A smoke exhaust duct and method for improving the measurement accuracy of smoke in a fire experiment

Abstract

The present application provides a smoke exhaust duct and method for improving the measurement accuracy of smoke in a fire experiment. The smoke exhaust duct includes a first pipe section and a second pipe section. The air outlet end of the first pipe section is connected to the air inlet end of the second pipe section, and an opening degree adjusting component is provided at the connection. The opening degree adjusting component is used to dynamically adjust the opening degree of the first pipe section. The first pipe section includes an outer pipe and an inner pipe which are coaxially nested. A first smoke detection component and a second smoke detection component are respectively arranged in the inner pipe and the second pipe section. Through the opening degree adjusting component, the opening degree of the first pipe can be adjusted. During large-scale tests, the opening degree of the outer pipe can be increased to improve the smoke exhaust rate and avoid insufficient combustion. During small-scale tests, the smoke can be inhaled only from the inner pipe with a smaller diameter, which is convenient for better controlling the flow direction and flow rate of the smoke. Weak combustion reactions can also be effectively collected, improving the accuracy of smoke component analysis and ensuring the accuracy and reliability of the test data results.

Description

Technical Field

[0001] This application belongs to the technical field of fire experiment, and more specifically, it relates to an exhaust pipe and method for improving the measurement accuracy of flue gas in fire experiments. Background Art

[0002] In fire experiments, the efficiency of the exhaust pipe directly affects the combustion sufficiency and the accuracy of flue gas component analysis. Currently, in related technologies, the design of the exhaust pipe is difficult to meet the requirements of different-scale combustion experiments. In large-scale tests, the situation of insufficient exhaust rate of the exhaust pipe is likely to occur, resulting in insufficient combustion. In small-scale tests, the situation of too fast exhaust speed of the exhaust pipe is likely to occur. Both insufficient and excessive exhaust rates will lead to inaccurate measurement of the exhaust flow velocity, thus reducing the accuracy of flue gas component analysis and affecting the accuracy and reliability of test data results. Summary of the Invention

[0003] In view of this, this application proposes an exhaust pipe and method for improving the measurement accuracy of flue gas in fire experiments, so as to facilitate improving the accuracy of exhaust analysis in fire combustion experiments.

[0004] To achieve the above object, the technical solution adopted in this application is: In the first aspect, this application provides an exhaust pipe for improving the measurement accuracy of flue gas in fire experiments, including a first pipe section and a second pipe section. The air outlet end of the first pipe section is connected to the air inlet end of the second pipe section, and an opening degree adjusting component is provided at the connection, and the opening degree adjusting component is used to dynamically adjust the opening degree of the first pipe section; the first pipe section includes an outer pipe and an inner pipe coaxially nested, and a first flue gas detection component and a second flue gas detection component are respectively arranged in the inner pipe and the second pipe section.

[0005] Optionally, the opening degree adjusting component includes a limit housing, a driving mechanism, and a plurality of baffles arranged in the limit housing. The limit housing is annular, and an opening adapted to the size of the baffle is provided on its inner side. The baffles are arranged in an annular array centered on the center of the limit housing, and the driving mechanism is used to drive the plurality of baffles to approach or move away from the center simultaneously.

[0006] Optionally, the driving mechanism includes a transmission plate arranged in the limit housing and a driving component for driving the transmission plate to rotate. The transmission plate is provided with a plurality of gradually opening arc-shaped chutes, the number of the arc-shaped chutes corresponds to the number of the baffles, and a slider is arranged on the baffle, and the slider is located in the arc-shaped chute.

[0007] Optionally, the driving component includes a motor, the output shaft of the motor is connected with a gear, the transmission plate is connected with an arc-shaped rack, and the gear meshes with the arc-shaped rack.

[0008] Optionally, the limiting housing includes a first housing and a second housing. The first housing is provided with a through avoidance groove. One side of the arc-shaped rack is provided with a connecting rod, and one end of the connecting rod passes through the avoidance groove and is fixedly connected to the transmission plate. The second housing is provided with a plurality of sliding grooves in the radial direction, and the sliding grooves correspond to the baffle plates one by one. The baffle plates are slidably connected in the sliding grooves.

[0009] Optionally, the first flue gas detection assembly includes a first sample gas sampling probe, a pitot tube anemometer, and a thermocouple sampling probe. The first sample gas sampling probe, the pitot tube anemometer, and the thermocouple sampling probe all pass through the outer tube and extend into the inner side of the inner tube. The second flue gas detection assembly includes a second sample gas sampling probe and an orifice flowmeter.

[0010] Optionally, the ratio of the cross-sectional area of the outer tube to that of the inner tube is 2.5 - 3.

[0011] Optionally, the second pipe section is provided with a detection port, and both the first pipe section and the second pipe section are provided with hand-held anemometer input ports.

