A high frequency airflow generating device and method for dynamic calibration of temperature probes

Abstract

The application provides a high-frequency airflow generating device and method for dynamic calibration of a temperature probe, comprising a stable air source, an axial flow fan, a calibrated temperature probe, a probe support, a photoelectric sensor, a rotating speed controller and an experimental platform; the stable air source provides airflow with stable temperature and flow rate; the axial flow fan blade periodically sweeps the airflow, forming periodic temperature disturbance with blade passing frequency characteristics at the fan outlet, and applying periodic thermal excitation to the calibrated temperature probe; the photoelectric sensor provides a rotating speed and a reference phase signal; the rotating speed controller adjusts the rotating speed of the fan to change the thermal excitation frequency; by measuring the fluid temperature signal at the measuring point and the output signal of the temperature probe, combining the phase-locked average and frequency response analysis method, the amplitude-frequency and phase-frequency characteristics of the temperature probe are obtained, and dynamic characteristic calibration is realized; the application can provide a high-frequency, controllable and spectrum clear thermal excitation signal, is suitable for dynamic calibration of a temperature probe, and can realize periodic thermal excitation in a rotating environment.

Description

Technical Field

[0001] This invention belongs to the field of dynamic characteristic calibration technology for temperature probes, specifically relating to a high-frequency airflow generator and method for dynamic calibration of temperature probes. It is suitable for dynamic characteristic calibration of temperature probes used in unsteady flow field testing. The designed device has a high thermal excitation frequency response, a clear and controllable thermal excitation input frequency response, and is applicable to a variety of temperature probes, providing reliable technical support for dynamic temperature measurement of unsteady flow fields in compressors. Background Technology

[0002] During compressor operation, airflow temperature is a key parameter. However, when measuring airflow temperature changes over time, such as in compressor interstage flow and stall surge, the temperature probe's measured value deviates from the actual temperature value due to the thermal inertia of the probe. To determine this measurement deviation, it is necessary to clarify the dynamic characteristics of the temperature probe. Since many factors affect the dynamic characteristics of the temperature probe, it is difficult to determine specific values ​​through theoretical derivation. Therefore, in practical applications, a dynamic temperature calibration device is often used to apply thermal excitation to the temperature probe to obtain its dynamic characteristics.

[0003] To design a dynamic temperature excitation signal generator that meets the requirements for dynamic temperature calibration, existing methods heat the temperature sensing element with pulsed current to achieve a temperature step. This method can generate microsecond-level high-frequency thermal pulses, which is suitable for the dynamic characteristic calibration of small temperature sensing elements. However, since the temperature probe sensing element is generally set inside a hysteresis enclosure, it is difficult to achieve thermal excitation of the temperature probe sensing element with pulsed current. Therefore, this method is not suitable for the dynamic characteristic calibration of temperature probes.

[0004] In addition, a commonly used calibration method for temperature probes is the isothermal liquid immersion step excitation method. This typically uses a isothermal water bath or oil bath as the heat source. During dynamic calibration experiments, the temperature probe to be calibrated is rapidly placed from the external environment into the isothermal bath, thus creating a step temperature excitation. The speed at which the dynamic excitation signal is generated in this method is highly dependent on the speed at which the temperature probe enters the isothermal bath. If this method is used to calibrate high-frequency response temperature probes, the temperature probe needs to enter the isothermal bath at an extremely high speed. This presents significant problems in the structural design of the device and cannot be adapted to temperature probes with fast response speeds.

[0005] Given that both of the above methods have their advantages and disadvantages and neither can simultaneously achieve the ability to calibrate the dynamic characteristics of the temperature probe at high frequencies, there is an urgent need for a frequency response calibration device that integrates high-frequency thermal excitation, clear and controllable thermal excitation input frequency response, and applicability to various types of temperature probes, so as to achieve frequency response calibration of temperature probes and provide technical support for strengthening the research on unsteady flow fields in turbomachinery. Summary of the Invention

[0006] This invention relates to a high-frequency airflow generating device and method for dynamic calibration of a temperature probe, comprising a stable air source, an axial fan, a temperature probe to be calibrated, a probe holder, a photoelectric sensor, a speed controller, and an experimental platform. The stable air source provides a stable and uniform airflow in terms of temperature and flow rate. The axial fan is a high-speed rotating fan that periodically sweeps the airflow at high speed through its blades, creating a high-frequency, controllable periodic disturbance at the fan outlet. This periodic thermal excitation is applied to the temperature probe to be calibrated located at the outlet for high-frequency dynamic calibration of the temperature probe. The photoelectric sensor provides a phase-locked signal, facilitating the establishment of a correspondence between continuous sampling time and rotor angular position.

