阅读说明：本技术 一种液氮蒸发制冷大流量全新风空气补偿系统 (Liquid nitrogen evaporation refrigeration large-flow fresh air compensation system ) 是由 马建军 王彬文 吴敬涛 都亚鹏 杜文辉 许天龙 吴学敏 姜亚军 于 2021-08-16 设计创作，主要内容包括：本申请属于实验室气候环境适应性分析与试验技术领域,特别涉及一种液氮蒸发制冷大流量全新风空气补偿系统。包括：箱体,液氮蒸发制冷模块,控制模块。所述箱体内部具有补偿风道；所述液氮蒸发制冷模块包括液氮换热器,以及与所述液氮换热器相适配的水冲霜装置和液氮排放装置；其中,所述补偿风道从进风口至出风口依次设置有滤网、补偿风机、所述液氮换热器以及风阀；所述控制模块用于实现对所述液氮蒸发制冷模块、所述补偿风机以及所述风阀的控制。本申请的液氮蒸发制冷大流量全新风空气补偿系统,能够应用于大型综合气候实验室极端低温下的民用飞机发动机的起动试验；还具有可靠性和安全性高、可控性好、配置灵活等优点。(The application belongs to the technical field of laboratory climatic environment adaptability analysis and test, and particularly relates to a liquid nitrogen evaporation refrigeration large-flow fresh air compensation system. The method comprises the following steps: the device comprises a box body, a liquid nitrogen evaporation and refrigeration module and a control module. A compensation air duct is arranged inside the box body; the liquid nitrogen evaporation and refrigeration module comprises a liquid nitrogen heat exchanger, and a water defrosting device and a liquid nitrogen discharging device which are matched with the liquid nitrogen heat exchanger; the compensation air duct is sequentially provided with a filter screen, a compensation fan, the liquid nitrogen heat exchanger and an air valve from the air inlet to the air outlet; the control module is used for controlling the liquid nitrogen evaporation refrigeration module, the compensation fan and the air valve. The liquid nitrogen evaporation refrigeration high-flow full fresh air compensation system can be applied to the starting test of the civil aircraft engine under the extremely low temperature of a large-scale comprehensive climate laboratory; the system also has the advantages of high reliability and safety, good controllability, flexible configuration and the like.)

1. The utility model provides a large-traffic new wind air compensation system of liquid nitrogen evaporation refrigeration which characterized in that includes:

the box body is internally provided with a compensation air duct;

the liquid nitrogen evaporation and refrigeration module comprises a liquid nitrogen heat exchanger, and a water defrosting device and a liquid nitrogen discharging device which are matched with the liquid nitrogen heat exchanger;

the compensation air duct is sequentially provided with a filter screen, a compensation fan, the liquid nitrogen heat exchanger and an air valve from the air inlet to the air outlet;

and the control module is used for controlling the liquid nitrogen evaporation and refrigeration module, the compensation fan and the air valve.

2. The liquid nitrogen evaporation refrigeration high-flow fresh air compensation system according to claim 1, wherein the box body is made of a 150mm thick PIR polyvinyl chloride insulation board.

3. The liquid nitrogen evaporation refrigeration large-flow fresh air compensation system according to claim 2, wherein access doors are arranged on the box bodies on the air inlet side and the air outlet side of the liquid nitrogen heat exchanger, the access doors are made of PIR (Polychloroethyl carbonate) insulation boards with the thickness of 150mm, and an electric tracing band is arranged on a door frame of each access door.

4. The liquid nitrogen evaporation refrigeration high-flow fresh air compensation system according to claim 1, wherein the liquid nitrogen heat exchanger is a finned tube heat exchanger and comprises a 316L stainless steel heat exchange tube and a 8011 aluminum alloy fin.

5. The liquid nitrogen evaporative refrigeration high-flow fresh air compensation system as claimed in claim 4, wherein a plurality of liquid nitrogen heat exchangers are arranged in series.

6. The liquid nitrogen evaporative refrigeration large-flow fresh air compensation system according to claim 5, wherein the plurality of liquid nitrogen heat exchangers are respectively connected with the liquid nitrogen tanker through liquid nitrogen liquid inlet pipelines, and liquid nitrogen switch valves and liquid nitrogen regulating valves are arranged on the liquid nitrogen liquid inlet pipelines.