[0012] Optionally, a fan is provided at one end of the second pipe section away from the first pipe section.

[0013] Optionally, the outer tube and the inner tube are fixedly connected by a support flange. A first rectifying plate is arranged inside the inner tube, and a second rectifying plate is arranged inside the second pipe section.

[0014] In a second aspect, the present application further provides a method for improving the flue gas measurement accuracy. This method is based on the aforementioned exhaust pipe for exhausting flue gas, and this method includes the following steps:

[0015] Match the corresponding volume flow rate range of the flue gas according to the combustion scale;

[0016] Determine the differential pressure value range according to the volume flow rate range, and the differential pressure value is not less than 20% of the measuring range of the measuring instrument;

[0017] Dynamically adjust the opening degree of the first pipe section according to the differential pressure value and the volume flow rate, that is, dynamically adjust the cross-sectional area of the first pipeline.

[0018] The beneficial effects of the smoke exhaust pipe for improving the measurement accuracy of smoke in fire experiments provided by this application are as follows: Compared with the prior art, this application is provided with a first pipe section and a second pipe section, and the first pipe section includes an outer pipe and an inner pipe coaxially nested. The opening of the first pipe section can be adjusted through an opening adjustment component. During large-scale tests, the opening adjustment component can be adjusted to increase the opening of the first pipe section, improve the smoke exhaust rate, and avoid incomplete combustion; during small-scale tests, the opening adjustment component can be adjusted to reduce the opening of the first pipe section, so that the smoke is only inhaled from the inner pipe with a smaller diameter, which is convenient for better controlling the flow direction and flow rate of the smoke. In this way, even weak combustion reactions can be effectively collected, effectively improving the analysis accuracy of smoke components and the accuracy and reliability of the analysis results of combustion test data.

[0019] The beneficial effects of the smoke exhaust method for improving the measurement accuracy of smoke in fire experiments provided by this application are as follows: This application can match the corresponding volume flow rate range according to the combustion scale, determine the differential pressure value range according to the volume flow rate range, and control the differential pressure value to be not less than 20% of the measurement range of the measuring instrument. Finally, according to the differential pressure value and the volume flow rate, the opening of the first pipe section is dynamically adjusted, that is, the first pipe is limited to a suitable cross-sectional area, so that the smoke volume flow rate relied on during calorimetry, gas generation, particulate generation, and toxicity generation calculations is within a suitable range, and under low smoke flow conditions, the measurement of various components is within the effective range of the instrument, thereby improving the measurement accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of this application, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the following drawings are only some embodiments of this application. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0021] Figure 1 It is a schematic structural diagram of the smoke exhaust pipe for improving the measurement accuracy of smoke in fire experiments provided by the embodiment of this application;

[0022] Figure 2 It is a schematic cross-sectional view of the smoke exhaust pipe for improving the measurement accuracy of smoke in fire experiments provided by the embodiment of this application;

[0023] Figure 3 It is a schematic structural diagram of the opening adjustment mechanism provided by the embodiment of this application;

[0024] Figure 4 It is a schematic structural diagram of the driving mechanism provided by the embodiment of this application;

[0025] Figure 5 It is a schematic structural diagram of the second housing provided by the embodiment of this application;

[0026] Figure 6 Differential pressure value curve diagram of a Pitot tube anemometer when the pipe diameter is 250 mm;

[0027] Figure 7 Differential pressure value curve diagram of a Pitot tube anemometer when the pipe diameter is 150 mm.

[0028] Among them, each reference numeral in the figure:

[0029] 1. First pipe section; 11. Outer pipe; 12. Inner pipe; 13. Support flange; 14. Pitot tube anemometer; 15. First sample gas sampling probe; 16. Thermocouple sampling probe; 17. First hand-held anemometer input port; 18. First rectifying plate; 2. Second pipe section; 21. First detection port; 22. Second sample gas sampling probe; 23. Orifice flowmeter; 24. Second detection port; 25. Second hand-held anemometer input port; 3. Opening adjustment assembly; 31. First housing; 311. Avoidance groove; 32. Second housing; 321. Slide groove; 33. Motor; 34. Gear; 35. Arc-shaped rack; 36. Baffle; 361. Slide block; 37. Transmission plate; 371. Arc-shaped slide groove; 4. Fan. Detailed implementation manners

[0030] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application clearer and more understandable, the present application will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0031] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0032] It should be understood that the orientation or positional relationship indicated by the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present application 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 should not be construed as a limitation to the present application.

[0033] In addition, the terms "first" and "second" are for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of this application, "a plurality of" means two or more, unless otherwise specifically defined.

[0034] Please refer to Figures 1 - 7 together for an illustration of the exhaust duct and method for improving the measurement accuracy of flue gas in a fire experiment provided by the embodiments of this application.