[0007] This invention provides a high-frequency airflow generator and method for dynamic calibration of temperature probes. The technical problems to be solved are: First, to address the difficulty of providing high-frequency response thermal excitation in existing dynamic temperature calibration devices. Second, to address the problem of unstable and unclear frequency response of thermal excitation input in existing dynamic temperature calibration devices. Third, to address the problem that existing dynamic temperature calibration devices cannot meet the calibration requirements of multiple types of probes. Fourth, to address the problem that existing dynamic temperature calibration devices cannot obtain periodic frequency response excitation signals under rotating environments.

[0008] The technical solution of this invention is:

[0009] 1. A high-frequency airflow generator for dynamic calibration of a temperature probe, comprising a stable air source (1), an axial fan (2), a temperature probe to be calibrated (3), a probe holder (4), a photoelectric sensor (5), a speed controller (6), and an experimental platform (7), characterized in that: the stable air source (1) can provide a stable airflow with uniform spatial distribution and temperature and flow rate; the axial fan (2) is a high-speed rotating fan, forming a periodic flow field with blade passing frequency characteristics in the near field of the outlet of the axial fan (2), which is used to calibrate the temperature probe located at the outlet of the axial fan (2). The temperature probe (3) applies periodic thermal excitation for dynamic calibration of the temperature probe (3) being calibrated. The photoelectric sensor (5) measures the rotational speed signal of the axial fan (2) to establish a reference phase synchronized with the rotation of the axial fan (2). The speed controller (6) is connected to the motor of the axial fan (2) to adjust the rotational speed of the axial fan (2) so that the blades of the axial fan (2) cover the frequency range to be measured of the temperature probe (3) being calibrated. The experimental platform (7) is used to install and arrange the stable air source (1), the axial fan (2) and the speed controller (6).

[0010] 2. The stable air source (1) has the function of generating and regulating airflow, forming a stable and uniform air-heat flow field in the inlet of the axial fan (2). The Mach number of the outlet airflow of the stable air source (1) is 0.1 to 0.9, and the total temperature is 20℃ to 1000℃, without limiting the specific structural form of the stable air source (1).

[0011] 3. Axial flow fan (2) with a diameter of 50 mm to 500 mm, a speed of 2000 rpm to 120000 rpm, and 5 to 40 blades. The passing frequency of the blades of the axial flow fan (2) meets the following requirements: ,in, For the number of blades of the axial fan (2), The rotational speed of the axial fan (2) is expressed in revolutions per minute. The blade passing frequency serves as the reference frequency for the periodic temperature excitation, resulting in a high-frequency periodic thermal excitation at the outlet of the axial fan (2).

[0012] 4. The local fluid temperature at the downstream dynamic calibration measuring point of the axial fan (2) outlet can be expressed as: ,in: The local average temperature of the fluid at the measuring point. For the first First harmonic amplitude, For the first First harmonic phase, The angular frequency at which the blade passes through is ω.

[0013] 5. Under the influence of wake diffusion, thermal diffusion, and spatial averaging, the high-order harmonics of the outlet airflow temperature signal of the axial fan (2) are attenuated. When the measuring point satisfies the fundamental frequency component... When the frequency is significantly greater than that of higher harmonic components, the fundamental frequency component dominates, and the local fluid temperature fluctuation at this measuring point can be approximated as: This measurement point is defined as a periodic temperature excitation measurement point that can be used for dynamic calibration. This is the phase relative to the reference point.

[0014] 6. The candidate region for dynamic calibration measurement points is the axial range of 0.1D~3D downstream of the outlet of the axial fan (2), and the radial range of 0.2R~0.9R. The outlet diameter of the axial fan (2) is... The outlet radius of the axial fan (2).

