Dynamic temperature probe based on double-wire thermocouple

Abstract

The utility model relates to the technical field of dynamic temperature testing, in particular to a dynamic temperature probe based on a double-filament thermocouple, which comprises a thermocouple wire support rod, a probe support rod, an alundum tube and a thermocouple wire. The thermocouple wire support rod is wedge-shaped, the front edge is provided with an inverted L-shaped through hole, the alundum tube is fixed in the through hole and is insulated, the thermocouple wire penetrates through the alundum tube to be led out and tensioned to form a linear structure, and the measuring contact is positioned in the middle of the thermocouple wire. The thermocouple wire and the thermocouple wire supporting rod form an n shape, and the exposed part is arranged in parallel and windward, thereby reducing the influence of turbulent flow, and improving the response frequency.

Description

Technical Field

[0001] The invention belongs to the technical field of aviation engine temperature testing, and in particular relates to a double-wire thermocouple dynamic temperature probe. Background Art

[0002] During aircraft engine operation, dynamic temperature distortion (DTD) may occur at the fan / compressor inlet due to environmental factors. For example, dynamic temperature distortion (DTD) can occur when an aircraft is in high maneuverability, ingests missile exhaust during missile launch, ingests engine exhaust and water vapor during catapult launch from the deck of a carrier-based aircraft, or when the anti-icing system in the inlet is heated. When this DTD passes through the inlet, the increased air velocity can cause boundary layer separation at the steep bend, disrupting the uniformity of the inlet flow field. For turboshaft engines, the airflow also passes through a particle separator, causing pre-swirl diffusion. Once this DTD reaches the fan / compressor inlet, it can alter the operating environment and load of the fan / compressor. DTD not only affects the engine's surge threshold (and in severe cases, can even directly trigger surge) but also affects the engine's common operating line, significantly impacting the engine's aerodynamic stability. To accurately understand the impact of engine inlet dynamic temperature distortion on fan / compressor aerodynamic stability, it is necessary to conduct relevant compression system inlet dynamic temperature distortion tests to simulate the changes in fan / compressor characteristics under various dynamic temperature distortion conditions. This requires precise measurement of the compression system inlet dynamic temperature distortion (primarily the temperature rise rate) and its development in subsequent compressor stages, thereby providing support for accurately understanding the compression system's aerodynamic stability under various distortion conditions.

[0003] Currently, domestic research institutions have conducted theoretical analysis and experimental testing of imported dynamic temperature distortion, primarily using low-inertia thermocouples, combined-wire thermocouples, and hot-wire / hot-film thermometers. However, these approaches, including frequency response, temperature measurement accuracy, temperature field testing methods, data processing, and dynamic temperature calibration, often fail to meet model requirements and lag significantly behind advanced international standards. These approaches suffer from four key drawbacks: First, the response speed of thermocouple sensors is closely related to the wire diameter. While extremely fine wires offer fast response speeds, meeting the requirements of high-frequency measurements, their material strength limits their application in harsh testing environments. Excessively thin wires are susceptible to physical damage or performance degradation when exposed to high temperature gradients, high-velocity airflow, and other harsh conditions, making it difficult to achieve the desired high-frequency response characteristics. Second, existing thermocouple temperature compensation solutions typically rely on first-order compensation methods. While simple, this approach often results in significant errors when dealing with complex dynamic temperature changes. Third, in the prior art, in the design of traditional double-wire thermocouples, the distance between the two wires is usually large, which results in low spatial resolution when measuring dynamic temperature changes. When dealing with measurement tasks of complex dynamic temperature fields such as aircraft engines, this poor spatial resolution will greatly reduce the accuracy of the test. In addition, the larger distance between the two wires will affect the accuracy of the compensation scheme. Fourth, the layout of the traditional total temperature probe thermocouple wires is parallel to the incoming flow direction. This layout can provide more accurate measurement results under low-speed or subsonic conditions. However, under high-speed or supersonic conditions, due to the high-speed impact of the airflow, the thermocouple wires are easily bent, which greatly affects the response frequency of the thermocouple.

