WO2021035824A1

WO2021035824A1 - Independent liquid nitrogen supply and regulation device for ultralow-temperature cooling machining

Info

Publication number: WO2021035824A1
Application number: PCT/CN2019/105935
Authority: WO
Inventors: 王永青; 韩灵生; 刘阔; 孔繁泽; 刘海波; 刘树源
Original assignee: 大连理工大学
Priority date: 2019-08-28
Filing date: 2019-09-16
Publication date: 2021-03-04
Also published as: CN110529730A

Abstract

Provided is an independent liquid nitrogen supply and regulation device for ultralow-temperature cooling machining. The independent liquid nitrogen supply and regulation device comprises a liquid nitrogen supply transmission unit, a sensing execution unit and a control unit. A pressure-reducing valve (2.2) is mounted at an inlet end of the liquid nitrogen supply and regulation device. An ultralow-temperature-resistant Coriolis force flowmeter (2.4) is used. Stable control over a liquid nitrogen transmission pressure, real-time determination and monitoring of gas phase proportion in a pipeline, real-time monitoring of states such as the liquid nitrogen pressure, flow, temperature, density and reserves, and combined control over pressure, flow and temperature in ultralow-temperature cooling machining are realized by means of detection units such as a flowmeter (2.4), a liquid level meter (1.4), pressure sensors (2.3, 2.8) and a temperature sensor (2.7), execution units such as an adjusting valve (2.6) and the pressure-reducing valve (2.2), and control units such as an industrial flat plate (3.1) and acquisition cards (3.4, 3.5). The independent liquid nitrogen supply and regulation device uses a movable design and provides support for ultralow-temperature cooling machining of a common machine tool.

Description

An independent liquid nitrogen supply and control device for ultra-low temperature cooling processing

Technical field

The invention belongs to the technical field of low-temperature processing, and specifically relates to an independent liquid nitrogen supply and control device for ultra-low-temperature cooling processing.

Background technique

Ultra-low temperature machining with liquid nitrogen (saturation temperature -196°C) as the cooling medium can greatly reduce the cutting temperature, and has unique advantages in improving the processing quality and processing efficiency of difficult-to-machine material parts, and extending tool life. In recent years, the continuous supply, stable transmission and reliable control technology of liquid nitrogen and other cooling media have received extensive attention.

The supply and reliable control of the cooling medium are the prerequisite and guarantee for the implementation of ultra-low temperature cooling processing. Due to the diversity of materials and structures of the processed parts, the ultra-low temperature medium is required to have multi-variable, large-scale, and quantitative control capabilities. For example, the milling of narrow grooves requires a higher jet pressure to ensure the smooth entry of liquid nitrogen into the cutting area due to the structural characteristics of its large aspect ratio and effective cooling; materials such as stainless steel can cause surface hardening after cryogenic treatment, so During ultra-low temperature cooling processing, it is required to control the flow of liquid nitrogen to avoid increasing the hardness of the unprocessed surface, thereby aggravating tool wear. At the same time, controlling the flow of liquid nitrogen can increase the utilization of the cooling medium and avoid waste. However, due to the low saturation temperature and low latent heat of vaporization, liquid nitrogen is easily vaporized during storage and transmission due to the influence of the external environment temperature. The vaporization phenomenon will seriously damage the stability of liquid nitrogen transmission, thereby increasing the pressure, It is difficult to control the flow rate and temperature. The above-mentioned problems put forward high requirements on the thermal insulation capacity, transmission stability, low temperature resistance of the sensor, and real-time monitoring and control of status information of the liquid nitrogen supply and control device.