[0015] 7. The temperature probe (3) to be calibrated has a diameter of 4 mm to 12 mm and a length of 100 mm to 500 mm. The temperature probe (3) to be calibrated is arranged at the airflow outlet of the axial fan (2) through the probe bracket (4). The sensing part of the temperature probe (3) to be calibrated is located at the selected dynamic calibration measurement point. The blades of the axial fan (2) sweep to form a periodic airflow, thereby forming a periodic thermal excitation input to the sensing part of the temperature probe (3) to be calibrated.

[0016] 8. The photoelectric sensor (5) is located on the wall of the inlet pipe of the axial fan (2) to detect the reflected light signal of the axial fan (2) shaft and output a reference signal for each revolution to establish the correspondence between the continuous sampling time and the rotor angular position. Its signal response frequency is 25kHz~1MHz.

[0017] 9. The speed controller (6) can set and control the speed of the axial fan (2), and adjust the periodic thermal excitation frequency of the outlet of the axial fan (2) by the relationship between the speed and the blade passing frequency.

[0018] 10. Experimental platform (7) Length 600 mm ~ 8000 mm, width 300 mm ~ 2000 mm, height 600 mm ~ 1200 mm, with threaded holes evenly distributed on the upper surface, threaded hole size M6 ~ M8, and threaded hole center distance 20 mm ~ 40 mm.

[0019] 11. Based on a high-frequency airflow generator for dynamic calibration of temperature probes, this invention proposes a calibration method for dynamic calibration of temperature probes. After completing the device installation preparation according to the above requirements, the signal output terminal of the temperature probe (3) to be calibrated and the signal output terminal of the photoelectric sensor (5) are connected to the signal acquisition system and time synchronization is adopted. The signal acquisition frequency is not less than 10 times the periodic thermal excitation frequency, i.e., 10 times the blade passing frequency, and not less than the signal response frequency of the photoelectric sensor (5).

[0020] 12. Turn on the stable air source (1), set the airflow temperature and flow rate, provide a uniform and stable hot airflow to the inlet of the axial fan (2), start the axial fan (2) and adjust it to the target speed condition, obtain the speed signal through the photoelectric sensor (5), calculate the blade passing frequency, and use this frequency as the reference frequency for periodic temperature excitation.

[0021] 13. In the candidate area downstream of the outlet of the axial fan (2), the local fluid temperature at multiple spatial measurement points is measured, phase-locked averaged and synchronous spectrum analyzed to obtain the fluid temperature signal at each measurement point. Based on the fundamental frequency component, the calibration measurement point with significant periodic temperature fluctuation characteristics is determined.

[0022] 14. The sensing part of the temperature probe (3) to be calibrated is placed at the determined dynamic calibration measurement point so that the temperature probe (3) to be calibrated receives the excitation of the periodic change of local fluid temperature. Under the target speed condition, the output signal and reference phase signal of the temperature probe (3) to be calibrated are collected synchronously, and the collected signals are extracted by phase-locked averaging to obtain the output amplitude and phase of the temperature probe (3) under the condition.

[0023] 15. Using the fundamental frequency component of the fluid temperature at the dynamic calibration measuring point at the blade passage frequency as input, and the output component of the temperature probe (3) to be calibrated at the same blade passage frequency as output, establish the frequency response function of the temperature probe at that frequency: ,in: To dynamically calibrate the complex amplitude value of the local fluid temperature at the measuring point, , is the complex amplitude value output by the calibrated temperature probe (3). Input the amplitude of the fundamental frequency component of the temperature. To output the amplitude of the fundamental frequency component of temperature. The initial phase of the input temperature fundamental frequency component. This represents the initial phase of the output temperature fundamental frequency component.

[0024] 16. The corresponding amplitude-frequency response and phase-frequency response are as follows: By changing the speed of the axial fan (2), the frequency of the dynamic temperature excitation signal is changed, and the amplitude frequency curve and phase frequency curve of the calibrated temperature probe (3) are obtained, and the characteristic frequency of the calibrated temperature probe (3) is determined.

[0025] This invention provides a high-speed fan calibration device and method for dynamic calibration of temperature probes, which has the following beneficial effects:

[0026] Beneficial effect 1: The high-frequency airflow generating device and method for dynamic calibration of temperature probes designed in this invention provides high-frequency dynamic thermal excitation input for temperature probes through periodic airflow disturbances generated by the high-speed rotation of an axial fan, thus meeting the high-frequency response calibration requirements of temperature probes.

