Experimental device for analyzing safety of natural water circulation of boiler

Abstract

The invention discloses a boiler natural water circulation safety analysis experiment device, and relates to the technical field of boiler water circulation, the boiler natural water circulation safety analysis experiment device comprises a water circulation system, the water circulation system comprises a boiler barrel, at least one downcomer, at least one water cooling wall tube set and a lower header, the boiler barrel is used for containing water, a water inlet and a water outlet are formed in the boiler barrel, the downcomer is vertically arranged, and the water cooling wall tube set is arranged below the downcomer; the top end of the downcomer is communicated with the boiler barrel, the bottom end of the downcomer is communicated with the lower header, the water-cooled wall tube group comprises two vertically arranged water-cooled wall tubes, the top ends of the two water-cooled wall tubes are communicated with the boiler barrel, and the bottom ends of the two water-cooled wall tubes are communicated with the lower header; the heating control system comprises a heating assembly and a regulation and control assembly, the heating assembly is used for heating the two water cooling wall pipes in the water cooling wall pipe set, and the regulation and control assembly is used for regulating and controlling the heating intensity of the heating assembly. The device has the advantages that working conditions in actual boiler operation can be simulated, and serious accidents such as tube explosion of the water cooling wall are effectively avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of boiler water circulation, and particularly to an experimental device for analyzing the safety of natural water circulation in a boiler. Background Art

[0002] In the fields of industrial production and energy supply, boilers, as important heat energy conversion devices, are widely used in industries such as electric power, chemical engineering, and metallurgy. The natural water circulation system of a boiler is one of the key links to ensure the safe and stable operation of the boiler. Through natural water circulation, the water in the boiler is heated to form steam, and at the same time, heat is transferred to the steam, enabling the steam to drive equipment such as steam turbines to do work.

[0003] The water circulation structure of a boiler is a key system to ensure the safe and efficient operation of the boiler. Its main purpose is to take away the heat absorbed by the heating surface through circulating water or steam-water mixture, and at the same time ensure that the metal of the heating surface is cooled. However, in actual boiler operation, situations such as low-load operation, deviation of the heating center, and slagging will affect the stability of the boiler water circulation, which may lead to problems such as water circulation stagnation, reverse flow, and deterioration of heat transfer, and further cause water wall tube burst accidents. Ensuring a safe and reliable water circulation is a basic and necessary requirement for safe operation. Currently, there is a lack of a device for analyzing the safety of boiler water circulation, and a safe and reliable water circulation cannot be guaranteed.

[0004] In summary, a device for analyzing the safety of boiler water circulation is needed, which can simulate the working conditions in actual boiler operation, facilitate the observation of various phenomena in the boiler water circulation process, and reduce the frequency of water wall tube burst accidents. Summary of the Invention

[0005] To solve the above technical problems, the present invention provides an experimental device for analyzing the safety of natural water circulation in a boiler, which can simulate the working conditions in actual boiler operation and effectively avoid serious accidents such as water wall tube burst.

[0006] The present invention provides an experimental device for analyzing the safety of natural water circulation in a boiler, including: A water circulation system, including a steam drum, at least one downcomer, at least one group of water wall tube groups, and a lower header. The steam drum is used to hold water, and an inlet and a drain are provided on the steam drum. The downcomer is vertically arranged, the top end of the downcomer is communicated with the steam drum, the bottom end of the downcomer is communicated with the lower header. The water wall tube group includes two vertically arranged water wall tubes, the top ends of the two water wall tubes are communicated with the steam drum, and the bottom ends of the two water wall tubes are communicated with the lower header; A heating control system, including a heating component and a regulation component. The heating component is used to heat the two water wall tubes in the water wall tube group, and the regulation component is used to regulate the heating intensity of the heating component; The water in the drum is fed into the lower header through the downcomer. The lower header transports the water to the water wall tubes. The heating component heats two water wall tubes in the water wall tube group, and the regulation component regulates the heating intensity of the heating component.

