Dynamic temperature probe comb based on double thermocouples

Abstract

The utility model belongs to the technical field of temperature testing, and relates to a dynamic temperature measuring device for measuring air inlet temperature distortion of an air compressor, in particular to a dynamic temperature probe comb based on a double-filament thermocouple. Comprising a left thermocouple wire supporting rod, a right thermocouple wire supporting rod, a supporting rod, a thermocouple wire with a relatively small diameter, a thermocouple wire with a relatively large diameter and a mounting seat. The supporting rod is of a cylinder structure with a wing-shaped section, the cylinder is provided with at least three measuring points right facing an incoming flow surface, a left thermocouple wire supporting rod and a right thermocouple wire supporting rod are welded at each measuring point, each thermocouple wire supporting rod is in a flat shape with a wedge-shaped section and a rounded tip, two thermocouples with different diameters are led out from the top ends of the thermocouple wire supporting rods and straightened to be in a straight line shape, and the lower ends of the supporting rods are welded with mounting seats. The device is suitable for measuring the dynamic temperature field, and can directly extract key information from the measurement data of the thermocouple, thereby accurately correcting the heat conduction error and improving the measurement precision.

Description

Technical Field

[0001] The present invention belongs to the technical field of temperature testing, and relates to a dynamic temperature measuring device for measuring compressor intake temperature distortion, in particular to a dynamic temperature probe comb based on double thermocouples. Background Art

[0002] Engine aerodynamic stability is a key metric for evaluating engine performance. A well-designed aircraft engine, in addition to achieving high performance and reliability, must also maintain sufficient stability margin throughout the entire flight envelope. Temperature distortion is a key factor affecting engine aerodynamic stability. Temperature distortion reduces engine stability margins. Currently, research on temperature distortion in China lags behind that on pressure distortion.

[0003] The temperature distortion of the engine inlet flow field is mainly caused by the airflow of different total temperatures before being sucked into the inlet. When the hot flow is sucked into the inlet, all components of the propulsion system will respond. The combined response of each component will lead to a decrease in propulsion system performance. Among the various engine components, the compressor is the most sensitive to inlet temperature distortion. During the compressor stall surge process, the airflow temperature changes in amplitude are small but the frequency is high. In order to optimize and improve the design parameters of the compressor critical distortion level and improve the aerodynamic stability of the compressor, it is necessary to accurately understand the engine inlet temperature distortion and simulate the changes in fan / compressor characteristics under various dynamic temperature distortion conditions. The development of inlet flow field temperature distortion measurement technology is very important for aircraft engine performance analysis.

[0004] In practical engineering applications, flow fields are generally highly unsteady, making it crucial to obtain simultaneous temperatures at different radial locations within the flow field for studying temperature field distortion. Previous studies have mostly employed a single probe for measurement, requiring a probe displacement mechanism to move the probe to different radial positions to complete multi-point measurements. This results in long experimental times and high costs. Furthermore, due to the short effective test time of compressor inlet distortion tests, existing temperature probes are unable to quickly measure the distribution of the test piece's temperature field parameters along the blade height, failing to accurately replicate actual inlet distortion conditions.

[0005] Currently, domestic research on inlet temperature distortion has focused on theoretical research, including simulation analysis, as well as a limited number of experimental testing techniques. Temperature sensors used to measure compressor inlet temperature distortion are often thin-wire thermocouples or hot wires / films, but they still struggle to balance response speed, measurement accuracy, measurement efficiency, and data processing methods. Existing testing technologies suffer from several key deficiencies: First, the engine inlet airflow often contains particulate matter, which can damage the extremely fine thermocouple filaments. A thicker thermocouple diameter can also slow response speed, making it difficult to balance the reliability and response speed of the measurement system. Second, existing thermocouple temperature compensation schemes typically rely on first-order compensation methods. While simple, these methods often result in significant errors when dealing with complex dynamic temperature variations. Third, compressor inlet distortion tests have a short effective test time, and the use of single-point temperature probes is inefficient, making it difficult to quickly obtain valid data on the temperature field along the blade height.

[0006] Therefore, there is an urgent need for a dynamic temperature measurement device with high precision, fast response, stable operation and the ability to measure the distribution of temperature field parameters along the blade height direction, so as to realize the dynamic measurement of compressor inlet temperature distortion and accurately understand the impact of engine inlet dynamic temperature distortion on the fan / compressor aerodynamic stability. Summary of the Invention

[0007] The technical problem to be solved by the present invention is: in view of the above-mentioned problems existing in the existing temperature probes, the present invention provides a dynamic temperature probe comb based on double thermocouples.

