Liquid ammonia low-temperature flow experiment system and experiment method

Abstract

The invention provides a liquid ammonia low-temperature flow experiment system and an experiment method. The system comprises an ammonia gas storage device, a condensation box, a magnetic pump, a temperature control coil pipe, a two-dimensional flow channel, a data acquisition instrument and a computer, the ammonia gas storage device, the condensing box, the magnetic pump, the temperature control box and the two-dimensional flow channel are connected through a pipeline; a condensing coil is arranged in the condensing box; a temperature control coil pipe is arranged in the temperature control box; a thermocouple pressure sensor is arranged on the pipeline and used for measuring the temperature and air pressure of the fluid; the thermocouple and the pressure sensor are electrically connected with the data acquisition instrument, acquired data are transmitted to the data acquisition instrument, and the data acquisition instrument is electrically connected with the computer. According to the invention, ammonia gas is condensed into liquid ammonia through the condensation system, and then the liquid ammonia is heated through the temperature control system, so that the temperature of the liquid ammonia is adjusted, and the cavitation and flash boiling characteristics of heat-sensitive fluid liquid ammonia at different temperatures can be researched; and experimental support is provided for revealing the characteristics of the liquid ammonia at different temperatures and accelerating the application process of the liquid ammonia on an engine.

Description

Technical Field

[0001] The invention belongs to the field of liquid flow in a low-temperature flow channel, and in particular to a liquid ammonia low-temperature flow experimental system and an experimental method. Background Art

[0002] Internal combustion engines are widely used in automobiles, ships, engineering machinery, agricultural machinery, and national defense equipment, and play an important supporting role in the development of the national economy. In the current global low-carbon and zero-carbon transformation context, the transition of engines from gasoline and diesel to renewable biofuels, especially zero-carbon fuels such as hydrogen and ammonia, has become a general trend. Hydrogen energy is considered to be the most ideal secondary energy source for mankind after electricity. Hydrogen fuel has low volume energy density and storage and transportation challenges. Ammonia fuel, as a hydrogen-rich carrier, has attracted much attention for its application in engines due to its high energy density, easy liquefaction, easy storage and transportation, higher output and production efficiency than liquid hydrogen, low cost, and safe use.

[0003] From the perspective of the physical and chemical properties of ammonia, it exists in a gaseous state at room temperature and pressure, and its saturation temperature at one atmosphere is about -33.5°C, that is, when ammonia is cooled to -33.5°C, it will change from a gaseous state to a liquid state. The cavitation flow in the nozzle under ultra-high speed, high turbulence, strong transient and small scale during the high-pressure injection and spray atomization of liquid ammonia belongs to the research scope of cavitation flow of heat-sensitive fluids. The flash boiling spray is also much stronger than gasoline and methanol. In addition to the cavitation at the nozzle inlet, the internal area of ​​the nozzle near the nozzle outlet is more prone to flash boiling steam bubbles than methanol. The interaction mechanism between the two and the synergistic influence mechanism on the fragmentation of flash boiling spray will be the key to the development of liquid ammonia high-pressure injection systems and the precise control of high-pressure injection and spraying. As a heat-sensitive fluid, how to achieve ammonia liquefaction and temperature control of liquid ammonia is a major challenge. Summary of the invention

[0004] In view of the above technical problems, the present invention provides a liquid ammonia low-temperature flow experimental system and experimental method, which realizes low-temperature condensation of ammonia gas and heat absorption and heating through a condenser and a temperature control box, so that the liquid ammonia reaches a predetermined injection temperature, which is conducive to obtaining liquid ammonia nozzle internal flow experimental data at different temperatures.

[0005] The present invention condenses ammonia gas into liquid ammonia through a condensation system, and then heats the liquid ammonia through a temperature control system to adjust the temperature of the liquid ammonia, which is beneficial to studying the cavitation and flash boiling characteristics of the thermosensitive fluid liquid ammonia at different temperatures, and provides experimental support for revealing the characteristics of liquid ammonia at different temperatures and accelerating the process of using liquid ammonia in engines.

[0006] Note that the description of these objectives does not prevent the existence of other objectives. One embodiment of the present invention does not need to achieve all of the above objectives. Objectives other than the above objectives can be extracted from the description of the specification, drawings, and claims.

[0007] The present invention achieves the above technical objectives through the following technical means.

[0008] A liquid ammonia low temperature flow experimental system, comprising an ammonia storage device, a condensing box, a magnetic pump, a temperature control coil, a two-dimensional flow channel, a data acquisition instrument and a computer;

[0009] The ammonia storage tank, condensing tank, magnetic pump, temperature control tank and two-dimensional flow channel are connected by pipelines;

[0010] The condensing box is provided with a condensing coil; the temperature control box is provided with a temperature control coil;

[0011] The pipeline is provided with a first thermocouple, a second thermocouple, a third thermocouple, a first pressure sensor, a second pressure sensor and a third pressure sensor; the first thermocouple and the first pressure sensor are respectively used to measure the temperature and air pressure of the fluid at the inlet of the temperature control box; the second thermocouple and the second pressure sensor are respectively used to measure the temperature and air pressure of the fluid at the inlet of the two-dimensional flow channel; the third thermocouple and the third pressure sensor are respectively used to measure the temperature and air pressure of the fluid at the outlet of the two-dimensional flow channel; the first thermocouple, the second thermocouple, the third thermocouple, the first pressure sensor, the second pressure sensor and the third pressure sensor are respectively electrically connected to the data acquisition instrument to transmit the collected data to the data acquisition instrument, and the data acquisition instrument is electrically connected to the computer.

[0012] In the above solution, a first visual observation window is provided at one end of the two-dimensional flow channel, and a second visual observation window is provided at the other end. The two-dimensional flow channel is connected to the first visual observation window and the second visual observation window respectively through a corrugated hose.

