Device and method for measuring air inlet quantity in test box for cable combustion performance detection

Abstract

The invention discloses a device and method for measuring the air inlet amount in a test box for cable combustion performance detection, and the device comprises a fixed bottom support which is located on the inner bottom wall of the test box, the fixed bottom support is provided with a rectification hole plate, and the periphery of the edge of the fixed bottom support is provided with a plurality of fixed side supporting rods. The fixed bottom support and the fixed side supporting rods form a fixed frame, the outer side of the fixed frame is coated with a wind shield, a bottom end opening of the fixed frame is connected with one end of a rectangular air inlet pipe at the bottom of the test box, the other end of the rectangular air inlet pipe is connected with a frequency conversion fan through a round straight pipe, and a plurality of absolute pressure sensors are arranged at a top end opening of the fixed frame. An atmospheric pressure sensor is arranged on the outer side of the fixing frame, a plurality of temperature sensors and a plurality of humidity sensors are arranged on the inner side of the fixing side supporting rod, and the atmospheric pressure sensor, the absolute pressure sensors, the temperature sensors and the humidity sensors are all in communication connection with the control unit. According to the invention, the air inlet amount in the test box can be accurately measured, so that the accuracy of cable combustion process and result analysis is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of cable combustion performance detection, and in particular relates to a device and method for measuring air intake volume in a test box for cable combustion performance detection. Background Art

[0002] Electrical cables and optical cables are collectively referred to as cables. When conducting combustion performance tests on cables, in order to completely discharge the gases consumed and generated by the combustion of cables inside the test box, it is necessary to apply a wind source with a flow rate of 8000±400L / min to the test box. The wind source is specifically a variable frequency fan. The variable frequency fan is connected to a rectangular air inlet pipe with a size of 800mm×300mm×80mm at the bottom of the test box through a relatively long stainless steel round tube, wherein a long straight pipe section with a length not less than 12 times the inner diameter of the pipe needs to be set on the round tube, and an air volume measuring device is set at a distance not less than 8 times the inner diameter of the pipe from the upstream elbow or obstacle of the long straight pipe section and not less than 4 times the inner diameter of the pipe from the downstream elbow or obstacle of the long straight pipe section, and the air volume measured by the air volume measuring device is used as the actual air volume entering the test box, wherein the air volume measuring device is specifically a vortex flowmeter or a differential pressure flowmeter, and the vortex flowmeter or the differential pressure flowmeter has high requirements for the installation position. The specific reasons are:

[0003] The traditional vortex flowmeter calculates the flow rate by measuring the vortex generated by the rotation of the fluid in the pipeline. This method requires that the inner diameter of the pipeline is small and the flow rate of the fluid in the pipeline is fast; while the commonly used differential pressure flowmeter calculates the flow rate by measuring the pressure difference of the fluid in the pipeline. This method requires that the inner diameter of the pipeline is large and the flow rate of the fluid in the pipeline is slow. Specifically, for the case where the fluid is air, the wind field in the pipeline is required to be uniform. Moreover, whether it is a vortex flowmeter or a differential pressure flowmeter, it is cumbersome to disassemble after installation, and the vortex flowmeter and the differential pressure flowmeter are prone to zero drift during the disassembly process, resulting in measurement deviations; in addition, since the combustion performance testing equipment of the cable, i.e. the test box, requires a large area, the pipeline layout of the test box often has large differences. In addition, the traditional air volume measurement device itself often has differences, and the installation position of the air volume measurement device also has large differences, which leads to certain differences in the air intake measured by each laboratory, and thus the analysis of the combustion process and results of the cable is different.

[0004] In summary, how to accurately and stably measure the air intake volume in the test chamber before the cable is tested for combustion performance in order to improve the accuracy and stability of the cable combustion process and result analysis is an urgent need in the current field of cable combustion performance testing. Summary of the invention

[0005] In view of the above-mentioned defects of the prior art, the present invention provides a device and method for measuring the air intake volume in a test box for cable combustion performance testing. Before the cable is subjected to combustion performance testing, the air intake volume in the test box can be accurately and stably measured, thereby improving the accuracy and stability of the cable combustion process and result analysis.