At present, domestic and foreign institutions have researched and developed a variety of flow control systems and devices for ultra-low temperature cooling media such as liquid nitrogen. In 2017, Dalian University of Technology disclosed in the invention patent 201710535356.9 "A method for regulating and controlling the steady flow of liquid nitrogen jet state". This method uses vacuum pipeline insulation, real-time monitoring of liquid nitrogen flow through a flow meter, and PID algorithm to achieve flow adjustment. , But did not involve the regulation of liquid nitrogen pressure. In 2017, Huazhong University of Science and Technology disclosed in the invention patent 201710099659.0 "a cryogenic processing system for difficult-to-process materials with automatic liquid nitrogen flow control". The system relies on actively adjusting the air pressure above the liquid surface in the gas-liquid separator to achieve liquid nitrogen. The automatic flow control, but does not regulate the output pressure and temperature of liquid nitrogen, and the system is more complicated. In 2018, the University of Jinan disclosed in the invention patent 201811181076.3 "A liquid nitrogen flow intelligent control cooling system suitable for low-temperature cutting". The system uses an infrared thermometer to detect the temperature of the front and flank surfaces online and feed it back to the processor. The flow of liquid nitrogen is controlled by a flow meter and a regulating valve, and finally reaches the set temperature, but the stable regulation of the pressure of liquid nitrogen is not involved.

Summary of the invention

In view of the above defects or improvement requirements of the prior art, the present invention proposes an independent liquid nitrogen supply and control device for ultra-low temperature cooling processing, which realizes stable control of liquid nitrogen pressure, flow, and temperature in ultra-low temperature cooling processing. The device includes a liquid nitrogen storage tank and a control device to realize the supply and control of liquid nitrogen; adopts vacuum pipelines and cold preservation measures to minimize liquid nitrogen gasification caused by pipeline heat leakage; install a pressure reducing valve at the inlet of the control device to achieve Stable control of liquid nitrogen transmission pressure; ultra-low temperature resistant Coriolis flowmeter is used to accurately measure the mass flow and mixing density of liquid nitrogen to achieve real-time discrimination and monitoring of the gas phase ratio in the pipeline; through flowmeters, level gauges, and pressure sensors , Temperature sensors and other detection units, control valves, pressure reducing valves and other execution units, as well as industrial flat panels, data acquisition cards and other control units to achieve real-time monitoring of liquid nitrogen (pressure, flow, temperature, density, reserves) and pressure and flow , Temperature control: The design of the device conforms to the theoretical requirements of fluid dynamics, with compact structure and reasonable layout. As an independent system, it occupies a small area and is easy to move.

The technical scheme of the present invention:

An independent liquid nitrogen supply and control device for ultra-low temperature cooling processing, including a liquid nitrogen supply and transmission unit, a sensing execution unit and a control unit, wherein the liquid nitrogen supply and transmission unit includes a liquid nitrogen source and a transmission pipeline; the sensing execution unit Including various sensors and valve components, which are responsible for the detection and adjustment of liquid nitrogen status; the control unit is mainly composed of a controller and a data transmission module, which is responsible for data collection and calculation, status information display and command transmission;