[0007] Preferably, there are three sets of the water circulation systems, namely the first circulation loop, the second circulation loop, and the third circulation loop. The drums in the first circulation loop, the second circulation loop, and the third circulation loop are interconnected. There is a water space and a steam space in the drum. The first circulation loop includes three sets of water wall tube groups, two downcomers, and a lower header. The top of one set of water wall tube groups is connected to the steam space at the top of the drum. The top of one set of water wall tube groups is connected to the steam space in the middle of the drum. The top of one set of water wall tube groups is connected to the water space at the bottom of the drum. The two downcomers are respectively arranged on one side of two sets of water wall tube groups. The second circulation loop includes two sets of water wall tube groups, a downcomer, and a lower header. The tops of the two sets of water wall tube groups are both connected to the water space at the bottom of the drum. The third circulation loop includes one set of water wall tube groups, a downcomer, and a lower header. The top of the water wall tube group is connected to the water space at the bottom of the drum. Overflow pipe faucets are respectively connected to the lower headers in the first circulation loop, the second circulation loop, and the third circulation loop.

[0008] Preferably, the volume of the lower header in the second circulation loop is larger than the volume of the lower header in the third circulation loop, and the volume of the lower header in the second circulation loop is smaller than the volume of the lower header in the first circulation loop.

[0009] Preferably, two sets of water wall tube groups and downcomers in the first circulation loop, the second circulation loop, and the third circulation loop are respectively arranged on both sides of the drum and the lower header.

[0010] Preferably, the heating component includes: A plurality of electric heating wires, which are respectively wound around the circumferences of two water wall tubes in multiple sets of water wall tube groups. A control console. The regulation component is arranged on the control console, and the regulation component is electrically connected to the plurality of electric heating wires.

[0011] Preferably, there are multiple sets of the regulation components. The multiple sets of regulation components correspond to the multiple sets of water wall tube groups one by one. The multiple sets of regulation components are used to regulate the heating intensity of the plurality of electric heating wires. The regulation component includes: A voltage regulator, which is arranged on the control console. The voltage regulator is electrically connected to the electric heating wire, and the voltage regulator is used to regulate the voltage passing through the electric heating wire. A switch, arranged on the console, the switch is electrically connected to the heating wire, and the switch is used to turn the heating wire on and off; An ammeter is arranged on the console, the ammeter is electrically connected to the heating wire, and the ammeter is used to measure the current passing through the heating wire.

[0012] Preferably, the water inlet of the boiler drum is connected to a water inlet pipe; the water outlet of the boiler drum is connected to a drain pipe, and the end of the drain pipe away from the water outlet is connected to a drain faucet; a water supply pump is provided at the end of the water inlet pipe away from the water inlet, and the water inlet pipe is connected to the output end of the water supply pump.

[0013] Preferably, both ends of the water-cooled wall tube and the downcomer are connected to the boiler drum and the lower header respectively through hoses.

[0014] Preferably, the boiler drum, the water-cooled wall tubes, the downcomer and the lower header are all made of heat-resistant glass.

[0015] Compared with the prior art, the present invention discloses a boiler natural water circulation safety analysis experimental device, which has the following beneficial effects: This device can simulate the actual working conditions of the natural water circulation of the boiler, including abnormal conditions such as low-load operation and deflection of the heating center, discover potential safety hazards in advance, observe the stagnation, backflow, deterioration of heat transfer and other problems that may occur in the water circulation, and effectively avoid serious accidents such as water wall tube burst. Through this experimental device, we can have a deep understanding of the flow characteristics and heat transfer characteristics in the natural water circulation process. According to the water flow distribution under different working conditions obtained in the experiment, we can reasonably adjust the pipeline layout and pipe diameter to improve the efficiency and stability of the water circulation, thereby optimizing the overall design of the boiler. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 It is a structural schematic diagram of the present invention; Figure 2 It is a front view of the present invention; Figure 3 is a side view of the present invention; Figure 4 It is a circuit diagram of the control system of the present invention.

[0018] The meanings of the reference numerals in the figure are as follows: 1—drum, 2—downcomer, 3—overflow pipe, 4—start / stop button for the feed pump, 5—power supply on / off button for the heating wire, 6—switch, 7—voltage regulator, 8—ammeter, 9—lower header, 10—heating wire, 11—water wall tube, 12—drain pipe, 13—feed pump, 14—fixed base, 15—main power switch, 16—overflow pipe faucet, 17—drain pipe faucet, 18—rheostat, 19—control console. Specific Embodiment

[0019] The following combines the accompanying drawings to describe in detail a specific embodiment of the present invention. However, it should be understood that the protection scope of the present invention is not limited by the specific embodiment.