[0027] Second beneficial effect: The high-frequency airflow generating device and method for dynamic calibration of temperature probes designed in this invention establishes a candidate area for dynamic calibration measurement points and measures the local fluid temperature of multiple spatial measurement points to determine the calibration measurement points with significant periodic temperature fluctuation characteristics, making the thermal excitation signal output by the device clearer and the calibration results more reliable.

[0028] Benefit 3: The high-frequency airflow generating device and method for dynamic calibration of temperature probes designed in this invention provides a stable and uniform inlet flow field with stable temperature and flow rate through a stable air source. The sweeping of fan blades forms periodic airflow disturbances, causing periodic changes in the temperature field of the sensing part of the temperature probe being calibrated, generating thermal excitation input. Whether it is a bare probe or a probe with a stagnation shroud, a clear thermal excitation can be felt. This enables the calibration of different types of temperature probes under the same device, improving the applicability and practicality of the device.

[0029] Fourthly, the high-frequency airflow generator and method for dynamic calibration of temperature probes designed in this invention generate periodic airflow by sweeping axial fan blades, providing periodic frequency response excitation signals for the temperature probe being calibrated, thus achieving effective calibration of the dynamic characteristics of the temperature probe under rotating conditions. Attached Figure Description

[0030] Figure 1 This is a top view of a high-speed fan calibration device used for dynamic calibration of temperature probes in an embodiment of the present invention.

[0031] Figure 2 This is a front view of a high-speed fan calibration device for dynamic calibration of temperature probes in an embodiment of the present invention.

[0032] Figure 3 This is a right view of a high-speed fan calibration device used for dynamic calibration of temperature probes in an embodiment of the present invention.

[0033] Among them: 1-Stable air source, 2-Axial flow fan, 3-Calibrated temperature probe, 4-Probe holder, 5-Photoelectric sensor, 6-Speed ​​controller, 7-Experimental platform. Detailed Implementation

[0034] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more explicit definition of the scope of protection of the present invention.

[0035] like Figures 1-3 As shown, a high-frequency airflow generating device and method for dynamic calibration of temperature probes includes a stable air source (1), an axial fan (2), a temperature probe to be calibrated (3), a probe holder (4), a photoelectric sensor (5), a speed controller (6), and an experimental platform (7).

[0036] The stable air source (1) is a subsonic wind tunnel with an outlet airflow Mach number of 0.2 and a total temperature of 100℃.

[0037] The axial fan (2) has a diameter of 120 mm, a maximum speed of 45,000 rpm, 8 blades, and a maximum blade pass frequency of 6 kHz.

[0038] Temperatures at multiple spatial measuring points were measured within an axial range of 0.1D to 3D downstream of the outlet of the axial fan (2), and within a radial range of 0.2R to 0.9R. The measuring points were selected such that the fundamental frequency component A1 was significantly greater than the higher harmonic components. The local fluid temperature can be expressed as: The dynamic calibration measurement points, among which The local average temperature of the fluid at the measuring point. The fundamental frequency amplitude, The phase relative to the reference point, The angular frequency of the blade passage. The outlet diameter of the axial fan (2) is... The outlet radius of the axial fan (2).

[0039] The temperature probe (3) being calibrated has a diameter of 6 mm and a length of 300 mm. The sensing part is a bare thin wire thermocouple. The temperature probe (3) being calibrated is arranged at the airflow outlet of the ducted fan (2) through the probe bracket (4). The sensing part of the temperature probe (3) being calibrated is located at the selected dynamic calibration measurement point. The blades of the axial fan (2) sweep to form a periodic airflow, thereby forming a periodic thermal excitation input to the sensing part of the temperature probe (3) being calibrated.

[0040] The photoelectric sensor (5) is located on the wall of the inlet pipe of the axial fan (2) to detect the reflected light signal of the axial fan (2) shaft and output a reference signal for each revolution to establish the correspondence between the continuous sampling time and the rotor angular position. Its signal response frequency is 10kHz.

[0041] The speed controller (6) sets and controls the speed of the axial fan (2), and adjusts the periodic thermal excitation frequency at the outlet of the axial fan (2) by means of the relationship between the speed and the blade passing frequency.