The liquid nitrogen supply and transmission unit includes a trolley 1.1, a liquid nitrogen storage tank 1.2, a shut-off valve 1.3, an inlet vacuum hose 1.6, a vacuum hard tube 1.7, a hard pipe 1.8, a hard pipe two 1.9, a hard pipe three 1.10, and an outlet. End vacuum hose 1.11 and nozzle 1.12; the liquid nitrogen storage tank 1.2 is placed on the trolley 1.1 for easy movement; the top of the liquid nitrogen storage tank 1.2 is equipped with a shut-off valve 1.3 for controlling the liquid nitrogen in and out and a level gauge 1.4 for detecting the storage of liquid nitrogen ; The liquid nitrogen storage tank 1.2 is connected to the inlet side vacuum hose 1.6 through the joint 1.5, the inlet side vacuum hose 1.6 and the vacuum hard tube 1.7 are connected through flange 1.a, and the other end of the vacuum hard tube 1.7 is located inside the control cabinet 2.1 , The vertical distance from the bottom of the cabinet is 1/3 of the height of the cabinet; inside the control cabinet 2.1, the vacuum hard pipe 1.7 and the pressure reducing valve 2.2 are connected by flange two 1.b to ensure that the pressure reducing valve 2.2 is installed vertically; The other end of the pressure valve 2.2 is connected with the hard pipe 1.8 through the flange 3.c, drill a hole in the middle of the hard pipe 1.8 and extend the measuring end of the inlet pressure sensor 2.3 into the pipe, and then seal the hole; the hard pipe 1.8 The other end is connected to the flowmeter 2.4 through flange four 1.d to ensure that the flowmeter 2.4 is installed vertically; the other end of the flowmeter 2.4 is connected to the hard pipe two 1.9 through flange five 1.e, and a hole is drilled in the hard pipe two 1.9 And install the safety valve 2.5; one end of the electric control valve 2.6 is connected to the hard pipe two 1.9 through flange six 1.f, the other end is connected to the hard pipe three 1.10 through flange seven 1.g, the electric control valve 2.6 is installed vertically and passed The two bolts 1.i are fixed to the control cabinet 2.1; two holes are drilled at a certain interval on the hard pipe 3.10, and the measuring ends of the temperature sensor 2.7 and the outlet pressure sensor 2.8 are extended into the pipe in turn, and then the holes are sealed; Pipe three 1.10 is connected with the vacuum hose 1.11 at the outlet end through flange eight 1.h; the end of the vacuum hose at the outlet end 1.11 is installed with a threaded connection nozzle 1.12; all pipes except the hose are installed horizontally, and the flange is connected The surfaces are sealed with PTFE gaskets; the horizontal pipelines in the control cabinet 2.1 are insulated to form a cold insulation layer 2.9, thereby reducing the vaporization during the transmission of liquid nitrogen and ensuring the stability of pressure, flow and temperature ; The cold insulation layer 2.9 is a two-layer structure, the first layer is an aerogel cushion wrapped around the outside of the pipeline, and the second layer is a polyurethane foam filled between the outer shell of the cold insulation layer 2.9 and the aerogel cushion;

The sensing execution unit includes a liquid level gauge 1.4, a flow meter 2.4, a safety valve 2.5, an inlet pressure sensor 2.3, an outlet pressure sensor 2.8, a temperature sensor 2.7, a pressure reducing valve 2.2 and an electric regulating valve 2.6;

The control unit includes industrial flat panel 3.1, 24V power supply 3.2, relay 3.3, A/D capture card 3.4, D/A capture card 3.5, open key 3.6 and close key 3.7; the control unit is installed in the upper right area of the control cabinet 2.1 , The inside of the control unit, the control unit and the sensing execution unit are connected by wires; the open button 3.6 and the close button 3.7 are respectively connected to the relay 3.3 to control the on and off of the 220V circuit; the relay 3.3 is respectively connected to the industrial panel 3.1, the 24V power supply 3.2, Electric regulating valve 2.6 is connected to provide 220V power supply; 24V power supply 3.2 and liquid level gauge 1.4, flow meter 2.4, temperature sensor 2.7, inlet pressure sensor 2.3, outlet pressure sensor 2.8, pressure reducing valve 2.2, A/D capture card 3.4 Connect with D/A capture card 3.5 and supply power for it; industrial flat panel 3.1 is connected with A/D capture card 3.4 and D/A capture card 3.5; level gauge 1.4 converts the liquid nitrogen storage in liquid nitrogen storage tank 1.2 in real time In the same way, the flow meter 2.4 transmits the liquid nitrogen flow rate and mixing density to the industrial flat panel 3.1 in real time, and the temperature sensor 2.7 transfers the liquid nitrogen to the industrial flat panel 3.1. The real-time temperature of nitrogen is transmitted to the industrial plate 3.1, the inlet pressure sensor 2.3 transmits the real-time input pressure of liquid nitrogen to the industrial plate 3.1, and the outlet pressure sensor 2.8 transmits the real-time output pressure of liquid nitrogen to the industrial plate 3.1; the industrial plate 3.1 realizes real-time data processing and Real-time display of numerical value and change curve. At the same time, the inlet pressure value and valve opening value can be input in the industrial flat panel 3.1, and converted into analog quantity by D/A acquisition card 3.5, and the analog quantity is transmitted to the pressure reducing valve 2.2 With the electric regulating valve 2.6, it realizes the adjustment of liquid nitrogen pressure, flow and temperature; the pressure reducing valve 2.2 can also stabilize the pressure in addition to regulating the pressure of liquid nitrogen; the valve port opening value h of the electric regulating valve 2.6 and the liquid The relationship between the nitrogen flow rate q is:

In the formula, K _vs is the rated flow coefficient of the regulating valve, S is the density ratio of liquid nitrogen to water, and △P is the pressure difference before and after the regulating valve;

When implementing liquid nitrogen supply and control, first press the open button 3.6 to ensure that the control device is powered on, and then adjust the valve opening value of the electric control valve 2.6 to the maximum to ensure the smooth flow of the transmission pipeline and reduce the pre-cooling of the pipeline After time, unscrew the shut-off valve 1.3 on the liquid nitrogen storage tank 1.2, and the liquid nitrogen is sprayed from the nozzle 1.12 through the pipeline; observe the real-time monitoring data in the industrial flat plate 3.1, and wait for the liquid nitrogen temperature to drop below -170℃ and basically After stabilization, control the pressure reducing valve 2.2 and the electric regulating valve 2.6 to adjust the pressure and flow of liquid nitrogen. At this time, the control of liquid nitrogen temperature can be realized by adjusting the flow; after the ultra-low temperature cooling process is completed, first close the shut-off valve 1.3, and then Press the close key 3.7 to ensure that the control device is powered off.

The beneficial effect of the present invention is that the transmission pipeline adopts a vacuum structure and an aerogel cushion-polyurethane foam composite cold-preservation structure to prevent the heat transfer of the external environment from causing liquid nitrogen to be converted, and to ensure the low dryness and high stable transmission of liquid nitrogen; the liquid nitrogen storage tank and A pressure reducing valve is installed between the control devices to solve the problem of unstable pressure when liquid nitrogen is output from the storage tank, and lay the foundation for the stable control of liquid nitrogen transmission pressure; the use of ultra-low temperature resistant Coriolis flowmeter solves the problem of liquid nitrogen The problem of inaccurate flow measurement due to gasification, and real-time monitoring of the proportion of liquid nitrogen in the pipeline, which provides a basis for the adjustment of pressure, flow or heat insulation structure; the monitoring interface can display liquid nitrogen temperature, flow, and inlet pressure at the same time , Real-time values of outlet pressure, mixing density, and tank storage, as well as real-time change curves of temperature, flow, and outlet pressure, to achieve comprehensive monitoring and control of the supply and transmission status of liquid nitrogen; the device has a compact structure, a reasonable layout, and an area The advantages of small area and convenient movement.

Description of the drawings

Figure 1 is a schematic diagram of the structure of a liquid nitrogen supply and control device;

Figure 2 is a schematic diagram of the circuit connection between the sensing execution unit and the control unit;

Figure 3 is a schematic diagram of the control software interface;

Figure 4 shows the real-time change curve of liquid nitrogen temperature;

Figure 5 shows the real-time change curve of liquid nitrogen outlet pressure;

Figure 6 shows the real-time change curve of liquid nitrogen flow.

