Self-induced fire whirlwind experimental device with adjustable boundary height

Abstract

The invention discloses a boundary height-adjustable self-induced fire whirlwind experimental device, which comprises a frame, the cross section of the frame is of a polygonal structure, a water cooling table is fixed in the middle of the frame, and a through hole is formed in the middle of the water cooling table; the lifting system is installed at the bottom in the frame, and a distance detection module is arranged between the lifting system and the water cooling table; the combustion system is mounted at the top of the lifting system; the measuring bracket is arranged on one side outside the frame; the measuring system is mounted on the measuring bracket, and the measuring system extends into the frame; a plurality of groups of telescopic tempered glass boundaries are arranged, and the telescopic tempered glass boundaries are positioned on the top surface of the water cooling table; and an adjustable slit is formed between the boundary of the telescopic toughened glass and the frame body of the frame. Simulation of fire whirlwind under different vortex generation and fire source conditions can be realized, the formation and evolution rules of the fire whirlwind are disclosed, and a scientific basis is provided for fire safety prevention and control.

Description

Technical Field

[0001] The present invention relates to the technical field of fire safety, and particularly to an experimental device for self-induced fire whirlwind with adjustable boundary height. Background Art

[0002] Fire whirlwind is an extreme fire behavior in forest and urban fires, which is a violently burning rotating flame induced by the interaction between combustion and a rotating flow field. Compared with ordinary flames, the flame temperature and height of fire whirlwind are greatly increased, thus significantly enhancing its heat radiation ignition ability. In addition, fire whirlwind has a very high axial velocity, which can carry combustibles on the ground into the air and fly to a long distance, triggering a large number of new fire points and accelerating the spread of the fire. Therefore, it is of great theoretical and practical significance to study the formation, evolution mechanism and rules of fire whirlwind under different rotating flow fields and fire source conditions. By establishing the formation criterion of fire whirlwind, it helps to predict the spread trend of the fire and promote the development of early warning technology, thereby reducing the risk of fire damage to personnel and property.

[0003] Laboratory simulation is an effective way to study the characteristics of fire whirlwind. The experimental devices for generating fire whirlwind in the laboratory can be divided into forced-induced fire whirlwind devices and natural-induced fire whirlwind devices according to the concept of generating vortices. Emmons earliest carried out quantitative experimental research on fire whirlwind using a rotating screen device (forced-induced fire whirlwind device, height: 3.05 m, diameter: 2.2 m, fuel: acetone, oil pan diameter 0.1 m). The results show that the combustion rate and flame height increase with the increase of the applied circulation. Hartl used a two-half-cylinder + slit-type small-scale fire whirlwind experimental device (natural-induced fire whirlwind device, device diameter 30 cm, height 89 cm, maximum flame height 63 cm, using dimethyl ether as fuel, burner diameter 3.8 cm), and obtained the expression of dimensionless flame height by changing the slit width. Lei Jiao used a four-wall + slit-type fire whirlwind experimental device (natural-induced fire whirlwind device, device height 15 m, side length 2 m, each corner with a 20-cm-wide slit; using liquid fuel n-heptane, oil pan diameter 10 - 55 cm) to establish a semi-physical model of combustion rate and flame height.

[0004] Although the fire whirlwinds generated by two typical experimental devices in the laboratory are basically formed under the condition of a relatively high rotating flow field height, a large number of fire scene observations show that fire whirlwinds are completely possible to be generated under the condition of a relatively low rotating flow field height. For the mechanically driven rotating screen device, buoyancy and the flow field are independent of each other, and the intensity of the rotating flow field can be considered to be uniformly distributed in the height direction. For the fixed-frame device, buoyancy and the rotating flow field are coupled, and the intensity of the rotating flow field is non-uniformly distributed in the height direction.

[0005] Based on the above technical problems, the present invention provides a self-induced fire whirlwind experimental device with adjustable boundary height. Summary of the Invention

[0006] The object of the present invention is to provide a self-induced fire whirlwind experimental device with adjustable boundary height to solve the problems existing in the prior art.