[0004] Therefore, there is an urgent need to develop a high-precision, stable operation, small spatial resolution and simultaneous measurement of fan / compressor inlet dynamic temperature distortion test probe to achieve accurate measurement of dynamic temperature distortion and provide direct data support for high-performance design of fans / compressors at all levels. Summary of the Invention

[0005] The present invention discloses a dynamic temperature probe based on a dual thermocouple. The probe comprises a wire support rod, a probe support rod, a thermocouple measuring junction, and a thermocouple wire. To reduce the potential interference of the vortex generated by the wire support rod in the flow field on the temperature measurement of the thermocouple measuring junction, the wire support rod is formed into a wedge shape. The wire support rod supports the thermocouple wires. The dual-wire thermocouple is placed at the leading edge of the support rod, parallel to the incoming flow, to reduce the influence of the vortex on the measuring junction and improve the response frequency of the temperature probe. The thermocouple wires are straightened by the wire support rod into an "I" shape, with the thermocouple measuring junction located in the middle. Facing the direction of the airflow, the two thermocouples are placed in parallel to ensure that the same temperature point is measured. The exposed thermocouple wires and the wire support rod form an "П" shape. This shape can ensure that the thermocouple is in full contact with the flow field and facilitates the replacement of the thermocouple wires.

[0006] Compared to traditional thermocouple dynamic temperature probes, this paper proposes a new dual-wire thermocouple dynamic temperature probe. By conducting in-depth research on the dynamic relationship between different wire diameters, a temperature measurement method based on a second-order compensation strategy is proposed, which can adjust the compensation parameters according to the actual temperature dynamic changes. This design enables the thermocouple wire to maintain strength and rigidity under the impact of high-speed airflow and is less likely to bend and deform. Through the compensation strategy, the dynamic response is achieved that is the same as that of an ideal thin-wire thermocouple. The second-order transfer function of the thermocouple is as follows:

[0007]

[0008] The second-order transfer function is considered to be the sum of two first-order transfer functions, which are related to the thermocouple measurement junction and the thermocouple wire respectively. The specific expression is:

[0009]

[0010] H(z)=m1H1(z)+m2H2(z)

[0011] The four parameters that affect the dynamic characteristics of thermocouples are obtained, namely m1, m2, τ1, and τ2. The present invention systematically analyzes the four key parameters that affect the dynamic characteristics of thermocouples: m1, m2, τ1, and τ2 through CFD simulation technology. After simulation analysis under a variety of different working conditions, it is finally concluded that thermocouples with different wire diameters remain unchanged in the values ​​of m1 and m2, and the ratio of τ1 and τ2 is closely related to the wire diameter of the thermocouple. By averaging the m1 and m2 values ​​of two thicker thermocouples, we can approximately estimate the m1 and m2 values ​​of the thinner thermocouple. This method not only simplifies the actual measurement process, but also can predict the performance of thin-wire thermocouples without directly measuring them. Furthermore, by analyzing the ratio of τ1 and τ2 of the two thermocouples, we can determine the τ1 and τ2 parameters of the thin-wire thermocouple, thereby accurately obtaining its transfer function.

[0012] The present invention provides a double-wire thermocouple dynamic temperature probe that can measure the dynamic temperature distortion of the fan / compressor inlet. The technical problems to be solved are: first, it solves the contradiction between the high response frequency and high strength of the existing small-inertia thermocouples. Second, by introducing the temperature measurement method of the second-order compensation strategy, it solves the significant deviation between the rapid change of the existing temperature field and the prediction of the first-order model, greatly improving the accuracy and reliability of the overall measurement. Third, it solves the problems of the existing dynamic temperature probe being large in size, having great interference on the flow field, and having low spatial resolution due to the large spacing between the thermocouples of the combined wire diameter. Fourth, it solves the problem that when the existing dynamic temperature probe measures high Mach airflow, the thermocouple wire is difficult to maintain strength and rigidity under the impact of high-speed airflow and is prone to bending and deformation.

[0013] The technical solution of the present invention is:

[0014] 1. A dynamic temperature probe based on a double thermocouple, comprising a thermocouple wire support rod (1), a probe support rod (2), a corundum tube (3), a thick thermocouple measuring junction (4), a thin thermocouple measuring junction (5), a thick thermocouple wire (6), and a thin thermocouple wire (7), characterized in that: the thermocouple wire support rod (1) is connected to the probe support rod (2), two "Г"-shaped through holes are opened at the front edge of the thermocouple wire support rod (1) and pass through the probe support rod (2), and the frustum-shaped probe support rod (2) is reduced. The small support rod interferes with the flow field. The corundum tube (3) is fixed in the "Г"-shaped through hole of the thermocouple support rod (1) and the probe support rod (2) and is used for heat insulation of the thick thermocouple wire (6) and the thin thermocouple wire (7). The thick thermocouple wire (6) and the thin thermocouple wire (7) are led out through the inner hole of the corundum tube (3). The exposed thermocouple wires at the head of the double-wire thermocouple probe are tightened and in a "-" shape. The thick thermocouple measuring junction (4) and the thin thermocouple measuring junction (5) are located in the middle of the exposed thermocouple wires.