In the picture: 1.1-trolley; 1.2-liquid nitrogen storage tank; 1.3-stop valve; 1.4-level gauge; 1.5-connector; 1.6-inlet vacuum hose; 1.7-vacuum hard tube; 1.8-hard tube one; 1.9 -Rigid pipe two; 1.10- Rigid pipe three; 1.11-vacuum hose at the outlet end; 1.12-nozzle; 1.a-flange one; 1.b-flange two; 1.c-flange three; 1.d -Flange four; 1.e-flange five; 1.f-flange six; 1.g-flange seven; 1.h-flange eight; 1.i-bolt; 2.1-control cabinet; 2.2- Pressure reducing valve; 2.3-inlet pressure sensor; 2.4-flowmeter; 2.5-safety valve; 2.6-electric regulating valve; 2.7-temperature sensor; 2.8-outlet pressure sensor; 2.9-cold insulation layer; 3.1-industrial flat panel; 3.2-24V Power supply; 3.3-relay; 3.4-A/D acquisition card; 3.5-D/A acquisition card; 3.6-open key; 3.7-close key.

detailed description

The specific embodiments of the present invention will be described in detail below with reference to the drawings and technical solutions.

In this embodiment, the liquid nitrogen storage tank 1.2 is a DPL high-pressure series dewar, with a nominal pressure of 2.3 MPa, a maximum filling mass of 133 kg (effective volume 165L), and an external dimension of φ505×1540 mm; the liquid nitrogen storage tank 1.2 is The output liquid nitrogen temperature is -196℃; the maximum load of the cart 1.1 is 300kg; the display range of the liquid level gauge 1.4 is 0～165L; the inner diameter of the inlet end vacuum hose 1.6 and the outlet end vacuum hose 1.11 are 5mm and outer diameter It is 40mm; the inner and outer diameters of the vacuum hard tube 1.7 and the hard tube-1.8 are 5mm and 35mm, and the material is 304 stainless steel; the nozzle 1.12 has an inner diameter of 2mm; the length, width and height of the control cabinet 2.1 is 1100×570×1280mm; The working range of the pressure valve 2.2 is 0.1～1.6MPa; the pressure relief threshold of the safety valve 2.5 is 1.8MPa; the range of the flow meter 2.4 is 0～81kg/h, the measurement accuracy is ±0.1% FS, and the medium temperature range is -200～350 ℃; The range of inlet pressure sensor 2.3 and outlet pressure sensor 2.8 is 0～1.6MPa, and the measurement accuracy is ±0.5% FS; the range of temperature sensor 2.7 is -200～50℃; the adjustment range of electric regulating valve 2.6 is 0～100kg /h, the rated flow coefficient K _vs is 0.12; the above-mentioned sensor output and actuator input are both 4-20mA signals; the cold insulation layer 2.9 shell is made of stainless steel, the radius is 100mm, the thickness of the aerogel pad is 10mm, and the thermal conductivity is 0.009 W/(m·K), the thermal conductivity of polyurethane foam is 0.02W/(m·K); the industrial panel 3.1 model is IPPC-6172A; the A/D capture card 3.4 is 16 inputs, and the D/A capture card 3.5 is 8 Road output.

The installation process of the independent liquid nitrogen supply and control device is as follows: As shown in Figures 1 and 2, the first step is to place the liquid nitrogen storage tank 1.2 filled with liquid nitrogen on the trolley 1.1, and use the connector 1.5 to enter and exit the liquid nitrogen storage tank 1.2 The liquid port is connected with the threaded end of the vacuum hose 1.6 at the inlet end and sealed with raw tape;

The second step is to install vacuum hard pipe 1.7, pressure reducing valve 2.2, hard pipe one 1.8, flow meter 2.4, hard pipe two 1.9, electric regulating valve 2.6 and hard pipe three in sequence from right to left inside the control cabinet 2.1. 1.10, where the free ends of the vacuum hard tube 1.7 and the hard tube 1.10 extend out of the control cabinet 2.1, the pressure reducing valve 2.2 and the electric regulating valve 2.6 ensure vertical installation; the connection between the two is flanged, followed by Flange two 1.b, flange three 1.c, flange four 1.d, flange five 1.e, flange six 1.f and flange seven 1.g, the middle of the flange is made of PTFE The gasket is sealed and the pipeline level is ensured. Then use two bolts 1.i to fix the electric regulating valve 2.6 and the control cabinet 2.1; finally, connect the flange end of the inlet end vacuum hose 1.6 to the vacuum through flange 1.a Connect the outer end of the hard pipe 1.7, connect the outer end of the hard pipe three 1.10 with the flange end of the outlet end vacuum hose 1.11 through the flange 8 1.h, and install the nozzle 1.12 on the outlet end vacuum hose by threaded connection 1.11 end;