[0013] The above solution also includes a filter; the filter is arranged on the pipeline between the condensation tank and the magnetic pump.

[0014] The above scheme also includes a mass flow meter; the mass flow meter is arranged on the pipeline between the magnetic pump and the temperature control box.

[0015] The above scheme also includes a nitrogen storage device; the nitrogen storage device is connected to the inlet of the condensing box through a left pipeline, the nitrogen storage device is connected to the pipeline between the magnetic pump and the temperature control box through a middle pipeline, and the nitrogen storage device is connected to the outlet of the two-dimensional flow channel through a right pipeline; the outlet pipeline, the left pipeline, the middle pipeline and the right pipeline of the nitrogen storage device are connected through a second four-way joint; a sixth two-way valve is provided on the outlet pipeline between the nitrogen storage device and the flow regulating valve; a fifth two-way valve is provided on the left pipeline between the second four-way joint and the condensing box, a fifth two-way valve and a flow regulating valve are provided on the right pipeline between the second four-way joint and the two-dimensional flow channel in sequence, and a third two-way valve is provided on the pipeline between the outlet of the temperature control box and the inlet of the two-dimensional flow channel; the middle pipeline is connected to the pipeline between the magnetic pump and the temperature control box through a three-way joint; and a seventh two-way valve is provided on the middle pipeline.

[0016] The above scheme also includes a water tank and a vacuum pump; the inlets of the ammonia storage tank, the vacuum pump, the water tank and the condensation tank are connected by pipelines; the pipeline between the ammonia storage tank and the vacuum pump is connected to the first three-way valve; the pipeline between the water tank and the first three-way valve, and the pipeline between the inlet of the condensation tank and the second four-way joint are respectively connected to the first four-way joint; the water outlet of the water tank is respectively connected to the pipeline between the safety valve and the first four-way joint through the second three-way valve; a first two-way valve is provided between the ammonia storage tank and the first three-way valve; a second two-way valve is provided between the vacuum pump and the first three-way valve.

[0017] The above scheme also includes a third visualization window and a vacuum gauge; the third visualization window is arranged on the pipeline between the second four-way joint and the first four-way joint; the vacuum gauge is arranged on the pipeline between the first four-way joint and the third visualization window.

[0018] A test method according to the liquid ammonia low temperature flow test system comprises the following steps:

[0019] The ammonia gas is condensed into liquid ammonia through the condensation system, and then the liquid ammonia is heated up through the temperature control system to adjust the temperature of the liquid ammonia.

[0020] Ammonia flows from the ammonia storage into a condenser box, passes through a condenser coil, and a coolant for heat exchange is contained in the condenser box. The ammonia gas is condensed into liquid ammonia by the condenser box, and the liquid ammonia is supercooled and pumped into a temperature control box by a magnetic pump. The temperature of the liquid ammonia is adjusted by the temperature control coil, and the flow pattern in the two-dimensional flow channel is changed by adjusting different inlet pressures and liquid ammonia temperatures;

[0021] The first thermocouple and the first pressure sensor respectively measure the temperature and air pressure of the fluid at the inlet of the temperature control box, the second thermocouple and the second pressure sensor respectively measure the temperature and air pressure of the fluid at the inlet of the two-dimensional flow channel, the third thermocouple and the third pressure sensor respectively measure the temperature and air pressure of the fluid at the outlet of the two-dimensional flow channel, and transmit the collected data to the data acquisition instrument, which displays the collected temperature and air pressure in real time and transmits the data to the computer for studying the cavitation and flash boiling characteristics of liquid ammonia at different temperatures.

[0022] The above scheme also includes a vacuuming step and a step of removing liquid ammonia and ammonia gas, which specifically includes the following steps:

[0023] Step S1. Open the sixth two-way valve to fill with nitrogen, cut off the exhaust of the second three-way valve, open the fifth two-way valve and the sixth two-way valve, fully open the flow regulating valve, and blow out the gas in the left pipeline;

[0024] Step S2. Open the sixth two-way valve to fill with nitrogen, cut off the exhaust of the second three-way valve, open the sixth two-way valve and the seventh two-way valve, and fully open the flow regulating valve to blow out the gas in the middle pipeline;

[0025] Step S3. Open the sixth two-way valve to fill with nitrogen, cut off the exhaust of the second three-way valve, open the sixth two-way valve, the fourth two-way valve and the third two-way valve, and fully open the flow regulating valve to blow out the gas in the right pipeline;

[0026] Step S4. After the purge is completed, all the gas in the tube is replaced by nitrogen, and the valve is adjusted to a fully closed state;

[0027] Step S4. Cut off the vacuum at the first three-way valve, open the second two-way valve, the third two-way valve, the fourth two-way valve, the fifth two-way valve and the seventh two-way valve, fully open the flow regulating valve, turn on the vacuum pump to extract all the nitrogen in the tube, and the value of the vacuum gauge must be negative;

[0028] Step S5. Before charging ammonia, the condenser and the temperature control box are precooled to a specified value, and it is determined that the current pipeline is in a vacuum state;

[0029] Step S6. Keep the unit turned on, cut off the ammonia gas with the valve, open the fourth two-way valve and the fifth two-way valve, set the flow in the pipe to the left small cycle, and finally open the first two-way valve to start charging ammonia gas, and condense the cycle to produce liquid ammonia;

[0030] Step S7. Fill a certain amount of ammonia. When obvious condensed liquid ammonia appears in the storage tank of the condensing box, start the magnetic pump to operate at a low speed. After the filling is completed, do not turn off the magnetic pump to maintain low-speed liquid ammonia circulation. Note that the pressure pointer of the vacuum gauge does not exceed the range. When there is more than 80% liquid ammonia in the storage tank of the condensing coil, the filling is considered complete and the first two-way valve connected to the ammonia storage is closed.