7. The liquid nitrogen evaporation refrigeration high-flow all fresh air compensation system according to claim 6, wherein a dehumidification heat exchanger is arranged on the windward side of a plurality of liquid nitrogen heat exchangers arranged in series, the dehumidification heat exchanger is a variable-fin-pitch heat exchanger, and the fin pitches from the windward side to the leeward side are 20mm, 16mm and 9mm in sequence.

8. The liquid nitrogen evaporative cooling high flow fresh air compensation system as claimed in claim 7, wherein said water defrosting device comprises a water collection tank, a spray pipe and a defrosting water discharge pipe, wherein,

the water collection tank is provided with normal-temperature water;

the spraying pipeline is arranged above the liquid nitrogen heat exchanger, one end of the spraying pipeline is connected with the water collecting tank, the spraying pipeline is provided with electromagnetic valves, small holes which are uniformly distributed are formed in the spraying pipeline, and normal-temperature water is sprayed to the liquid nitrogen heat exchanger through the spraying pipeline;

the defrosting water discharge pipeline is connected with a water outlet arranged on the box body at the lower part of the compensation air duct.

9. The liquid nitrogen evaporative refrigeration large-flow fresh air compensation system as claimed in claim 8, wherein the liquid nitrogen discharge device comprises a nitrogen gas collecting pipeline and a nitrogen gas discharge tower, nitrogen gas flowing out of the liquid nitrogen heat exchanger enters the nitrogen gas discharge tower through the nitrogen gas collecting pipeline, and a dilution fan is arranged at the bottom of the nitrogen gas discharge tower and used for forced ventilation of the nitrogen gas discharge tower.

10. The liquid nitrogen evaporation refrigeration high-flow fresh air compensation system according to claim 9, wherein the control module comprises a PLC controller, a pitot tube, a differential pressure transmitter, a temperature sensor, a flowmeter and an upper computer, wherein,

the pitot tube is arranged at the center of the air outlet side of the compensation fan and is used for being matched with the differential pressure transmitter to realize real-time monitoring of air quantity;

the temperature sensor is arranged on the air outlet side of the liquid nitrogen heat exchanger and used for realizing real-time monitoring of the air temperature;

the flow meter is arranged on the liquid nitrogen inlet pipeline and is used for realizing real-time monitoring of the flow of liquid nitrogen entering the liquid nitrogen heat exchanger;

the PLC is used for acquiring signals of the pitot tube, the differential pressure transmitter, the temperature sensor and the flowmeter and controlling the compensation fan, the liquid nitrogen switch valve, the liquid nitrogen regulating valve, the electromagnetic valve, the dilution fan and the air valve;

the upper computer is used for realizing setting and state display of test process parameters.

Technical Field

The application belongs to the technical field of laboratory climatic environment adaptability analysis and test, and particularly relates to a liquid nitrogen evaporation refrigeration large-flow fresh air compensation system.

Background

The large-scale comprehensive climate laboratory can simulate the climate environments on the earth surface such as extreme low temperature, high temperature, damp and hot, snowfall, solar irradiation, ice and rain accumulation, rain drenching, freezing fog and the like, and the size of the large-scale comprehensive climate laboratory can meet the climate test requirements of large-scale equipment or complete machines. Of all the test items for an aircraft, the starting and working tests of engines under extreme climatic conditions are one of the most important assessment items. The method is characterized in that an aircraft engine starting test at an extremely low temperature is carried out in a closed space of an aircraft climate environment laboratory, and high-temperature tail gas of the aircraft engine needs to be discharged out of the laboratory, and the test is realized through an engine tail gas discharge system. Meanwhile, low-temperature air with the emission equivalent to that of an engine tail gas emission system needs to be supplemented into the laboratory, so that the air quality in the laboratory is guaranteed to be unchanged or the indoor pressure is stable, the test temperature is stable, and the test safety is guaranteed, which is realized through an air compensation system.