The third step is to extend the measuring end of the inlet pressure sensor 2.3 into the pre-drilled hole of the hard pipe 1.8, and then seal the hole; similarly, install the safety valve 2.5 in the outer wall of the hard pipe 1.9, from the right to the On the left, extend the measuring ends of the temperature sensor 2.7 and the outlet pressure sensor 2.8 into the hole of the hard pipe three 1.10, and then seal the hole; after the pipeline and the sensing actuator are installed and ensure that there is no leakage, in the hard pipe one 1.8. The outer wall of the hard pipe two 1.9 and the hard pipe three 1.10 are covered with a 10mm thick aerogel cushion, and then the outer shell of the cold insulation layer 2.9 is installed in the pipeline, and the interior is filled with polyurethane foam;

The fourth step is to fix the industrial panel 3.1, 24V power supply 3.2, relay 3.3, A/D capture card 3.4, D/A capture card 3.5, open key 3.6 and close key 3.7 in a certain order in the upper right corner of the control cabinet 2.1; The schematic diagram of the circuit connection in Figure 2 uses wires to connect the control unit and the sensing execution unit, and installs the control software in the industrial panel 3.1;

The implementation process of liquid nitrogen supply and regulation is as follows: As shown in Figure 3, the first step is to press the open button 3.6 to power on the control device, turn on the industrial panel 3.1 and start the control software; adjust the valve opening of the electric control valve 2.6 Adjust the value to 100% to ensure the smooth flow of the transmission pipeline and reduce the pre-cooling time of the pipeline; unscrew the shut-off valve 1.3 on the liquid nitrogen storage tank 1.2, and the liquid nitrogen will be sprayed from the nozzle 1.12 through the pipeline; The pressure reducing valve 2.2 is adjusted to 0.6MPa as the inlet pressure of liquid nitrogen; after about 25 minutes, the temperature of liquid nitrogen drops to below -170℃, and the range of change is gradually reduced. At this time, the transmission of liquid nitrogen is basically stable and the pre-cooling is completed;

The second step is to set the valve port opening value h of the electric control valve 2.6 to 39%, and observe the real-time value of the state in the control software. At this time, the liquid nitrogen outlet pressure is 0.45MPa, the liquid nitrogen temperature is -182℃, and the liquid nitrogen The mixing density is 780kg/m ³ , so the density ratio of liquid nitrogen to water S=0.78, the pressure difference before and after the regulating valve is △P=0.15MPa, and the liquid nitrogen flow rate q=32.4kg/h can be calculated according to formula (1). The real-time change curves of nitrogen temperature, outlet pressure and flow rate are shown in Figures 4, 5 and 6; it ^{can be seen from the liquid nitrogen mixing density of 780kg/m 3} that the gas content of liquid nitrogen at this time is 3.8%, which is a bubbly flow ；

The third step is to implement ultra-low temperature cooling processing with the above-mentioned liquid nitrogen temperature, pressure, and flow as cooling parameters. After processing is completed, first close the shut-off valve 1.3, then close the industrial plate 3.1, and finally press the close button 3.7 to ensure that the control device is powered off.

The invention effectively guarantees the stability of the pressure, flow, temperature and other states in the liquid nitrogen transmission through cold-preservation measures and the pressure-stabilizing effect of the pressure reducing valve; through a series of sensors and adjustment control elements, the multi-transmission state of liquid nitrogen is realized Real-time monitoring and control; the independent and movable design of the device provides support for the ultra-low temperature cooling processing of ordinary machine tools.