[0015] 2. The even-wire support rod (1) is made of a high-temperature resistant alloy material. The even-wire support rod (1) is a wedge-shaped support rod with a hollow "Г"-shaped cylindrical support rod inside. It is composed of a semi-cylinder and a triangular prism. The diameter of the semi-cylinder is 2 to 4 mm and the height is 8 to 20 mm. The side length of the triangular prism is 4 to 8 mm. The diameter of the hollow "Г"-shaped cylinder is 1 to 2 mm and the height is 6 to 15 mm. The even-wire support rod (1) adopts an elbow design to avoid the even-wire from breaking and prolong the service life of the even-wire. The distance between the central axis of the even-wire support rod (1) and the central axis of the probe support rod (2) is 4 to 6 mm.

[0016] 3. The shape of the probe support rod (2) is a frustum, which helps to reduce the disturbance of the probe support rod in the flow field. The frustum adopts a design of small top and large bottom, with the diameter of the upper circle being 6 to 12 mm and the diameter of the lower circle being 10 to 20 mm. A through hole with a diameter of 1 to 2 mm is opened at the fixed position of the even-wire support rod (1).

[0017] 4. The corundum tube (3) is provided with an F-shaped through hole for passing the thick thermocouple wire (6) and the thin thermocouple wire (7), the diameter of which is 0.2 mm to 0.5 mm. The corundum tube (3) is fixed to the wire support rod (1) and the probe support rod (2) by means of a heat-insulating adhesive material.

[0018] 5. The thick thermocouple wire (6) and the thin thermocouple wire (7) pass through and are fixed in the corundum tube (3), and are straightened by the wire support rod (1). The exposed parts of the thick thermocouple wire (6) and the thin thermocouple wire (7) are parallel to the upper surface of the probe support rod (2) head, forming a "-" shape. The thick thermocouple measuring junction (4) and the thin thermocouple measuring junction (5) are located in the middle of the exposed thermocouple wire, facing the incoming flow direction. The exposed parts of the thick thermocouple wire (6) and the thin thermocouple wire (7) and the two wire support rods are respectively in a "П" shape. The diameter of the thick thermocouple wire (6) is 50 microns to 100 microns, and the diameter of the thin thermocouple wire (7) is 25 microns to 50 microns.

[0019] The present invention provides a dynamic temperature probe based on a double-wire thermocouple, which has the following beneficial effects:

[0020] Beneficial Effect 1: After steady-state and dynamic calibration in a calibration wind tunnel, the present invention uses two thicker thermocouples through compensation technology to obtain the rapid response of thinner thermocouples, and can accurately capture rapidly changing temperature fields. These wires are far superior to traditional small-inertia thermocouples due to their physical strength and stability. In practical applications, they provide a reliable and accurate means for dynamic temperature distortion testing of fan / compressor inlets.

[0021] Beneficial Effect 2: By analyzing and simulating the behavior of different wire diameters under dynamic temperature changes, this paper introduces a precise temperature measurement method based on a second-order compensation strategy. This improves upon the traditional first-order compensation scheme, optimizes the compensation method, and achieves more accurate compensation results. This strategy allows for effective compensation of two relatively thick thermocouple wires.

[0022] Advantageous Effect 3: This invention achieves extremely high spatial resolution by designing the measurement junction spacing of the double-wire thermocouple to be very small. This design enables the probe to capture even subtler temperature changes, making it suitable for applications with extremely high temperature distribution requirements.

[0023] Beneficial Effect 4: The thermocouple wire of the present invention is fixed and straightened by the wire support rod, forming a "-" shape. The thermocouple temperature measurement junction is located in the center, facing the direction of airflow, and the exposed wire and the wire support rod form a "П" shape. This support structure ensures the strength of the thermocouple wire, making it less likely to bend or break in the flow field.

[0024] Beneficial Effect 5: The probe head of the present invention has a simple and compact structure, is "I"-shaped, and has a small size. The double-wire parallel hot wires are arranged vertically without crossing or affecting each other. It is also suitable for measurement between narrow fan / compressor and turbine stages.