[0006] The technical solution adopted by the present invention to solve its technical problem is:

[0007] A device for measuring the air intake volume in a test box for detecting the combustion performance of cables, comprising a fixed bottom bracket fixed on the bottom wall of the test box, a rectifying orifice plate fixed on the fixed bottom bracket, a plurality of fixed side support rods fixed around the edge of the fixed bottom bracket, the fixed bottom bracket and the fixed side support rods form a fixed frame, the outer side of the fixed frame is covered with a wind shield, the bottom end opening of the fixed frame is connected to one end of a rectangular air inlet pipe at the bottom of the test box, the other end of the rectangular air inlet pipe is connected to an exhaust port of a variable frequency fan through a circular straight pipe equipped with a flow meter, the top end opening of the fixed frame forms an air outlet and a plurality of absolute pressure sensors are fixed at the air outlet, an atmospheric pressure sensor is fixed on the outer side of the fixed frame at a position away from the air outlet, a plurality of temperature sensors and a plurality of humidity sensors are fixed on the inner side of the fixed side support rods, and the atmospheric pressure sensor, the absolute pressure sensors, the temperature sensors and the humidity sensors are all communicatively connected to the signal input end of a control unit.

[0008] Furthermore, the control unit is used to calculate the real-time air intake volume in the test box based on the atmospheric pressure in the test box measured in real time by the received atmospheric pressure sensor, the pressure of the wind entering the area surrounded by the wind shield acting on the corresponding absolute pressure sensor measured in real time by each absolute pressure sensor, the temperature of the wind entering the area surrounded by the wind shield measured in real time by each temperature sensor, and the relative humidity of the wind entering the area surrounded by the wind shield measured in real time by each humidity sensor, and according to the area of ​​the air outlet.

[0009] Furthermore, a display unit is provided on the outside of the fixing frame, and the signal output end of the control unit is communicatively connected with the display unit. The control unit is used to transmit the calculated real-time air intake volume to the display unit, and the real-time air intake volume displayed by the display unit is observed through an observation window on the opening and closing door of the test chamber.

[0010] Furthermore, the average pressure value obtained by adding and averaging the pressures measured in real time by the absolute pressure sensors is represented by P1, the atmospheric pressure measured in real time by the atmospheric pressure sensor is represented by P2, the average temperature value obtained by adding and averaging the temperatures measured in real time by the temperature sensors is represented by T, the average relative humidity value obtained by adding and averaging the relative humidity measured in real time by the humidity sensors is represented by RH, the area of ​​the air outlet is represented by A, and the calculated real-time air intake volume in the test chamber is represented by Q, then Q = (P1-P2)×A×(T×a)×(RH×b), wherein a represents the temperature correction coefficient, and b represents the relative humidity correction coefficient.

[0011] Furthermore, the rectifying orifice plate is arranged horizontally, and a plurality of rectifying holes are evenly distributed on the rectifying orifice plate, and the plurality of rectifying holes cooperate to make the wind entering the area surrounded by the wind shield from the rectangular air inlet pipe flow vertically upward and be discharged into the test box from the air outlet.

[0012] Furthermore, the fixed bottom bracket is in a rectangular shape, and there are four fixed side support rods, each of which is arranged at one corner of the fixed bottom bracket, and each of the fixed side support rods is arranged at the same angle inclined upward toward the inner side of the area surrounded by the wind shield, and the orthographic projection connecting the top ends of the four fixed side support rods is in a square shape.

[0013] Furthermore, the plurality of absolute pressure sensors are evenly distributed at the air outlet; the plurality of temperature sensors are divided into a number equal to the number of fixed side support rods, and the temperature sensors in each portion are distributed in sequence from top to bottom on the inner side of the corresponding fixed side support rod; the plurality of humidity sensors are divided into a number equal to the number of fixed side support rods, and the humidity sensors in each portion are distributed in sequence from top to bottom on the inner side of the corresponding fixed side support rod.

[0014] Furthermore, a first sensor bracket is fixed at the air outlet of the fixed frame, and each of the absolute pressure sensors is fixed on the first sensor bracket; the atmospheric pressure sensor is fixed at the outer edge of the first sensor bracket and is located on one side of the air outlet; each of the temperature sensors is fixed to the inner side of the corresponding fixed side support rod through the second sensor bracket, and each of the humidity sensors is fixed to the inner side of the corresponding fixed side support rod through the third sensor bracket.

[0015] A method for measuring the air intake volume in a test box for detecting the combustion performance of a cable, using the above-mentioned device for measuring the air intake volume in a test box for detecting the combustion performance of a cable to perform measurement, comprises the following steps:

[0016] S1. Turn on the variable frequency fan. The wind blown by the variable frequency fan passes through the circular straight pipe and the rectangular air inlet pipe in turn and enters the area surrounded by the wind shield from the bottom opening of the fixing frame. The flow meter measures the flow rate of the wind in the circular straight pipe, and the flow value measured by the flow meter is stabilized at the set flow value by adjusting the frequency of the variable frequency fan. The wind entering the area surrounded by the wind shield flows upward after the flow direction is adjusted by the rectifying orifice plate and enters the test box from the air outlet.