[0020] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "axial", "radial", "circumferential", etc. is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the technical solution of the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present invention.

[0021] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the term "connection" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meaning of the above terms in this application can be understood according to specific circumstances.

[0022] In addition, in the description of the present invention, "a plurality of" means two or more than two. The terms "first" and "second" are only used for descriptive purposes and cannot be understood as implying or indicating relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features.

[0023] Embodiment 1 The embodiment of the present invention provides an experimental device for analyzing the safety of natural water circulation in a boiler as Figure 1As shown in the figure, it includes: a support frame, a water circulation system, and a heating control system. The support frame is vertically arranged and plays a supporting role for the entire device. The support frame is a three-dimensional rectangular frame structure; the water circulation system is used to simulate the process of natural water circulation in actual boiler operation. The water circulation system includes a steam drum 1, at least one downcomer 2, at least one group of water wall tube groups, and a lower header 9. The steam drum 1 is arranged at the top of the support frame. The steam drum 1 is fixed to the support frame through a fixed base 14. The fixed base 14 is erected on the support frame, and the steam drum 1 is tied to the fixed base 14. The steam drum 1 is used to hold water. The steam drum 1 is provided with a water inlet and a drain outlet. Water is added or drained into the steam drum 1 through the water inlet and the drain outlet. The lower header 9 is arranged at the bottom of the support frame. The water wall tube group includes two water wall tubes 11. In this embodiment, the water wall tubes are arranged in pairs. The main function of the water wall tubes is to absorb heat and transfer it to the water or steam inside the tubes. By arranging them in pairs or similar pairs, the heat can be better evenly distributed, reducing the phenomenon of local overheating. The arrangement method of pairs or similar pairs can simplify the connection structure of the water wall and reduce the number of components to be installed, thereby reducing the maintenance cost of this experimental device. At the same time, the water wall tubes arranged in pairs can improve the reliability of the system through redundant design. Even if one tube fails, the other tube can still continue to work, thereby reducing the downtime of this experimental device. The two water wall tubes 11 are parallel to each other. The downcomer 2 and the two water wall tubes 11 are both vertically arranged between the steam drum 1 and the lower header 9, and the two ends of the downcomer 2 and the two water wall tubes 11 are respectively connected to the steam drum 1 and the lower header 9. The downcomer 2 is used to transport the water in the steam drum 1 into the lower header 9. The lower header 9 serves as a distribution device to evenly distribute the water transported by the downcomer 2 into each water wall tube. Among them, the lower header 9 can be supported by the water wall tubes 11 and the downcomer 2, or it can be arranged at the bottom of the support frame and supported by the support frame; the heating control system includes a heating component and a regulation component. The heating component is used to heat the two water wall tubes 11 in the water wall tube group. The water absorbs heat in the water wall tubes 11, and part of the water evaporates to form a steam-water mixture and is transported into the steam drum 1 to complete the water circulation. This circulating flow is driven by the density difference between the steam-water mixture and the water in the downcomer; the regulation component is used to regulate the heating intensity of the heating component, that is, to adjust the heating temperature in the heating component;Working process of this experimental device: The water in the steam drum 1 is sent into the lower header 9 through the downcomer 2. The lower header 9 evenly delivers the water to the water wall tubes 11. Meanwhile, the heating component heats two of the water wall tubes 11 in the water wall tube group. The water absorbs heat in the water wall tubes 11, and part of the water evaporates to form a steam-water mixture, which is transported into the steam drum 1, enabling a steam-water mixing space to be formed in the steam drum 1. The control component regulates the heating intensity of the heating component, that is, adjusts the heating temperature. By adjusting the heating temperature, subcooled boiling, nucleate boiling, and columnar boiling phenomena (three different states in the boiling phenomenon) can occur in the water wall tubes 11. Phenomena such as stagnation and backflow can be observed. Additionally, the two-phase flow structure and water level changes in the steam drum 1 can be observed. During use, it is convenient for experimenters to observe various phenomena. Through these phenomena, various unsafe phenomena in an actual boiler can be analyzed. This device can simulate the actual working conditions of the natural water circulation in a boiler, including abnormal conditions such as low-load operation and heating center deviation, discover potential safety hazards in advance, observe problems such as stagnation, backflow, and heat transfer deterioration that may occur in the water circulation, and effectively avoid serious accidents such as water wall tube rupture. Through this experimental device, the flow characteristics and heat transfer characteristics during the natural water circulation process can be deeply understood. According to the water flow distribution under different working conditions obtained from the experiment, the pipeline layout and pipe diameter size can be reasonably adjusted to improve the efficiency and stability of the water circulation, thereby optimizing the overall design of the boiler.;

