A device for measuring average temperature in a non-uniform temperature field and its application

Abstract

The present invention discloses a device for measuring the average temperature of a non-uniform temperature field and its application. The measuring device of the present invention is designed to have a length according to the flow cross section, and four thermal resistors connected by set rules are arranged in the measuring device to form a thermal resistor group, thereby measuring the average temperature on a line. The four measuring devices are further arranged by setting rules to form a thermal resistor group, and the average temperature of the flow cross section can be measured. For example, when applied to the measurement of flue gas temperature in a coal-fired power plant, a large flue only needs one temperature signal output to represent the average temperature of 16 grid measurements. Under the conditions of an average temperature of 120°C and a maximum temperature deviation of 20°C, the theoretical limit error value of the measurement does not exceed 0.27°C, and under normal circumstances the error is less than 0.1°C, which is sufficient to meet the industrial measurement accuracy of the flue gas temperature. The present invention solves the problem of difficulty in measuring the average temperature of a non-uniform temperature field or too many measuring points during precise measurement, and can achieve precise measurement of a non-uniform temperature field at a low cost.

Description

Technical Field

[0001] The present invention relates to exhaust gas temperature measurement technology in the technical field of power station boiler temperature measurement, and in particular to a non-uniform temperature field average temperature measurement device and application thereof. Background Art

[0002] Boiler efficiency calculations and combustion optimization control rely heavily on accurate measurement of boiler exhaust temperature. Dynamic changes in the boiler's combustion, heat exchange, and flow processes lead to a certain degree of unevenness in the exhaust temperature distribution within the flue, making effective measurement of the average temperature crucial.

[0003] At present, most of the units in power plants only have a single or a few exhaust gas temperature measurement points arranged in the tail flue cross section, but the distribution of the actual exhaust gas temperature in the spatial cross section is somewhat uneven. The temperature values ​​measured by a single or a few measurement points are difficult to represent the actual temperature field on the entire cross section. Even if a representative point under a certain working condition is obtained through calibration, the representative point also has the problem of migration as the flow field changes. In manual testing, the standard method is to use the grid method to perform multi-point measurements and then take the average value to represent the average temperature. However, for online measurement, the grid method has the problem of too many measurement points when arranging measurement points. There are relatively few patents on flue gas temperature measurement. One patent proposes to arrange multiple thermocouples into a group along the length of the flue. The measurement method conforms to the basic principle of the grid method, but each thermocouple signal in the thermocouple group needs to be connected to the measurement and control system. There is a problem of high equipment, installation and maintenance costs of the measurement and control system due to the large number of measurement points.

[0004] Therefore, a device is needed that can effectively and reliably measure the non-uniform temperature field in the entire cross-section of the tail flue and simplify the signal processing method, which is of great significance for the accurate evaluation of boiler efficiency. Summary of the Invention

[0005] In order to solve the above problems and measurement problems in similar scenarios, the present invention provides an average temperature measurement device and application for non-uniform temperature fields, which achieves the effect of accurate measurement of exhaust temperature by evenly distributing multiple measuring points and simplifying the connection method of temperature signal processing complexity.

[0006] The present invention solves the technical problem by the following technical solutions:

[0007] The present invention comprises a temperature sensor assembly (1), a sleeve (2), a filler (3), a junction box (4) and a mounting assembly (5);

[0008] The temperature sensor assembly (1) is arranged in a sleeve (2); a junction box (4) is fixedly arranged at one end of the temperature sensor assembly (1) and is used to fix the lead wire and the user-end wiring; the mounting assembly is connected to the outer wall of the sleeve and is used to install the temperature measuring device in the measured channel; and a filler (3) is provided in the inner cavity of the sleeve (2).

[0009] Furthermore, the temperature sensor assembly (1) is a core assembly, wherein the temperature sensor assembly (1) comprises a temperature sensor (1-1), a semicircular nut (1-2), an insulating pressing piece (1-3), a clamping screw (1-4), an elastic steel bar (1-5), and a supporting screw (1-6); the semicircular diameter of the semicircular nut (1-2) is slightly smaller than the inner diameter of the sleeve (2), so that the semicircular surface of the semicircular nut (1-2) is in full contact with the inner wall surface of the sleeve (2); the temperature sensor (1-1) is clamped between the flat end of the semicircular nut (1-2) and the insulating pressing piece (1-3); the clamping screw (1-4) passes through the elastic steel bar (1-5) and the insulating pressing piece (1-3) and is tightened to the semicircular nut (1-2); and the supporting screws (1-6) are respectively fixed to the elastic steel bar (1-5) with matching nuts and are distributed on both sides of the temperature sensor (1-1).