[0008] Compared with existing dynamic temperature probes, this probe comb can simultaneously measure the incoming flow parameters of multiple spatial positions, which can shorten the measurement time to the greatest extent. Each probe adopts a parallel dual thermocouple arrangement for dynamic compensation to obtain the true temperature of the measured airflow, taking into account the strength of the thermocouple and the requirements of real-time measurement.

[0009] The present invention discloses a dynamic temperature probe comb based on dual thermocouples. In order to reduce fluid mechanics blockage, the probe comb as a whole adopts a cylindrical design with a wing-shaped cross section. By optimizing the surface curvature and contour, a streamlined shape is achieved to help the airflow flow smoothly along the probe surface, minimize the flow separation and the generation of vortices, and ensure the stability and measurement accuracy of the probe in high-speed airflow. The left and right thermocouple struts are symmetrically distributed on both sides of the center line of the probe struts, and are hollow cylinders, which reduce the resistance and turbulent interference of the airflow on the struts and improve the structural strength of the thermocouple struts. The sensing part of the probe comb is based on a thin-wire thermocouple temperature sensor and consists of two thermocouple wires of different diameters. The left and right thermocouple struts are built-in thermocouple wires, and are straightened and arranged in a straight line through the top. This not only reduces the influence of the circumferential flow on the measuring junction, improves the response frequency of the temperature probe, but also increases the service life of the wires.

[0010] The present invention proposes a temperature measurement correction method based on a dynamic temperature probe comb with dual thermocouples. The dynamic characteristics of the thermocouples can be described by a second-order transfer function, which is expressed as:

[0011]

[0012] This function can be regarded as the superposition of two first-order transfer functions, which are related to the thermocouple measurement junction and the thermocouple wire respectively. Its specific expression is:

[0013]

[0014] H(z)=m1H1(z)+m2H2(z)

[0015] The analysis shows that the values ​​of m1 and m2 remain unchanged for thermocouples with different wire diameters, and the relationship between τ1 and Reynolds number satisfies the formula:

[0016] log(Δ)=a0+a1 log(Re),Δ=(m1 / τ1+m2 / τ2)

[0017] The relationship between τ2 and Reynolds number satisfies the formula:

[0018] log(τ2)=β0+β1log(Re)

[0019] Under the same inlet flow conditions, the ratio of τ2 between different wire diameters is a constant. The τ2 of the thinner thermocouple can be inferred from the ratio of τ2 between the two thicker thermocouples, and the τ1 value of the thinner thermocouple can be obtained through the above relationship. By processing the m1 and m2 values ​​of the two thicker thermocouples, the m1 and m2 values ​​of the thinner thermocouple can be approximately estimated, and the second-order transfer function of the thinner thermocouple can be obtained. The present invention significantly improves the performance of thermocouples in dynamic temperature measurement through innovative design and a temperature measurement method based on a second-order compensation strategy, improves the accuracy and reliability of measurement, enables thermocouples to perform well in high-speed airflow environments, and meets complex measurement requirements.

[0020] The technical solution of the present invention is:

[0021] 1. A dynamic temperature probe comb based on a double thermocouple, characterized by: a left thermocouple support rod (1), a right thermocouple support rod (2), a support rod (3), a first thermocouple wire (4), a second thermocouple wire (5), and a mounting seat (6), wherein the left thermocouple support rod (1) and the right thermocouple support rod (2) are distributed along the center line to form a pair, have the same geometric shape, and are hollow cylinders. According to the measurement requirements of the Chinese aviation industry standard, they are respectively fixed on the support rod (3) in the span direction and the measurement points are arranged according to the equal annular surface. The left thermocouple support rod (1) and the right thermocouple support rod (2) are welded to the support rod (3), and the thermocouple wire (4) and the thermocouple wire (5) are built in and are led out and straightened from the top ends of the left thermocouple support rod (1) and the right thermocouple support rod (2), and the connection collection system part is led out from the bottom end of the support rod (3); the support rod (3) is welded to the mounting seat (6).

[0022] 2. Furthermore, each of the left and right even-wire support rods (1) and (2) has two even-wire support rods on the left and right sides, and the angles are adjusted according to the airflow angle.

[0023] 3. Furthermore, there are at least three sets of arrangements of the left even-wire support rod (1) and the right even-wire support rod (2), which can be adjusted according to the CFD simulation results.

[0024] 4. Furthermore, the first thermocouple wire (4) and the second thermocouple wire (5) are K-type or T-type thin-wire thermocouples, with wire diameters of 0.05 mm and 0.1 mm respectively, drawn out from the top of the wire support rod, and the exposed wires of the two thermocouple heads are placed in parallel, tightened and in a "U" shape.

[0025] 5. Furthermore, the support rod (3) is a column with an airfoil-shaped cross section.