[0024] Further, both ends of the water wall tubes 11 and the downcomer 2 are connected to the steam drum 1 and the lower header 9 through hoses respectively, that is, hoses are provided between the upper and lower ends of the water wall tubes 11 and the downcomer 2 and the steam drum 1 and the lower header 9.

[0025] Further, the steam drum 1, the water wall tubes 11, the downcomer 2, and the lower header 9 are all made of heat-resistant glass. Using transparent glass material is convenient for observing the two-phase flow state of the water in the steam drum 1 and can also observe various phenomena in the water wall tubes 11.

[0026] Embodiment 2 As a further improved solution based on Embodiment 1, in order to more perfectly simulate the working conditions in actual boiler operation, further, there are three groups of water circulation systems, namely the first circulation loop, the second circulation loop, and the third circulation loop. The steam drums 1 in the first circulation loop, the second circulation loop, and the third circulation loop are interconnected, that is, the three groups of water circulation systems share one steam drum 1. There is a water space and a steam space in the steam drum 1. The water space refers to the water injected into the steam drum 1, and the steam space refers to the steam generated after heating the water in the water wall tubes being transported into the steam drum 1, enabling the inside of the steam drum 1 to be in a steam-water mixing space. In the steam drum 1, the water space is located below and the steam space is located above; the first circulation loop corresponds to Figure 1 the leftmost circulation. In this embodiment, the first circulation loop includes four groups of water wall tube groups ( Figure 1From left to right are the first pair of water wall tubes, the second pair of water wall tubes, the third pair of water wall tubes, and the fourth pair of water wall tubes), two downcomers 2 and a lower header 9. The tops of the two groups of water wall tube groups (the third pair of water wall tubes and the fourth pair of water wall tubes) are connected to the steam space at the top of the steam drum 1, that is, they communicate with the top of the steam drum 1. The top of a group of water wall tube groups (the second pair of water wall tubes) is connected to the steam space in the middle of the steam drum 1, that is, at a position slightly above the water level in the steam drum 1. The top of a group of water wall tube groups (the first pair of water wall tubes) is connected to the water space at the bottom of the steam drum 1. Since there are four groups of water wall tube groups in the first circulation loop, two downcomers 2 are set to transport water to these four groups of water wall tube groups to complete the water circulation; the second circulation loop corresponds to Figure 1 the middle circulation in it. The second circulation loop includes two groups of water wall tube groups ( Figure 1 from left to right are the fifth pair of water wall tubes and the sixth pair of water wall tubes), a downcomer 2 and a lower header 9. The tops of the two groups of water wall tube groups are both connected to the water space at the bottom of the steam drum 1; the third circulation loop corresponds to Figure 1 the rightmost circulation in it. The third circulation loop includes a group of water wall tube groups ( Figure 1 from left to right, the seventh pair of water wall tubes), a downcomer 2 and a lower header 9. The top of the water wall tube group is connected to the water space at the bottom of the steam drum 1; as Figure 2As shown, the lower header 9 in the first circulation loop, the second circulation loop, and the third circulation loop is respectively connected to an overflow pipe faucet 16. When there is too much water in the lower header 9, it can flow out through the overflow pipe faucet 16, and the water flowing out can also be injected into the drum 1 for circulation. In this embodiment, dividing the three circulation loops has three functions. The first function: The water wall tube groups in the first circulation loop are respectively connected to different positions of the drum 1 (connected to the water space, the steam-water space, and the steam space respectively), which is convenient for observing the different phenomena generated when the water wall tubes 11 are connected to different spaces. The second function: Water wall tube groups connected to the water space at the bottom of the drum 1 are provided in all three circulation loops, that is, the most direct way of transporting the water in the water wall tubes 11 to the drum 1 is retained. By adjusting the components to control the different heating temperatures of the water wall tubes 11 in these three loops, it is convenient to observe the phenomena generated in the water wall tubes 11 at different heating temperatures. The third function: Since the number of water wall tube groups connected in the three circulation loops is different, the sizes of the lower headers are also different (the volume of the lower header 9 in the second circulation loop is larger than that of the lower header 9 in the third circulation loop and smaller than that of the lower header 9 in the first circulation loop). The lower header in the first circulation loop is the largest, the second circulation loop is the second, and the lower header in the third circulation loop is the smallest, which is convenient for exploring the different phenomena generated in the water wall tubes 11 when connecting lower headers of different specifications. Among them, two groups of water wall tube groups in the first circulation loop are connected to the steam space at the top of the drum 1, and two groups of water wall tube groups in the second circulation loop are connected to the water space at the bottom of the drum 1. On the one hand, it is to better observe various phenomena, and on the other hand, the specifications of the lower headers are different. Also, in order not to waste the resources of the lower headers, an additional group of water wall tube groups with the same function is set. This experimental device considers the influence of multiple parameters such as heating load, lower header specifications, and steam-water connection points on the water circulation, can comprehensively evaluate the safety of the natural water circulation system, make the safety evaluation results more reliable, and thus provide strong support for formulating more perfect safety control strategies. Among them, in this embodiment, the outer diameter of the water wall tube 11 is 12 mm, and the inner diameter is 10 mm; the outer diameter of the downcomer 2 is 12 mm, and the wall thickness is 1 mm; the outer diameter of the drum 1 is 13.1 cm, the wall thickness is 1 mm, and the length is 67 cm; the outer diameter of the lower header 9 in the first circulation loop is 5.1 cm, the wall thickness is 1 mm, and the length is 36 cm; the outer diameter of the lower header 9 in the second circulation loop is 5.1 cm, the wall thickness is 1 mm, and the length is 11 cm; the outer diameter of the lower header 9 in the third circulation loop is 5.1 cm, the wall thickness is 1 mm, and the length is 8 cm.