[0017] S2. Each of the absolute pressure sensors measures in real time the pressure exerted on the corresponding absolute pressure sensor by the wind entering the area surrounded by the wind shield. The atmospheric pressure sensor measures in real time the atmospheric pressure in the test box. Each of the temperature sensors measures in real time the temperature of the wind entering the area surrounded by the wind shield. Each of the humidity sensors measures in real time the relative humidity of the wind entering the area surrounded by the wind shield. The control unit calculates the real-time air intake volume in the test box based on the atmospheric pressure measured in real time by the atmospheric pressure sensor, the pressure measured in real time by the absolute pressure sensors, the temperature measured in real time by the temperature sensors, the relative humidity measured in real time by the humidity sensors, and the area of ​​the air outlet.

[0018] Further,

[0019] The following steps are also included before step S1: energizing the atmospheric pressure sensor, each absolute pressure sensor, each temperature sensor and each humidity sensor and preheating them for 15-20 minutes, and zeroing them after preheating;

[0020] In step S1: the set flow value is 8000±400L / min;

[0021] Step S2 also includes: the control unit generates an air intake curve according to the real-time air intake volume recorded within a certain time period, and calculates the average air intake volume within the corresponding time period according to the air intake curve, and calculates the difference between the highest point and the lowest point on the air intake curve to obtain the air volume drift, and calculates the difference between the fitting value and the actual measurement value at each moment on the air intake curve to obtain the air volume noise at each moment, and obtains the maximum air volume noise within the corresponding time period according to the air volume noise at each moment, the control unit compares the average air intake volume within the corresponding time period with the average air intake volume threshold pre-stored in the control unit, and compares the air volume drift within the corresponding time period with the air volume drift threshold pre-stored in the control unit, and compares the maximum air volume noise within the corresponding time period with the maximum air volume noise threshold pre-stored in the control unit, to determine whether the air intake volume in the test box is qualified.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] The device for measuring the air intake volume in a test box for detecting the combustion performance of cables in the present invention comprises a fixed bottom bracket fixed on the bottom wall of the test box, a rectifying orifice plate is fixed on the fixed bottom bracket, a plurality of fixed side support rods are fixed around the edge of the fixed bottom bracket, the fixed bottom bracket and the fixed side support rods form a fixed frame, the outer side of the fixed frame is covered with a wind shield, the bottom opening of the fixed frame is connected to one end of a rectangular air inlet pipe at the bottom of the test box, the other end of the rectangular air inlet pipe is connected to the exhaust port of a variable frequency fan through a circular straight pipe equipped with a flow meter, the top opening of the fixed frame forms an air outlet and a plurality of absolute pressure sensors are fixed at the air outlet An atmospheric pressure sensor is fixed on the outside of the fixed frame at a position away from the air outlet, and multiple temperature sensors and multiple humidity sensors are fixed on the inside of the fixed side support rod. The atmospheric pressure sensor, each absolute pressure sensor, each temperature sensor and each humidity sensor are all communicatively connected with the signal input end of the control unit; the control unit receives the atmospheric pressure in the test box measured in real time by the atmospheric pressure sensor, the pressure of the wind entering the area surrounded by the wind shield measured in real time by each absolute pressure sensor and acting on the corresponding absolute pressure sensor, the temperature of the wind entering the area surrounded by the wind shield measured in real time by each temperature sensor, and the humidity sensor. The relative humidity of the wind entering the area surrounded by the wind shield is measured in real time, and the real-time air intake volume in the test box is calculated based on the area of ​​the air outlet; the atmospheric pressure sensor, each absolute pressure sensor, each temperature sensor and each humidity sensor in the measuring device are all arranged in the test box, and there will be no difference in the real-time air intake volume in the test box due to the difference in the pipeline layout outside the test box, and there is no difference in the measured air intake volume due to the difference in the traditional air volume measurement device in the background technology and the difference in the installation position in the pipeline. In addition, the atmospheric pressure sensor, each absolute pressure sensor, each temperature sensor and each humidity sensor in the measuring device are all arranged in the test box. The sensor, each temperature sensor and each humidity sensor are arranged in the test box through a fixing frame. By removing the fixed bottom bracket in the fixing frame from the inner bottom wall of the test box, the atmospheric pressure sensor, each absolute pressure sensor, each temperature sensor and each humidity sensor in the measuring device can be removed from the test box, so the disassembly is relatively simple; in addition, the rectifying orifice plate in the measuring device can adjust the flow direction of the wind entering the area surrounded by the wind shield from the rectangular air inlet pipe, so as to ensure that the pressure of the wind entering the area surrounded by the wind shield measured by each absolute pressure sensor acting on the corresponding absolute pressure sensor is more accurate and stable. In summary, before the combustion performance test of the cable is carried out, the air intake in the test box can be accurately and stably measured by the measuring device, thereby improving the accuracy and stability of the combustion process and result analysis of the cable.