[0026] The beneficial effects created by the dual-thermocouple-based dynamic temperature probe comb of the present invention are:

[0027] Beneficial Effect 1: When using a single thermocouple to measure temperature distortion, dynamic compensation requires knowing the thermocouple's time constant in advance. Because the thermocouple's time constant is closely related to test conditions, such as the velocity of the distorted airflow, the magnitude and direction of the temperature distortion, the thermocouple's dynamic characteristics can only be calibrated for the typical operating conditions of the measured airflow to obtain the time constant under these conditions. It is unrealistic to obtain the time constant under all arbitrary operating conditions. By using a dual-filament thermocouple probe to measure temperature distortion, the different responses of the two probes can be analyzed to determine the pulsation time constant and dynamic transfer function of either probe, thus achieving real-time online compensation of temperature distortion.

[0028] Beneficial effect 2: Two straightened, parallel thin-wire thermocouples are fixed through the wire rods, so that the thermocouples directly face the airflow, and the measurement node is located in the center. The fast response nature of the thin-wire thermocouples, combined with their direct exposure to undisturbed airflow, enables instant and accurate capture of airflow temperature changes. In addition, in high-speed airflow environments, the structural strength of the thermocouple is particularly important. This design cleverly utilizes the fixation of the wire rods to significantly enhance the structural strength of the thermocouple, effectively resist the impact of airflow impact, prevent the thermocouple from bending or breaking, ensure the long-term stable operation of the equipment, and meet the needs of high-precision and high-reliability measurements in aircraft engine testing.

[0029] Beneficial effect three: The support rod of the present invention is a column with a wing-shaped cross-section. The wing-shaped cross-section design achieves a streamlined shape by optimizing the surface curvature and contour, thereby significantly reducing the friction and collision between the airflow and the probe surface, and effectively reducing the resistance. This design helps the airflow flow smoothly along the probe surface, minimizes flow separation and the generation of vortices, and thus reduces airflow interference. In high-speed airflow, these characteristics ensure the stability and accurate position maintenance of the probe comb, avoiding deviation or vibration caused by resistance. It can provide more accurate and reliable measurement results in aircraft engine testing, ensuring the efficiency and effectiveness of the entire testing process.

[0030] Beneficial Effect 4: The hollow cylindrical design of the dual-filament support rod of the present invention can reduce airflow resistance and turbulent interference on the rod, reduce flow separation, and thus make the airflow around the probe more stable. The cylindrical support rod can enhance structural strength, resist the impact of high-speed airflow, and maintain stability. At the same time, this design can also improve thermal conductivity, reduce the heat radiation area, and reduce measurement errors caused by thermal radiation, allowing the temperature sensor to respond more quickly and accurately to changes in airflow temperature. This enables more accurate, stable, and rapid temperature measurement in high-speed airflow environments. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of the structure of a dynamic temperature probe comb based on dual thermocouples in an embodiment of the present invention.

[0032] Among them: 1-left thermocouple wire support rod, 2-right thermocouple wire support rod, 3-support rod, 4-first thermocouple wire, 5-second thermocouple wire, 6-mounting seat, DETAILED DESCRIPTION

[0033] The present invention is described in detail below with reference to the accompanying drawings and specific implementation examples, 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 precise definition of the protection scope of the present invention.

[0034] Example 1: Figure 1The present invention shows a dynamic temperature probe comb based on a double thermocouple, which is composed of a left thermocouple support rod (1), a right thermocouple support rod (2), a support rod (3), a first thermocouple wire (4), a second thermocouple wire (5), and a mounting seat (6). The present invention is characterized in that the left thermocouple support rod (1) and the right thermocouple support rod (2) are distributed along the center line to form a pair, have the same geometric shape, and are hollow cylinders. According to the measurement requirements of the Chinese aviation industry standard, three measuring points are respectively fixed on the support rod (3) in the span direction according to the equal annular surface. The left thermocouple support rod (1) and the right thermocouple support rod (2) are welded to the support rod (2), and the first thermocouple wire (4) and the second thermocouple wire (5) are built in and are led out and straightened from the top ends of the left thermocouple support rod (1) and the right thermocouple support rod (2). The connection collection system part is led out from the bottom end of the support rod (3); the support rod (3) is welded to the mounting seat (6).

[0035] The left even-wire support rod (1) and the right even-wire support rod (2) are made of high-temperature resistant insulating material, are 6 mm long, have an inner diameter of 0.3 mm and an outer diameter of 1 mm, and are arranged at an angle of 45° along the center line to form a pair.

[0036] The support rod (3) is made of stainless steel and has a wing-shaped cross section with a maximum width of 7 mm and a maximum length of 15 mm. According to the measurement requirements of the Chinese aviation industry standard, 5 measuring points are arranged along the span direction of the probe comb using the equal annular surface method.

