CN107102095B - Liquid alkali metal combustion propagation velocity measuring device - Google Patents

Abstract

The object of the present invention is to provide a liquid alkali metal combustion propagation velocity measurement device, the upper part is a heating combustion device, a crucible with double nozzles is placed in the upper chamber, and there is a combustion chamber for extruding liquid sodium just above the opening of the crucible. Rod, the combustion rod is driven up and down by a motor located above it. The plexiglass cover on the upper part of the container keeps the liquid sodium in the crucible in the protective gas. The middle part of the combustion container is the combustion chamber and observation room for the sodium droplet oxidation combustion experiment. The mixed gas is heated, and the lower part is equipped with a sodium receiving device to accommodate the sodium drops that fell before the experiment, so as to prevent it from flowing around and affecting the experiment. The invention can complete combustion experiments under different conditions, can measure the combustion propagation velocity of liquid alkali metal under different initial oxygen concentrations and different initial sodium temperatures, lays the foundation for large-scale spray sodium fire experiment research, and provides technology for the prevention and response of sodium fire accidents support.

Description

Measuring device for combustion propagation velocity of liquid alkali metal

technical field

The present invention relates to an alkali metal experimental device, in particular to an alkali metal combustion experimental device.

Background technique

There are many forms of liquid alkali metal fires. The sodium fire in the fast reactor basically has two modes, one is released into the containment in the form of spray due to the rupture of the pipeline, and the other is accumulated on the ground to form a pool-type sodium fire. That is, spray sodium fire and pool sodium fire. Sodium spray fire is a more serious combustion mode than pool sodium fire because sodium spray combustion has a higher velocity, and spray sodium fire combustion is carried out in a highly fragmented state, that is, in the form of sodium droplets. Sodium droplet combustion is the basis of various forms of sodium fire research, so the study of sodium droplet combustion characteristics is of great significance.

At present, some theoretical and experimental studies on sodium fire accidents have been carried out in the world. Most of the research on sodium drop combustion is based on a single sodium drop, and the interaction between sodium drops after leakage has been ignored. The interaction between energetic droplets is not limited to the transfer of mass and energy, but also affects the movement speed, burning rate and evaporation constant of sodium droplets. Therefore, the experiment mainly focuses on the conditions for the interaction of double sodium droplets when they approach each other, that is, the size of the distance between sodium droplets, and the combustion rate and heat change after considering the interaction. Basis of Sodium Fire Research. The research on double sodium droplet combustion is based on single sodium droplet, taking into account the interaction between sodium droplets, and at the same time, as with single sodium droplet combustion, the factors related to the oxygen concentration in the reaction space and the temperature of the initial liquid metal sodium are taken into account , which requires the experimental device to be able to simulate a variety of situations, and to flexibly change the experimental conditions.

Contents of the invention

The object of the present invention is to provide a liquid alkali metal combustion propagation velocity measurement device that can conduct experimental research on double-droplet metal sodium fires with different diameters and different spacings.

The purpose of the present invention is achieved like this:

The device for measuring the combustion propagation velocity of liquid alkali metals of the present invention is characterized in that: it comprises a plexiglass cover, a housing, and a sodium tank, and the plexiglass cover and the housing are sequentially arranged from top to bottom to form a closed experimental space. Set the motor, set the clamp pot and the mixed gas shell in the shell, fill the clamp pot with alkali metal, set the upper heating wire outside the clamp pot, connect the motor to the combustion rod, and the combustion rod extends into the clamp pot and squeezes the alkali metal, and the mixed gas The outlet of the shell is located directly below the alkali metal drip outlet of the clamp pot. The inlet of the sodium tank extends from the bottom of the mixed gas shell to the bottom of the mixed gas shell outlet and forms a mixed gas channel with it. The mixed gas outlet pipe extends into the mixed gas shell , a rare gas hole is provided on the shell, and the rare gas outlet pipe communicates with the rare gas hole.

The present invention may also include:

1. It also includes an exhaust water washing system. The exhaust water washing system includes a filter water tank and a circulation pipeline. The filter water tank includes an upper box and a lower box. The upper box and the lower box are communicated through raised pipes to circulate One end of the pipeline is connected to the upper box, and the other end of the circulation pipeline is connected to the lower box. A circulating water pump is installed on the circulation pipeline, a baffle is set in the upper box, and the washed gas on both sides of the baffle is arranged on the upper box. The gas outlet and the spray head, the spray head is connected to the circulation pipeline, the gas outlet after washing is connected to the gas outlet pipe after washing, the air pump is arranged on the gas outlet pipe after washing, the aerosol exhaust port is arranged on the shell, and the aerosol exhaust port passes through The aerosol exhaust pipe is connected to the upper box.

