Large-diameter cable test model real fire test device and test method

Abstract

The invention discloses a real fire test device and test method for a large-diameter cable test model. The device comprises a multi-dimensional adjusting system, a real fire control system, a temperature monitoring system, a calorimetric and flue gas purification system, a high-temperature-resistant video recording device, a thermal imager and the large-diameter cable test model. The multi-dimensional adjusting system comprises a stand column fixed with a guide rail, a cross beam capable of moving along the guide rail, and a height adjusting system and an angle adjusting system capable of adjusting the height and the angle of the large-diameter cable test model; the real fire control system can control the opening degree of a premixing burner and the frequency of a fan so as to control the intensity of a fire source, so that real fire scenes of different types of vehicle fires are provided; before the large-diameter cable test model is tested, a space temperature field needs to be calibrated, and then the space position of the large-diameter cable test model is determined. According to the invention, a scheme can be provided for the fireproof performance test of the large-diameter cable test model of the bridge in a real space state, and technical support is provided for the fireproof design of the large-diameter cable test model of the large-span bridge.

Description

Technical Field

[0001] The invention relates to the technical field of bridge fire resistance testing, and in particular to a real fire testing device and a testing method for a large-diameter cable test model. Background Art

[0002] Cables are the core load-bearing components of long-span bridges, and their performance is directly related to the safety of bridge structures. Vehicle fires are the main cause of bridge fire accidents. After a vehicle fire occurs, it is often parked in an emergency lane close to the cable. In addition, vehicle fires have the characteristics of high heat release rate and rapid fire growth. Cables are easily exposed to high-temperature fire environments, and the degradation of the mechanical properties of cables in high-temperature environments may lead to catastrophic consequences. Most of the existing cable fire tests are furnace temperature tests, that is, the cable is fixed on the internal bracket of the combustion furnace. During the test, the cable is in a uniform temperature field. This type of test has the following main problems: 1. In the furnace temperature test, the cable is evenly exposed to fire all around, and the fire field is in a uniform temperature field. In the real fire situation, one side of the cable is exposed to fire, and the fire field is in an uneven temperature field; 2. The cable has an inclination, and the cable fire prevention measures change due to the different cable heights. In the conventional test method, the height and inclination of the fixed cable cannot be changed, and it is difficult to reflect the real spatial state of the cable. Summary of the invention

[0003] The purpose of the present invention is to provide a real fire test device and test method for a large-diameter cable test model. Through a multi-dimensional adjustment system, real fire control technology and high-fidelity model design, the core problems of fire scene distortion, fixed spatial state, model reduction deviation and so on in traditional furnace temperature tests are solved, which significantly improves the accuracy and practicality of the fire performance test of the large-diameter cable test model, and provides key technical support for the fire-resistant optimization design of the large-diameter cable test model for large-span bridges.

[0004] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0005] The present invention provides a large-diameter cable test model real fire test device, comprising:

[0006] The multi-dimensional adjustment system includes two columns, a beam slidably connected to the columns, a height adjustment system, and an angle adjustment system; the angle adjustment system is arranged at the bottom of the beam and connected to the large-diameter cable test model;

[0007] The real fire control system includes a premix burner and a fan that are interconnected, and the opening of the premix burner and the frequency of the fan are both regulated by a control cabinet;

[0008] The temperature monitoring system includes a thermocouple tree and a collector, wherein the thermocouple tree and the thermocouples pre-buried in the large-diameter cable test model are electrically connected to the collector;

[0009] A calorimetry and flue gas purification system, including a smoke collecting hood arranged above the column. The smoke collecting hood is connected to a water circulation purifier through a smoke pipe, and a gas analyzer for analyzing the oxygen content in the smoke pipe is arranged beside the water circulation purifier;

[0010] It also includes high-temperature resistant video equipment and a thermal imager for real-time recording of the actual fire receiving and heat transfer processes of the fire scene and the large-diameter cable test model.