[0031] Step S8. Turn on the magnetic pump, open the third two-way valve, the fourth two-way valve, and the fifth two-way valve, tighten the flow control valve to fully close it first and then open it. Note that the flow control valve cannot be fully opened to ensure that the pressure pointer of the vacuum gauge does not exceed the range;

[0032] Step S9. By adjusting the speed of the magnetic pump, adjust the pressure value in the pipeline, observe the amplitude of the pressure rise of the vacuum gauge, and when an abnormality occurs, quickly tighten the flow regulating valve, and reduce the speed of the magnetic pump to prevent the pressure of the vacuum gauge from further increasing. Keep the condenser box open and adjust the temperature of the temperature control box to obtain the desired experimental conditions;

[0033] Step S10. After the experiment is over, turn off the magnetic pump; adjust the second three-way valve to the exhaust state, that is, repeat the operations of step S1, step S2, and step S3, and finally close all valves.

[0034] In the above scheme, in step S5, the temperature adjustment range of the condensing box is -40-40°C, and the temperature adjustment range of the temperature control box is -20-100°C.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] In the present invention, the ammonia gas is first cooled to below -33.5°C by a condensing box, so that the ammonia gas is converted from a gaseous state to a liquid state to form liquid ammonia, and then the liquid ammonia is heated to a target temperature by a temperature control box.

[0037] The present invention is provided with a filter, the outlet of the filter is connected to the inlet of the magnetic pump, and is used for filtering impurities in the pipeline to prevent the impurities from clogging the inlet of the magnetic pump and damaging the magnetic pump.

[0038] In order to prevent liquid ammonia from becoming ammonia gas after contacting the pump, on the one hand, this experiment uses a magnetic pump for driving, which can avoid excessive contact with liquid ammonia; on the other hand, the liquid ammonia is overcooled in the condensation tank to leave some surplus.

[0039] In the present invention, a vacuum pump is used to extract the residual gas in the pipeline before the experiment to achieve a vacuum state of the pipeline, thereby preventing the residual gas in the pipeline from affecting the experiment.

[0040] In the present invention, the liquid ammonia / ammonia gas in the entire system is discharged to the ammonia post-treatment equipment through the exhaust valve to complete the pressure relief of the system. If the liquid ammonia / ammonia gas is not removed in time after the experiment, on the one hand, it is easy to leak under abnormal conditions, causing safety hazards. On the other hand, the pipelines and devices are in a high-pressure environment for a long time, and the liquid ammonia / ammonia gas is corrosive, which is easy to cause wear and corrosion to the pipelines and equipment, and bring safety risks.

[0041] Note that the description of these effects does not prevent the existence of other effects. One embodiment of the present invention does not necessarily have all of the above effects. Effects other than the above can be clearly seen and extracted from the description of the specification, drawings, claims, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 This is a schematic diagram of a liquid ammonia low-temperature flow experimental system according to one embodiment of the present invention.

[0043] Figure 2 This is a schematic diagram of a condensation system according to an embodiment of the present invention.

[0044] Figure 3 Schematic diagram of a temperature control system according to one embodiment of the present invention.

[0045] In the figure, 1. ammonia storage; 2. vacuum pump; 3. water tank; 4. condensing box; 5. condensing coil; 6. filter; 7. magnetic pump; 8. mass flow meter; 9. first thermocouple; 10. first pressure sensor; 11. temperature control box; 12. temperature control coil; 13. first visualization window; 14. second thermocouple; 15. second pressure sensor; 16. two-dimensional flow channel; 17. third pressure sensor; 18. third thermocouple; 19. second visualization window; 20. nitrogen storage; 21. third visualization window; 22. vacuum gauge; 23. data acquisition instrument; 24. computer; 25. first two-way valve; 26. first three-way valve; 27. second two-way valve; 28. first four-way valve 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29 ...3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. 41. 42. 43. 44. 45. 46. 47. 48. 49. 49. 40. 41. 42. 4 DETAILED DESCRIPTION

[0046] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0047] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "front", "back", "left", "right", "up", "down", "axial", "radial", "vertical", "horizontal", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing 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 limiting the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0048] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like 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 a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0049] Figure 1 The figure shows a preferred embodiment of the liquid ammonia low temperature flow experimental system of the present invention, wherein the liquid ammonia low temperature flow experimental system comprises an ammonia storage 1, a condenser 4, a magnetic pump 7, a temperature control coil 12, a two-dimensional flow channel 16, a data acquisition instrument 23 and a computer 24;

[0050] The ammonia storage 1, condensation tank 4, magnetic pump 7, temperature control box 11 and two-dimensional flow channel 16 are connected by pipelines;

[0051] The condensing box 4 is provided with a condensing coil 5; the temperature control box 11 is provided with a temperature control coil 12;

[0052] The pipeline is provided with a first thermocouple 9, a second thermocouple 14, a third thermocouple 18, a first pressure sensor 10, a second pressure sensor 15 and a third pressure sensor 17; the first thermocouple 9 and the first pressure sensor 10 are respectively used to measure the temperature and air pressure of the fluid at the inlet of the temperature control box 11; the second thermocouple 14 and the second pressure sensor 15 are respectively used to measure the temperature and air pressure of the fluid at the inlet of the two-dimensional flow channel 16; the third thermocouple 18 and the third pressure sensor 17 are respectively used to measure the temperature and air pressure of the fluid at the outlet of the two-dimensional flow channel 16; the first thermocouple 9, the second thermocouple 14, the third thermocouple 18, the first pressure sensor 10, the second pressure sensor 15 and the third pressure sensor 17 are respectively electrically connected to the data acquisition instrument 23, and the collected data are transmitted to the data acquisition instrument 23 for recording and summarizing, and the data acquisition instrument 23 is electrically connected to the computer 24 to display the collected data in real time.