[0024] In the present invention, the fixed bottom bracket is rectangular, and there are four fixed side support rods, each of which is arranged at one corner of the fixed bottom bracket, and each of the fixed side support rods is arranged at the same angle inclined upward toward the inner side of the area surrounded by the windshield, and the orthographic projection connecting line of the top ends of the four fixed side support rods is square, so that the air outlet is located at the middle position of the top end of the fixed bracket; and the multiple absolute pressure sensors are evenly distributed at the air outlet, so that the pressure average value obtained by adding and averaging the pressures measured by the absolute pressure sensors in real time is more accurate and stable; and the multiple temperature sensors The plurality of humidity sensors are divided into a number equal to the number of fixed side support rods, and the temperature sensors in each portion are distributed from top to bottom in sequence on the inner side of the corresponding fixed side support rod, so that the average temperature value obtained by adding and averaging the temperatures measured by the temperature sensors in real time is more accurate and stable; and the plurality of humidity sensors are divided into a number equal to the number of fixed side support rods, and the humidity sensors in each portion are distributed from top to bottom in sequence on the inner side of the corresponding fixed side support rod, so that the average relative humidity value obtained by adding and averaging the relative humidity measured by the humidity sensors in real time is more accurate and stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a schematic diagram of the main structure of the device for measuring the air intake volume in the test box for detecting the burning performance of cables in the present invention, with the wind shield hidden;

[0026] Figure 2 It is a schematic diagram of the top view of the structure of the device for measuring the air intake volume in the test box for detecting the combustion performance of cables in the present invention;

[0027] Figure 3 The figure is a schematic diagram of the installation structure of a device for measuring the air intake volume in a test box for detecting the combustion performance of cables in the present invention.

[0028] Explanation of the reference numerals in the figure: 1. test box, 2. fixed bottom bracket, 3. rectifier orifice plate, 4. fixed side support rod, 5. wind shield, 6. rectangular air inlet pipe, 7. flow meter, 8. round straight pipe, 9. variable frequency fan, 10. absolute pressure sensor, 11. atmospheric pressure sensor, 12. temperature sensor, 13. humidity sensor, 14. control unit, 15. display unit, 16. first sensor bracket, 17. second sensor bracket, 18. third sensor bracket. DETAILED DESCRIPTION

[0029] The specific embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings. These embodiments are only used to illustrate the present invention, but not to limit the present invention.

[0030] In the description of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0031] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0032] Furthermore, in the description of the present invention, unless otherwise specified, “plurality” means two or more.

[0033] like Figure 1-Figure 3As shown, a device for measuring the air intake volume in a test box for detecting the combustion performance of a cable is shown, comprising a fixed bottom bracket 2 fixed on the inner bottom wall of the test box 1, a rectifying orifice plate 3 is fixed on the fixed bottom bracket 2, a plurality of fixed side support rods 4 are fixed around the edge of the fixed bottom bracket 2, the fixed bottom bracket 2 and the fixed side support rods 4 form a fixed frame, the outer side of the fixed frame is covered with a wind shield 5, the bottom end opening of the fixed frame is connected to one end of a rectangular air inlet pipe 6 at the bottom of the test box 1, the other end of the rectangular air inlet pipe 6 is connected to the exhaust port of a variable frequency fan 9 through a circular straight pipe 8 equipped with a flow meter 7, the top end opening of the fixed frame forms an air outlet and a plurality of absolute pressure sensors 10 are fixed at the air outlet, an atmospheric pressure sensor 11 is fixed to the outer side of the fixed frame at a position away from the air outlet, and the fixed side support rods 4 are provided on the outer side of the fixed frame. A plurality of temperature sensors 12 and a plurality of humidity sensors 13 are fixed on the inner side, and the atmospheric pressure sensor 11, each absolute pressure sensor 10, each temperature sensor 12 and each humidity sensor 13 are all communicatively connected with the signal input end of the control unit 14; the control unit 14 is used to calculate the real-time air intake volume in the test box 1 according to the atmospheric pressure in the test box 1 measured in real time by the atmospheric pressure sensor 11, the pressure of the wind entering the area surrounded by the wind shield 5 acting on the corresponding absolute pressure sensor 10 measured in real time by each absolute pressure sensor 10, the temperature of the wind entering the area surrounded by the wind shield 5 measured in real time by each temperature sensor 12, and the relative humidity of the wind entering the area surrounded by the wind shield 5 measured in real time by each humidity sensor 13, and according to the area of ​​the air outlet.