[0011] Preferably, the large-diameter cable test model includes:

[0012] A cable test model of the strand assembly type, whose cross-sectional diameter is reduced in proportion to the real cable. The cable test model is composed of multiple strands that are parallel to each other, of the same length and aligned at both ends, and are locked and fixed by a number of annular steel hoops. The reduction ratio of the strands is the same as that of the cable test model, and the strands are formed by squeezing multiple fine steel wires into a round shape and the fine steel wires are staggeredly tied and fixed at both ends and the middle position of the strands to reduce the porosity of the cable test model;

[0013] Thermocouples are welded to the measuring point surfaces of several strands inside the cable test model and led out through the gaps between the strands. Steel gaskets are installed on the surfaces of the thermocouples exposed outside the cable test model to isolate the flame; the strands welded with thermocouples are arranged and positioned in sequence in the cable test model according to the target measuring point positions;

[0014] Steel wires are wound around the surface of the cable test model to prevent the flame from directly contacting the cable test model.

[0015] Preferably, the minimum value of the diameter of the large-diameter cable test model is within the allowable error range of 5%, and its diameter is not less than the result determined by the following formula:

[0016]

[0017] In the formula, R 0 is the minimum cross-sectional diameter of the large-diameter cable test model, R is the prototype diameter of the large-diameter cable test model, e is the natural constant, and 80mm ≤ R ≤ 1500mm.

[0018] Preferably, there are two groups of the height adjustment systems, which are respectively arranged at the tops of two columns. The height adjustment system includes an electric hoisting device arranged on the non-fire side of the column. The steel wire rope on the electric hoisting device passes through several fixed pulleys arranged at the top of the column and is connected to the cross beam on the same side. A first hanging ring is arranged at the top of the cross beam, and a first hook adapted to the first hanging ring is arranged at the end of the steel wire rope. The height of the large-diameter cable test model is adjusted by lifting the cross beam.

[0019] Preferably, two sets of the angle adjustment systems are provided and symmetrically arranged along the middle of the cross beam. The angle adjustment system includes a chain and a second hanging ring connected to the cross beam. A number of bolt holes adapted to the second hanging ring are provided at the lower part of the cross beam. The lower end of the second hanging ring is connected to the second hook at the upper end of the chain, and the second hook at the lower end of the chain is connected to a steel strand. The steel strand is sleeved between two annular steel hoops at the end of the large-diameter cable test model. The inclination angle of the large-diameter cable test model is adjusted by adjusting the relative lengths of the two chains. Fire protection layers are provided on both the cross beam and the angle adjustment system.

[0020] Preferably, the thermocouple tree is arranged above and around the premixed burner to accurately measure the temperature of the fire field environment where the large-diameter cable test model is located. The acquisition instrument synchronously acquires the temperature data of the space and the large-diameter cable test model.

[0021] Preferably, upper limiters and lower limiters are provided on the column in its vertical direction. The lower limiter is slidably connected to the column and can be locked and fixed by bolts. Threaded holes adapted to the bolts are provided on both the lower limiter and the column. The lower limiter can ensure that the large-diameter cable test model does not contact the ground when the cross beam descends to the restricted position.

[0022] The present invention also provides a test method for a full-scale fire test device of a large-diameter cable test model, including the following steps:

[0023] S1: Conduct a fire numerical simulation of the large-diameter cable test model, summarize the most unfavorable fire scenarios, and determine the design temperature of the large-diameter cable test model in the real environment;

[0024] S2: Manufacture the large-diameter cable test model and determine its position during the test. Adjust the height of the cross beam to the specified position in advance through the multi-dimensional adjustment system;

[0025] S3: Arrange the thermocouple tree, thermal imager and high-temperature video recording equipment in the test area to the specified positions;

[0026] S4: According to the layout requirements of the full-scale fire control system, move the premixed burner to the position below the large-diameter cable test model as planned, connect the premixed burner and the fan through an air duct, connect the premixed burner to the gas source through a gas pipeline, connect the control cabinet and the premixed burner through a wire, and conduct fire protection on the wire, air duct and gas pipeline;