[0007] To achieve the above object, the present invention provides the following solution: The present invention provides a self-induced fire whirlwind experimental device with adjustable boundary height, including:

[0008] A frame, the cross-sectional shape of the frame is a polygonal structure, a water-cooling table is fixed at the middle position of the frame, and a through-hole is opened at the middle position of the water-cooling table;

[0009] A lifting system, the lifting system is installed at the inner bottom of the frame, and the lifting system is located below the water-cooling table, and a distance detection module is arranged between the lifting system and the water-cooling table;

[0010] A combustion system, the combustion system is installed at the top of the lifting system, and the combustion system is correspondingly arranged with the through-hole at the middle position of the water-cooling table;

[0011] A measurement bracket, the measurement bracket is arranged on one side outside the frame and is correspondingly arranged with the frame;

[0012] A measurement system, the measurement system is installed on the measurement bracket, and the measurement system extends into the frame;

[0013] A telescopic tempered glass boundary, there are several groups of telescopic tempered glass boundaries, several telescopic tempered glass boundaries are connected in series in sequence, and are respectively correspondingly arranged with the sides of the frame, and the telescopic tempered glass boundary is located on the top surface of the water-cooling table;

[0014] Wherein, an adjustable slit is formed between the telescopic tempered glass boundary and the frame body.

[0015] According to the self-induced fire whirlwind experimental device with adjustable boundary height provided by the present invention, the lifting system includes a scissor lift, the scissor lift is located below the water-cooling table, a mounting seat is installed at the top of the scissor lift, and the combustion system is installed on the mounting seat.

[0016] According to the self-induced fire whirlwind experimental device with adjustable boundary height provided by the present invention, the combustion system includes an oil pan or a burner, the oil pan or the burner is fixed on the top of the scissor lift through the mounting seat and is correspondingly arranged with the through-hole on the water-cooling plate.

[0017] According to the self-induced fire whirlwind experimental device with adjustable boundary height provided by the present invention, the measurement system includes a linear motor vertically fixed on the measurement bracket. A pitot tube and a thermocouple are installed on the slider of the linear motor, and one end of the pitot tube extends into the frame.

[0018] According to the self-induced fire whirlwind experimental device with adjustable boundary height provided by the present invention, the retractable tempered glass boundary includes a fixed glass and a movable glass. The fixed glass is fixed on the frame, and the fixed glass and the movable glass are in sliding fit. The movable glass is slidably connected to the frame through an electric slide rail.

[0019] According to the self-induced fire whirlwind experimental device with adjustable boundary height provided by the present invention, the water-cooling table has a side length of 1 m, a thickness of 5 cm, is made of aluminum, and the diameter of the through hole is 20 cm.

[0020] According to the self-induced fire whirlwind experimental device with adjustable boundary height provided by the present invention, the frame has a height of 3 m and a side length of 1 m.

[0021] According to the self-induced fire whirlwind experimental device with adjustable boundary height provided by the present invention, a spiral guide groove is arranged in the water-cooling table. The spiral guide groove is coaxially arranged with the through hole. Two groups of openings are provided on the side of the water-cooling table, and the two openings are respectively communicated with the spiral guide groove for realizing the circulation of cooling water.

[0022] The present invention discloses the following technical effects:

[0023] When the present invention works, the slit height is adjusted through the retractable tempered glass boundary to control the opening degree of the experimental space. The slit width affects the air intake rate of the external environment, thereby changing the swirl intensity. The lifting system adjusts the position of the burner according to the preset height, and the distance detection module real-time feedbacks the distance between the burner and the water-cooling table to ensure safe and accurate experimental conditions. Ignition and hot gas rise: The combustion system releases combustible gas, and a free buoyancy diffusion flame is formed under the action of the critical ignition energy. The hot plume moves upward due to the buoyancy generated by the density difference. The outside air moves towards the center of the device under the action of the horizontal pressure difference, and an initial rotational angular momentum is formed under the constraint of the polygonal structure of the frame. As the air moves towards the center, due to the conservation of angular momentum, the rotational speed of the air flow increases, and the air interacts with the flame to form a rotating diffusion flame (fire whirlwind). The fire whirlwind maintains the rotational momentum by entraining the surrounding air, and its combustion dynamics and geometric morphology are jointly affected by the boundary height and the heat release rate. The measurement system extends into the frame to collect data such as the temperature field, pressure pulsation, and flow velocity distribution in real time. After the flame goes out, the water-cooling table continues to work to absorb the residual heat and prevent equipment damage. The tempered glass boundary is fully unfolded to accelerate the ventilation and cooling of the experimental chamber.