[0042] The experimental platform (10) is 2000 mm long, 800 mm wide, and 1000 mm high. The upper surface is evenly distributed with threaded holes of size M6 and center distance of 40 mm.

[0043] The signal output terminals of the temperature probe (3) to be calibrated and the photoelectric sensor (5) are connected to the signal acquisition system, and time synchronization is set with a signal acquisition frequency of 100KHz.

[0044] Under the target speed condition, the output signal of the calibrated temperature probe (3) and the reference phase signal are synchronously acquired, and the acquired signal is extracted by phase-locked averaging to obtain the output amplitude and phase of the calibrated temperature probe (3) under this condition.

[0045] Using the fundamental frequency component of the fluid temperature at the dynamic calibration measurement point at the blade passage frequency as input, and the output component of the temperature probe (3) to be calibrated at the same blade passage frequency as output, the frequency response function of the temperature probe at that frequency is established: ,in: To dynamically calibrate the complex amplitude value of the local fluid temperature at the measuring point, , where A is the complex amplitude value output by the calibrated temperature probe (3). in For the input temperature fundamental frequency component amplitude, A out This is the amplitude of the fundamental frequency component of the output temperature. The initial phase of the input temperature fundamental frequency component. This represents the initial phase of the output temperature fundamental frequency component.

[0046] The corresponding amplitude-frequency response and phase-frequency response are as follows: By changing the speed of the high-speed fan and the frequency of the dynamic temperature excitation signal, the amplitude-frequency curve and phase-frequency curve of the temperature probe (3) being calibrated are obtained, and the characteristic frequency of the temperature probe (3) being calibrated is determined.

[0047] Those skilled in the art should recognize that the above embodiments are merely illustrative of the present invention and are not intended to limit the present invention. Any variations or modifications to the above embodiments that are within the essential spirit of the present invention will fall within the scope of the claims of the present invention.

Claims

1. A high-frequency airflow generator for dynamic calibration of a temperature probe, comprising a stable air source (1), an axial fan (2), a temperature probe to be calibrated (3), a probe holder (4), a photoelectric sensor (5), a speed controller (6), and an experimental platform (7), characterized in that: A stable air source (1) can provide a stable airflow with uniform spatial distribution and temperature and flow rate. An axial fan (2) is a high-speed rotating fan. A periodic flow field with blade passing frequency characteristics is formed in the near field of the outlet of the axial fan (2). Periodic thermal excitation is applied to the calibrated temperature probe (3) located at the outlet of the axial fan (2) for dynamic calibration of the calibrated temperature probe (3). A photoelectric sensor (5) measures the rotation speed signal of the axial fan (2) to establish a reference phase synchronized with the rotation of the axial fan (2). A speed controller (6) is connected to the motor of the axial fan (2) to adjust the speed of the axial fan (2) so that the blade passing frequency of the axial fan (2) covers the test frequency range of the calibrated temperature probe (3). An experimental platform (7) is used to install and arrange the stable air source (1), the axial fan (2) and the speed controller (6). The stable air source (1) has the function of generating and regulating airflow, forming a stable and uniform air-heat flow field in the inlet of the axial fan (2). The Mach number of the outlet airflow of the stable air source (1) is 0.1 to 0.9, and the total temperature is 20℃ to 1000℃, without limiting the specific structural form of the stable air source (1). Axial flow fan (2) with a diameter of 50 mm to 500 mm, a speed of 2000 rpm to 120000 rpm, and 5 to 40 blades, and the blade passing frequency of axial flow fan (2) meets the following requirements: ,in, For the number of blades of the axial fan (2), The rotational speed of the axial fan (2) is expressed in revolutions per minute. The blade passing frequency serves as the reference frequency for the periodic temperature excitation, thus generating a high-frequency periodic thermal excitation at the outlet of the axial fan (2). The local fluid temperature at the downstream dynamic calibration measuring point of the axial fan (2) outlet can be expressed as: ,in: The local average temperature of the fluid at the measuring point. For the first First harmonic amplitude, For the first First harmonic phase, The angular frequency at which the blade passes; Under the influence of wake diffusion, thermal diffusion, and spatial averaging, the high-order harmonics of the outlet airflow temperature signal of the axial fan (2) are attenuated. When the measuring point satisfies the fundamental frequency component... When the frequency is significantly greater than that of higher harmonic components, the fundamental frequency component dominates, and the local fluid temperature fluctuation at this measuring point can be approximated as: This measurement point is defined as a periodic temperature excitation measurement point that can be used for dynamic calibration. The phase relative to the reference point; The candidate region for dynamic calibration measurement points is the axial range of 0.1D~3D downstream of the outlet of the axial fan (2), and the radial range of 0.2R~0.9R. The outlet diameter of the axial fan (2) is... The outlet radius of the axial fan (2); The temperature probe (3) being calibrated has a diameter of 4 mm to 12 mm and a length of 100 mm to 500 mm. The temperature probe (3) being calibrated is arranged at the airflow outlet of the axial fan (2) through the probe bracket (4). The sensing part of the temperature probe (3) being calibrated is located at the selected dynamic calibration measurement point. The blades of the axial fan (2) sweep to form a periodic airflow, thereby forming a periodic thermal excitation input to the sensing part of the temperature probe (3) being calibrated. The photoelectric sensor (5) is located on the wall of the inlet pipe of the axial fan (2) to detect the reflected light signal of the axial fan (2) shaft and output a reference signal for each revolution to establish the correspondence between the continuous sampling time and the rotor angular position. Its signal response frequency is 25kHz~1MHz. The speed controller (6) can set and control the speed of the axial fan (2), and adjust the periodic thermal excitation frequency at the outlet of the axial fan (2) by the relationship between the speed and the blade passing frequency. The experimental platform (7) is 600 mm to 8000 mm long, 300 mm to 2000 mm wide, and 600 mm to 1200 mm high. The upper surface is evenly distributed with threaded holes of size M6 to M8 and center distance between the threaded holes of 20 mm to 40 mm.