[0034] The atmospheric pressure sensor 11, each absolute pressure sensor 10, each temperature sensor 12 and each humidity sensor 13 in the measuring device are all arranged in the test box 1, and the real-time air intake volume in the test box 1 will not be different due to the difference in the pipeline layout outside the test box 1, and there is no difference in the measured air intake volume due to the difference in the traditional air volume measurement device in the background technology and the difference in the installation position in the pipeline. In addition, the atmospheric pressure sensor 11, each absolute pressure sensor 10, each temperature sensor 12 and each humidity sensor 13 in the measuring device are arranged by a fixed frame In the test box 1, by removing the fixed bottom bracket 2 in the fixing frame from the inner bottom wall of the test box 1, the atmospheric pressure sensor 11, each absolute pressure sensor 10, each temperature sensor 12 and each humidity sensor 13 in the measuring device can be removed from the test box 1, so the disassembly is relatively simple; in addition, the rectifying orifice plate 3 in the measuring device can adjust the flow direction of the wind entering the area surrounded by the wind shield 5 from the rectangular air inlet pipe 6, so as to ensure that the pressure of the wind entering the area surrounded by the wind shield 5 measured by each absolute pressure sensor 10 acting on the corresponding absolute pressure sensor 10 is more accurate and stable. In summary, before the combustion performance test of the cable is carried out, the air intake volume in the test box 1 can be accurately and stably measured by the measuring device, thereby improving the accuracy and stability of the combustion process and result analysis of the cable.

[0035] In one embodiment,

[0036] A display unit 15 is also provided outside the fixing frame. Figure 2 The signal output end of the control unit 14 is communicatively connected with the display unit 15. The control unit 14 is used to transmit the calculated real-time air intake volume to the display unit 15. The real-time air intake volume displayed by the display unit 15 is observed through the observation window on the opening and closing door of the test box 1.

[0037] Preferably, the atmospheric pressure sensor 11, each absolute pressure sensor 10, each temperature sensor 12 and each humidity sensor 13 are serially connected to the signal input end of the control unit 14, and the signal output end of the control unit 14 is serially connected to the display unit 15, wherein the control unit 14 is a PLC controller, and the display unit 15 is a digital display instrument. By energizing the control unit 14, the atmospheric pressure sensor 11, each absolute pressure sensor 10, each temperature sensor 12, each humidity sensor 13 and the display unit 15 are energized. The PLC controller is arranged outside the test box 1.

[0038] In one embodiment, the average pressure value obtained by adding and averaging the pressures measured in real time by the absolute pressure sensors 10 is represented by P1, the atmospheric pressure measured in real time by the atmospheric pressure sensor 11 is represented by P2, the average temperature value obtained by adding and averaging the temperatures measured in real time by the temperature sensors 12 is represented by T, the average relative humidity value obtained by adding and averaging the relative humidity measured in real time by the humidity sensors 13 is represented by RH, the area of ​​the air outlet is represented by A, and the calculated real-time air intake volume in the test box 1 is represented by Q, then Q = (P1-P2)×A×(T×a)×(RH×b), where a represents the temperature correction coefficient, and b represents the relative humidity correction coefficient.

[0039] In one embodiment, Figure 1 As shown, the rectifying orifice plate 3 is arranged horizontally, and a plurality of rectifying holes are evenly distributed on the rectifying orifice plate 3. The plurality of rectifying holes cooperate to make the wind entering the area surrounded by the wind shield 5 from the rectangular air inlet pipe 6 flow vertically upward and be discharged from the air outlet into the test box 1. In this way, the pressure direction of the wind entering the area surrounded by the wind shield 5 acting on the corresponding absolute pressure sensor 10 is vertically upward, so that the pressure measured in real time by the corresponding absolute pressure sensor 10 is more accurate and stable.