2. It also includes a gas supply system. The gas supply system includes a nitrogen source and an argon source. The nitrogen source is connected to the mixed gas outlet pipe, the argon source is connected to the rare gas outlet pipe, and the mixed gas outlet pipe and the rare gas outlet pipe pass through the gas The mixing pipes are connected, the gas mixing pipe is provided with a gas mixing valve, and an air pipe is provided on the mixed gas outlet pipe between the gas mixing pipe and the nitrogen source, an air pump and an air valve are arranged on the air pipe, and a nitrogen valve is arranged at the nitrogen source outlet. A gas mixing device is installed on the mixed gas outlet pipe between the gas mixing pipe and the air pipe, a mixed gas pump and an oxygen concentration meter are installed on the mixed gas outlet pipe behind the gas mixing pipe, and an argon valve is installed at the outlet of the argon gas source.

3. The inside of the tong pan is a structure with a wide top and a narrow bottom. The inner diameter of the upper part of the tong pan is 12mm, the inner diameter of the lower part of the tong pan is 8mm, and the combustion rod is a structure with a narrow top and a wide bottom. The diameter is 7mm.

4. There is a lower heating wire on the outside of the mixed gas shell, and both the upper heating wire and the lower heating wire are threaded.

The advantages of the present invention are:

(1) The structure of the experimental device is accurate and reliable. The formation of alkali metal double droplets is formed through a stainless steel double-nozzle crucible, which replaces the traditional combustion research in the form of hanging droplets by visual inspection, which increases the reliability and accuracy of the droplet experiment, and the same crucible contains A sufficient amount of liquid alkali metal can carry out repeated experiments, and the above characteristics make the whole device work more accurately and reliably.

(2) The experimental device has strong expansibility. Double sodium drop experiments of different sizes and different spacings can be completed in the same combustion device. Different experiments do not need to be redesigned and manufactured, and can be realized by simply changing crucibles of different sizes. This feature saves the cost and experimental cycle of sodium fire experimental research.

(3) The experimental device has multiple functions. Combustion experiments under different conditions can be completed in the device, the oxygen concentration for combustion can be arbitrarily proportioned, the temperature of the initial liquid metal sodium can be preset, different initial oxygen concentrations can be measured, and liquid alkali metals (sodium and lithium etc.), lay the foundation for large-scale spray sodium fire experimental research, and provide technical support for the prevention and response of sodium fire accidents.

(4) The experimental device is highly safe. The combustion vessel is separated from the crucible, and the crucible is heated by the heating wire. This design can place the combustion container away from personnel, even if the combustion container leaks or is damaged during the experiment, it will not pose a threat to the safety of the operator.

Description of drawings

Fig. 1 is a structural representation of the present invention;

Fig. 2 is a schematic diagram of the gas supply system;

Fig. 3 is a top view of the combustion chamber of the combustion device;

Fig. 4 is a sectional view of the combustion chamber of the combustion device;

Figure 5a is a main sectional view of a crucible, Figure 5b is a side sectional view of a crucible, and Figure 5c is a top view of a crucible;

Fig. 6 is the structural representation of combustion rod;

Fig. 7 is a cross-sectional view of the ventilation equipment at the lower part of the combustion device;

Figure 8 is a schematic diagram of the exhaust water washing system.

Detailed ways

The present invention is described in more detail below in conjunction with accompanying drawing example:

1-8, the present invention includes a combustion container, a combustion crucible, a combustion rod, a heating device, and an electric control box. The combustion vessel used in the experiment is divided into upper, middle and lower parts. The upper part is a heating combustion device, a crucible 1-16 with double nozzles is placed in the upper chamber, and there are electric heating wires 1-17 around it to heat it. Just above the opening of the crucible 1-16, there is a combustion rod 1-14 for extruding liquid sodium 1-1, and the combustion rod 1-14 is pushed up and down by a motor 1-11 positioned above it. The plexiglass cover 1-9 on the top of the container makes the liquid sodium 1-1 in the crucible in the protective gas to avoid oxidation. The middle part of the combustion container is the combustion chamber and the observation chamber of the sodium drop oxidation combustion experiment, and the observation holes 1-4 are arranged at the same height as the nozzle to facilitate observation of the liquid sodium droplets 1-2. In the combustion chamber, with the sodium drop 1-2 as the center, multiple thermocouples are set at different angles and distances to record the space temperature data in the combustion chamber, and a thermocouple with a diameter of 0.5 mm is set under the crucible nozzle 1- 3. The movement can be fine-tuned horizontally to measure the temperature of sodium drops. The lower part of the container is also provided with electric heating wires and thermocouples to heat the mixed gas passing into the combustion chamber. The lower part is also equipped with sodium receiving devices 1-7 to accommodate the sodium drops that fell before the experiment, preventing them from flowing around and affecting the experiment. In order to study the interaction between double sodium droplets with different diameters and different spacings, the size of the nozzle was adjusted. The pitch of a nozzle size is 4mm and 8mm. The outer diameter of the rod used to squeeze the sodium drop is 7mm and 6mm.