[0035] On the one hand, this application provides an exhaust duct for improving the measurement accuracy of flue gas in a fire experiment, which includes a first pipe section 1 and a second pipe section 2. The air outlet end of the first pipe section 1 is connected to the air inlet end of the second pipe section 2, and an opening degree adjusting component 3 is arranged at the connection, and the opening degree adjusting component 3 is used to dynamically adjust the opening degree of the first pipe section 1; the first pipe section 1 includes an outer pipe 11 and an inner pipe 12 which are coaxially nested, and a first flue gas detection component and a second flue gas detection component are respectively arranged in the inner pipe 12 and the second pipe section 2.

[0036] In the embodiments of this application, the first pipe section 1 and the second pipe section 2 are provided, and the opening degree of the first pipe section 1 is dynamically adjusted by means of the opening degree adjusting component 3 to adapt to the flue gas emission analysis of combustion tests of different scales. Specifically, the first pipe section 1 is designed to include an outer pipe 11 and an inner pipe 12 which are coaxially nested, and the opening degree (i.e., the opening area) of the outer pipe 11 is adjusted by the opening degree adjusting component 3 to adapt to the accurate measurement of the flue gas flow rate in smoldering tests of different scales.

[0037] In some specific embodiments, the air inlet end of the outer pipe 11 can be connected to a large smoke collection hood (not shown in the figure), and the inner pipe 12 can be connected to a small smoke collection hood (not shown in the figure). The large smoke collection hood is mainly used for the emission analysis of a large amount of flue gas during large-scale combustion tests, and the small smoke collection hood is mainly used for the emission analysis of a small amount of flue gas during small-scale combustion tests.

[0038] During large-scale combustion tests, by adjusting the opening degree adjusting component 3, the opening degree of the outer pipe 11 is increased to the maximum, that is, the channel between the inner pipe 12 and the outer pipe 11 is in a fully open state, so as to avoid the situation that the combustion is not sufficient due to insufficient exhaust rate.

[0039] During small-scale combustion tests, the opening degree adjusting component 3 is adjusted simultaneously to reduce the opening degree of the outer pipe 11 to zero, that is, the channel between the outer pipe 11 and the inner pipe 12 is in a fully closed state, so that the flue gas is only inhaled from the inner pipe 12 with a smaller diameter, which is convenient for better controlling the flow direction and flow rate of the flue gas. Even a weak combustion reaction can be effectively collected, improving the accuracy of flue gas component analysis and ensuring the accuracy and reliability of the test data results.

[0040] In this embodiment, when a large-scale combustion test is carried out, the cross-sectional area of the first pipe section 1 reaches the maximum. Exhausting smoke through the outer pipe 11 can improve the efficiency of flue gas emission, thus avoiding incomplete combustion and ensuring the accuracy and reliability of the test data results.

[0041] When a small-scale combustion test is carried out, the cross-sectional area of the first pipe section 1 reaches the minimum. Only exhausting smoke through the inner pipe 12 can better control the flow direction and velocity of the flue gas, facilitating a quick response and adaptation to the transient characteristics of small-scale combustion. Even weak combustion reactions can be effectively collected. By using the inner pipe 12 with a smaller cross-sectional area, more precise control of flue gas emission can be carried out to improve the accuracy and repeatability of the flue gas collection data. In addition, due to the smaller cross-sectional area of the inner pipe 12, a pumping device with a smaller power can be used to achieve sufficient suction force, with lower energy consumption of the device, while still effectively exhausting the flue gas generated by small-scale combustion.

[0042] The inner pipe 12 is installed inside the outer pipe 11, and the opening degree of the outer pipe 11 is adjusted by the opening degree adjusting component 3. This layout enables the exhaust pipe to be applicable to different-scale combustion tests. It can not only promote the sufficiency of combustion by increasing the exhaust speed through the outer pipe 11 in large-scale tests, but also ensure the accuracy and repeatability of data in small-scale combustion tests. It should be noted that when the opening degree adjusting component 3 adjusts the opening degree of the outer pipe 11 to a partially open state, the exhaust pipe can also be applicable to medium-scale combustion tests. In this way, in medium-scale combustion tests, the outer pipe 11 effectively extracts the flue gas that the inner pipe 12 fails to exhaust in the smoke collecting hood, improving the safety and efficiency of the test.

[0043] It should be noted that in the embodiments of the present application, large-scale combustion tests, medium-scale combustion tests, and small-scale combustion tests can be defined according to actual combustion tests. For example, in the embodiments of the present application, a combustion power less than 10 kw is defined as a small-scale combustion test, a combustion power of 10 kw to 20 kw is defined as a medium-scale combustion test, and a combustion power greater than 20 kw is defined as a large-power combustion test. In other embodiments, other criteria can also be used to divide the combustion scale, and the present application does not make any limitations.