[0025] Beneficial Effect 6: The bending part of the thermocouple wire support rod of the present invention adopts an arc-shaped design, which effectively protects the thermocouple wire and makes it difficult to break. At the same time, the thermocouple wire support rod is designed to be wedge-shaped, which greatly reduces the interference with the flow field.

[0026] Advantageous Effect 7: The thermocouple wire of the present invention passes through the corundum tube, providing insulation and heat insulation for the thermocouple wire and facilitating wire replacement. The thermocouple can be of different types, such as K-type, J-type, and T-type. The twin wire diameter ratio can be a combination of different thicknesses, such as 1.5, 2, or 2.5. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the structure of a dynamic temperature probe based on a double-wire thermocouple in an embodiment of the present invention.

[0028] Figure 2 yes Figure 1 Top view of .

[0029] Among them: 1- thermocouple wire support rod, 2- probe support rod, 3- corundum tube, 4- thick thermocouple measuring junction, 5- thin thermocouple measuring junction, 6- thick thermocouple wire, 7- thin thermocouple wire. DETAILED DESCRIPTION

[0030] 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.

[0031] like Figures 1-2 The invention shows a dynamic temperature probe based on a double-wire thermocouple. The double-wire support rod (1) is connected to the probe support rod (2). Two "G"-shaped through holes are opened at the front edge of the double-wire support rod (1) and pass through the probe support rod (2). The frustum-shaped probe support rod (2) is used to reduce the interference of the support rod on the flow field. The corundum tube (3) is fixed in the "G"-shaped through holes of the double-wire support rod (1) and the probe support rod (2) and is used for heat insulation of the thick thermocouple wire (6) and the thin thermocouple wire (7). The thick thermocouple wire (6) and the thin thermocouple wire (7) are led out through the inner hole of the corundum tube (3). The exposed wire of the double-wire thermocouple probe head is tightened and in a "-" shape. The thick thermocouple measurement junction (4) and the thin thermocouple measurement junction (5) are located in the middle of the exposed wire.

[0032] The even-wire support rod (1) is made of a high-temperature resistant alloy material. The even-wire support rod (1) is a wedge-shaped support rod with a hollow "Г"-shaped cylindrical support rod inside. It is composed of a semi-cylinder and a triangular prism. The semi-cylinder has a diameter of 3 mm and a height of 10 mm. The triangular prism has a side length of 6 mm. The hollow "Г"-shaped cylinder has a diameter of 2 mm and a height of 8 mm. The even-wire support rod (1) adopts an elbow design to avoid the even-wire from breaking and prolong the service life of the even-wire. The distance between the central axis of the even-wire support rod (1) and the central axis of the probe support rod (2) is 2 mm.

[0033] The shape of the probe support rod (2) is a frustum, which helps to reduce the disturbance of the probe support rod in the flow field. The frustum adopts a design of being small at the top and large at the bottom, with an upper circle diameter of 8 mm and a lower circle diameter of 10 mm. A 2 mm through hole is opened at the fixed position of the even-wire support rod (1).

[0034] The corundum tube (3) has an F-shaped through hole for passing a thick thermocouple wire (6) and a thin thermocouple wire (7), and has a diameter of 0.5 mm. The corundum tube (3) is fixed to the wire support rod (1) and the probe support rod (2) through a heat-insulating adhesive material.

[0035] The thick thermocouple wire (6) and the thin thermocouple wire (7) pass through and are fixed in the corundum tube (3), and are straightened by the wire support rod (1). The exposed parts of the thick thermocouple wire (6) and the thin thermocouple wire (7) are parallel to the upper surface of the probe support rod (2) head, forming a "-" shape. The thick thermocouple measuring contact (4) and the thin thermocouple measuring contact (5) are located in the middle of the exposed thermocouple wire, facing the incoming flow direction. The exposed parts of the thick thermocouple wire (6) and the thin thermocouple wire (7) and the two wire support rods are respectively in a "П" shape. The diameter of the thick thermocouple wire (6) is 100 microns, and the diameter of the thin thermocouple wire (7) is 50 microns.