At present, only the american maijin laboratory and the korean ADD laboratory are equipped with engine start tests for the whole aircraft in various laboratory extreme climate environments worldwide. The main environmental chamber of the makini climate laboratory in the united states has an effective size of 76.2m wide, 61m deep and 22.8m mid-height, and an additional small environmental chamber of 18.3m x 26.0m is used for accommodating the tail of a very large aircraft such as a C-5 aircraft, and the cold energy provided by the refrigeration system when supplementing cold air is stored by two stages of secondary refrigerants, wherein the primary refrigerant is calcium chloride solution, the external air is dehumidified by heat exchange and the gas temperature is reduced to 4.4 ℃, the secondary refrigerant is dichloromethane, the gas temperature can be reduced from 4.4 ℃ to-54 ℃ by heat exchange, and the supplemented hot air is provided by heat exchange with the air in a heat exchanger by steam generated by a natural gas boiler. The test space of the korean ADD laboratory was 42m × 30m × 21 m. The flow rate of the matched air compensation system is 225kg/s, the cold energy stored every 24 hours can provide cold air consumption for 30 minutes of continuous running of the engine within the range of-18 ℃ to +54 ℃, the basic principle of the air compensation system is basically the same as that of a Macjinli laboratory, and the air compensation system adopts the cold accumulation/heat accumulation technology to indirectly process and compensate air. The problems of low refrigeration efficiency, low configuration flexibility and high cost exist in the prior art.

Accordingly, a technical solution is desired to overcome or at least alleviate at least one of the above-mentioned drawbacks of the prior art.

Disclosure of Invention

The application aims to provide a liquid nitrogen evaporation refrigeration large-flow fresh air compensation system to solve at least one problem in the prior art.

The technical scheme of the application is as follows:

a liquid nitrogen evaporation refrigeration large-flow fresh air compensation system comprises:

the box body is internally provided with a compensation air duct;

the liquid nitrogen evaporation and refrigeration module comprises a liquid nitrogen heat exchanger, and a water defrosting device and a liquid nitrogen discharging device which are matched with the liquid nitrogen heat exchanger;

the compensation air duct is sequentially provided with a filter screen, a compensation fan, the liquid nitrogen heat exchanger and an air valve from the air inlet to the air outlet;

and the control module is used for controlling the liquid nitrogen evaporation and refrigeration module, the compensation fan and the air valve.

In at least one embodiment of this application, the box adopts 150mm thick PIR polyvinyl chloride heated board preparation to form.

In at least one embodiment of this application, all be provided with the access door on the box of liquid nitrogen heat exchanger's the air-supply side and air-out side, the access door adopts the thick PIR polyvinyl chloride heated board of 150mm to make and forms, just be provided with the electric tracing area on the door frame of access door.

In at least one embodiment of the present application, the liquid nitrogen heat exchanger is a finned tube heat exchanger, and includes a heat exchange tube made of 316L stainless steel and a fin made of 8011 aluminum alloy.

In at least one embodiment of the present application, the liquid nitrogen heat exchangers are arranged in series.

In at least one embodiment of the application, a plurality of the liquid nitrogen heat exchangers are respectively connected with the liquid nitrogen tank wagon through liquid nitrogen liquid inlet pipelines, and liquid nitrogen switch valves and liquid nitrogen regulating valves are arranged on the liquid nitrogen liquid inlet pipelines.

In at least one embodiment of the application, a dehumidifying heat exchanger is arranged on the windward side of a plurality of liquid nitrogen heat exchangers arranged in series, the dehumidifying heat exchanger is a variable-fin-pitch heat exchanger, and the fin pitch from the windward side to the leeward side is 20mm, 16mm and 9mm in sequence.

In at least one embodiment of the present application, the water defrosting device includes a water collecting tank, a spray pipe, and a defrosting water discharging pipe, wherein,

the water collection tank is provided with normal-temperature water;

the spraying pipeline is arranged above the liquid nitrogen heat exchanger, one end of the spraying pipeline is connected with the water collecting tank, the spraying pipeline is provided with electromagnetic valves, small holes which are uniformly distributed are formed in the spraying pipeline, and normal-temperature water is sprayed to the liquid nitrogen heat exchanger through the spraying pipeline;

the defrosting water discharge pipeline is connected with a water outlet arranged on the box body at the lower part of the compensation air duct.