[0044] It should also be noted that in the embodiments of the present application, the cross-sectional area of the pipe refers to the opening area of the pipe, that is, at the opening of the pipe cross-section, the opening area at the pipe end cross-section where the flue gas flows from outside the pipe through the pipe. In other embodiments, the same explanation is also referred to.

[0045] The exhaust pipe provided by the embodiments of the present application has three working states:

[0046] 1. The passage between the inner tube 12 and the outer tube 11 is in a completely closed state. At this time, gas is only collected from the smoke hood through the inner tube 12 and measured through the inner tube 12;

[0047] 2. The passage between the inner tube 12 and the outer tube 11 is in a completely open state. At this time, part of the gas is collected from the inner tube 12 and part of the gas is collected from the outer tube 11. The collected data can be collected separately through the first flue gas detection component in the inner tube 12 or the second flue gas detection component in the second pipe section 2, or can be collected simultaneously;

[0048] 3. The passage between the inner tube 12 and the outer tube 11 is in a partially open state. At this time, data collection is mainly through the inner tube 12, and the outer tube 11 is mainly used to discharge excess flue gas.

[0049] Compared with the related prior art, the present application has the following advantages: First, in the related art, smoke is mainly discharged through a large tube and a small tube that are independent of each other; while in the present application, the inner tube 12 is arranged inside the outer tube 11, the appearance is more concise, there are fewer external leakage joints, and the risk of flue gas leakage is lower. Even if flue gas leakage occurs, the flue gas remains inside the outer tube 11 and will not leak to the outside. Second, the related art needs to set up two sets of sensors and needs to frequently switch different pipes to connect with the smoke hood according to the scale of the combustion test; while the present application only needs to set up one set of sensors and does not need to be frequently moved after installation. Third, in the related art, flue gas analysis can only be carried out through one set of flue gas detection components; while the present application can perform two detections on the flue gas through the first flue gas detection component arranged in the inner tube and the second flue gas detection component arranged in the second pipe section. By comparing and optimizing the data detected on both sides, the accuracy of the data can be improved.

[0050] Refer to Figure 3 In some embodiments of the present application, the opening degree adjustment component 3 includes a limit housing, a driving mechanism, and a plurality of baffles 36 arranged in the limit housing. The limit housing is annular, and an opening adapted to the size of the baffle 36 is provided on the inner side thereof. The baffles 36 are arranged in an annular array centered on the center of the limit housing, and the driving mechanism is used to drive the plurality of baffles 36 to approach or move away from the center simultaneously.

[0051] The driving mechanism can drive multiple baffles 36 to approach or move away from the center simultaneously, thereby adjusting the flow-through area. When the baffle 36 moves towards the center of the limiting housing, the flow-through area decreases. When the baffle 36 moves to the maximum position, the gap between the outer pipe 11 and the inner pipe 12 is completely blocked. When the baffle 36 moves away from the center of the limiting housing, the flow-through area increases. By adjusting the flow-through area, the flow rate ratio between the outer pipe 11 and the inner pipe 12 under the same fan 4 can be adjusted. This design allows for flexible adjustment of the flue gas emission speed and quantity according to test requirements, realizes the adjustment of the flow rate ratio, and ensures the precise control and effective analysis of flue gas emissions.

[0052] Refer to Figure 2 and Figure 3 , in some embodiments of the present application, the driving mechanism includes a transmission plate 37 disposed in the limiting housing and a driving assembly for driving the transmission plate 37 to rotate. The transmission plate 37 is provided with a plurality of involute arc-shaped chutes 371. The number of arc-shaped chutes 371 corresponds to the number of baffles 36. A slider 361 is disposed on the baffle 36, and the slider 361 is located in the arc-shaped chute 371.

[0053] The driving assembly can drive the transmission plate 37 to rotate. Since the arc-shaped chute 371 is an involute curve, the rotation of the transmission plate 37 can drive the slider 361 located in the arc-shaped chute 371 to move radially along the transmission plate 37, thereby driving the plurality of baffles 36 to move radially along the transmission plate 37 to achieve the adjustment of the opening degree.

[0054] In some embodiments of the present application, refer to Figure 3 and Figure 4 , the driving assembly includes a motor 33. The output shaft of the motor 33 is connected with a gear 34. The transmission plate 37 is fixedly connected with an arc-shaped rack 35, and the gear 34 meshes with the arc-shaped rack 35. The motor 33 can be fixedly connected to the first pipe section 1 or the second pipe section 2.