[0040] In one embodiment, the fixed bottom bracket 2 is rectangular, and there are four fixed side support rods 4. Each fixed side support rod 4 is arranged at one corner of the fixed bottom bracket 2, and each fixed side support rod 4 is arranged at the same angle to the inner side of the area surrounded by the windshield 5. The orthographic projection line of the top of the four fixed side support rods 4 is a square shape. Figure 2, so that the air outlet is located at the middle of the top of the fixing frame; and multiple absolute pressure sensors 10 are evenly distributed at the air outlet, see Figure 2 , so that the average pressure obtained by adding and averaging the pressures measured in real time by the absolute pressure sensors 10 is more accurate and stable; and the multiple temperature sensors 12 are evenly divided into a number equal to the number of fixed side support rods 4, and the temperature sensors 12 in each part are sequentially distributed from top to bottom on the inner side of the corresponding fixed side support rod 4, see Figure 1 In this way, the average temperature obtained by adding and averaging the temperatures measured in real time by each temperature sensor 12 is more accurate and stable; the plurality of humidity sensors 13 are evenly divided into a number equal to the number of fixed side support rods 4, and the humidity sensors 13 in each part are sequentially distributed from top to bottom on the inner side of the corresponding fixed side support rod 4, as shown in FIG. Figure 1 This makes the average relative humidity value obtained by adding and averaging the relative humidity measured in real time by each humidity sensor 13 more accurate and stable.

[0041] In one embodiment, a first sensor bracket 16 is fixed at the air outlet of the fixing frame, and each absolute pressure sensor 10 is fixed on the first sensor bracket 16. Figure 1 and Figure 2 The atmospheric pressure sensor 11 is fixed to the outer edge of the first sensor bracket 16 and is located on one side of the air outlet. Figure 2 Each temperature sensor 12 is fixed to the inner side of the corresponding fixed side support rod 4 through the second sensor bracket 17, and each humidity sensor 13 is fixed to the inner side of the corresponding fixed side support rod 4 through the third sensor bracket 18, see Figure 1 .

[0042] A method for measuring the air intake volume in a test box for detecting the combustion performance of a cable, using the above-mentioned device for measuring the air intake volume in a test box for detecting the combustion performance of a cable to perform measurement, comprises the following steps:

[0043] S1. Close the door of the test box 1, energize the atmospheric pressure sensor 11, each absolute pressure sensor 10, each temperature sensor 12 and each humidity sensor 13, and preheat them for 15-20 minutes. After preheating, calibrate to zero;

[0044] S2. Turn on the variable frequency fan 9. The wind blown by the variable frequency fan 9 passes through the circular straight pipe 8 and the rectangular air inlet pipe 6 in turn and enters the area surrounded by the wind shield 5 from the bottom opening of the fixed frame. The flow meter 7 measures the flow rate of the wind in the circular straight pipe 8. The flow rate value measured by the flow meter 7 is stabilized at 8000±400L / min by adjusting the frequency of the variable frequency fan 9. The wind entering the area surrounded by the wind shield 5 flows upward after the flow direction is adjusted by the rectifying orifice plate 3 and enters the test box 1 from the air outlet.

[0045] S2. Each absolute pressure sensor 10 measures in real time the pressure of the wind entering the area surrounded by the wind shield 5 acting on the corresponding absolute pressure sensor 10. The atmospheric pressure sensor 11 measures in real time the atmospheric pressure in the test box 1. Each temperature sensor 12 measures in real time the temperature of the wind entering the area surrounded by the wind shield 5. Each humidity sensor 13 measures in real time the relative humidity of the wind entering the area surrounded by the wind shield 5. The control unit 14 calculates the real-time air intake volume in the test box 1 according to the atmospheric pressure measured in real time by the atmospheric pressure sensor 11, the pressure measured in real time by the absolute pressure sensors 10, the temperature measured in real time by the temperature sensors 12, the relative humidity measured in real time by the humidity sensors 13, and the area of ​​the air outlet. The control unit 14 generates an air intake volume curve according to the real-time air intake volume recorded within 5 minutes. , and calculate the mean air volume within the 5 minutes according to the air volume curve, and calculate the difference between the highest point and the lowest point on the air volume curve to obtain the air volume drift, and calculate the difference between the fitting value and the actual measurement value at each moment on the air volume curve to obtain the air volume noise at each moment, and obtain the maximum air volume noise in the corresponding time period according to the air volume noise at each moment, the control unit 14 compares the mean air volume within the 5 minutes with the air volume mean threshold pre-stored in the control unit 14, and compares the air volume drift within the 5 minutes with the air volume drift threshold pre-stored in the control unit 14, and compares the maximum air volume noise within the 5 minutes with the maximum air volume noise threshold pre-stored in the control unit 14, to determine whether the air volume in the test box 1 is qualified.

