0.15 / 2=0.03℃ according to GB-T 17357-2008 Equipment and Pipeline Insulation Layer Surface Heat Loss Field Measurement Heat Flowmeter Method and Surface Temperature Method. The uncertainty U of the calibration device is calculated according to the following formula:

[0042]

[0043] In formula (2), k is a containing factor, and k=2 is taken.

[0044] According to formula (2), the factors influencing the uncertainty of the calibration device are designed in the embodiment, and the design value is the minimum requirement for achieving the beneficial effects of the embodiment.

[0045] The airflow small temperature rise high-precision sensing part calibration device provided by the embodiment can reduce the uncertainty of the temperature measurement deviation of the calibration device under small temperature rise from about 1℃ of the prior art to below 0.1℃, solving the problem of excessive uncertainty of the prior art.

[0046] Embodiment 2:

[0047] As an optional embodiment of the present application, a first-class standard platinum resistance is selected as the reference airflow temperature sensor 12. The specific implementation scheme of embodiment 2 is referred to embodiment 1. Compared with embodiment 1, embodiment 2 can reduce the uncertainty u1 introduced by the reference airflow temperature sensor 12 to 0.01℃, and the uncertainty of the calibration device is still calculated according to formula (2). Embodiment 2 needs to pay a higher cost compared with embodiment 1.

[0048] The above specific description further details the purpose, technical scheme, and beneficial effects of the application. It should be understood that the above description is only a specific embodiment of the application and does not limit the protection scope of the application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the application should be included in the protection scope of the application.

Claims

1. A device for calibrating a sensing element with high accuracy in low-temperature rise of airflow, characterized in that: The system includes a heating section, a rectification section, a stabilization section, a convergence section, and a test section; these sections are connected sequentially to form a wind tunnel. The heater is located within the heating section; the rectifier is located within the rectification section; the reference airflow temperature sensor and the total pressure sensor are located within the stabilization section; the calibrated airflow temperature sensor is located within the test section; the outer surfaces of the heating section, rectification section, stabilization section, convergence section, and test section are covered with an insulation layer; a surface temperature sensor is located on the outer surface of the insulation layer; an atmospheric pressure sensor and an atmospheric temperature sensor are located in the surrounding environment of the test section; the reference airflow temperature sensor, the calibrated airflow temperature sensor, the surface temperature sensor, and the atmospheric temperature sensor are connected to a temperature detector; the total pressure sensor and the atmospheric pressure sensor are connected to a pressure detector. The heater is an electric heater; The airflow flows sequentially through the heating section, rectification section, stabilization section, convergence section, and test section. The heater heats the airflow to the small temperature rise required for calibration. After the airflow is rectified by the rectifier, a uniform and stable temperature and velocity field is formed in the stabilization section. The convergence section accelerates the airflow to the Mach number required for calibration in the test section. The Mach number of the airflow in the test section can be accurately calculated based on the measurement results of the total pressure sensor and the atmospheric pressure sensor. The reference airflow temperature sensor is used to accurately measure the airflow temperature within the steady-state section. T 0; The surface temperature sensor is used to measure the outer surface temperature of the insulation layer between the reference airflow temperature sensor and the calibrated airflow temperature sensor, while the atmospheric temperature sensor is used to measure the atmospheric temperature. Based on the outer surface temperature of the insulation layer and the atmospheric temperature, the decrease in airflow temperature caused by heat dissipation from the calibration device to the surrounding environment as the airflow flows sequentially over the distance between the reference airflow temperature sensor and the calibrated airflow temperature sensor can be calculated. T loss The airflow temperature value measured by the airflow temperature sensor being calibrated is... T j The temperature measurement deviation calibration value of the airflow temperature sensor being calibrated is calculated using the following formula: .

2. The airflow small temperature rise accuracy sensing element calibration device as described in claim 1, characterized in that: The reference airflow temperature sensor is a second-class standard platinum resistance thermometer.

3. The airflow small temperature rise accuracy sensing element calibration device as described in claim 1, characterized in that: The reference airflow temperature sensor is a first-class standard platinum resistance thermometer.

4. The airflow small temperature rise accuracy sensing element calibration device as described in claim 1, characterized in that: The surface temperature sensor is placed on the outer surface of the insulation layer between the reference airflow temperature sensor and the calibrated airflow temperature sensor.

5. The airflow small temperature rise accuracy sensing element calibration device as described in claim 2, characterized in that: The non-uniformity of the temperature field in the stable section is no greater than 0.05℃, and the instability is no greater than 0.02℃.

6. The airflow small temperature rise accuracy sensing element calibration device as described in claim 5, characterized in that: The temperature of the outer surface of the insulation layer is no higher than the ambient temperature by 10°C.

7. The airflow small temperature rise accuracy sensing element calibration device as described in claim 5, characterized in that: The heating section heats the airflow to a temperature rise no higher than 100°C above the surrounding environment.

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