[0027] As Figure 3As shown in the figure, further, two sets of water-cooled wall tube groups and downcomers 2 are respectively provided in the first circulation loop, the second circulation loop, and the third circulation loop, and are located on both sides of the drum 1 and the lower header 9. That is, these three circulation loops are provided on both sides of the support frame, so that it is more convenient for people on both sides to observe various phenomena of the water-cooled wall tubes 11 in the loop in the demonstration application scenario. The power of each loop is 0 - 1 kW, and the voltage is 220V. The heating powers of the two electric heating wires 10 on each pair of water-cooled wall tubes 11 are equal, which is 500W.

[0028] Among them, the other structures of this embodiment are the same as those of Embodiment 1, except that it is an optimization of Embodiment 1.

[0029] Embodiment 3 As a further improvement on the basis of Embodiment 2, this embodiment provides a specific structure of the heating component. Further, the heating component includes: electric heating wires 10 and a control console 19. Multiple electric heating wires 10 are respectively wound around the circumferences of two water-cooled wall tubes 11 in multiple groups of water-cooled wall tube groups. The water-cooled wall tubes 11 are heated by conducting electricity through the electric heating wires 10. The heating powers of the electric heating wires 10 provided on each group of water-cooled wall tube groups are equal, that is, the heating intensities of each pair of water-cooled wall tubes 11 are the same; the control console 19 is horizontally arranged at the bottom of the support frame. The control console 19 can support the support frame, and at the same time, the control console 19 is also equivalent to an operating platform. The regulating component is arranged on the control console 19, and the regulating component is electrically connected to multiple electric heating wires 10. The regulating component can control the opening and closing of multiple electric heating wires 10 and the heating intensity.