Claims

An independent liquid nitrogen supply and control device for ultra-low temperature cooling processing, characterized in that the independent liquid nitrogen supply and control device includes a liquid nitrogen supply and transmission unit, a sensing execution unit and a control unit, wherein the liquid nitrogen supply and transmission unit Including the liquid nitrogen source and transmission pipeline; the sensing execution unit includes various sensors and valve components, which are responsible for the detection and adjustment of the liquid nitrogen state; the control unit is mainly composed of a controller and a data transmission module, which is responsible for data collection and operation and status Information display and command transmission;

The liquid nitrogen supply and transmission unit includes a trolley (1.1), a liquid nitrogen storage tank (1.2), a shut-off valve (1.3), an inlet vacuum hose (1.6), a vacuum hard tube (1.7), and a hard tube (1.8) , Hard tube two (1.9), hard tube three (1.10), vacuum hose (1.11) and nozzle (1.12) at the outlet end; liquid nitrogen storage tank (1.2) is placed on a trolley (1.1) for easy movement; liquid nitrogen storage The top of the tank (1.2) is equipped with a shut-off valve (1.3) for controlling the in and out of liquid nitrogen and a level gauge (1.4) for detecting the storage of liquid nitrogen; the liquid nitrogen storage tank (1.2) is connected to the vacuum hose (1.5) at the inlet end through a joint (1.5). 1.6) Connection, the inlet end of the vacuum hose (1.6) and the vacuum hard tube (1.7) are connected through flange one (1.a), and the other end of the vacuum hard tube (1.7) is located inside the control cabinet (2.1), vertical The upper distance from the bottom of the cabinet is 1/3 of the cabinet height; inside the control cabinet (2.1), the vacuum hard tube (1.7) and the pressure reducing valve (2.2) are connected through flange two (1.b) to ensure that the pressure reducing valve (2.2) ) Vertical installation; the other end of the pressure reducing valve (2.2) is connected to the hard pipe one (1.8) through the flange three (1.c), a hole is drilled in the middle of the hard pipe one (1.8) and the inlet pressure sensor (2.3) The measuring end extends into the pipe, and then the hole is sealed; the other end of the hard pipe (1.8) is connected to the flow meter (2.4) through the flange 4 (1.d) to ensure that the flow meter (2.4) is installed vertically; 2.4) The other end is connected to the second pipe (1.9) through flange five (1.e), the second end of the pipe (1.9) is drilled and the safety valve (2.5) is installed; one end of the electric regulating valve (2.6) is through the flange Six (1.f) is connected to the second pipe (1.9), and the other end is connected to the third pipe (1.10) through flange seven (1.g). The electric regulating valve (2.6) is installed vertically and passed two bolts ( 1.i) Fix it in the control cabinet (2.1); drill two holes at a certain interval on the third pipe (1.10), and extend the measuring ends of the temperature sensor (2.7) and the outlet pressure sensor (2.8) into the pipe in turn, and then Seal the hole; the third pipe (1.10) is connected to the vacuum hose (1.11) at the outlet end through flange eight (1.h); the end of the vacuum hose (1.11) at the outlet end is screwed to install the nozzle (1.12); All pipelines except hoses are installed horizontally, and the joint surface in the middle of the flange is sealed with PTFE gaskets; the horizontal pipelines in the control cabinet (2.1) are insulated to form a cold insulation layer (2.9), So as to reduce the gasification during the transmission of liquid nitrogen and ensure the stability of pressure, flow and temperature;

The sensing execution unit includes a level gauge (1.4), a flow meter (2.4), a safety valve (2.5), an inlet pressure sensor (2.3), an outlet pressure sensor (2.8), a temperature sensor (2.7), and a pressure reducing valve (2.2) and electric control valve (2.6);