[0037] The first thermocouple wire (4) and the second thermocouple wire (5) are K-type thermocouples with wire diameters of 50 microns and 100 microns, respectively. Except for the sensing portion, the wires are all wrapped with an insulating layer. The wires are placed in parallel, stretched tight, and in a "single" shape. The thermocouple measuring point is located in the center, and the distance between the centers of the two measuring points is 0.4 mm. The wires are fixed in the support rod by an adhesive material and the support rod is sealed.

[0038] The present invention utilizes a dual-thermocouple dynamic temperature probe comb, as described in an embodiment of the present invention, after static calibration of the thermocouple wires to obtain zero-point data and static temperature response. After installation as in Example 1, the temperature distortion of the compressor inlet surface (AIP) section is measured, and the voltage response of the thermocouple wires under different operating conditions is recorded. The measured data is then analyzed and processed.

[0039] The present invention proposes a temperature measurement correction method based on a dynamic temperature probe comb with dual thermocouples. The dynamic characteristics of the thermocouples can be described by a second-order transfer function, which is expressed as:

[0040]

[0041] This function can be regarded as the superposition of two first-order transfer functions, which are related to the thermocouple measurement junction and the thermocouple wire respectively. Its specific expression is:

[0042]

[0043] H(z)=m1H1(z)+m2H2(z)

[0044] The analysis shows that the values ​​of m1 and m2 remain unchanged for thermocouples with different wire diameters, and the relationship between τ1 and Reynolds number satisfies the formula:

[0045] log(Δ)=a0+a1 log(Re),Δ=(m1 / τ1+m2 / τ2)

[0046] The relationship between τ2 and Reynolds number satisfies the formula:

[0047] log(τ2)=β0+β1log(Re)

[0048] Under the same inlet flow conditions, the ratio of τ2 between different wire diameters is a constant. The τ2 of the thinner thermocouple can be inferred from the ratio of τ2 between the two thicker thermocouples, and the τ1 value of the thinner thermocouple can be obtained using the above relationship. By processing the m1 and m2 values ​​of the two thicker thermocouples, the m1 and m2 values ​​of the thinner thermocouple can be approximately estimated, and the second-order transfer function of the thinner thermocouple can be obtained.

[0049] After steady-state and dynamic calibration in a calibration wind tunnel, the m1, m2, τ1, and τ2 values ​​of the 50-μm and 100-μm thermocouples under different operating conditions can be obtained, respectively. The m1, m2, τ1, and τ2 values ​​of the 25-μm thermocouple can be estimated using the above relationships, thereby determining the transfer function of the 25-μm thermocouple. The dynamic response of the 25-μm thermocouple can then be obtained by compensating the 50-μm and 100-μm thermocouples.

Claims

1. A dynamic temperature probe comb based on dual thermocouples, characterized by: A left thermocouple support rod (1), a right thermocouple support rod (2), a support rod (3), a first thermocouple wire (4), a second thermocouple wire (5), and a mounting seat (6); the left thermocouple support rod (1) and the right thermocouple support rod (2) are distributed along the center line to form a pair, have the same geometric shape, and are hollow cylinders; according to the measurement requirements of the Chinese aviation industry standard, they are respectively fixed on the support rod (3) in the span direction and the measurement points are arranged according to the equal annular surface; the left thermocouple support rod (1) and the right thermocouple support rod (2) are welded to the support rod (3); the thermocouple wire (4) and the thermocouple wire (5) are built in and are led out and straightened from the top ends of the left thermocouple support rod (1) and the right thermocouple support rod (2); the connection collection system part is led out from the bottom end of the support rod (3); the support rod (3) is welded to the mounting seat (6); The left even-wire support rod (1) and the right even-wire support rod (2) are arranged at each distribution point, two on the left and two on the right, with a length of 6-8 mm, an inner diameter of 0.3-0.5 mm, and an outer diameter of 1-1.3 mm. The two distribution rods along the center line are arranged at an angle of 30-60 degrees to form a pair, and the angle can be adjusted according to the airflow angle; The left even-wire support rod (1) and the right even-wire support rod (2) are measured in accordance with the Chinese aviation industry standard and require at least three sets, which can be adjusted according to the CFD simulation results; The first thermocouple wire (4) and the second thermocouple wire (5) are K-type or T-type thin-wire thermocouples with different wire diameters, and are led out from the top ends of the left wire support rod (1) and the right wire support rod (2). The exposed wires at the heads of the two thermocouples are placed in parallel, tightened, and in a "one" shape. The support rod (3) is a column with a wing-shaped cross section and a maximum cross-sectional width of 7-9 mm and a maximum length of 15-20 mm.

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