[0024] The present invention realizes the adjustment with an accuracy of 0.1 mm through a retractable tempered glass boundary, can simulate actual scenarios such as the size of building windows and ventilation openings in forest fire sites, and reveals the critical conditions for the mutation of fire whirlwinds caused by boundary flow.

[0025] The present invention independently controls the telescopic amount of each side, studies the influence of irregular boundaries on the symmetry of swirling flow, and provides data for fire prediction in complex terrains. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] 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 embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0027] Figure 1 is a schematic structural diagram of an experimental device for self-induced fire whirlwind with adjustable boundary height according to the present invention;

[0028] Figure 2 is a schematic structural diagram of the water-cooling table according to the present invention;

[0029] Figure 3 is a top view of the frame according to the present invention;

[0030] Figure 4 is a schematic diagram of the slit inlet air flow.

[0031] Among them, 1, frame; 2, water-cooling table; 3, through hole; 4, measurement bracket; 5, retractable tempered glass boundary; 6, scissor lift; 7, combustion system; 8, pitot tube; 9, adjustable slit. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0032] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0033] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below with reference to the drawings and specific embodiments.

[0034] Referring to Figures 1-4 , the present invention provides an experimental device for self-induced fire whirlwind with adjustable boundary height, including:

[0035] Frame 1, the cross-sectional shape of Frame 1 is a polygonal structure, and a water-cooling table 2 is fixed at the middle position of Frame 1. A through-hole 3 is provided at the middle position of the water-cooling table 2;

[0036] A lifting system, the lifting system is installed at the inner bottom of Frame 1, and the lifting system is located below the water-cooling table 2. A distance detection module is provided between the lifting system and the water-cooling table 2;

[0037] A combustion system 7, the combustion system 7 is installed at the top of the lifting system, and the combustion system 7 is arranged corresponding to the through-hole 3 at the middle position of the water-cooling table 2;

[0038] A measuring bracket 4, the measuring bracket 4 is arranged on one side outside Frame 1 and is arranged corresponding to Frame 1;

[0039] A measuring system, the measuring system is installed on the measuring bracket 4, and the measuring system extends into Frame 1;

[0040] A retractable tempered glass boundary 5, several groups of retractable tempered glass boundaries 5 are provided. The several retractable tempered glass boundaries 5 are connected in series in sequence and are respectively arranged corresponding to the sides of Frame 1. The retractable tempered glass boundary 5 is located on the top surface of the water-cooling table 2;

[0041] Among them, an adjustable slit 9 is formed between the retractable tempered glass boundary 5 and the frame body of Frame 1.

[0042] When the present invention works, the width of the slit is adjusted through the retractable tempered glass boundary to control the opening degree of the experimental space. The slit width affects the intake rate of the air flow in the external environment, thereby changing the swirl intensity. The lifting system adjusts the position of the burner according to the preset height, and the distance detection module real-time feedbacks the distance between the burner and the water-cooling table 2 to ensure safe and accurate experimental conditions. Ignition and hot gas rise: The combustion system 7 releases fuel, and the flame flows upward through the through-hole 3 of the water-cooling table 2. The hot gas moves upward due to the buoyancy force generated by the density difference, and the ambient air flow moves towards the center of the device under the action of the horizontal pressure difference, and forms an initial rotation under the constraint of the polygonal structure of Frame 1. The retractable glass boundary restricts the radial diffusion of the air flow, forcing the ambient air flow to move along Frame 1 to form a rotating diffusion flame (fire whirlwind). The fire whirlwind maintains the rotational momentum by entraining the surrounding air, and its combustion dynamics and geometric morphology are jointly affected by the boundary height and the heat release rate. The measuring system extends into Frame 1 to collect data such as the temperature field, pressure pulsation, and flow velocity distribution in real time. After stopping fuel supply, the water-cooling table 2 continues to work to absorb the residual heat to prevent equipment damage. The tempered glass boundary is fully unfolded to accelerate the ventilation and cooling of the experimental chamber.