[0053] Preferably, a first visual observation window 13 is provided at one end of the two-dimensional flow channel 16, and a second visual observation window 19 is provided at the other end, and the two-dimensional flow channel 16 is connected to the first visual observation window 13 and the second visual observation window 19 respectively through a corrugated hose.

[0054] Preferably, a filter 6 is further included; the filter 6 is arranged on the pipeline between the condensation tank 4 and the magnetic pump 7. The outlet of the filter 6 is connected to the inlet of the magnetic pump 7, and is used to filter impurities in the pipeline to prevent the impurities from clogging the inlet of the magnetic pump 7 and damaging the magnetic pump 7.

[0055] The magnetic pump 7 is used as the driving pump. Compared with the electrically driven booster pump, since both ammonia gas and liquid ammonia are flammable, no arc or spark is generated during the boosting process, thus avoiding fire.

[0056] In the present invention, in order to prevent liquid ammonia from becoming ammonia gas after contacting the pump, on the one hand, this experiment uses a magnetic pump 7 for driving, and the use of the magnetic pump 7 for driving can avoid excessive contact with liquid ammonia; on the other hand, the liquid ammonia is partially overcooled in the condensation tank 4, leaving some surplus.

[0057] Preferably, a mass flow meter 8 is further included; the mass flow meter 8 is arranged on the pipeline between the magnetic pump 7 and the temperature control box 11.

[0058] Preferably, a nitrogen storage device 20 is further included; the nitrogen storage device 20 is connected to the inlet of the condensing box 4 through a left pipeline, the nitrogen storage device 20 is connected to the pipeline between the magnetic pump 7 and the temperature control box 11 through a middle pipeline, and the nitrogen storage device 20 is connected to the outlet of the two-dimensional flow channel 16 through a right pipeline; the outlet pipeline, the left pipeline, the middle pipeline and the right pipeline of the nitrogen storage device 20 are connected through a second four-way joint 35; a sixth two-way valve 37 is provided on the outlet pipeline between the nitrogen storage device 20 and the flow regulating valve; a fifth two-way valve 36 is provided on the left pipeline between the second four-way joint 35 and the condensing box 4, a fifth two-way valve 34 and a flow regulating valve 33 are provided on the right pipeline between the second four-way joint 35 and the two-dimensional flow channel 16 in sequence, and a third two-way valve 32 is provided on the pipeline between the outlet of the temperature control box 11 and the inlet of the two-dimensional flow channel 16; the middle pipeline is connected to the pipeline between the magnetic pump 7 and the temperature control box 11 through a three-way joint 31; and a seventh two-way valve 38 is provided on the middle pipeline.

[0059] In the present invention, the liquid ammonia / ammonia gas in the entire system is discharged into the water tank 3 of the ammonia post-treatment equipment through the second three-way valve 29 to complete the pressure relief of the system. If the liquid ammonia / ammonia gas is not removed in time after the experiment, on the one hand, it is easy to leak under abnormal conditions, causing safety hazards. On the other hand, the pipelines and devices are in a high-pressure environment for a long time, and liquid ammonia / ammonia gas are corrosive, which is easy to cause wear and corrosion to the pipelines and equipment, and bring safety risks.

[0060] Preferably, it also includes a water tank 3 and a vacuum pump 2; the inlets of the ammonia storage device 1, the vacuum pump 2, the water tank 3 and the condensation tank 4 are connected by a pipeline; the pipeline between the ammonia storage device 1 and the vacuum pump 2 is connected to the first three-way valve 26; the pipeline between the water tank 3 and the first three-way valve 26, and the pipeline between the inlet of the condensation tank 4 and the second four-way connector 35 are respectively connected to the first four-way connector 28; the water outlet of the water tank 3 is respectively connected to the pipeline between the safety valve 30 and the first four-way connector 28 through the second three-way valve 29; a first two-way valve 25 is provided between the ammonia storage device 1 and the first three-way valve 26; a second two-way valve 27 is provided between the vacuum pump 2 and the first three-way valve 26.

[0061] Before the experiment of the present invention, a vacuum pump 2 is used to extract the residual gas in the pipeline to achieve a vacuum state of the pipeline, thereby preventing the residual gas in the pipeline from affecting the experiment.

[0062] Preferably, a third visualization window 21 and a vacuum gauge 22 are further included; the third visualization window 21 is arranged on the pipeline between the second four-way joint 35 and the first four-way joint 28; the vacuum gauge 22 is arranged on the pipeline between the first four-way joint 28 and the third visualization window 21. The third visualization window 21 is used to observe the state of liquid ammonia after passing through the two-dimensional flow channel 16, and adjust the opening degree of the flow control valve 33 according to the observation result.

[0063] Furthermore, the inlet of the mass flow meter 8 is connected to the outlet of the magnetic pump 7 via a three-way joint 31, the outlet of the mass flow meter 8 is connected to the first pressure sensor 10, and the first thermocouple 9 is fixed to the outer wall of the tube.

[0064] like Figure 2 As shown, the condenser box 4 and the condenser coil 5 form a condensation system, and the condenser box 4 is also provided with a condensation cycle switch 39, a condensation refrigeration switch 40, a condensation power supply 41, a condensation upward adjustment button 42, a condensation rightward adjustment button 43, a condensation rightward adjustment button 44 and a condensation setting button 45; the condensation cycle switch 39 is used to start the condensation cycle of the condenser box, the condensation refrigeration switch 40 is used to start the condensation function of the condenser box, the condensation power supply 41 is used to start the condenser box, the condenser box upward adjustment button 42 is used to increase the set temperature, the condenser box rightward adjustment button 43 is used to reduce the set temperature, the condenser box leftward adjustment button 44 is used to move the cursor position to determine whether the condensation upward adjustment button 42 and the condensation rightward adjustment button 43 are adjusted in units of ten degrees or in units of zero point zero degrees, and the condensation setting button 45 is used to edit the set temperature of the condenser box and confirm after the temperature is set.