[0046] In summary, when the measuring device is used to measure the air intake volume in the test box 1, the measuring process is simple and can effectively improve the stability and reproducibility of the test.

[0047] The above are only preferred embodiments of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and substitutions can be made without departing from the technical principles of the present invention. These improvements and substitutions should also be regarded as the scope of protection of the present invention.

Claims

1. A device for measuring the air intake volume in a test box for detecting the combustion performance of cables, characterized in that: The invention comprises a fixed bottom bracket (2) fixed on the inner bottom wall of a test box (1), a rectifying orifice plate (3) being fixed on the fixed bottom bracket (2), a plurality of fixed side support rods (4) being fixed around the edge of the fixed bottom bracket (2), the fixed bottom bracket (2) and the fixed side support rods (4) forming a fixed frame, the outer side of the fixed frame being covered with a wind shield (5), the bottom opening of the fixed frame being connected to one end of a rectangular air inlet pipe (6) at the bottom of the test box (1), the other end of the rectangular air inlet pipe (6) being connected to a flow meter (7) through a round straight pipe (8) installed thereon. The fixed frame is connected to an exhaust port of a variable frequency fan (9), the top opening of the fixed frame forms an air outlet and a plurality of absolute pressure sensors (10) are fixed at the air outlet, an atmospheric pressure sensor (11) is fixed on the outside of the fixed frame at a position away from the air outlet, a plurality of temperature sensors (12) and a plurality of humidity sensors (13) are fixed on the inside of the fixed side support rod (4), and the atmospheric pressure sensor (11), the absolute pressure sensors (10), the temperature sensors (12) and the humidity sensors (13) are all communicatively connected to a signal input end of a control unit (14).

2. The device for measuring the air intake volume in a test box for detecting the burning performance of a cable according to claim 1, characterized in that: The control unit (14) is used to calculate the real-time air intake volume in the test box (1) based on the atmospheric pressure in the test box (1) measured in real time by the atmospheric pressure sensor (11), the pressure of the wind in the area surrounded by the wind shield (5) acting on the corresponding absolute pressure sensor (10) measured in real time by each absolute pressure sensor (10), the temperature of the wind in the area surrounded by the wind shield (5) measured in real time by each temperature sensor (12), and the relative humidity of the wind in the area surrounded by the wind shield (5) measured in real time by each humidity sensor (13), and based on the area of ​​the air outlet.

3. The device for measuring the air intake volume in a test box for detecting the burning performance of a cable according to claim 2, characterized in that: A display unit (15) is also provided on the outside of the fixing frame. The signal output end of the control unit (14) is communicatively connected to the display unit (15). The control unit (14) is used to transmit the calculated real-time air intake volume to the display unit (15). The real-time air intake volume displayed by the display unit (15) is observed through an observation window on the opening and closing door of the test box (1).

4. The device for measuring the air intake volume in a test box for detecting the burning performance of a cable according to claim 2, characterized in that: The pressure average value obtained by adding and averaging the pressures measured in real time by the absolute pressure sensors (10) is represented by P1, the atmospheric pressure measured in real time by the atmospheric pressure sensor (11) is represented by P2, the temperature average value obtained by adding and averaging the temperatures measured in real time by the temperature sensors (12) is represented by T, the relative humidity average value obtained by adding and averaging the relative humidity measured in real time by the humidity sensors (13) is represented by RH, the area of ​​the air outlet is represented by A, and the calculated real-time air intake volume in the test box (1) is represented by Q, then Q = (P1-P2) × A × (T × a) × (RH × b), wherein a represents the temperature correction coefficient, and b represents the relative humidity correction coefficient.

5. The device for measuring the air intake volume in a test box for detecting the burning performance of a cable according to claim 2, characterized in that: The rectifying orifice plate (3) is arranged horizontally, and a plurality of rectifying holes are evenly distributed on the rectifying orifice plate (3). The plurality of rectifying holes cooperate to make the wind entering the area surrounded by the wind shield (5) from the rectangular air inlet pipe (6) flow vertically upward and be discharged from the air outlet into the test box (1).

6. The device for measuring the air intake volume in a test box for detecting the burning performance of a cable according to claim 2, characterized in that: The fixed bottom bracket (2) is in a rectangular shape, and there are four fixed side support rods (4), each of which is arranged at one corner of the fixed bottom bracket (2), and each of the fixed side support rods (4) is arranged to be inclined upward at the same angle toward the inside of the area surrounded by the windshield (5), and the orthographic projection line of the top ends of the four fixed side support rods (4) is in a square shape.