[0055] The output shaft of the motor 33 drives the gear 34 to rotate. The gear 34 meshes with the arc-shaped rack 35, thereby driving the arc-shaped rack 35 to perform a circular motion. The arc-shaped rack 35 drives the transmission plate 37 connected thereto to rotate. When the transmission plate 37 rotates, the slider 361 slides along the arc-shaped chute 371. Since the arc-shaped chute 371 is of an involute curve structure, the plurality of sliders 361 move radially along the transmission plate 37, thereby driving the plurality of baffles 36 to move radially along the transmission plate 37 to achieve the adjustment of the opening degree. When the plurality of baffles 36 move in a direction away from the center of the transmission plate 37, the opening degree of the outer pipe 11 increases and the flow-through area increases. When the plurality of baffles 36 move towards the center of the transmission plate 37, the opening degree of the outer pipe 11 decreases and the flow-through area decreases.

[0056] In some other embodiments of the present application, the driving component may also adopt other structures, as long as it can drive the transmission plate 37 to rotate, and the present application does not make any limitations.

[0057] In some embodiments of the present application, referring to Figure 3 and Figure 5 , the limiting housing includes a first housing 31 and a second housing 32. The first housing 31 is provided with an avoidance groove 311 penetrating along its thickness direction. One side of the arc-shaped rack 35 is provided with a connecting rod, and one end of the connecting rod passes through the avoidance groove 311 and is fixedly connected to the transmission plate 37. The second housing 32 is provided with a plurality of sliding grooves 321 along the radial direction, and the sliding grooves 321 correspond to the baffle plates 36 one by one. The baffle plates 36 are slidably connected in the sliding grooves 321.

[0058] The avoidance groove 311 allows the connecting rod to pass through, facilitating the connecting rod to make a circular motion along with the arc-shaped rack 35. The arc-shaped rack 35 makes a circular motion driven by the gear 34, thereby driving the connecting rod to make a circular motion, and the connecting rod drives the transmission plate 37 connected thereto to make a circular motion. The plurality of sliding grooves 321 provided in the second housing 32 along the radial direction can limit the baffle plates 36, so that the baffle plates 36 can only make a linear reciprocating motion along the extending direction of the sliding grooves 321 (i.e., the radial direction of the second housing 32). Through the cooperation between the arc-shaped sliding groove 371 provided on the transmission plate 37 and the slider 361 provided on the baffle plate 36, when the transmission plate 37 rotates, it drives the baffle plate 36 to slide along the extending direction of the sliding groove 321, thereby realizing the adjustment of the opening degree.

[0059] In some embodiments of the present application, referring to Figure 5 , one side of the baffle plate 36 close to the center of the second housing 32 is arc-shaped. The maximum width of the baffle plate 36 is the same as the width of the sliding groove 321, and the width of the baffle plate 36 gradually decreases along the direction close to the center of the second housing 32. When the plurality of baffle plates 36 are closest (i.e., the opening degree is the smallest), a circular through hole is formed in the middle of the plurality of baffle plates 36, and the sides of the plurality of baffle plates 36 are in close contact with each other without gaps. At this time, the flue gas can only pass through the circular through hole surrounded by the plurality of baffle plates 36 and enter the second pipe section 2. When the plurality of baffle plates 36 move away from each other (the opening degree increases), the flue gas can pass through the through hole in the middle and the gaps between the adjacent baffle plates 36 and enter the second pipe section 2. When the opening degree reaches the maximum, the baffle plates 36 are completely received inside the first housing 31 and the second housing 32, without affecting the emission of the flue gas.

[0060] In some embodiments of the present application, referring to Figure 1 and Figure 2 , the first flue gas detection assembly includes a first sample gas sampling probe 15, a pitot tube anemometer 14, and a thermocouple sampling probe 16. The first sample gas sampling probe 15, the pitot tube anemometer 14, and the thermocouple sampling probe 16 all pass through the outer tube 11 and extend into the inner tube 12.

[0061] When conducting weak and small-scale combustion tests, the gap between the outer tube 11 and the inner tube 12 can be blocked by the opening adjustment assembly 3, and only the inner tube 12 is used for smoke exhaust, improving the detection accuracy. The types and concentrations of the smoke in the inner tube 12 can be detected by the first sample gas sampling probe 15, the air flow rate in the inner tube 12 can be detected by the pitot tube anemometer 14, and the temperature of the smoke in the inner tube 12 can be detected by the thermocouple sampling probe 16. By collecting the above data, the types and concentrations, flow rates, and temperatures of the smoke can be analyzed.

[0062] In some embodiments of the present application, refer to Figure 1 and Figure 2 , the second smoke detection assembly includes a second sample gas sampling probe 22 and an orifice flowmeter 23.

[0063] The types and concentrations of the smoke in the second pipe section 2 can be detected by the second sample gas sampling probe 22, and the total flow rate of the smoke can be measured by the orifice flowmeter 23. By simultaneously measuring the smoke flow rate in the inner tube 12 and the total flow rate of the smoke in the second pipe section 2, precise control and effective analysis of smoke emissions in small-scale combustion experiments and large-scale combustion experiments can be achieved.