[0030] Further, multiple groups of regulating components are provided, and multiple groups of regulating components correspond to multiple groups of water-cooled wall tube groups one by one. Multiple groups of regulating components are used to regulate the heating intensities of multiple electric heating wires 10. One group of regulating components adjusts the heating temperature of one group of water-cooled wall tube groups. This embodiment provides a specific way of the regulating component. The regulating component includes: a voltage regulator 7, a switch 6, and an ammeter 8. The voltage regulator 7 is arranged on the control console 19, and the voltage regulator 7 is electrically connected to the electric heating wire 10. The voltage regulator 7 is used to regulate the voltage passing through the electric heating wire 10; the switch 6 is arranged on the control console 19, and the switch 6 is electrically connected to the electric heating wire 10. The switch 6 is used to turn on and off the electric heating wire 10; the ammeter 8 is arranged on the control console 19, and the ammeter 8 is electrically connected to the electric heating wire 10. The ammeter 8 is used to measure the current passing through the electric heating wire 10. In this embodiment, the heating intensity of the electric heating wire 10 is controlled by regulating the voltage of the electric heating wire 10, that is, the heating temperature of the electric heating wire 10 is regulated, which is convenient for observing various phenomena in the loop under different temperature states.

[0031] Such as Figure 2As shown in the figure, further, the water inlet of the boiler drum 1 is connected to a water inlet pipe 12, and the other end of the water inlet pipe 12 is connected to a water source, and water is introduced into the boiler drum 1 through the water inlet pipe 12; the water outlet of the boiler drum 1 is connected to a drain pipe 3, and the end of the drain pipe 3 away from the water outlet is connected to a drain faucet 17. After the test, the drain faucet 17 is used for drainage. When there is too much water in the boiler drum 1, the drain faucet 17 is opened to drain the boiler drum 1; a water pump 13 is provided at the end of the water inlet pipe 12 away from the water inlet, and the water inlet pipe 12 is connected to the output end of the water pump 13, and the water pump 13 is connected to the water source. Through the water pump 13, water can be pumped into the boiler drum 1.

[0032] Among them, as Figure 1 , Figure 2 shown, a main power switch 15, a water pump start-stop button 4, and an electric heating wire power supply-on / off button 5 are also provided on the control console 19. The main power switch 15 can control the power supply and cut-off in the main circuit. The water pump start-stop button 4 can control the working state of the water pump 13, and the electric heating wire power supply-on / off button 5 can control the power supply and cut-off of multiple electric heating wires 10. As Figure 4 , it is the circuit diagram for controlling heating in each group of water-cooled wall tube groups, which respectively includes a first branch L1, a second branch L2, and a third branch L3. Three-phase air switches are provided at the connection ends of the first branch L1, the second branch L2, and the third branch L3, which is the main power switch 15. Each branch has multiple circuits for regulating the heating intensity of the electric heating wire 10. Each regulating circuit corresponds to a pair of water-cooled wall tubes 11, and each regulating circuit is equal. Each regulating circuit consists of a live wire, a switch 6, a 5A ammeter 8, a voltage regulator 7, a sliding rheostat 18, an electric heating wire 10, and an N wire. One end of the switch 6 is connected to the live wire, the other end of the switch 6 is connected to one end of the 5A ammeter 8, the other end of the ammeter 8 is connected to the third end of the voltage regulator 7, the fourth end of the voltage regulator 7 is connected to one end of the electric heating wire 10, the other end of the electric heating wire 10 is connected to the N wire, and the N wire is the neutral wire. The first end of the voltage regulator 7 is connected to one end of the sliding rheostat 18, and the second end of the voltage regulator 7 is connected to the other end of the sliding rheostat 18. The principle of regulating the heating intensity of the electric heating wire 10 in the regulating circuit is to adjust the resistance in the circuit by moving the position of the sliding piece in the sliding rheostat 18, thereby changing the voltage in the circuit, so that the voltage across the electric heating wire 10 is changed, and thus the heating temperature of the electric heating wire 10 is adjusted. Among them, the first end, the second end, the third end, and the fourth end of the voltage regulator 7 respectively refer to Figure 4 the 1, 2, 3, and 4 marked on the voltage regulator 7 in

[0033] Among them, the other structures of this embodiment are the same as those of Embodiment 2, only an optimization is made to Embodiment 2.