7. The device for measuring the air intake volume in a test box for detecting the burning performance of a cable according to claim 6, characterized in that: The plurality of absolute pressure sensors (10) are evenly distributed at the air outlet; the plurality of temperature sensors (12) are evenly divided into a number of portions equal to the number of fixed side support rods (4), and the temperature sensors (12) in each portion are distributed in sequence from top to bottom on the inner side of the corresponding fixed side support rod (4); the plurality of humidity sensors (13) are evenly divided into a number of portions equal to the number of fixed side support rods (4), and the humidity sensors (13) in each portion are distributed in sequence from top to bottom on the inner side of the corresponding fixed side support rod (4).

8. The device for measuring the air intake volume in a test box for detecting the burning performance of a cable according to claim 2, characterized in that: A first sensor bracket (16) is fixed at the air outlet of the fixing frame, and each of the absolute pressure sensors (10) is fixed on the first sensor bracket (16); the atmospheric pressure sensor (11) is fixed at the outer edge of the first sensor bracket (16) and is located on one side of the air outlet; each of the temperature sensors (12) is fixed to the inner side of the corresponding fixed side support rod (4) through a second sensor bracket (17), and each of the humidity sensors (13) is fixed to the inner side of the corresponding fixed side support rod (4) through a third sensor bracket (18).

9. A method for measuring the air intake volume in a test box for detecting the burning performance of a cable, using a device for measuring the air intake volume in a test box for detecting the burning performance of a cable as claimed in any one of claims 2 to 8, characterized in that: The following steps are involved: S1. Turn on the variable frequency fan (9), and the wind blown by the variable frequency fan (9) passes through the circular straight tube (8) and the rectangular air inlet tube (6) in sequence and enters the area surrounded by the wind shield (5) from the bottom opening of the fixing frame, and the flow meter (7) measures the flow rate of the wind in the circular straight tube (8), and the flow rate value measured by the flow meter (7) is stabilized at a set flow rate value by adjusting the frequency of the variable frequency fan (9), and the wind entering the area surrounded by the wind shield (5) flows upward after the flow direction is adjusted by the rectifying orifice plate (3) and enters the test box (1) from the air outlet; S2. Each of the absolute pressure sensors (10) measures in real time the pressure exerted on the corresponding absolute pressure sensor (10) by the wind entering the area surrounded by the wind shield (5); the atmospheric pressure sensor (11) measures in real time the atmospheric pressure in the test box (1); each of the temperature sensors (12) measures in real time the temperature of the wind entering the area surrounded by the wind shield (5); each of the humidity sensors (13) measures in real time the relative humidity of the wind entering the area surrounded by the wind shield (5); and the control unit (14) calculates the real-time air intake volume in the test box (1) based on the atmospheric pressure measured in real time by the atmospheric pressure sensor (11), the pressure measured in real time by the absolute pressure sensors (10), the temperature measured in real time by the temperature sensors (12), the relative humidity measured in real time by the humidity sensors (13), and the area of ​​the air outlet.

10. A method for measuring the air intake volume in a test box for detecting the burning performance of a cable according to claim 9, characterized in that: Before step S1, the following steps are also included: energizing the atmospheric pressure sensor (11), each absolute pressure sensor (10), each temperature sensor (12) and each humidity sensor (13) and preheating them for 15-20 minutes, and zeroing them after the preheating is completed; In step S1: the set flow value is 8000±400L / min; Step S2 also includes: the control unit (14) generates an air intake curve according to the real-time air intake recorded within a certain time period, and calculates the average air intake within the corresponding time period according to the air intake curve, and calculates the difference between the highest point and the lowest point on the air intake curve to obtain the air volume drift, and calculates the difference between the fitting value and the actual measurement value at each moment on the air intake curve to obtain the air volume noise at each moment, and obtains the maximum air volume noise within the corresponding time period according to the air volume noise at each moment, and the control unit (14) compares the average air intake within the corresponding time period with the average air intake threshold pre-stored in the control unit (14), and compares the air volume drift within the corresponding time period with the air volume drift threshold pre-stored in the control unit (14), and compares the maximum air volume noise within the corresponding time period with the maximum air volume noise threshold pre-stored in the control unit (14), and compares the maximum air volume noise within the corresponding time period with the maximum air volume noise threshold pre-stored in the control unit (14), to determine whether the air intake in the test box (1) is qualified.

Images