[0043] For a further optimized solution, the lifting system includes a scissor lift 6. The scissor lift 6 is located below the water-cooling table 2. An installation seat is installed at the top of the scissor lift 6, and the combustion system 7 is installed on the installation seat.

[0044] For a further optimized solution, the combustion system 7 includes an oil pan or a burner, which is fixed to the top of the scissor lift 6 through a mounting base and is arranged corresponding to the through hole 3 on the water-cooled plate.

[0045] The scissor structure cooperates with a screw / hydraulic drive system through cross-hinged arms to achieve height adjustment in the vertical direction. The bottom of the bracket is fixed to the experimental bench base, and the top mounting base can carry the combustion system 7. When the drive motor or hydraulic device is started, the screw rotates or the hydraulic cylinder expands and contracts, pushing the scissor arms to expand or contract, thereby driving the overall lifting of the combustion system 7.

[0046] The combustion system 7 includes a fuel supply module, an ignition device, and a flame monitoring device. During the experiment, after the fuel is ignited, the combustion system 7 ensures the stability of the flame during rotation through modular design.

[0047] The water-cooled table 2 is located below the bracket and absorbs the high-temperature radiation of the flame on the table during the experiment through circulating cooling water. Its double-layer structure design (the upper layer is a heat-conducting layer, and the lower layer is a water-cooled cavity) effectively prevents heat from conducting downward, avoids deformation of the bracket or overheating of electronic components, and at the same time ensures the safety and stability of the experimental environment.

[0048] In the closed experimental space, the heat released by the combustion system 7 forms an upward heat plume, which forms a shear layer with the surrounding cold air. When the slit width is reduced, the air flow channel becomes narrower, the tangential velocity gradient increases, resulting in an enhanced vorticity at the flame root, and finally inducing a fire whirlwind.

[0049] For a further optimized solution, the measurement system includes a linear motor, which is vertically fixed on the measurement bracket 4. A pitot tube 8 and a thermocouple are installed on the slider of the linear motor, and one end of the pitot tube 8 extends into the frame 1.

[0050] The linear motor adopts a "rotor-stator" structure, the stator is fixed on the measurement bracket 4, and the rotor (slider) drives the pitot tube 8 and the thermocouple to move in the vertical direction through electromagnetic thrust.

[0051] By adjusting the frequency and amplitude of the input current, the moving speed (0.1 - 200 mm / s) and positioning accuracy (±0.01 mm) of the slider can be precisely controlled, supporting continuous scanning or fixed-point sampling of measurement points.

[0052] The long secondary design enables the measurement range to cover the full height of the combustion system 7 (for example, 50 - 200 cm), meeting the experimental requirements for different boundary heights.

[0053] The pitot tube 8 is installed at the front end of the slider, the total pressure hole is facing the oncoming flow direction, and the static pressure hole is perpendicular to the flow field direction.

[0054] The total pressure hole senses the total air pressure (dynamic pressure + static pressure), and the static pressure hole measures the ambient static pressure. The pressure difference between the two is converted into an electrical signal by a differential pressure sensor.

[0055] Calculate the flow velocity in real time according to Bernoulli's equation (accuracy ±0.5 m / s), and support high-frequency sampling in the turbulent flow field (sampling rate > 1 kHz).

[0056] The thermocouple (type K or S) is embedded in the surface of the slider, and the differential connection method is used to eliminate interference.