[0027] S5: Turn on the fan and the gas source, control the fan frequency and the opening degree of the premixed burner through the control cabinet and ignite, and record the space temperature field through the acquisition instrument;

[0028] S6: Adjust the fan frequency and the opening degree of the premixed burner multiple times, record the spatial temperature field respectively, and determine the height of the large-diameter cable test model, the fan frequency and the opening degree of the premixed burner according to the design temperature of the large-diameter cable test model obtained by simulation.

[0029] S7: Move the large-diameter cable test model under the crossbeam, connect the first hook to the first hanging ring, use the multi-dimensional adjustment system to adjust the height and vertical inclination of the large-diameter cable test model, complete the positioning of the large-diameter cable test model, and connect the thermocouples arranged inside and outside the large-diameter cable test model to the data collector respectively.

[0030] S8: Start the calorimetry and flue gas purification system.

[0031] S9: Open the fan and the gas pipeline, adjust the frequency of the fan and the opening degree of the premixed burner to the target values through the control cabinet, ignite and start the test.

[0032] S10: After the test, obtain the temperature field of the large-diameter cable test model monitored by the data collector, determine whether the fireproof structure meets the fire resistance requirements according to the surface temperature of the steel wire on the large-diameter cable test model and the fire resistance time, conduct the real fire test on the large-diameter cable test models with different fireproof structures, and explore the influence of different structures on the fire resistance performance of the large-diameter cable test model.

[0033] Preferably, before the fire test, it is necessary to calibrate the spatial temperature field to obtain the temperature field of the space above the premixed burner, and determine the position of the large-diameter cable test model according to the target temperature of the large-diameter cable test model required and the spatial temperature field.

[0034] Preferably, after the test, detect the flue gas components through a gas analyzer to obtain the heat release rate during the test process, and use a water circulation purifier to treat harmful gases to ensure that the emissions meet the environmental protection requirements.

[0035] The beneficial effects of the present invention are as follows:

[0036] 1. Dynamically adjust the fire source intensity through the premixed burner, the fan and the control cabinet, and can simulate the real fire scenes of different vehicle fires, such as the heat release rate and the flame distribution, and combine the temperature monitoring system thermocouple tree + thermal imager to realize the calibration and control of the spatial temperature field, significantly improving the fidelity of the test scene.

[0037] 2. Adopt height adjustment and angle adjustment, and can flexibly adjust the height, inclination and horizontal position of the large-diameter cable test model to adapt to the real space state of the large-diameter cable test model of the bridge, such as the curve form of the large-diameter cable test model of the suspension bridge, providing data support for the fire resistance design under different scenarios.

[0038] 3. The model diameter can be designed to be over 500 mm as required. Through geometric scaling design, the porosity is ensured to be close to that of the real large-diameter cable test model. The multi-strand parallel arrangement and wire-rounding process are adopted to accurately simulate the heat transfer path and structural characteristics of the real large-diameter cable test model of the bridge.

[0039] 4. Thermocouple embedding technology. Steel gaskets are set on the surface of the thermocouples outside the strands to reduce the interference of heat convection and ensure the accuracy of temperature data.

[0040] 5. The calorimetry and flue gas purification system and gas analyzer process harmful flue gas in real time to avoid environmental pollution during the test. The height adjustment system is far away from the fire side to reduce the risk of equipment damage due to heat.