[0065] Click the condensation power supply 41 to turn on the device, click the condensation setting button 45, adjust the temperature setting value and condensation time according to the experimental requirements, and set the upper and lower limits of the temperature. If the set value is exceeded, the condensation box 4 will alarm. Since the liquefaction of ammonia will release a large amount of heat, the temperature of the refrigerant in the condensation box 4 will rise rapidly. When the alarm sounds, it is necessary to quickly stop the introduction of ammonia, and continue to introduce ammonia after the temperature drops, or increase the set upper and lower limits of the temperature. After setting the temperature value, click the condensation refrigeration switch 40, the condensation box 4 starts to refrigerate, and after clicking the condensation circulation switch 39, the refrigerant starts to circulate inside, accelerating the removal of the heat released by the liquefaction of ammonia in the condensation coil 5. After the ammonia is condensed into liquid ammonia, it is stored in the liquid ammonia storage tank in the condensation coil 5. The quartz glass window above the liquid ammonia storage tank can be used to observe the liquid ammonia reserves. When there is some liquid ammonia in the tank, turn on the magnetic pump 7 to make it run at a low speed. On the one hand, the magnetic pump 7 provides a certain pressure to accelerate the liquefaction of ammonia, and on the other hand, it can pre-cool the pipeline to reduce the heat taken away from the liquid ammonia by the pipeline during the formal experiment. After the experiment is over, first click the condensation circulation switch 39 and the condensation refrigeration switch 40, and after the temperature rises appropriately, close the condensation system and cut off the power supply.

[0066] like Figure 3As shown, the temperature control box 11 and the temperature control coil 12 form a temperature control system, and the temperature control box 11 is also provided with a temperature control circulation switch 46, a temperature control refrigeration switch 47, a temperature control power supply 48, a temperature control upward adjustment button 49, a temperature control right adjustment button 50, a temperature control left adjustment button 51 and a temperature control setting button 52; the temperature control circulation switch 46 is used to start the condensation cycle of the temperature control box, the temperature control refrigeration switch 47 is used to start the refrigeration function of the temperature control box, the temperature control power supply 48 is used to start the temperature control box 11, the temperature control box upward adjustment button 49 is used to increase the set temperature, the temperature control box right adjustment button 50 is used to reduce the set temperature, the temperature control box left adjustment button 51 is used to move the cursor position, and decide whether the temperature control box upward adjustment button 49 and the temperature control box right adjustment button 50 are adjusted in units of ten degrees or in units of zero point zero degrees, and the temperature setting button 52 is used to edit the set temperature of the temperature control box and confirm after the temperature is set.

[0067] Click the temperature control power 48 to turn on the device, click the temperature control setting button 52, and adjust the temperature setting value and condensation time according to the experimental requirements. Since the flow rate of liquid ammonia is different under different pressures, the heat lost and the temperature reduced when passing through the temperature control box 11 will be slightly different. Therefore, the temperature setting value should be adjusted according to different experimental conditions. The condensation system, magnetic pump 7 and temperature control system jointly control the temperature and pressure of liquid ammonia.

[0068] First, turn on the condensation power supply 41, the condensation refrigeration switch 40 and the condensation circulation switch 39 in sequence to precool the temperature in the box to below -33.5°C. The internal pipeline of the condensation box 4 adopts the form of a condensation coil 5 to enhance the heat exchange efficiency, so that the ammonia gas introduced is quickly converted from gas to liquid to form liquid ammonia. By adjusting the valve, the ammonia gas is condensed to produce liquid ammonia first in the small cycle on the left, such as Figure 1As shown in the middle blue pipeline; on the one hand, the small circulation pipeline is shorter, which increases the efficiency of liquid ammonia production. On the other hand, it avoids the existence of too much uncondensed ammonia in the pipeline after the condensation is completed, which affects the reliability of the experimental results. Since the liquid ammonia is provided with pressure by the magnetic pump 7, the temperature of the liquid ammonia will inevitably rise when the magnetic pump 7 is running. If the liquid ammonia absorbs too much heat and turns into ammonia, it will affect the experimental results on the one hand, and pose a potential threat to the safety of the pipeline on the other hand. Therefore, it is necessary to set the temperature of the condensation box 4 to -35°C through the condensation setting button 45 to provide a certain degree of supercooling for the condensation coil 5 and the liquid ammonia in the storage tank. The condensation coil 5, the filter 6 and the magnetic pump 7 are connected by a pipeline. The function of the filter 6 is mainly to block the solid impurities that may appear in the pipeline to prevent the impurities from clogging or entering the interior of the magnetic pump 7, causing damage to the magnetic pump 7. According to the experimental requirements, the temperature of the temperature control box is set through the temperature control setting button 52, and then the temperature control power supply 48, the temperature control refrigeration switch 47 and the temperature control circulation switch 46 are turned on for precooling. After the liquid ammonia passes through the temperature control box 11, it reaches the temperature required for the experiment. The flow state of the liquid ammonia is observed through the first visual window 13 to determine that the liquid ammonia in the pipeline is not mixed with too many bubbles. The second thermocouple 14, the third thermocouple 18, the second pressure sensor 15 and the third pressure sensor 17 before and after the two-dimensional flow channel 16 are used to collect the pressure and temperature of the inlet and outlet of the two-dimensional flow channel 16 respectively. The third visual window 21 is used to observe the state of liquid ammonia after passing through the two-dimensional flow channel 16, and adjust the opening degree of the flow control valve 33 according to the observation results. During the formal experiment, the flow control valve 33 must be slightly opened first, and adjusted according to the experimental situation to avoid excessive pressure in the pipe and damage to the vacuum gauge 22 and the pipeline. The indication range of the vacuum gauge 22 is -0.1MPa-2.4MPa. When the pressure of the vacuum gauge 22 is observed to increase suddenly, the flow control valve 33 should be tightened quickly, and the magnetic force 7 should be closed for pressure reduction. The indication adjustment range of the safety valve 30 is 0.8MPa-3MPa. When the pressure is too high, the safety valve 30 will automatically open to release the pressure to avoid excessive pressure in the pipe and damage to the experimental equipment.