[0036] This paper proposes a novel dual-wire thermocouple dynamic temperature probe. Through in-depth research on the dynamic relationship between different wire diameters, a temperature measurement method based on a second-order compensation strategy is proposed, which can adjust the compensation parameters according to the actual temperature dynamics. This design ensures that the thermocouple wires maintain their strength and rigidity under the impact of high-speed airflow, making them less susceptible to bending and deformation. Through this compensation strategy, the dynamic response is equivalent to that of an ideal thin-wire thermocouple. The second-order transfer function of the thermocouple is expressed as follows:

[0037]

[0038] The second-order transfer function is considered to be the sum of two first-order transfer functions, which are related to the thermocouple measurement junction and the thermocouple wire respectively. The specific expression is:

[0039]

[0040] H(z)=m1H1(z)+m2H2(z)

[0041] Four parameters affecting the dynamic characteristics of thermocouples are identified: m1, m2, τ1, and τ2. This paper systematically analyzes these four key parameters, m1, m2, τ1, and τ2, using CFD simulation technology. Simulations and analyses under various operating conditions ultimately reveal that thermocouples with varying wire diameters maintain the same m1 and m2 values. The ratio of τ1 to τ2 is closely related to the wire diameter of the thermocouple. By averaging the m1 and m2 values ​​of two thicker thermocouples, we can approximate the m1 and m2 values ​​for a thinner thermocouple.

Claims

1. A dynamic temperature probe based on a double-wire thermocouple, comprising a double-wire support rod (1), a probe support rod (2), a corundum tube (3), a thick thermocouple measuring junction (4), a thin thermocouple measuring junction (5), a thick thermocouple wire (6), and a thin thermocouple wire (7), characterized in that: The wire support rod (1) is connected to the probe support rod (2). Two "Г"-shaped through holes are opened at the front edge of the wire support rod (1) and pass through the probe support rod (2). The frustum-shaped probe support rod (2) is used to reduce the interference of the support rod on the flow field. The corundum tube (3) is fixed in the "Г"-shaped through holes of the wire support rod (1) and the probe support rod (2) and is used for heat insulation of the thick thermocouple wire (6) and the thin thermocouple wire (7). The thick thermocouple wire (6) and the thin thermocouple wire (7) are led out through the inner hole of the corundum tube (3). The exposed wire of the double-wire thermocouple probe head is tightened and in a "—" shape. The thick thermocouple measurement junction (4) and the thin thermocouple measurement junction (5) are located in the middle of the exposed wire. The even-wire support rod (1) is made of a high-temperature resistant alloy material. The even-wire support rod (1) is a wedge-shaped support rod with a hollow "Г"-shaped cylindrical support rod inside. It is composed of a semi-cylinder and a triangular prism. The semi-cylinder has a diameter of 2 to 4 mm and a height of 8 to 20 mm. The triangular prism has a side length of 4 to 8 mm. The hollow "Г"-shaped cylinder has a diameter of 1 to 2 mm and a height of 6 to 15 mm. The even-wire support rod (1) adopts an elbow design to avoid even-wire breakage and extend the service life of the even-wire. The distance between the center axis of the even-wire support rod (1) and the center axis of the probe support rod (2) is 4 to 6 mm. The probe support rod (2) is in the shape of a truncated cone, which helps to reduce the disturbance of the probe support rod in the flow field. The truncated cone adopts a design of being small at the top and large at the bottom, with an upper circle diameter of 6 to 12 mm and a lower circle diameter of 10 to 20 mm. A through hole with a diameter of 1 to 2 mm is opened at the fixed position of the even-wire support rod (1); The corundum tube (3) has an "F"-shaped through hole for passing a thick thermocouple wire (6) and a thin thermocouple wire (7), the diameter of which is 0.2 mm to 0.5 mm. The corundum tube (3) is fixed to the wire support rod (1) and the probe support rod (2) by means of a heat-insulating adhesive material; The thick thermocouple wire (6) and the thin thermocouple wire (7) pass through and are fixed in the corundum tube (3), and are straightened by the wire support rod (1). The exposed parts of the thick thermocouple wire (6) and the thin thermocouple wire (7) are parallel to the upper surface of the probe support rod (2) head, forming a "-" shape. The thick thermocouple measuring junction (4) and the thin thermocouple measuring junction (5) are located in the middle of the exposed thermocouple wire, facing the incoming flow direction. The exposed parts of the thick thermocouple wire (6) and the thin thermocouple wire (7) and the two wire support rods are respectively in a "П" shape. The diameter of the thick thermocouple wire (6) is 50 microns to 100 microns, and the diameter of the thin thermocouple wire (7) is 25 microns to 50 microns.

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