2. According to claim 1, a high-frequency airflow generator for dynamic calibration of temperature probe is proposed. After completing the device installation preparation according to the above requirements, the signal output terminal of the temperature probe (3) to be calibrated and the signal output terminal of the photoelectric sensor (5) are connected to the signal acquisition system and time synchronization is adopted. The signal acquisition frequency is not less than 10 times the periodic thermal excitation frequency, i.e., 10 times the blade passing frequency, and not less than the signal response frequency of the photoelectric sensor (5). Turn on the stable air source (1), set the airflow temperature and flow rate, provide a uniform and stable hot airflow to the inlet of the axial fan (2), start the axial fan (2) and adjust it to the target speed condition, obtain the speed signal through the photoelectric sensor (5), calculate the blade passing frequency, and use this frequency as the reference frequency for periodic temperature excitation. In the candidate area downstream of the outlet of the axial fan (2), the local fluid temperature at multiple spatial measurement points is measured, phase-locked averaged and synchronous spectrum analyzed to obtain the fluid temperature signal at each measurement point. Based on the fundamental frequency component, the calibration measurement point with significant periodic temperature fluctuation characteristics is determined. The sensing part of the temperature probe (3) to be calibrated is arranged at the determined dynamic calibration measurement point so that the temperature probe (3) to be calibrated receives the excitation of the periodic change of local fluid temperature. Under the target speed condition, the output signal and reference phase signal of the temperature probe (3) to be calibrated are collected synchronously, and the collected signals are extracted by phase-locked averaging to obtain the output amplitude and phase of the temperature probe (3) under the condition. Using the fundamental frequency component of the fluid temperature at the dynamic calibration measurement point at the blade passage frequency as input, and the output component of the temperature probe (3) to be calibrated at the same blade passage frequency as output, the frequency response function of the temperature probe at that frequency is established: ,in: To dynamically calibrate the complex amplitude value of the local fluid temperature at the measuring point, , is the complex amplitude value output by the calibrated temperature probe (3). Input the amplitude of the fundamental frequency component of the temperature. To output the amplitude of the fundamental frequency component of temperature. The initial phase of the input temperature fundamental frequency component. This is the initial phase of the output temperature fundamental frequency component; The corresponding amplitude-frequency response and phase-frequency response are as follows: By changing the rotation speed of the axial fan (2), the frequency of the dynamic temperature excitation signal is changed, and the amplitude frequency curve and phase frequency curve of the temperature probe (3) being calibrated are obtained, thus determining the characteristic frequency of the temperature probe (3) being calibrated.

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