[0034] According to the above principle, when the device is in use, it includes the following steps: Step 1: The controller controls the water pump 13 to open, and water is injected into the drum 1 through the water inlet pipe 12. When the water injection level rises to 60%-70% of the total water level of the drum 1, the water pump 13 is closed to stop water injection; Step 2: After the controller controls the heating wire 10 to open for 30 minutes, observe the water level change in the drum 1, observe the two-phase flow structure, and observe the phenomena of subcooled boiling, nucleate boiling, and columnar boiling in each water wall tube 11; Step 3: Adjust the heating intensities of the first pair of water wall tubes, the second pair of water wall tubes, the third pair of water wall tubes, and the fourth pair of water wall tubes to be the same. Observe the first circulation loop. Due to the different positions where the water wall tubes 11 are connected to the drum 1, the free water surface and steam-water stratification phenomena can be observed; Step 4: Observe the fifth pair of water wall tubes and the sixth pair of water wall tubes. Keep the indication of the ammeter of the fifth pair of water wall tubes unchanged, and rotate the voltage regulator 7 of the sixth pair of water wall tubes to gradually reduce the heating intensity of the sixth pair of water wall tubes. When it drops to a certain extent, the "stagnation" phenomenon can be observed. Continue to rotate the voltage regulator 7 to reduce the heating intensity, and the "backflow" phenomenon can be observed;

[0035] Step 5: Adjust the heating intensities of the first pair of water wall tubes, the fifth pair of water wall tubes, and the seventh pair of water wall tubes to be the same. Due to the different specifications of the lower header 9 they are connected to, the free water surface phenomenon and steam-water stratification phenomenon can be observed; Step 6: Rotate the voltage regulators 7 of each group to "0", turn off the power switch of each group of voltage regulators, and finally turn off the main power switch 15. After the water cools down, open the three drain faucets 17 at the rear to drain the water in each loop.

[0036] The advantages of the present invention are that this device can simulate the actual working conditions of the natural water circulation of the boiler, including abnormal conditions such as low-load operation and heating center deviation, discover potential safety hazards in advance, observe problems such as stagnation, backflow, and heat transfer deterioration that may occur in the water circulation, and effectively avoid serious accidents such as water wall tube explosions. Through this experimental device, the flow characteristics and heat transfer characteristics in the process of natural water circulation can be deeply understood. According to the water flow distribution under different working conditions obtained from the experiment, the pipeline layout and pipe diameter can be reasonably adjusted to improve the efficiency and stability of the water circulation, thereby optimizing the overall design of the boiler. At the same time, this experimental device considers the influence of multiple parameters such as heating load, lower header specifications, and steam-water connection on the water circulation, can comprehensively evaluate the safety of the natural water circulation system, make the safety assessment results more reliable, and thus provide strong support for formulating more perfect safety control strategies.

[0037] The above are only several specific embodiments of the present invention disclosed. However, the embodiments of the present invention are not limited thereto, and any changes that can be thought of by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A boiler natural water circulation safety analysis experimental device, characterized in that: include: A water circulation system, comprising a boiler drum (1), at least one downcomer (2), at least one group of water-cooled wall tube groups and a lower header (9), wherein the boiler drum (1) is used to contain water, and the boiler drum (1) is provided with a water inlet and a water outlet, the downcomer (2) is vertically arranged, the top end of the downcomer (2) is connected to the boiler drum (1), and the bottom end of the downcomer (2) is connected to the lower header (9), and the water-cooled wall tube group comprises two vertically arranged water-cooled wall tubes (11), the top ends of the two water-cooled wall tubes (11) are connected to the boiler drum (1), and the bottom ends of the two water-cooled wall tubes (11) are connected to the lower header (9); A heating control system, comprising a heating component and a regulating component, wherein the heating component is used to heat two water-cooled wall tubes (11) in the water-cooled wall tube group, and the regulating component is used to regulate the heating intensity of the heating component; The water in the boiler drum (1) is sent into the lower header (9) through the downcomer (2), and the lower header (9) transports the water to the water-cooled wall tubes (11). The heating component heats two water-cooled wall tubes (11) in the water-cooled wall tube group, and the regulating component regulates the heating intensity of the heating component.