[0069] A test method according to the liquid ammonia low temperature flow test system comprises the following steps:

[0070] The ammonia gas is condensed into liquid ammonia through the condensation system, and then the liquid ammonia is heated up through the temperature control system to adjust the temperature of the liquid ammonia.

[0071] Ammonia flows from the ammonia storage 1 into the condenser 4, passes through the condenser coil 5, and the condenser 4 contains a coolant for heat exchange. The ammonia is condensed into liquid ammonia by the condenser 4, and the liquid ammonia is supercooled and pumped into the temperature control box 11 by the magnetic pump 7. The pipe inside the temperature control box 11 is a temperature control coil 12. The temperature control box 11 contains a coolant for heat exchange. The temperature of the liquid ammonia is adjusted by the temperature control coil 12. The flow pattern in the two-dimensional flow channel 16 changes by adjusting different inlet pressures and liquid ammonia temperatures;

[0072] The first thermocouple 9 and the first pressure sensor 10 respectively measure the temperature and air pressure of the fluid at the inlet of the temperature control box 11, the second thermocouple 14 and the second pressure sensor 15 respectively measure the temperature and air pressure of the fluid at the inlet of the two-dimensional flow channel 16, the third thermocouple 18 and the third pressure sensor 17 respectively measure the temperature and air pressure of the fluid at the outlet of the two-dimensional flow channel 16, and transmit the collected data to the data acquisition instrument 23, the data acquisition instrument 23 displays the collected temperature and air pressure in real time, and transmits the data to the computer 24 for studying the cavitation and flash boiling characteristics of liquid ammonia at different temperatures.

[0073] Preferably, it also includes a vacuuming step and a step of removing liquid ammonia and ammonia gas. Specifically, it includes the following steps (all valves are closed at the beginning of each step by default):

[0074] Step S1. Open the sixth two-way valve 37 to charge nitrogen, cut off the exhaust of the second three-way valve 29, open the fifth two-way valve 36 and the sixth two-way valve 37, and fully open the flow regulating valve 33 to blow out the gas in the left pipeline. After charging nitrogen for a period of time, spray phenolphthalein reagent at the exhaust port until the phenolphthalein reagent no longer turns red, indicating that there is no residual ammonia in the left circuit;

[0075] Step S2. Open the sixth two-way valve 37 to charge nitrogen, cut off the exhaust of the second three-way valve 29, open the sixth two-way valve 37 and the seventh two-way valve 38, and fully open the flow regulating valve 33 to blow out the gas in the intermediate pipeline. After charging nitrogen for a period of time, spray phenolphthalein reagent at the exhaust port until the phenolphthalein reagent no longer turns red, indicating that there is no residual ammonia in the intermediate circuit;

[0076] Step S3. Open the sixth two-way valve 37 to charge nitrogen, cut off the exhaust of the second three-way valve 29, open the sixth two-way valve 37, the fourth two-way valve 34 and the third two-way valve 32, and fully open the flow regulating valve 33 to blow out the gas in the right pipeline. After charging nitrogen for a period of time, spray phenolphthalein reagent at the exhaust port until the phenolphthalein reagent no longer turns red, indicating that there is no residual ammonia in the right circuit;

[0077] Step S4. After nitrogen is filled into the three loops and the phenolphthalein reagent no longer turns red, the purge is completed, the gas in the tube is completely replaced by nitrogen, and the valve is adjusted to a fully closed state;

[0078] Step S4. The first three-way valve 26 is cut off from vacuum, the second two-way valve 27, the third two-way valve 32, the fourth two-way valve 34, the fifth two-way valve 36 and the seventh two-way valve 38 are opened, and the flow regulating valve 33 is fully opened, and the vacuum pump 2 is turned on to extract all the nitrogen in the tube, and the value of the vacuum gauge 22 must be negative;

[0079] Step S5. Before charging ammonia, the condenser 4 and the temperature control box 11 are precooled to a specified value, and it is determined that the current pipeline is in a vacuum state;

[0080] Step S6. Keep the unit turned on, cut off the ammonia gas with the valve, open the fourth two-way valve 34 and the fifth two-way valve 36, set the flow in the pipe to the left small cycle, and finally open the first two-way valve 25 to start charging ammonia gas, and condense the cycle to produce liquid ammonia;

[0081] Step S7. Fill a certain amount of ammonia gas. When obvious condensed liquid ammonia appears in the storage tank of the condensing box 4, start the magnetic pump 7 at a low speed, pay attention to the noise to prevent the ammonia pump from idling for a long time. After the filling is completed, do not turn off the magnetic pump 7 to maintain the low-speed liquid ammonia circulation. Note that the pressure pointer of the vacuum gauge 22 is not within the range. When there is more than 80% liquid ammonia in the storage tank of the condensing coil 5, the filling is considered to be completed (it can be judged by the naked eye that the liquid level is not higher than the top of the coil inside), and close the first two-way valve 25 connected to the ammonia storage 1.