[0064] In some embodiments of the present application, the ratio of the cross-sectional area of the outer tube 11 to the cross-sectional area of the inner tube 12 is 2.5 to 3. Limiting the cross-sectional area ratio of the outer tube 11 to the inner tube 12 within this range can make the cross-sectional areas of the outer tube 11 and the inner tube 12 match the combustion scale, so that the smoke measurement accuracy and the smoke exhaust speed reach the best matching state.

[0065] In some specific embodiments, the diameter of the outer tube 11 is 250 mm, and the diameter of the inner tube 12 is 150 mm. Optionally, in some other embodiments of the present application, the outer tube 11 and the inner tube 12 can also adopt other diameters, which are not limited in the present application. In some embodiments of the present application, the second pipe section 2 is provided with a detection port, and both the first pipe section 1 and the second pipe section 2 are provided with hand-held anemometer input ports.

[0066] The detection port can be used as a reserved interface for connecting other detection devices, and the hand-held anemometer input port can be used for connecting a hand-held anemometer to facilitate verifying the gas flow rate in the pipe using the hand-held anemometer.

[0067] In some embodiments of the present application, the number of detection ports is two, namely the first detection port 21 and the second detection port 24. In other embodiments of the present application, the number of detection ports can also be set according to actual needs, which is not limited in the present application.

[0068] In some embodiments of the present application, the number of input ports of the handheld anemometer is two, namely the first handheld anemometer input port 17 provided on the first pipe section 1 and the second handheld anemometer input port 25 provided on the second pipe section 2.

[0069] In some embodiments of the present application, a first rectifying plate 18 is provided inside the inner pipe 12, and a second rectifying plate is provided inside the second pipe section 2.

[0070] Through the first rectifying plate 18 and the second rectifying plate, it is possible to ensure uniform mixing of the flue gas and make the detection result more accurate.

[0071] In some embodiments of the present application, refer to Figure 1 and Figure 2 , a blower 4 is provided at one end of the second pipe section 2 away from the first pipe section 1 for providing the suction force for exhausting smoke. Compared with the related art, in the related art, when conducting large-scale or small-scale combustion tests, it is necessary to connect the two ends of the large pipe or small pipe to the blower 4 and the smoke collecting hood respectively. When switching the combustion scale, it is necessary to remove the large pipe (or small pipe) and then install the small pipe (or large pipe), which has a large workload and affects the test efficiency. In the present application, only the second pipe section 2 needs to be connected to the blower 4, and the first pipe section 1 needs to be connected to the smoke collecting hood. When switching the combustion scale, only the opening degree of the first pipe section 1 needs to be adjusted, saving the work of disassembling and installing the exhaust pipe. Moreover, keeping the power of the blower 4 unchanged, only by adjusting the opening degree of the first pipe section 1, the flow rate and proportion of the flue gas in the inner pipe 12 and the outer pipe 11 can be adjusted.

[0072] In some embodiments of the present application, refer to Figure 1 and Figure 2 , the outer pipe 11 and the inner pipe 12 are fixedly connected through a support flange 13.

[0073] The support flange 13 includes a coaxial outer fixing ring and an inner fixing ring. The outer fixing ring is fixedly connected to the outer appearance, and the inner fixing ring is fixedly connected to the inner pipe 12, which can coaxially fix and connect the outer pipe 11 and the inner pipe 12. The number of support flanges 13 can be 2, 3 or other numbers, which are not limited in the present application.

[0074] Second, the present application also provides a smoke exhaust method for improving the measurement accuracy of fire experiment flue gas. This method is based on the aforementioned smoke exhaust pipe for smoke exhaust, and this method includes the following steps:

[0075] Match the corresponding volume flow rate range according to the combustion scale;

[0076] Determine the differential pressure value range according to the volume flow rate range, and the differential pressure value is not less than 20% of the range of the measuring instrument;

[0077] Determine the cross-sectional area of the pipe according to the differential pressure value and the volume flow rate, and dynamically adjust the opening degree of the first pipe section.

[0078] In the fire test of this embodiment, the combustion measurement is mainly based on the data of the gas analyzer (including oxygen and toxicity) and the volumetric flow rate of the flue gas. When conducting the test, it is necessary to pre-determine the scale range of the sample to match the corresponding volumetric flow rate. When the combustion power is constant, the larger the volumetric flow rate, the higher the oxygen concentration of the sample gas (i.e., less oxygen consumption), and the smaller the volumetric flow rate, the lower the oxygen concentration of the sample gas (i.e., more oxygen consumption).