[0010] Furthermore, the elastic steel strip (1-5) is a long strip of stainless steel with a certain elasticity, with a width slightly smaller than the inner diameter of the sleeve (2), a thickness of about 1 mm, and a length slightly shorter than the length of the sleeve (2).

[0011] Furthermore, the support screws (1-6) are symmetrically distributed on both sides of the temperature sensor (1-1), and the distance between the support screws (1-6) and the temperature sensor (1-1) is 5-20 cm; the support screws (1-6) and the temperature sensor (1-1) work together to form a certain curvature of the elastic steel bar (1-5), so that the semicircular surface of the semicircular nut (1-2) can be fixed and tightly attached to the inner wall surface of the sleeve (2).

[0012] Furthermore, there are four groups of temperature sensor assemblies (1), which are evenly spaced on the elastic steel bars (1-5) to achieve grid temperature measurement; the spacing between two adjacent groups of temperature sensor assemblies (1) is 1 / 4 of the depth of the air duct or flue in the installation insertion direction; and the four groups of temperature sensor assemblies (1) are connected in a cross-series-parallel manner.

[0013] Furthermore, the sleeve (2) serves as a mounting support and protective component for the temperature sensor assembly (1); the sleeve (2) is made of a stainless steel tube, and the length of the sleeve (2) is determined by the length of the temperature sensor assembly (1).

[0014] Furthermore, the filler (3) in the sleeve (2) is made of a powder material with insulating and thermal conductive properties.

[0015] Furthermore, the temperature sensor (1-1) is a thermal resistor.

[0016] Furthermore, the insulating pressed sheet (1-3) is a mica board.

[0017] Furthermore, the cross-series and parallel connection method of the four temperature sensors is implemented as follows: assuming that the four temperature sensors are sequentially numbered 1, 2, 3, and 4, the cross-series and parallel connection method is: 1 and 3 are connected in series, 2 and 4 are connected in series, and the two series temperature sensors are then connected in parallel; the length of the connecting line between the temperature sensors is solved as follows: assuming that the temperature sensor arrangement spacing is L, the length of the series connecting line is 2L, the length of the parallel connecting line is also 2L, and the lead wire is connected at the midpoint of the parallel connecting line; the length of the lead wire is determined by the length of the sleeve, assuming that the length of the short side lead wire is X, the length of the long side lead wire is X+2L, and two long side lead wires are connected in parallel; thereby forming a three-wire thermal resistor type temperature measurement device with equal internal line resistance.

[0018] The present invention has the following beneficial effects:

[0019] The present invention is used to accurately measure the average temperature of an uneven temperature field, minimizing the interference caused by uneven temperature distribution. The invention has the following beneficial effects:

[0020] 1. The present invention simplifies the complexity of conventional non-uniform temperature field average temperature grid method measurement, directly obtains the average temperature in a large space of non-uniform temperature field, solves the problem of representativeness of the measurement of the average temperature of the non-uniform temperature field, and realizes the simple measurement of the non-uniform temperature field.

[0021] 2. The present invention simplifies the complexity of signal processing when multiple measuring points are arranged in a large space using a grid method in an uneven temperature field, effectively reducing the cost of signal acquisition.

[0022] 3. Easy to install, maintain and disassemble. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the overall structure of the device of the present invention;

[0024] Figure 2 This is a schematic diagram of the wiring method of the temperature sensor in the device of the present invention;

[0025] Figure 3 It is an installation schematic diagram of the application method of the device of the present invention.