[0041] 6. The most unfavorable scenario is predicted through fire numerical simulation, and the position of the large-diameter cable test model is determined by combining with the calibration of the spatial temperature field, realizing the scientific optimization of the test scheme. It supports repeated tests under multiple working conditions to adjust the fire source intensity and the position of the large-diameter cable test model, etc., and can systematically evaluate the fire resistance limit of different fire protection structures, providing a comprehensive technical basis for the fire resistance design of the large-diameter cable test model of long-span bridges. Brief Description of the Drawings

[0042] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0043] Figure 1 It is a schematic structural diagram of a real fire test device for a large-diameter cable test model provided by an embodiment of the present invention;

[0044] Figure 2 It is a schematic structural diagram of a multi-dimensional adjustment system provided by an embodiment of the present invention;

[0045] Figure 3 It is a schematic structural diagram of a column provided by an embodiment of the present invention;

[0046] Figure 4 It is a schematic structural diagram of a calorimetry and flue gas purification system provided by an embodiment of the present invention;

[0047] Figure 5 It is a schematic structural diagram of a real fire control system provided by an embodiment of the present invention;

[0048] Figure 6 It is a schematic structural diagram of a temperature monitoring system provided by an embodiment of the present invention;

[0049] Figure 7Schematic structural diagram of the large-diameter cable test model provided by the embodiment of the present invention;

[0050] Figure 8 Schematic cross-sectional view of the large-diameter cable test model provided by the embodiment of the present invention;

[0051] Figure 9 Schematic structural diagram of the angle adjustment system provided by the embodiment of the present invention.

[0052] Description of reference numerals: 1 - multi-dimensional adjustment system; 11 - column; 12 - cross beam; 121 - first lifting ring; 13 - guide rail; 14 - height adjustment system; 141 - electric hoisting equipment; 142 - fixed pulley; 143 - steel wire rope; 144 - first hook; 15 - upper limit switch; 16 - lower limit switch; 17 - angle adjustment system; 171 - second lifting ring; 172 - chain; 173 - second hook; 174 - steel strand; 2 - real fire control system; 21 - premixed burner; 22 - fan; 23 - control cabinet; 24 - air duct; 25 - gas pipeline; 26, wire; 3 - temperature monitoring system; 31 - thermocouple tree; 32 - collector; 4 - calorimetry and flue gas purification system; 41 - smoke hood; 42 - gas analyzer; 43 - water circulation purifier; 44 - smoke pipe; 5 - high-temperature video recording equipment; 6 - thermal imager; 7 - large-diameter cable test model; 71 - cable strand; 72 - annular steel hoop; 73 - steel wire; 74 - thermocouple. Detailed implementation manners

[0053] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0054] As Figures 1 to 9 shown, a real fire test device for a large-diameter cable test model includes:

[0055] A multi-dimensional adjustment system 1, including two columns 11, a cross beam 12 adapted to the guide rail 13 on the column 11 and capable of moving up and down, a height adjustment system 14 for adjusting the height of the cross beam 12, and an angle adjustment system 17 for adjusting the inclination angle of the large-diameter cable test model 7; the angle adjustment system 17 is arranged at the bottom of the cross beam 12 and is connected to the large-diameter cable test model 7;

[0056] The height adjustment system 14 is provided with two groups, which are respectively arranged at the tops of two columns 11. The height adjustment system 14 includes an electric hoisting device 141 arranged on the non-fire side of the column 11. The steel wire rope 143 on the electric hoisting device 141 passes through a number of fixed pulleys 142 arranged at the top of the column 11 and then is connected to the cross beam 12 on the same side. A first lifting ring 121 is arranged at the top of the cross beam 12, and a first hook 144 adapted to the first lifting ring 121 is arranged at the end of the steel wire rope 143.

[0057] The angle adjustment system 17 is provided with two groups, which are symmetrically arranged along the middle of the cross beam 12 and arranged on the non-fire side. The angle adjustment system 17 includes a chain 172 and a second lifting ring 171 connected to the cross beam 12. A number of bolt holes adapted to the second lifting ring 171 are arranged at the lower part of the cross beam 12. The lower end of the second lifting ring 171 is connected to a second hook 173 at the upper end of the chain 172. The second hook 173 at the lower end of the chain 172 is connected to a steel strand 174. The steel strand 174 is sleeved between two annular steel hoops 72 at the end of the large-diameter cable test model 7. By adjusting the relative lengths of the two chains 172, the inclination angle of the large-diameter cable test model 7 is adjusted; Fire protection layers are arranged on both the cross beam 12 and the angle adjustment system 17 to ensure the system safety during the test.