[0082] Step S8. Turn on the magnetic pump 7, open the third two-way valve 32, the fourth two-way valve 34, and the fifth two-way valve 36, tighten the flow regulating valve 33 to fully close it first, and then open it appropriately. Note that the flow regulating valve 33 cannot be fully opened to ensure that the pressure pointer of the vacuum gauge 22 does not exceed the range;

[0083] Step S9. By adjusting the speed of the magnetic pump 7, the pressure value in the pipeline is adjusted, and the pressure rise of the vacuum gauge 22 is observed. When an abnormality occurs, the flow regulating valve 33 needs to be quickly tightened, and the speed of the magnetic pump 7 is reduced to prevent the pressure of the vacuum gauge 22 from further increasing. The condenser box 4 is kept open and the temperature of the temperature control box 11 is adjusted to obtain the desired experimental conditions. During the experiment, the flow morphology changes in the test section of the two-dimensional flow channel 16 are observed by adjusting different inlet pressures and liquid ammonia temperatures, and the qualitative experimental images are combined with quantitative flow, temperature and pressure data to analyze the influence of pressure and temperature on the characteristics of liquid ammonia.

[0084] Step S10. After the experiment is over, turn off the magnetic pump 7; adjust the second three-way valve 29 to the exhaust state, that is, repeat the operations of step S1, step S2, and step S3, and finally close all valves.

[0085] In step S4, the indication of the vacuum gauge 22 is adjusted within a range of -0.1-2.5 MPa.

[0086] In step S5, the temperature of the condensing box 4 is adjusted within a range of -40-40°C, and the temperature of the temperature control box 11 is adjusted within a range of -20-100°C.

[0087] It should be understood that although this specification is described according to various embodiments, not every embodiment contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0088] The series of detailed descriptions listed above are only specific descriptions of feasible embodiments of the present invention. They are not intended to limit the scope of protection of the present invention. All equivalent embodiments or changes that do not deviate from the technical spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A liquid ammonia low temperature flow experimental system, characterized in that: It comprises an ammonia storage device (1), a condensation box (4), a magnetic pump (7), a temperature control coil (12), a two-dimensional flow channel (16), a data acquisition device (23) and a computer (24); The ammonia storage (1), condensation box (4), magnetic pump (7), temperature control box (11) and two-dimensional flow channel (16) are connected via pipelines; The condensing box (4) is provided with a condensing coil (5); the temperature control box (11) is provided with a temperature control coil (12); The pipeline is provided with a first thermocouple (9), a second thermocouple (14), a third thermocouple (18), a first pressure sensor (10), a second pressure sensor (15) and a third pressure sensor (17); the first thermocouple (9) and the first pressure sensor (10) are respectively used to measure the temperature and air pressure of the fluid at the inlet of the temperature control box (11); the second thermocouple (14) and the second pressure sensor (15) are respectively used to measure the temperature and air pressure of the fluid at the inlet of the two-dimensional flow channel (16); the third thermocouple (18) and the third pressure sensor (17) are respectively used to measure the temperature and air pressure of the fluid at the outlet of the two-dimensional flow channel (16); the first thermocouple (9), the second thermocouple (14), the third thermocouple (18), the first pressure sensor (10), the second pressure sensor (15) and the third pressure sensor (17) are respectively electrically connected to a data acquisition instrument (23) to transmit the collected data to the data acquisition instrument (23); the data acquisition instrument (23) and the computer (24) are electrically connected.

2. The liquid ammonia low temperature flow experimental system according to claim 1, characterized in that: A first visual observation window (13) is provided at one end of the two-dimensional flow channel (16), and a second visual observation window (19) is provided at the other end; the two-dimensional flow channel (16) is respectively connected to the first visual observation window (13) and the second visual observation window (19) through a corrugated hose.

3. The liquid ammonia low temperature flow experimental system according to claim 1, characterized in that: The invention also comprises a filter (6); the filter (6) is arranged on the pipeline between the condensation tank (4) and the magnetic pump (7).

4. The liquid ammonia low temperature flow experimental system according to claim 1, characterized in that: It also comprises a mass flow meter (8); the mass flow meter (8) is arranged on the pipeline between the magnetic pump (7) and the temperature control box (11).

5. The liquid ammonia low temperature flow experimental system according to claim 1, characterized in that: The invention also comprises a nitrogen storage device (20); the nitrogen storage device (20) is connected to the inlet of the condensing box (4) through a left pipeline, the nitrogen storage device (20) is connected to the pipeline between the magnetic pump (7) and the temperature control box (11) through a middle pipeline, and the nitrogen storage device (20) is connected to the outlet of the two-dimensional flow channel (16) through a right pipeline; the outlet pipeline of the nitrogen storage device (20), the left pipeline, the middle pipeline and the right pipeline are connected through a second four-way joint (35); a sixth two-way joint (36) is provided on the outlet pipeline between the nitrogen storage device (20) and the flow regulating valve A valve (37); a fifth two-way valve (36) is provided on the left pipeline between the second four-way joint (35) and the condenser (4); a fifth two-way valve (34) and a flow regulating valve (33) are provided in sequence on the right pipeline between the second four-way joint (35) and the two-dimensional flow channel (16); a third two-way valve (32) is provided on the pipeline between the outlet of the temperature control box (11) and the inlet of the two-dimensional flow channel (16); the intermediate pipeline is connected to the pipeline between the magnetic pump (7) and the temperature control box (11) via a three-way joint (31); and a seventh two-way valve (38) is provided on the intermediate pipeline.

6. The liquid ammonia low temperature flow experimental system according to claim 5, characterized in that: The invention also comprises a water tank (3) and a vacuum pump (2); the inlets of the ammonia storage device (1), the vacuum pump (2), the water tank (3) and the condensation tank (4) are connected via a pipeline; the pipeline between the ammonia storage device (1) and the vacuum pump (2) is connected to a first three-way valve (26); the pipeline between the water tank (3) and the first three-way valve (26) and the pipeline between the inlet of the condensation tank (4) and the second four-way connector (35) are respectively connected to a first four-way connector (28); the water outlet of the water tank (3) is respectively connected to the pipeline between the safety valve (30) and the first four-way connector (28) via a second three-way valve (29); a first two-way valve (25) is provided between the ammonia storage device (1) and the first three-way valve (26); and a second two-way valve (27) is provided between the vacuum pump (2) and the first three-way valve (26).