[0079] The volumetric flow rate of the flue gas in the exhaust pipe of this embodiment can be calculated by the following formula:

[0080] (1)

[0081] In the formula, represents the volumetric flow rate in the exhaust pipe when the external combustion environment is at normal temperature and pressure, with the unit of m³ / s; is the cross-sectional area of the exhaust pipe; is the ratio of the average mass flow per unit area to the mass flow at the center of the exhaust pipe; is the Reynolds number correction of the two-way velocity measurement probe, which can be taken as 1.08; is the pressure difference of the Pitot tube anemometer; is the gas temperature in the exhaust pipe.

[0082] In some embodiments of the present application, when using an orifice flowmeter to measure the flow rate, it can be calculated by the following formula:

[0083] (2)

[0084] In the formula, represents the volumetric flow rate in the exhaust pipe when the external combustion environment is at normal temperature and pressure, with the unit of m³ / s; C is the orifice flowmeter constant; is the pressure difference measured by the micro manometer; is the gas temperature in the exhaust pipe.

[0085] Currently, when measuring the wind speed based on a Pitot tube anemometer, a differential pressure sensor with a range of 0~100PA and an accuracy of 1% is generally selected.

[0086] To study the influence of exhaust pipes with different pipe diameters under low wind pressure on the exhaust measurement accuracy, the following comparative analysis examples are provided. The pipe diameter of the exhaust pipe is set to 250mm, and the pipe diameter of the exhaust pipe is set to 150mm. When the diameter of the exhaust pipe is 250mm, at normal temperature and pressure, the volumetric flow rate is between 0.01 m³ / s and 0.6 m³ / s, and the differential pressure value curve of the Pitot tube anemometer is as Figure 6 shown; when the diameter of the exhaust pipe is 150mm, at normal temperature and pressure, the volumetric flow rate is between 0.01 m³ / s and 0.2 m³ / s, and the differential pressure value curve of the pitot tube anemometer is as Figure 7 shown. According to Figure 6 and Figure 7 the curves shown, it can be known that the differential pressure and the flow velocity are non-linear relationships, and the influence on the wind speed with the same measurement accuracy is greater under the low wind pressure state. For example, when the volumetric flow rate is 0.2 m³ / s, Figure 6 the differential pressure value measured by using a 250 mm exhaust pipe in Figure 7 is about 10 Pa, accounting for 10% of the range of the differential pressure sensor, and the measurement error (such as reading error, etc.) is relatively large. Figure 7 the differential pressure value measured by using a 150 mm exhaust pipe in

[0087] is about 80 Pa, accounting for 80% of the range of the differential pressure sensor. Compared with using a 250 mm exhaust pipe, the error is smaller and the measurement accuracy is higher. In the embodiments of the present application, by designing exhaust pipes with different diameters, a smaller-diameter exhaust pipe is selected when the wind speed is low, and a larger-diameter exhaust pipe is selected when the wind speed is high, so that the measured differential pressure value is not less than 20% of the range of the measuring instrument and does not exceed the range of the measuring instrument, and the measurement error is smaller, thereby achieving high-precision measurement of combustion tests of different scales.

[0088] Example 1

[0089] In this embodiment, the inner diameter of the outer pipe 11 is 250 mm, and the cross-sectional area is about 0.0491 ㎡. The inner diameter of the inner pipe 12 is 150 mm, and the cross-sectional area is about 0.0177 ㎡. Under the condition that the ambient temperature is 25 °C, the data of a 3 kW standard fire source are measured at the maximum opening and the minimum opening respectively with different wind speeds. The data are shown in Table 1 below:

[0090] Table 1 Data of the exhaust pipe in this embodiment for measuring a 3 kW standard fire source

[0091]

[0092] It can be seen from this embodiment that when the fire source power is small (3 kW) and the smoke flow velocity is low, the inner pipe 12 with a smaller cross-sectional area is used for testing, and the measured power is closer to the fire source power, and the accuracy is higher than that of using the outer pipe 11 for testing. High-precision measurement at low smoke flow velocities can be achieved, and at this time, using the inner pipe 12 for measurement can improve the measurement accuracy.

[0093] Example 2

[0094] In this embodiment, the inner diameter of the outer pipe 11 is 250 mm, and the cross-sectional area is approximately 0.0491 ㎡. The inner diameter of the inner pipe 12 is 150 mm, and the cross-sectional area is approximately 0.0177 ㎡. Under the condition that the ambient temperature is 25 °C, the data of a 10 kW standard fire source are measured using different wind speeds at the maximum opening and the minimum opening respectively. The data are shown in Table 2 below:

[0095] Table 2 Data of Measuring a 10 kW Standard Fire Source in the Smoke Exhaust Duct of this Embodiment

[0096]

[0097] It can be seen from this embodiment that when the fire source power is 10 kW, this embodiment measures medium-power flames through the inner pipe 12 with a smaller cross-sectional area or the outer pipe 11 with a larger cross-sectional area, and the measurement accuracies are not much different.