[0058] Upper limiters 15 and lower limiters 16 are arranged on the column 11 in its vertical direction to prevent the cross beam 12 from disengaging from the guide rail 13 during the lifting process. The lower limiter 16 is slidably connected to the guide rail on the column 11 and can be locked and fixed by bolts. Threaded holes adapted to the bolts are arranged on both the lower limiter 16 and the column 11. The position of the lower limiter 16 can ensure that the large-diameter cable test model 7 does not contact the ground when the cross beam 12 descends to the restricted position.

[0059] The thermocouple tree 31 is arranged above and around the premixed burner 21 to accurately measure the fire field environment temperature where the large-diameter cable test model 7 is located. The data collector 32 synchronously collects the temperature data of the space and the large-diameter cable test model 7.

[0060] The real fire control system 2 includes a premixed burner 21 and a blower 22 that are respectively electrically connected to the control cabinet 23. The premixed burner 21 is connected to the blower 22 through an air duct 24. The control cabinet 23 is used to adjust the opening of the premixed burner 21 and the frequency of the blower 22 to simulate the vehicle fire source;

[0061] The temperature monitoring system 3 includes a thermocouple tree 31 for monitoring the space temperature field and a data collector 32 for recording temperature data. Both the thermocouple tree 31 and the thermocouples 74 embedded in the large-diameter cable test model 7 are electrically connected to the data collector 32;

[0062] The calorimetry and flue gas purification system 4 includes a smoke collecting hood 41 arranged above the column 11. The smoke collecting hood 41 is connected to the water circulation purifier 43 through a smoke pipe 44. A gas analyzer 42 for analyzing the oxygen content in the smoke pipe 44 to test the heat release rate of the test is provided beside the water circulation purifier 43;

[0063] The high-temperature video recording equipment 5 and the thermal imager 6 are used to record the real fire exposure and heat transfer process of the fire scene and the large-diameter cable test model 7 in real time;

[0064] The large-diameter cable test model 7 includes:

[0065] A cable test model of the strand assembly type, whose cross-sectional diameter is reduced in proportion to the real cable. The cable test model is composed of multiple strands 71 that are parallel to each other, of the same length and aligned at both ends, and are locked and fixed by a number of annular steel hoops 72. The reduction ratio of the strand 71 is the same as that of the cable test model. The strand 71 is formed by squeezing a number of fine steel wires into a round shape, and the fine steel wires are staggeredly tied and fixed at both ends and the middle position thereof by steel straps to reduce the porosity of the cable test model;

[0066] The thermocouple 74 is welded to the surface of the measuring points of several strands 71 inside the cable test model and led out through the gaps between the strands 71. A steel gasket is installed on the surface of the thermocouple 74 exposed outside the cable test model to isolate the flame; the strands 71 welded with the thermocouple 74 are arranged and positioned in sequence in the cable test model according to the target measuring point positions;

[0067] The steel wire 73 is wound around the surface of the cable test model to prevent the flame from directly contacting the cable test model.

[0068] The minimum value of the diameter of the large-diameter cable test model is within the allowable error range of 5%, and its diameter is not less than the result determined by the following formula;

[0069]

[0070] In the formula, R 0 is the minimum cross-sectional diameter of the large-diameter cable test model, R is the prototype diameter of the large-diameter cable test model, e is the natural constant, and 80mm ≤ R ≤ 1500mm.