In at least one embodiment of this application, liquid nitrogen discharging equipment includes nitrogen gas collection pipeline and nitrogen gas discharge tower, the nitrogen gas that the liquid nitrogen heat exchanger flowed out passes through the nitrogen gas collection pipeline gets into the nitrogen gas discharge tower, nitrogen gas discharge tower bottom is provided with the dilution fan for to nitrogen gas exhaust tower forced draft.

In at least one embodiment of the present application, the control module comprises a PLC controller, a pitot tube, a differential pressure transmitter, a temperature sensor, a flow meter, and an upper computer, wherein,

the pitot tube is arranged at the center of the air outlet side of the compensation fan and is used for being matched with the differential pressure transmitter to realize real-time monitoring of air quantity;

the temperature sensor is arranged on the air outlet side of the liquid nitrogen heat exchanger and used for realizing real-time monitoring of the air temperature;

the flow meter is arranged on the liquid nitrogen inlet pipeline and is used for realizing real-time monitoring of the flow of liquid nitrogen entering the liquid nitrogen heat exchanger;

the PLC is used for acquiring signals of the pitot tube, the differential pressure transmitter, the temperature sensor and the flowmeter and controlling the compensation fan, the liquid nitrogen switch valve, the liquid nitrogen regulating valve, the electromagnetic valve, the dilution fan and the air valve;

the upper computer is used for realizing setting and state display of test process parameters.

The invention has at least the following beneficial technical effects:

the application discloses large-traffic new wind air compensation system of liquid nitrogen evaporation refrigeration: the test device can be applied to the starting test of civil aircraft engines under the extreme low temperature in large-scale comprehensive climate laboratories, particularly can meet the starting test of aircraft engines with smaller discharge amount of an engine tail gas discharge system, can directly cool outdoor air of 50kg/s at most to-50 ℃ and then send the outdoor air into the laboratories so as to compensate the laboratory air discharged by the operation of the aircraft engines under the extreme low temperature environment of the laboratories, and ensure the test conditions and the test safety; the system also has the advantages of high reliability and safety, good controllability, flexible configuration and the like.

Drawings

FIG. 1 is a schematic diagram of a liquid nitrogen evaporative refrigeration high flow fresh air compensation system according to an embodiment of the present application;

FIG. 2 is a schematic diagram of a liquid nitrogen evaporative refrigeration module according to one embodiment of the present application.

Wherein:

1-a box body; 2-filtering the screen; 3-a compensation fan; 4-liquid nitrogen heat exchanger; 5-an air valve; 6-nitrogen gas discharge tower; 7-a pitot tube; 8-temperature sensor.

Detailed Description

In order to make the implementation objects, technical solutions and advantages of the present application clearer, the technical solutions in the embodiments of the present application will be described in more detail below with reference to the drawings in the embodiments of the present application. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The described embodiments are a subset of the embodiments in the present application and not all embodiments in the present application. The embodiments described below with reference to the drawings are exemplary and intended to be used for explaining the present application and should not be construed as limiting the present application. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application. Embodiments of the present application will be described in detail below with reference to the accompanying drawings.

In the description of the present application, it is to be understood that the terms "center", "longitudinal", "lateral", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate orientations or positional relationships based on those shown in the drawings, and are used merely for convenience in describing the present application and for simplifying the description, and do not indicate or imply that the referenced device or element must have a particular orientation, be constructed in a particular orientation, and be operated, and therefore should not be construed as limiting the scope of the present application.

The present application is described in further detail below with reference to fig. 1-2.

The application provides a large-traffic new wind air compensation system of liquid nitrogen evaporation refrigeration, includes: the device comprises a box body, a liquid nitrogen evaporation and refrigeration module and a control module.

As shown in fig. 1, a compensation air duct is arranged inside the box body 1, and the liquid nitrogen evaporation and refrigeration module comprises a liquid nitrogen heat exchanger 4, a water defrosting device and a liquid nitrogen discharging device. The compensation air duct is sequentially provided with a filter screen 2, a compensation fan 3, a liquid nitrogen heat exchanger 4 and an air valve 5 from an air inlet to an air outlet, outdoor air is subjected to air impurity removal through the filter screen 2, and is sent into a laboratory after being subjected to dehumidification and cooling through the liquid nitrogen heat exchanger 4 driven by the fan. The control module is used for controlling the liquid nitrogen evaporation refrigeration module, the compensation fan 3 and the air valve 5. The compensation fan 3 is preferably a variable frequency fan, and the air quantity requirement is met by adjusting the rotating speed of the fan.