2. A boiler natural water circulation safety analysis experimental device according to claim 1, characterized in that: The water circulation system is provided with three groups, namely a first circulation loop, a second circulation loop and a third circulation loop, wherein the boiler drum (1) in the first circulation loop, the second circulation loop and the third circulation loop are interconnected, and the boiler drum (1) has a water space and a steam space; The first circulation loop comprises three groups of water-cooled wall tube groups, two downcomers (2) and a lower header (9), the top end of one group of water-cooled wall tube groups being connected to the steam space at the top of the boiler drum (1), the top end of one group of water-cooled wall tube groups being connected to the steam space in the middle of the boiler drum (1), and the top end of one group of water-cooled wall tube groups being connected to the water space at the bottom of the boiler drum (1), and the two downcomers (2) being respectively arranged on one side of the two groups of water-cooled wall tube groups; The second circulation loop comprises two groups of water-cooled wall tube groups, a downcomer (2) and a lower header (9), and the top ends of the two groups of water-cooled wall tube groups are connected to the water space at the bottom of the boiler drum (1); The third circulation loop comprises a group of water-cooled wall tubes, a downcomer (2) and a lower header (9), the top end of the water-cooled wall tube group being connected to the water space at the bottom of the boiler drum (1); The lower headers (9) in the first circulation loop, the second circulation loop and the third circulation loop are respectively connected to overflow pipe faucets (16).

3. A boiler natural water circulation safety analysis experimental device according to claim 2, characterized in that: The volume of the lower tank (9) in the second circulation loop is greater than the volume of the lower tank (9) in the third circulation loop, and the volume of the lower tank (9) in the second circulation loop is less than the volume of the lower tank (9) in the first circulation loop.

4. A boiler natural water circulation safety analysis experimental device according to claim 2, characterized in that: Two groups of water-cooled wall tube groups and downcomers (2) in the first circulation loop, the second circulation loop and the third circulation loop are respectively provided and are located on both sides of the boiler drum (1) and the lower header (9).

5. A boiler natural water circulation safety analysis experimental device according to claim 2, characterized in that: The heating assembly comprises: A plurality of electric heating wires (10) are respectively wound around the circumference of two water-cooled wall tubes (11) in the plurality of water-cooled wall tube groups; A control console (19), wherein the regulating component is arranged on the control console (19), and the regulating component is electrically connected to the plurality of heating wires (10).

6. A boiler natural water circulation safety analysis experimental device according to claim 5, characterized in that: The regulating components are provided in a plurality of groups, and the plurality of groups of regulating components correspond one-to-one to the plurality of groups of water-cooled wall tube groups. The plurality of groups of regulating components are used to regulate the heating intensity of the plurality of electric heating wires (10). The regulating components include: A voltage regulator (7) is arranged on the console (19), the voltage regulator (7) is electrically connected to the heating wire (10), and the voltage regulator (7) is used to regulate the voltage passing through the heating wire (10); A switch (6) is arranged on the console (19), the switch (6) is electrically connected to the heating wire (10), and the switch (6) is used to turn the heating wire (10) on and off; An ammeter (8) is arranged on the console (19); the ammeter (8) is electrically connected to the heating wire (10); and the ammeter (8) is used to measure the current passing through the heating wire (10).

7. A boiler natural water circulation safety analysis experimental device according to claim 5, characterized in that: The water inlet of the drum (1) is connected to a water inlet pipe (12); the water outlet of the drum (1) is connected to a drain pipe (3), and one end of the drain pipe (3) away from the water outlet is connected to a drain faucet (17); a water supply pump (13) is provided at one end of the water inlet pipe (12) away from the water inlet, and the water inlet pipe (12) is connected to an output end of the water supply pump (13).

8. A boiler natural water circulation safety analysis experimental device according to claim 1, characterized in that: The two ends of the water-cooled wall tube (11) and the downcomer (2) are respectively connected to the boiler drum (1) and the lower header (9) through hoses.

9. A boiler natural water circulation safety analysis experimental device according to claim 1, characterized in that: The boiler drum (1), the water-cooled wall tube (11), the downcomer (2) and the lower header (9) are all made of heat-resistant glass.

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