[0071] The present invention also provides a test method for a real fire test device of a large-diameter cable test model, including the following steps:

[0072] S1: Conduct a fire numerical simulation of the large-diameter cable test model, summarize the most unfavorable fire scenarios, and determine the design temperature of the large-diameter cable test model in the real environment;

[0073] S2: Fabricate the large-diameter cable test model 7 and determine its position during the test. Adjust the height of the crossbeam 12 to the specified position in advance through the multi-dimensional adjustment system 1;

[0074] S3: Arrange the thermocouple tree 31, thermal imager 6, and high-temperature resistant video equipment 5 in the test area to the specified positions;

[0075] S4: According to the layout requirements of the real fire control system 2, move the premixed burner 21 to the position below the proposed position of the large-diameter cable test model 7. Connect the premixed burner 21, air duct 24, and fan 22. The premixed burner 21 is connected to the gas source through the gas pipeline 25. Connect the control cabinet 23 to the premixed burner 21 through the wire 26. Provide fire protection for the wire 26, air duct 24, and gas pipeline 25;

[0076] S5: Turn on the fan 22 and the gas source. Control the frequency of the fan 22 and the opening degree of the premixed burner 21 through the control cabinet 23 and ignite. Record the spatial temperature field through the acquisition instrument 32;

[0077] S6: Adjust the frequency of the fan 22 and the opening degree of the premixed burner 21 multiple times, record the spatial temperature field respectively. According to the fire protection temperature of the large-diameter cable test model 7 obtained by simulation, determine the height of the large-diameter cable test model 7, the frequency of the fan 22, and the opening degree of the premixed burner 21;

[0078] S7: Move the large-diameter cable test model 7 below the crossbeam 12. Connect the first hook 144 to the first eyebolt 121. Use the multi-dimensional adjustment system 1 to adjust the height and vertical inclination of the large-diameter cable test model 7 to complete the positioning of the large-diameter cable test model 7. Connect the thermocouples 74 arranged inside and outside the large-diameter cable test model 7 to the acquisition instrument 32;

[0079] S8: Turn on the calorimetry and flue gas purification system 4;

[0080] S9: Turn on the fan 22 and the gas pipeline 25. Adjust the fan frequency and the premixed burner opening degree to the target values through the control cabinet, ignite and start the test;

[0081] S10: After the test, obtain the temperature field of the large-diameter cable test model 7 monitored by the acquisition instrument 32. Determine whether the fire protection structure meets the fire resistance requirements according to the surface temperature of the steel wire of the large-diameter cable test model 7 and the fire resistance time. Conduct real fire tests on the large-diameter cable test model 7 with different fire protection structures to explore the influence of different structures on the fire resistance performance of the large-diameter cable test model 7.

[0082] Before the fire test, it is necessary to calibrate the spatial temperature field to obtain the spatial temperature field above the premixed burner 21. Determine the position of the large-diameter cable test model 7 according to the target temperature of the large-diameter cable test model 7 and the spatial temperature field as required.

[0083] After the test is completed, the flue gas components are detected by the gas analyzer 42, and the harmful gases are treated by the water circulation purifier 43 to ensure that the emissions meet the environmental protection requirements.

[0084] Through the multi-dimensional adjustment system 1, true fire control technology and high-fidelity model design, this method solves the core problems such as fire field distortion, fixed space state, and model reduction deviation in traditional furnace temperature tests, significantly improves the accuracy and practicability of the fire performance test of the large-diameter cable test model 7, and provides key technical support for the fire resistance optimization design of the large-diameter cable test model 7 of long-span bridges.

[0085] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these changes and modifications.

Claims

1. A large diameter cable test model real fire test device, characterized in that: include: A multi-dimensional adjustment system (1) comprises two columns (11), a crossbeam (12) slidably connected to the columns (11), a height adjustment system (14) and an angle adjustment system (17); the angle adjustment system (17) is arranged at the bottom of the crossbeam (12) and connected to a large-diameter cable test model (7); A real fire control system (2) comprises a premix burner (21) and a fan (22) which are interconnected, wherein the opening degree of the premix burner (21) and the frequency of the fan (22) are both regulated by a control cabinet (23); The temperature monitoring system (3) comprises a thermocouple tree (31) and a collector (32), wherein the thermocouple tree (31) and the thermocouples (74) pre-buried in the large-diameter cable test model (7) are electrically connected to the collector (32); The calorimetric and flue gas purification system (4) comprises a smoke collecting hood (41) arranged above the column (11), the smoke collecting hood (41) being connected to a water circulation purifier (43) via a smoke pipe (44), and a gas analyzer (42) for analyzing the oxygen content in the smoke pipe (44) being arranged next to the water circulation purifier (43); It also includes high temperature resistant video recording equipment (5) and a thermal imager (6) for real-time recording of the fire scene and the actual fire exposure and heat transfer process of the large diameter cable test model (7).