[0026] Description of reference numerals:

[0027] Figure 1In the figure: 1. Temperature sensor assembly; 2. Bushing; 3. Filler; 4. Junction box; 5. Mounting assembly. The temperature sensor assembly 1 includes: 1-1. Temperature sensor; 1-2. Semicircular nut; 1-3. Insulation pressing piece; 1-4. Clamping screw; 1-5. Elastic steel bar; 1-6. Support screw. DETAILED DESCRIPTION

[0028] The present invention will be further described in detail below through specific examples. The following examples are only illustrative and not restrictive, and the scope of protection of the present invention cannot be limited thereto.

[0029] like Figure 1 As shown, a device for measuring the average temperature of a non-uniform temperature field includes a temperature sensor assembly 1, a sleeve 2, a filler 3, a junction box 4, and a mounting assembly 5. The temperature sensor assembly 1 includes a temperature sensor 1-1, a semicircular nut 1-2, an insulating pressing piece 1-3, a pressing screw 1-4, an elastic steel bar 1-5, and a supporting screw 1-6.

[0030] The temperature sensor assembly 1 is the core component of the present invention, which is composed of a temperature sensor 1-1 and its mounting accessories. The temperature sensor 1-1 is a thermal resistor (such as PT100). The semicircular diameter of the semicircular nut 1-2 is basically the same as the inner diameter of the sleeve 2, so that the semicircular surface of the semicircular nut 1-2 is in full contact with the inner wall surface of the sleeve 2, thereby enhancing the thermal conductivity. The insulating pressing piece 1-3 is made of a material such as a mica plate, and the temperature sensor 1-1 is clamped between the flat end of the semicircular nut 1-2 and the insulating pressing piece 1-3. The tightening screw 1-4 passes through the elastic steel bar 1-5 and the insulating pressing piece 1-3 and is tightened to the semicircular nut 1-2. The elastic steel bar 1-5 is a long strip of stainless steel with a certain elasticity. Its width is slightly smaller than the inner diameter of the sleeve 2, the thickness is about 1mm, and the length is slightly shorter than the length of the sleeve 2. The support screws 1-6 are fixed to the elastic steel bar 1-5 with matching nuts respectively, distributed on both sides of the temperature sensor 1-1, and the distance is preferably 5-20cm. The support screws 1-6 are symmetrically distributed on both sides of the temperature sensor 1-1. The support screws 1-6 and the temperature sensor 1-1 and other components work together to form a certain degree of curvature of the elastic steel bar 1-5, so that the semicircular surface of the semicircular nut 1-2 can be fixed and tightly attached to the inner wall of the sleeve 2.

[0031] There are four groups of temperature sensor assemblies 1, which are evenly spaced on the elastic steel bars 1-5 to achieve grid temperature measurement. The distance between two adjacent groups of temperature sensor assemblies 1 is 1 / 4 of the depth of the air duct or flue in the installation insertion direction. The four groups of temperature sensor assemblies 1 are connected in a cross-series and parallel manner. Assuming that the distance between the four temperature sensors 1 is L, the cross-series and parallel connection method and the length of the connecting wire are as follows: Figure 2 As shown, the length X of the lead wire is determined by the length of the sleeve 2. Figure 2The overall structure is a three-wire RTD temperature measurement device with equal internal wire resistance.

[0032] The sleeve 2 serves as a mounting support and protective element for the temperature sensor assembly 1. Stainless steel tubing is required, and its wall thickness must be sufficient to prevent wear and tear in dust-laden airflow, which could affect its service life. For use in corrosive atmospheres, corrosion-resistant steel such as 316L is preferred, as it requires a certain level of corrosion resistance. The length of the sleeve 2 is determined by the length of the temperature sensor assembly 1.

[0033] The filler 3 in the sleeve 2 is generally made of a powder material with insulating and thermal conductive properties, such as magnesium oxide powder.

[0034] The junction box 4 is used to fix the lead wires and facilitate user-side wiring. A conventional temperature sensor junction box is used.

[0035] The mounting assembly 5 is connected to the outer wall of the sleeve 2, either fixedly or flexibly. Mounting assembly 5 is used to mount the measuring device on the channel being measured, and can employ either a flange or cap-type structure. For example, sleeve 2 is embedded within the central through-hole of mounting assembly 5. Alternatively, sleeve 2 may be fixed to the outer wall of mounting assembly 5.