The control unit includes industrial flat panel (3.1), 24V power supply (3.2), relay (3.3), A/D acquisition card (3.4), D/A acquisition card (3.5), open button (3.6) and close button ( 3.7); The control unit is installed in the upper right area of the control cabinet (2.1). The inside of the control unit and between the control unit and the sensing execution unit are connected by wires; the open button (3.6) and the close button (3.7) are respectively connected with the relay (3.3) ) Connection to control the on-off of the 220V circuit; the relay (3.3) is connected to the industrial panel (3.1), 24V power supply (3.2), and electric regulating valve (2.6) to provide 220V power supply; 24V power supply (3.2) and liquid level Meter (1.4), flow meter (2.4), temperature sensor (2.7), inlet pressure sensor (2.3), outlet pressure sensor (2.8), pressure reducing valve (2.2), A/D capture card (3.4) and D/A The acquisition card (3.5) is connected and power is supplied; the industrial flat panel (3.1) is connected with the A/D acquisition card (3.4) and the D/A acquisition card (3.5); the level gauge (1.4) connects the liquid nitrogen storage tank (1.2) The liquid nitrogen storage in) is converted into an analog signal in real time, which is converted into a digital signal through the A/D acquisition card (3.4) and transmitted to the industrial panel (3.1); in the same way, the flow meter (2.4) compares the flow of liquid nitrogen with The mixing density is transmitted to the industrial plate (3.1) in real time, the temperature sensor (2.7) transmits the real-time temperature of liquid nitrogen to the industrial plate (3.1), the inlet pressure sensor (2.3) transmits the real-time input pressure of liquid nitrogen to the industrial plate (3.1), and the outlet The pressure sensor (2.8) transmits the real-time output pressure of liquid nitrogen to the industrial flat panel (3.1); the industrial flat panel (3.1) realizes real-time data processing and real-time display of values and change curves, and can input settings in the industrial flat panel (3.1) The inlet pressure value and the valve port opening value are converted into analog quantities through the D/A acquisition card (3.5), and the analog quantities are transmitted to the pressure reducing valve (2.2) and the electric regulating valve (2.6) to realize the pressure and flow of liquid nitrogen And temperature adjustment; in addition to regulating the pressure of liquid nitrogen, the pressure reducing valve (2.2) can also play a role in stabilizing the pressure; the relationship between the valve port opening value h of the electric regulating valve (2.6) and the liquid nitrogen flow q is:

In the formula, K vs is the rated flow coefficient of the regulating valve, S is the density ratio of liquid nitrogen to water, and △P is the pressure difference before and after the regulating valve;

When implementing liquid nitrogen supply and control, first press the open button (3.6) to ensure that the control device is powered on, and then adjust the valve opening value of the electric control valve (2.6) to the maximum to ensure that the transmission pipeline is unblocked while reducing The pipeline pre-cooling time, then unscrew the shut-off valve (1.3) on the liquid nitrogen storage tank (1.2), the liquid nitrogen is sprayed from the nozzle (1.12) through the pipeline; observe the real-time monitoring data in the industrial flat panel (3.1), After waiting for the temperature of the liquid nitrogen to drop below -170℃ and it is basically stable, control the pressure reducing valve (2.2) and the electric regulating valve (2.6) to adjust the pressure and flow rate of the liquid nitrogen. At this time, the liquid nitrogen temperature can be adjusted by adjusting the flow rate. To achieve; after the ultra-low temperature cooling process is completed, first close the shut-off valve (1.3), and then press the close button (3.7) to ensure that the control device is powered off.
The independent liquid nitrogen supply and control device for ultra-low temperature cooling processing according to claim 1, characterized in that the cold insulation layer (2.9) is a double-layer structure, and the first layer is a gas condensate that is wrapped on the outside of the pipeline. The rubber pad, the second layer is the polyurethane foam filled between the outer shell of the cold insulation layer (2.9) and the aerogel pad.