2. A large diameter cable test model real fire test device as claimed in claim 1, characterized in that: The large diameter cable test model (7) comprises: A cable test model of a cable strand assembly type, wherein the cross-sectional diameter is proportionally reduced according to the actual cable, the cable test model is composed of a plurality of cable strands (71) which are parallel to each other, of the same length and aligned at both ends, which are locked and fixed by a plurality of annular steel clamps (72), the reduction ratio of the cable strands (71) is consistent with the reduction ratio of the cable test model, and the cable strands (71) are formed by extruding a plurality of bundles of thin steel wires into a circle, and the thin steel wires are staggered and fixed at both ends and the middle position of the cable strands by steel tie bands, so as to reduce the porosity of the cable test model; Thermocouples (74) are welded to the measuring point surfaces of a plurality of cable strands (71) inside the cable test model and are led out through the gaps between the cable strands (71). Steel gaskets are installed on the surfaces of the thermocouples (74) exposed outside the cable test model to isolate flames. The cable strands (71) welded with thermocouples (74) are placed and positioned in sequence within the cable test model according to the locations of the target measuring points. The steel wire (73) is wound around the surface of the cable test model to prevent the flame from directly contacting the cable test model.

3. A large diameter cable test model real fire test device as claimed in claim 2, characterized in that: The minimum value of the diameter of the large diameter cable test model (7) is within the allowable error range of 5%, and its diameter is not less than the result determined by the following formula: ， Where R0 is the minimum cross-sectional diameter of the large diameter cable test model, R is the prototype diameter of the large diameter cable test model, and e is a natural constant, 80mm≤R≤1500mm.

4. A large diameter cable test model real fire test device as claimed in claim 3, characterized in that: The height adjustment system (14) is provided with two groups, which are respectively arranged at the top of two columns (11). The height adjustment system (14) includes an electric lifting device (141) arranged at the non-fire-exposed side of the column (11). The steel wire rope (143) on the electric lifting device (141) passes through a plurality of fixed pulleys (142) arranged at the top of the column (11) and is connected to the crossbeam (12) on the same side. The top of the crossbeam (12) is provided with a first lifting ring (121). The end of the steel wire rope (143) is provided with a first hook (144) adapted to the first lifting ring (121). The height of the large-diameter cable test model (7) is adjusted by raising and lowering the crossbeam (12).

5. A large diameter cable test model real fire test device as claimed in claim 4, characterized in that: The angle adjustment system (17) is provided with two groups, which are symmetrically arranged along the middle part of the crossbeam (12). The angle adjustment system (17) includes a chain (172) and a second lifting ring (171) connected to the crossbeam (12). The lower part of the crossbeam (12) is provided with a plurality of bolt holes adapted to the second lifting ring (171). The lower end of the second lifting ring (171) is connected to the second hook (173) at the upper end of the chain (172). The second hook (173) at the lower end of the chain (172) is connected to a steel strand (174). The steel strand (174) is sleeved between two annular steel hoops (72) at the ends of the large-diameter cable test model (7). The inclination angle of the large-diameter cable test model (7) is adjusted by adjusting the relative length of the two chains (172). The crossbeam (12) and the angle adjustment system (17) are both provided with a fireproof protective layer.