The design of the double sodium drop combustion crucible 1-16 considers the properties of liquid sodium drops, and the crucible 1-16 is designed to have an inner diameter of 12 mm at the upper part and an inner diameter of 8 mm at the lower part. On the one hand, it can promote the stable heating of sodium droplets, and on the other hand, it is also verified by experiments that it is beneficial to the formation of liquid double sodium droplets. In order to correspond to the double sodium drop crucible 1-16, impel the formation of the double sodium drop smoothly, the combustion rod 1-14 is designed as an upper narrow part with a lower width of 7 mm at the top and a bottom of 5 mm.

The heating device is composed of two independent units. Part of the threaded armored heating wire 1-17 is set on the outside of the crucible 1-16 fixing ring to heat the metal sodium 1-1 in the crucible; the other part of the threaded armored wire The heating wire 1-19 is set on the outside of the lower air passage, and is used to heat the mixed gas and control the temperature of the combustion chamber. The heating power of the heating wire is changed by the voltage control box.

The exhaust water washing system connects the combustion container with the system by a hose. During the experiment, a large amount of aerosol 8-1 will be generated. During the combustion process, the system can be activated to discharge the aerosol 8-1 inside the combustion container and purify it with water, thereby reducing Impurities damage the equipment, and the operation of the whole system is mainly controlled by the switches of the exhaust pump 8-8 and the drain pump 8-2.

The gas supply system includes: argon gas cylinder 2-2, nitrogen gas cylinder 2-1, air pump 2-3, mixing pipeline, ventilation pipeline and valves. The system can independently supply gas to the glove box and the combustion chamber through the cooperation of several valves , Air and argon can also be fed into the combustion vessel in a certain proportion.

The voltage control box is the control system of the electrical equipment of the whole test device, which can control the up and down movement of the heating device and the combustion rod 1-14.

The sodium outlet crucibles 1-16 can be easily replaced, and are designed with multiple calibers and caliber spacing, which can be replaced according to the different flow rates required by the experiment.

The transparent window can be used to set up cameras 1-5 for recording experimental phenomena.

The lower part of the combustion vessel has a sodium tank 1-7, which can receive completely burned and incompletely burned metal sodium and its oxides.

As shown in Figure 2, the gas supply system includes high-purity nitrogen 2-1, high-purity argon 2-2, air pump 2-3, gas mixing device 2-4, mixed gas pump 2-5, oxygen concentration meter 2- 6, a-p is the valve. The ambient gas control system is composed of 99.999% high-purity argon, 99% general nitrogen and air. First, high-purity argon is used to control the entire experimental environment to protect the smooth formation of sodium droplets and avoid oxidation. Since the combustion container is placed in the glove box, the oxygen content in the glove box can be controlled below 4% by continuously feeding high-purity argon into the glove box. A gas of any oxygen concentration used in the experiment can be supplied by mixing nitrogen and standard air (oxygen: 20% by volume, nitrogen: 80% by volume). The oxygen concentration of the mixed gas can be measured by the oxygen concentration meter 6. At this time, the valve e is closed, the upper valves c, d, n are opened (wherein the valve n leads to indoor air), and the air pump (70L/min, 85W) and Nitrogen, by adjusting the size of b and a, the mixed gas is mixed uniformly through the mixer, and then the desired oxygen concentration is obtained through the oxygen concentration meter 6. When the desired oxygen concentration is reached, the oxygen can be sent into the combustion chamber by closing the valve n and opening the valve p leading to the combustion chamber. Regulating valves j, k, m respectively lead to the plexiglass cover, the combustion chamber and the glove box.