[0098] Embodiment 3

[0099] In this embodiment, the inner diameter of the outer pipe 11 is 250 mm, and the cross-sectional area is approximately 0.0491 ㎡. The inner diameter of the inner pipe 12 is 150 mm, and the cross-sectional area is approximately 0.0177 ㎡. Under the condition that the ambient temperature is 25 °C, the data of a 30 kW standard fire source are measured using different wind speeds at the maximum opening and the minimum opening respectively. The data are shown in Table 3 below:

[0100] Table 3 Data of Measuring a 30 kW Standard Fire Source in the Smoke Exhaust Duct of this Embodiment

[0101]

[0102] It can be seen from this embodiment that when the fire source power is relatively large (30 kW), using the outer pipe 11 with a larger cross-sectional area for testing has a higher accuracy than using the inner pipe 12 for testing. At this time, using the outer pipe 11 for testing can improve the measurement accuracy.

[0103] The above are only the preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A smoke exhaust method for improving the measurement accuracy of smoke in a fire experiment, which uses a smoke exhaust pipe for smoke exhaust, is characterized in that, The smoke exhaust duct includes a first pipe section and a second pipe section. The air outlet end of the first pipe section is connected to the air inlet end of the second pipe section, and an opening degree adjusting component is provided at the connection, and the opening degree adjusting component is used to dynamically adjust the opening degree of the first pipe section; the first pipe section includes an outer pipe and an inner pipe nested coaxially, and a first flue gas detection component and a second flue gas detection component are respectively arranged in the inner pipe and the second pipe section; wherein, the air inlet end of the first pipe section is connected to a smoke collecting hood; the ratio of the cross-sectional area of the outer pipe to that of the inner pipe is 2.5-3; The smoke exhaust method includes the following steps: Match the corresponding volume flow rate range of the flue gas according to the combustion scale; Determine the differential pressure value range according to the volume flow rate range, and the differential pressure value is not less than 20% of the measuring range of the measuring instrument; Dynamically adjust the opening degree of the first pipe section according to the differential pressure value and the volume flow rate.

2. The smoke exhaust method for improving the measurement accuracy of flue gas in a fire experiment according to claim 1, characterized in that: The opening degree adjusting component includes a limiting housing, a driving mechanism and a plurality of baffles arranged in the limiting housing. The limiting housing is annular, and an opening adapted to the size of the baffle is provided on the inner side thereof. The baffles are arranged in an annular array centered on the center of the limiting housing, and the driving mechanism is used to drive the plurality of baffles to approach or move away from the center simultaneously.

3. The smoke exhaust method for improving the measurement accuracy of smoke in a fire experiment according to claim 2, characterized in that: The driving mechanism includes a transmission plate arranged in the limiting housing and a driving component for driving the transmission plate to rotate. The transmission plate is provided with a plurality of gradually opened arc-shaped chutes, the number of the arc-shaped chutes corresponds to the number of the baffles, and a slider is arranged on the baffle, and the slider is located in the arc-shaped chute.

4. The smoke exhaust method for improving the measurement accuracy of smoke in a fire experiment according to claim 3, characterized in that: The driving component includes a motor, the output shaft of the motor is connected with a gear, the transmission plate is connected with an arc-shaped rack, and the gear meshes with the arc-shaped rack.

5. The smoke exhaust method for improving the measurement accuracy of smoke in a fire experiment according to claim 4, characterized in that: The limiting housing includes a first housing and a second housing. The first housing is provided with a through avoidance groove. One side of the arc-shaped rack is provided with a connecting rod, and one end of the connecting rod passes through the avoidance groove and is fixedly connected with the transmission plate; the second housing is provided with a plurality of chutes along the radial direction, the chutes correspond to the baffles one by one, and the baffles are slidably connected in the chutes.

6. The smoke exhaust method for improving the measurement accuracy of smoke in a fire experiment according to claim 1, wherein: The first flue gas detection component includes a first sample gas sampling probe, a pitot tube anemometer and a thermocouple sampling probe. The first sample gas sampling probe, the pitot tube anemometer and the thermocouple sampling probe all pass through the outer pipe and extend into the inner side of the inner pipe; the second flue gas detection component includes a second sample gas sampling probe and an orifice flowmeter.

7. The smoke exhaust method for improving the measurement accuracy of smoke in a fire experiment according to claim 1, characterized in that: The second pipe section is provided with a detection port, and both the first pipe section and the second pipe section are provided with hand-held anemometer input ports.

8. The smoke exhaust method for improving the measurement accuracy of smoke in a fire experiment according to claim 1, characterized in that: A fan is arranged at one end of the second pipe section far away from the first pipe section; and / or, the outer pipe and the inner pipe are fixedly connected by a support flange; a first rectifying plate is arranged inside the inner pipe, and a second rectifying plate is arranged in the second pipe section.

Images