[0057] Cover the temperature range from room temperature to 1300 °C (special coating can measure up to 1600 °C), and the response time < 50 ms.

[0058] Through the built-in temperature sensor and compensation circuit, eliminate the influence of ambient temperature fluctuations on the measurement accuracy.

[0059] The position encoder of the linear motor, the differential pressure sensor of the Pitot tube 8, and the thermocouple signal are synchronously recorded by a high-speed data acquisition card (sampling rate ≥ 10 kHz).

[0060] The spacing between measurement points can be as low as 1 mm, and support three-dimensional flow field reconstruction.

[0061] After the data is filtered, it can be synchronously transmitted to the control system to adjust the experimental parameters.

[0062] The fast response characteristic of the linear motor (acceleration > 5g) supports the measurement of transient flow fields, can capture the vorticity mutation at the initial stage of the formation of the fire whirlwind (time resolution < 0.01 s), and reveals the flame instability mechanism.

[0063] Further optimize the scheme, the retractable tempered glass boundary 5 includes a fixed glass and a movable glass. The fixed glass is fixed on the frame 1, and the fixed glass and the movable glass are slidably matched. The movable glass is slidably connected to the frame 1 through an electric slide rail. The Pitot tube 8 and the thermocouple move up and down, and the moving range is 0 - 30 cm.

[0064] The fixed glass is permanently fixed on the top of the experimental frame 1 through a rigid bracket, serving as a stable base for the boundary system. It is made of tempered glass material (thickness ≥ 8 mm), and the surface is treated with an explosion-proof film, which can withstand high temperature (> 600 °C) and instantaneous impact.

[0065] The movable glass (the size matches the fixed glass) is initially located at the starting end of the slide rail at the bottom of the frame 1 and remains stationary through the locking mechanism of the electric slide rail.

[0066] Adopt a synchronous belt drive slide rail (accuracy ±0.05 mm), which is driven by a servo motor. After the control system inputs the target height, the motor drives the synchronous belt to rotate through a gearbox reduction (reduction ratio 1:30).

[0067] The moving glass is fixed to the synchronous belt through a slider connecting piece at the top of the slide rail, and realizes vertical lifting with the movement of the belt. Its movement speed (5 - 50 mm / s) can be controlled by the PLC, supporting uniform speed, acceleration or segmented variable speed modes.

[0068] An L-shaped sealing strip is installed at the edge of the moving glass, and forms a compression contact with the surface of the fixed glass during the sliding process (pressure > 5 kPa), ensuring the airtightness of the experimental space (leakage rate < 0.1%).

[0069] For a further optimized solution, the side length of the water-cooling table 2 is 1 m, the thickness is 5 cm, the material is aluminum, and the diameter of the through hole 3 is 20 cm.

[0070] For a further optimized solution, the height of the frame 1 is 3 m and the side length is 1 m.

[0071] The frame 1 is divided into ten layers, each layer is 30 cm high. The unilateral boundary of each layer is composed of a fixed glass and a moving glass. The moving glass is placed in the electric track, and the slit width can be arbitrarily changed within the range of 0 to 0.2 m, and the step accuracy can reach 0.001 m. The fixed glass and the moving glass are assembled into a modular structure, which is convenient for installation and disassembly, and the slit width can be arbitrarily adjusted at different heights. In order to reduce the influence of the gap between the fixed glass and the moving glass on the experimental flow field, two pieces of glass are required for the fixed part. The modular structure has three groups of tracks built-in. The fixed glass is placed on the inner and outer sides, and the moving glass is placed in the middle. By moving the tempered glass horizontally along the frame 1, the slit width is changed, thereby changing the inflow velocity. By increasing or decreasing the modular tempered glass vertically along the frame 1, the boundary height is changed. To study the influence of different rotational flow field heights and intensities on the formation and evolution of the fire whirlwind.

[0072] For a further optimized solution, a spiral guide groove is provided inside the water-cooling table 2. The spiral guide groove is coaxially arranged with the through hole 3. Two sets of openings are provided on the side of the water-cooling table 2, and the two openings are respectively communicated with the spiral guide groove for realizing the circulation of the cooling water.