As shown in Figure 7, the ventilation equipment at the lower part of the combustion device has a heating sleeve 7-1, a mixed gas vent hole 7-2, and a mixed gas chamber 7-3, and the mixed gas is heated in this space, which is conducive to the combustion of metal sodium droplets , mixed gas ventilation pipe 7-4, connect sodium pipeline 7-5, can take out remaining waste sodium after connecting sodium tank and opening.

As shown in Figure 8, the exhaust water washing system includes a circulating water pump 8-2, a spray nozzle 8-3, a baffle plate 8-5, an air pump 8-8, and a pipeline 8-7, wherein 8-1, 8-4 And 8-6 represent sodium drop burning aerosol, washed gas and filtered water respectively. Because the aerosols produced by sodium combustion are harmful to the human body, exhaust gas discharge pipes are added to the combustion system, and the pipes are connected to a spraying device. The spraying device is divided into upper and lower boxes, which are connected by raised pipes, and the upper box The upper part of the body is the spray head and the lower part is the circulating water. The baffles in it can make the exhaust gas fully contact with the filtered water. When the circulating water is higher than the raised pipe, the water in the upper box will flow into the lower box. At the same time, the water in the upper and lower tanks can be circulated through a circulating water pump. The spray device is connected with an air pump to maintain negative pressure in the spray device, so that the aerosol and other exhaust gases in the combustion chamber can enter the spray device smoothly and completely so that it can fully contact with water to react, and the filtered gas will not contain harmful substances. substance.

The basic experimental process for the double sodium drop combustion experiment is as follows:

1) Check the circuit, the opening and closing state of the pipeline to ensure that the valves are all closed, and whether the equipment in the glove box is complete. The glove box should contain: crucible, crucible hook, sodium block (enough), sodium cutter, backing plate, rubber gloves, tweezers, lamp, screwdriver.

2) Put the gloves on the glove box, close the inlet door of the glove box, close the waste gas valve, open the valves for argon, including the valve m leading to the glove box, the plexiglass cover j, the regulating valve k of the combustion chamber and the bottom of the combustion chamber The air inlet of the glove box was fed with argon gas at a flow rate of 25 L/min for about 50 seconds. Close the argon gas and the main valve i leading to the glove box, and turn on the vacuum pump button to pump the glove box for about 20 seconds. The valve is used to ensure that the gas in the combustion chamber is exhausted. If there is air leakage in the box of the glove box, first check whether the glove opening and the transition compartment door are closed tightly and whether they are damaged. If there is still air leakage, check the pipe valve of the glove box in contact with the outside, the "O" ring and the vacuum rubber on the outer door.

3) Control the oxygen concentration below 4% through the automatic program of the glove box. After reaching the specified oxygen concentration, open the argon valve and let it in at a small flow rate of 1 L/min.

4) Cut the sodium in the glove box, cut off the oxide and kerosene layer on the surface of the sodium block, cut about 6 grams of sodium, put it into a crucible and compact it with a rod. After the crucible was placed in the heating system, the crucible was isolated from the glove box environment by closing the clip of the front door of the plexiglass cover.

5) Turn down the regulating valve k leading to the combustion chamber, open the regulating valves m and j in the glove box and the plexiglass cover, and open the argon gas valve after the gas regulating valve in the lower part of the combustion chamber is closed to keep the argon gas in the heating process. Keep a small flow rate of 1L/min leading to the combustion system and the glove box.

6) Slowly heat the upper crucible and the lower combustion chamber through the pressure regulator, the heating rate is about 0.2°C/0.5s, and the lower pressure regulating box is controlled at about 50v to heat the temperature of the combustion chamber to about 180°C (as the experiment The condition can slightly increase the temperature but should not be higher than the initial temperature of the sodium droplet) and at the same time, the mixed gas passed through can reach a certain temperature through the heating of the lower part to avoid the cooling of the sodium droplet by the mixed gas. The initial temperature control of the sodium droplet was heated to 150°C (200°C, 250°C, 300°C, 350°C).

7) Turn on the motor and move the rod down slowly until sodium drops appear in the lower part of the crucible. The horizontal diameter of the sodium drop is controlled at about 5 mm, and then adjust the tip of the thermocouple so that it is just close to the surface of the sodium drop. Open the high-speed camera now and start high-speed shooting to the sodium drop, generally be set as 100 frames/s, pass into the oxygen 21% (16%, 12%, 12%) of the certain oxygen concentration that has adjusted to the combustion chamber after the temperature of the sodium drop is stable. 8%, 4%) and let the gas enter the combustion chamber through the pipeline at a certain flow rate, observe and record the experimental phenomena and data.