[0036] like Figure 2 As shown, the four temperature sensors 1 are connected in a cross-series-parallel manner. Assuming that the four temperature sensors are numbered 1, 2, 3, and 4 in sequence, the cross-series-parallel connection method is: 1 and 3 are connected in series, 2 and 4 are connected in series, and the two series temperature sensors are then connected in parallel. The length of the connecting wire between the temperature sensors is: Assuming the temperature sensor arrangement spacing is L, the length of the series connection wire is 2L, the length of the parallel connection wire is also 2L, and the lead wire is connected at the midpoint of the parallel connection wire. The length of the lead wire is determined by the length of the sleeve. Assuming the length of the short side lead wire is X, the length of the long side lead wire is X+2L. Two long side lead wires are connected in parallel. Overall, a three-wire thermal resistor type temperature measurement device with equal internal wire resistance is formed.

[0037] The device and application for measuring the average temperature of a non-uniform temperature field can obtain an equivalent resistance R value representing the average temperature in the insertion direction, thereby simplifying the complexity of temperature signal processing. During operation, the average resistance measured by the four RTDs within a single temperature measurement device is equivalent to that of a conventional single RTD. This resistance is transmitted to a data acquisition system via a single signal line, thereby obtaining the average temperature within the flue.

[0038] Taking the present invention as an example, when applied to measuring the exhaust temperature of a power plant boiler, the exhaust temperature of a boiler generally ranges from 110°C to 140°C. Based on field experience, the flue gas temperature nonuniformity does not exceed 20°C. To verify the accuracy of the equivalent resistance method when the resistance values ​​of the four thermal resistors are unequal, calculations were performed using several temperature deviation scenarios, with the results shown in Table 1. Table 1 selects calculations for temperature differences of 10°C and 20°C, respectively. A 20°C temperature difference with a cross-distribution is considered quite extreme in practice. For example, on the same straight line, the measurement error is greatest when the temperature distribution exhibits a jump. Therefore, taking the extreme cases of T1 = 110°C, T2 = 130°C, T3 = 110°C, and T4 = 130°C, the measured resistance values ​​are R1 = 142.29Ω, R2 = 149.83Ω, R3 = 142.29Ω, and R4 = 149.83Ω. Under such large temperature deviations, the average temperature obtained using the method of the present invention has a temperature measurement error of only 0.27°C compared to the true average temperature, fully meeting the accuracy requirements of practical applications. The last three columns select the case of a gradual temperature difference of four PT100 thermal resistors within a 20°C temperature range to simulate actual temperature differences that may occur in the field. Under this more realistic simulation environment, the maximum temperature difference caused by the equivalent resistance method is only 0.04°C. Overall, under the non-uniform temperature field conditions that may occur in reality, the measurement error is less than 0.1°C, which is sufficient to meet the accuracy requirements of most industrial field temperature measurements.

[0039] Table 1 Calculation of temperature deviation under extreme conditions

[0040]

[0041] In practical applications, the present invention is used to measure the exhaust gas temperature of a power plant boiler. For example, if the temperature measuring device of the present invention is inserted vertically into the flue, four exhaust gas temperature measuring holes are arranged at equal intervals on a plane perpendicular to the flue gas flow direction of the air preheater outlet flue of the boiler, and a temperature measuring device is inserted into each measuring hole. Figure 3 As shown. Four temperature measuring devices are used Figure 2 The connection method is further equivalent to a single thermal resistor, requiring only a single signal line to measure the exhaust temperature across the entire cross-section. This exhaust temperature represents the average temperature of the 16 temperature measurement points in the grid method. This average temperature minimizes measurement errors caused by uneven flue gas distribution, simplifies signal processing, and effectively reduces signal acquisition costs.