7. The liquid ammonia low temperature flow experimental system according to claim 6, characterized in that: It also comprises a third visualization window (21) and a vacuum gauge (22); the third visualization window (21) is arranged on the pipeline between the second four-way connector (35) and the first four-way connector (28); and the vacuum gauge (22) is arranged on the pipeline between the first four-way connector (28) and the third visualization window (21).

8. A test method for a liquid ammonia low temperature flow test system according to any one of claims 1 to 7, characterized in that: The following steps are involved: The ammonia gas is condensed into liquid ammonia through the condensation system, and then the liquid ammonia is heated up through the temperature control system to adjust the temperature of the liquid ammonia. Ammonia flows from the ammonia storage (1) into a condenser (4) and passes through a condenser coil (5). The condenser (4) contains a coolant for heat exchange. The ammonia is condensed into liquid ammonia by the condenser (4), and the liquid ammonia is supercooled. The liquid ammonia is pumped into a temperature control box (11) by a magnetic pump (7). The temperature of the liquid ammonia is adjusted by the temperature control coil (12). The flow pattern in the two-dimensional flow channel (16) is changed by adjusting different inlet pressures and liquid ammonia temperatures. The first thermocouple (9) and the first pressure sensor (10) respectively measure the temperature and air pressure of the fluid at the inlet of the temperature control box (11), the second thermocouple (14) and the second pressure sensor (15) respectively measure the temperature and air pressure of the fluid at the inlet of the two-dimensional flow channel (16), and the third thermocouple (18) and the third pressure sensor (17) respectively measure the temperature and air pressure of the fluid at the outlet of the two-dimensional flow channel (16), and transmit the collected data to a data acquisition instrument (23). The data acquisition instrument (23) displays the collected temperature and air pressure in real time and transmits the data to a computer (24) for studying the cavitation and flash boiling characteristics of liquid ammonia at different temperatures.

9. The test method of the liquid ammonia low temperature flow test system according to claim 8, characterized in that: The following steps are also included: Step S1. Open the sixth two-way valve (37) to charge nitrogen, cut off the exhaust of the second three-way valve (29), open the fifth two-way valve (36) and the sixth two-way valve (37), and fully open the flow regulating valve (33) to blow out the gas in the left pipeline; Step S2. Open the sixth two-way valve (37) to charge nitrogen, cut off the exhaust of the second three-way valve (29), open the sixth two-way valve (37) and the seventh two-way valve (38), and fully open the flow regulating valve (33) to blow out the gas in the middle pipeline; Step S3. Open the sixth two-way valve (37) to charge nitrogen, cut off the exhaust of the second three-way valve (29), open the sixth two-way valve (37), the fourth two-way valve (34) and the third two-way valve (32), and fully open the flow regulating valve (33) to blow out the gas in the right pipeline; Step S4. After the purge is completed, all the gas in the tube is replaced by nitrogen, and the valve is adjusted to a fully closed state; Step S4. The first three-way valve (26) is cut off from vacuum, the second two-way valve (27), the third two-way valve (32), the fourth two-way valve (34), the fifth two-way valve (36) and the seventh two-way valve (38) are opened, and the flow regulating valve (33) is fully opened, and the vacuum pump (2) is turned on to completely extract the nitrogen in the tube. The value of the vacuum gauge (22) must be a negative value; Step S5. Before charging ammonia, the condenser (4) and the temperature control box (11) are precooled to a specified value, and it is determined that the current pipeline is in a vacuum state; Step S6. Keep the unit turned on, cut off the ammonia gas with the valve, open the fourth two-way valve (34) and the fifth two-way valve (36), set the flow in the pipe to the left small cycle, and finally open the first two-way valve (25) to start charging ammonia gas, condensing and circulating to produce liquid ammonia; Step S7. When a certain amount of ammonia is filled and obvious condensed liquid ammonia appears in the storage tank of the condensing box (4), the magnetic pump (7) is started to operate at a low speed. After the filling is completed, the magnetic pump (7) is not turned off to maintain the low-speed liquid ammonia circulation. Note that the pressure pointer of the vacuum gauge (22) does not exceed the range. When more than 80% of liquid ammonia is stored in the storage tank of the condensing coil (5), the filling is considered to be completed, and the first two-way valve (25) connected to the ammonia storage device (1) is closed. Step S8. Turn on the magnetic pump (7), open the third two-way valve (32), the fourth two-way valve (34), and the fifth two-way valve (36), first tighten the flow control valve (33) to fully close it and then open it. Note that the flow control valve (33) cannot be fully opened to ensure that the pressure pointer of the vacuum gauge (22) does not exceed the range; Step S9. By adjusting the speed of the magnetic pump (7), the pressure value in the pipeline is adjusted, and the pressure rise of the vacuum gauge (22) is observed. When an abnormality occurs, the flow control valve (33) needs to be quickly tightened, and the speed of the magnetic pump (7) is reduced to prevent the pressure of the vacuum gauge (22) from further increasing. The condenser (4) is kept open and the temperature of the temperature control box (11) is adjusted to obtain the desired experimental conditions; Step S10. After the experiment is over, turn off the magnetic pump (7); adjust the second three-way valve (29) to the exhaust state, that is, repeat the operations of step S1, step S2, and step S3, and finally close all valves.

10. The test method of the liquid ammonia low temperature flow test system according to claim 9, characterized in that: In the step S5, the temperature adjustment range of the condensing box (4) is -40-40°C, and the temperature adjustment range of the temperature control box (11) is -20-100°C.

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