[0073] For a further optimized solution, the inlet velocity u of the slit θ , the slit width s, and the heat release rate satisfy the relationship:

[0074]

[0075] Among them, s * = s / L, ρ ∞ is the ambient air density, c ∞ is the specific heat capacity of the ambient air, and T ∞ is the ambient air temperature.

[0076] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings, and are only for the convenience of describing the present invention, 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 thus should not be construed as a limitation to the present invention.

[0077] The embodiments described above are only descriptions of the preferred embodiments of the present invention, and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A self-induced fire whirlwind experimental device with adjustable boundary height, characterized in that: include: A frame (1), wherein the cross-sectional shape of the frame (1) is a polygonal structure, a water cooling platform (2) is fixed in the middle of the frame (1), and a through hole (3) is opened in the middle of the water cooling platform (2); A lifting system, the lifting system being installed at the bottom of the frame (1), and the lifting system being located below the water cooling table (2), and a spacing detection module being provided between the lifting system and the water cooling table (2); A combustion system (7), the combustion system (7) being installed on the top of the lifting system, and the combustion system (7) being arranged corresponding to the through hole (3) at the middle position of the water cooling platform (2); A measuring bracket (4), the measuring bracket (4) being arranged on a side outside the frame (1) and arranged corresponding to the frame (1); A measuring system, the measuring system being mounted on the measuring support (4) and extending into the frame (1); A retractable tempered glass border (5), wherein the retractable tempered glass border (5) is provided in a plurality of groups, wherein the plurality of retractable tempered glass borders (5) are sequentially connected in series and are arranged one-to-one corresponding to the side surfaces of the frame (1), and the retractable tempered glass border (5) is located on the top surface of the water cooling platform (2); Wherein, an adjustable slit (9) is formed between the retractable tempered glass boundary (5) and the frame body of the frame (1).

2. The self-induced fire whirlwind experimental device with adjustable boundary height according to claim 1, characterized in that: The lifting system comprises a scissor-type lifting frame (6), the scissor-type lifting frame (6) is located below the water-cooling platform (2), a mounting seat is installed on the top of the scissor-type lifting frame (6), and the combustion system (7) is installed on the mounting seat.

3. The self-induced fire whirlwind experimental device with adjustable boundary height according to claim 2, characterized in that: The combustion system (7) comprises an oil pan or a burner, wherein the oil pan or the burner is fixed to the top of the scissor-type lifting frame (6) through the mounting seat and is arranged corresponding to the through hole (3) on the water-cooling plate.

4. The self-induced fire whirlwind experimental device with adjustable boundary height according to claim 1, characterized in that: The measuring system comprises a linear motor, which is vertically fixed on the measuring bracket (4). A Pitot tube (8) and a thermocouple are mounted on a slider of the linear motor, and one end of the Pitot tube (8) extends into the frame (1).

5. The self-induced fire whirlwind experimental device with adjustable boundary height according to claim 1, characterized in that: The retractable tempered glass border (5) comprises a fixed glass and a movable glass, wherein the fixed glass is fixed on the frame (1), the fixed glass and the movable glass are slidably matched, and the movable glass is slidably connected to the frame (1) via an electric slide rail.

6. The self-induced fire whirlwind experimental device with adjustable boundary height according to claim 1, characterized in that: The water cooling platform (2) has a side length of 1 m and a thickness of 5 cm, is made of aluminum, and has a through hole (3) with a diameter of 20 cm.

7. The self-induced fire whirlwind experimental device with adjustable boundary height according to claim 1, characterized in that: The frame (1) has a height of 3 m and a side length of 1 m.

8. The self-induced fire whirlwind experimental device with adjustable boundary height according to claim 1, characterized in that: The water cooling platform (2) is provided with a spiral guide groove, the spiral guide groove is coaxially arranged with the through hole (3), and two groups of through openings are opened on the side of the water cooling platform (2), and the two through openings are respectively connected to the spiral guide groove to realize cooling water circulation.

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