6. A large diameter cable test model real fire test device as claimed in claim 5, characterized in that: The thermocouple tree (31) is arranged above and around the premix burner (21) to accurately measure the temperature of the fire environment where the large-diameter cable test model (7) is located, and the data collector (32) synchronously collects temperature data of the space and the large-diameter cable test model (7).

7. A large diameter cable test model real fire test device as claimed in claim 6, characterized in that: The column (11) is provided with an upper limiter (15) and a lower limiter (16) in the vertical direction thereof. The lower limiter (16) is slidably connected to the column (11) and can be fixed by bolts. The lower limiter (16) and the column (11) are provided with threaded holes adapted to the bolts. The lower limiter (16) can ensure that the large-diameter cable test model (7) does not contact the ground when the cross beam (12) is lowered to a restricted position.

8. A test method for a large diameter cable test model real fire test device as claimed in claim 7, characterized in that: The following steps are involved: S1: Conduct numerical simulation of fire on the large-diameter cable test model (7), summarize the most unfavorable fire scenario, and determine the design temperature of the large-diameter cable test model (7) under real environment; S2: making a large diameter cable test model (7) and determining its position during the test, and adjusting the height of the crossbeam (12) to the specified position in advance through the multi-dimensional adjustment system (1); S3: Arrange the thermocouple tree (31), the thermal imager (6) and the high temperature resistant video recording device (5) at designated locations in the test area; S4: According to the layout requirements of the real fire control system (2), the premix burner (21) is moved to the lower part of the proposed position of the large diameter cable test model (7), the premix burner (21) and the fan (22) are connected through the air duct (24), the premix burner (21) is connected to the gas source through the gas pipeline (25), the control cabinet (23) is connected to the premix burner (21) through the wire (26), and the wire (26), the air duct (24) and the gas pipeline (25) are fire-proofed; S5: Turn on the fan (22) and the gas source, control the frequency of the fan (22) and the opening of the premix burner (21) through the control cabinet (23), ignite, and record the space temperature field through the data acquisition instrument (32); S6: adjusting the frequency of the fan (22) and the opening of the premix burner (21) multiple times, recording the spatial temperature field respectively, and determining the height of the large-diameter cable test model (7), the frequency of the fan (22) and the opening of the premix burner (21) according to the fortification temperature of the large-diameter cable test model (7) obtained by simulation; S7: Move the large-diameter cable test model (7) to below the crossbeam (12), connect the first hook (144) to the first suspension ring (121), use the multi-dimensional adjustment system (1) to adjust the height and vertical inclination of the large-diameter cable test model (7), complete the positioning of the large-diameter cable test model (7), and connect the thermocouples (74) arranged inside and outside the large-diameter cable test model (7) to the data collector (32) respectively; S8: Start the calorimetric and flue gas purification system (4); S9: Turn on the fan (22) and the gas pipeline (25), adjust the frequency of the fan (22) and the opening of the premix burner (21) to the target values ​​through the control cabinet (23), ignite and start the test; S10: After the test, the temperature field of the large-diameter cable test model (7) monitored by the collector (32) is obtained, and whether the fireproof structure meets the fireproof requirements is determined based on the surface temperature of the steel wire (73) on the large-diameter cable test model (7) and the fireproof time. A real fire test of the large-diameter cable test model (7) with different fireproof structures is carried out to explore the influence of different structures on the fireproof performance of the large-diameter cable test model (7).

9. The test method of a large diameter cable test model real fire test device according to claim 8, characterized in that: Before the fire test, the spatial temperature field calibration is required to obtain the spatial temperature field above the premixed burner (21), and the position of the large diameter cable test model (7) is determined according to the required target temperature of the large diameter cable test model (7) and the spatial temperature field.

10. The test method of a large diameter cable test model real fire test device according to claim 8, characterized in that: After the test, the smoke composition is detected by a gas analyzer (42) to obtain the heat release rate of the test process, and the harmful gas is treated by a water circulation purifier (43) to ensure that the emission meets environmental protection requirements.

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