8) In order to prevent the aerosol generated by the oxidation reaction from clogging the observation hole, the exhaust pump can be turned on according to the conditions to adjust the size during the sodium drop combustion process, and the exhaust gas burned in the combustion chamber is discharged into the exhaust gas spraying device.

9) Turn off the pressure regulator after the burning of sodium droplets is over, and observe whether there is exhaust gas in the combustion chamber. If there is, continue to let the exhaust gas enter the spray system through the exhaust pump. After confirming that there is no exhaust gas, open the front door of the plexiglass cover to quickly dissipate the heat of the crucible. When the temperature of the crucible drops to normal temperature, take out the crucible and the rod from the combustion chamber with tweezers, and take out the lower sodium connection valve at the same time. Take it out through the tool compartment of the glove box and put it into a stainless steel tank filled with 99.7% absolute ethanol for soaking and cleaning. After the sodium remaining in the crucible disappears, take out the crucible for drying treatment.

Claims (2)

1. The liquid alkali metal combustion propagation velocity measuring device is characterized in that: the device comprises an organic glass cover, a shell, a sodium receiving tank, an exhaust water washing system and a gas supply system, wherein the organic glass cover and the shell are sequentially arranged from top to bottom to form a closed experimental space, a motor is arranged in the organic glass cover, a clamp pot and a mixed gas shell are arranged in the shell, alkali metal is filled in the clamp pot, an upper heating wire is arranged outside the clamp pot, the motor is connected with a combustion rod, the combustion rod extends into the clamp pot and extrudes the alkali metal, an outlet of the mixed gas shell is positioned right below an alkali metal dripping outlet of the clamp pot, an inlet of the sodium receiving tank extends into the lower part of the outlet of the mixed gas shell from the lower part of the mixed gas shell and forms a mixed gas channel with the outlet, a mixed gas outlet pipe extends into the mixed gas shell, a gas hole is formed in the shell, and the rare gas;

The exhaust washing system comprises a filter water tank and a circulating pipeline, wherein the filter water tank comprises an upper tank body and a lower tank body, the upper tank body is communicated with the lower tank body through a raised pipeline, one end of the circulating pipeline is communicated with the upper tank body, the other end of the circulating pipeline is communicated with the lower tank body, a circulating water pump is mounted on the circulating pipeline, a baffle plate is arranged in the upper tank body, a washed gas outlet and an atomizing spray head are arranged on the upper tank body and are respectively arranged on two sides of the baffle plate, the atomizing spray head is communicated with the circulating pipeline, the washed gas outlet is communicated with a washed gas outlet pipeline, an air suction pump is arranged on the washed gas outlet pipeline, an aerosol exhaust port is arranged on the shell, and the aerosol exhaust port;

the gas supply system comprises a nitrogen source and an argon source, the nitrogen source is communicated with a mixed gas outlet pipe, the argon source is communicated with a rare gas outlet pipe, the mixed gas outlet pipe is communicated with the rare gas outlet pipe through a gas mixing pipe, a gas mixing valve is arranged on the gas mixing pipe, an air pipe is arranged on the mixed gas outlet pipe between the gas mixing pipe and the nitrogen source, an air pump and an air valve are arranged on the air pipe, a nitrogen valve is arranged at a nitrogen source outlet, a gas mixing device is arranged on the mixed gas outlet pipe between the gas mixing pipe and the air pipe, a mixed gas pump and an oxygen concentration meter are arranged on the mixed gas outlet pipe behind the gas mixing pipe, and an argon valve is arranged at an argon source outlet;

The interior of the tong-pan is of a structure with a wide upper part and a narrow lower part, wherein the inner diameter of the upper part of the tong-pan is 12mm, the inner diameter of the lower part of the tong-pan is 8mm, the combustion rod is of a structure with a narrow upper part and a wide lower part, the diameter of the upper part of the combustion rod is 5mm, and the diameter of the lower part of the combustion rod is 7 mm;

The clamp pot is a double-nozzle clamp pot, the outer diameter of a nozzle of the crucible is 2mm, the inner diameter of the nozzle is 1.0mm, 0.8mm, 0.5mm and 0.1mm respectively, the distance between every two nozzle sizes is 4mm and 8mm, and the outer diameter of a rod for extruding sodium drops is 7mm and 6 mm.

2. The apparatus for measuring the propagation velocity of combustion of a liquid alkali metal as set forth in claim 1, wherein: the outer part of the mixed gas shell is sleeved with a lower heating wire, and the upper heating wire and the lower heating wire are both in a thread shape.