[0042] The above is only a preferred embodiment of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and modifications without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A device for measuring the average temperature of a non-uniform temperature field, characterized in that It comprises a temperature sensor assembly (1), a sleeve (2), a filler (3), a junction box (4) and a mounting assembly (5); The temperature sensor assembly (1) is arranged in the casing (2); the junction box (4) is fixedly arranged at one end of the temperature sensor assembly (1) and is used to fix the lead wire and the user-end wiring; the mounting assembly (5) is connected to the outer wall of the casing (2) and is used to install the temperature measuring device in the measured channel; the inner cavity of the casing (2) is provided with a filler (3); The temperature sensor assembly (1) is a core assembly, wherein the temperature sensor assembly (1) comprises a temperature sensor (1-1), a semicircular nut (1-2), an insulating pressing piece (1-3), a clamping screw (1-4), an elastic steel bar (1-5), and a supporting screw (1-6); the semicircular diameter of the semicircular nut (1-2) is slightly smaller than the inner diameter of the sleeve (2), so that the semicircular surface of the semicircular nut (1-2) is in full contact with the inner wall surface of the sleeve (2); the temperature sensor (1-1) is clamped between the flat end of the semicircular nut (1-2) and the insulating pressing piece (1-3); the clamping screw (1-4) passes through the elastic steel bar (1-5) and the insulating pressing piece (1-3) and is tightened onto the semicircular nut (1-2); the supporting screws (1-6) are respectively fixed to the elastic steel bar (1-5) with matching nuts and are distributed on both sides of the temperature sensor (1-1); The elastic steel strip (1-5) is a long strip of stainless steel with a certain elasticity, with a width slightly smaller than the inner diameter of the sleeve (2), a thickness of about 1 mm, and a length slightly shorter than the length of the sleeve (2); The support screws (1-6) are symmetrically distributed on both sides of the temperature sensor (1-1), and the distance between the support screws (1-6) and the temperature sensor (1-1) is 5-20 cm; the support screws (1-6) and the temperature sensor (1-1) assembly work together to form a certain curvature of the elastic steel bar (1-5), so that the semicircular surface of the semicircular nut (1-2) can be fixed and tightly attached to the inner wall surface of the sleeve (2); There are four groups of temperature sensor assemblies (1) distributed at equal intervals on the elastic steel bars (1-5) to achieve grid temperature measurement; the distance between two adjacent groups of temperature sensor assemblies (1) is 1 / 4 of the depth of the air duct or flue in the installation insertion direction; the four groups of temperature sensor assemblies (1) are connected in a cross-series and parallel manner; The cross-series and parallel connection method of four temperature sensors is implemented as follows: assuming that the four temperature sensors are arranged in sequence and numbered 1, 2, 3, and 4, the cross-series and parallel connection method is: 1 and 3 are connected in series, 2 and 4 are connected in series, and the two series temperature sensors are then connected in parallel; the length of the connecting line between the temperature sensors is solved as follows: assuming that the arrangement spacing of the temperature sensors is L, the length of the series connection line is 2L, the length of the parallel connection line is also 2L, and the lead wire is connected at the midpoint of the parallel connection line; the length of the lead wire is determined by the length of the sleeve. assuming that the length of the short side lead wire is X, the length of the long side lead wire is X+2L, and two long side lead wires are connected in parallel; thus, a three-wire thermal resistor type temperature measurement device with equal internal line resistance is formed.

2. The device for measuring the average temperature of a non-uniform temperature field according to claim 1, characterized in that The sleeve (2) is a mounting support and protective component for the temperature sensor assembly (1); the sleeve (2) is made of a stainless steel tube, and the length of the sleeve (2) is determined by the length of the temperature sensor assembly (1).

3. The device for measuring the average temperature of a non-uniform temperature field according to claim 2, characterized in that The filler (3) in the sleeve (2) is made of powder material with insulating and thermal conductive properties.

4. The device for measuring the average temperature of a non-uniform temperature field according to claim 3, characterized in that The temperature sensor (1-1) is a thermal resistor, and the insulating pressing sheet (1-3) is a mica plate.

5. Application of the device for measuring average temperature of a non-uniform temperature field according to claim 4, characterized in that Applied to the measurement of exhaust gas temperature of power plant boilers, the specific application is implemented as follows: if the temperature measuring device is inserted vertically into the flue, four exhaust gas temperature measuring holes are arranged at equal intervals on the plane perpendicular to the flue gas flow direction of the boiler's air preheater outlet flue, and a temperature measuring device is inserted into each measuring hole; the four temperature measuring devices are connected in cross-series and parallel, and are further equivalent to one thermal resistor. Only one signal line is needed to measure the exhaust gas temperature of the entire cross section, which represents the average temperature of the 16 temperature measuring points using the grid method.

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