In the preferred embodiment of this application, box 1 adopts 150mm thick PIR polyvinyl chloride heated board preparation to form. In order to facilitate maintenance, the box bodies 1 on the air inlet side and the air outlet side of the liquid nitrogen heat exchanger 4 are respectively provided with an access door, the access doors are made of PIR polyvinyl chloride insulation boards with the thickness of 150mm, and a door frame of each access door is provided with an electric tracing band for heat preservation.

The large-flow full fresh air compensation system for liquid nitrogen evaporative refrigeration, the liquid nitrogen heat exchanger 4 is a fin tube type heat exchanger, wherein the heat exchange tube is made of 316L stainless steel materials, and the fins are made of 8011 aluminum alloy so as to bear extreme low temperature and rapid temperature change. In this embodiment, the liquid nitrogen heat exchanger 4 is in a form of a manifold structure, that is, after liquid nitrogen enters the capillary tube connected with the heat exchange tube through the manifold, the liquid nitrogen absorbs heat in the heat exchange tube and evaporates to cool air.

Advantageously, in this embodiment, in order to achieve an extremely low temperature while avoiding an excessive pressure drop in the pipe, the liquid nitrogen heat exchangers 4 are connected in series.

Advantageously, in the present embodiment, in order to avoid frosting of the humid air on the surface of the heat exchanger and reduce the efficiency and the air circulation area of the heat exchanger, one dehumidifying heat exchanger is arranged on the windward side of the plurality of liquid nitrogen heat exchangers 4 arranged in series. This dehumidification heat exchanger is the variable pitch heat exchanger, and the fin interval from windward side to leeward side is 20mm, 16mm, 9mm in proper order for carry out dehumidification in advance to the incoming flow air, can not seriously influence the air flow area because the heat exchanger surface frosts, cause compensation air mass flow decay serious, reduce the frosting rate of follow-up heat exchanger, guarantee heat transfer ability.

In the preferred embodiment of the present application, as shown in fig. 2, a liquid nitrogen tank car is used to supply liquid nitrogen to a plurality of liquid nitrogen heat exchangers 4, a liquid nitrogen switching valve and a liquid nitrogen regulating valve are arranged on a liquid nitrogen inlet pipeline of the liquid nitrogen heat exchangers 4, the liquid nitrogen switching valve can be a manual or automatic switching valve, the liquid nitrogen regulating valve can be an electric or pneumatic regulating valve, and in order to prevent the valves from freezing, the valves are all extreme low temperature resistant valves.

According to the liquid nitrogen evaporation refrigeration high-flow fresh air compensation system, the water defrosting device comprises a water collecting tank, a spraying pipeline and a defrosting water discharging pipeline, wherein normal-temperature water is arranged in the water collecting tank, tap water is connected to the upper end of the water collecting tank for water supplement, the water collecting tank can be omitted, and the tap water is directly connected to the water collecting tank; the spraying pipeline is arranged above the liquid nitrogen heat exchanger, one end of the spraying pipeline is connected with the water collecting tank, the spraying pipeline is provided with electromagnetic valves, small holes which are uniformly distributed are formed in the spraying pipeline, and when the liquid nitrogen heat exchanger 4 is frosted seriously, normal-temperature water is sprayed to the liquid nitrogen heat exchanger through the spraying pipeline, so that the heat exchanger is defrosted quickly; the defrosting water discharge pipeline is connected with a water outlet arranged on the box body at the lower part of the compensation air duct, and the defrosting water is discharged through the defrosting water discharge pipeline.

According to the liquid nitrogen evaporation refrigeration large-flow fresh air compensation system, liquid nitrogen absorbs heat in the liquid nitrogen heat exchanger 4 to be evaporated and gasified, and the gasified nitrogen is collected in a concentrated mode through the discharge port and then discharged through the nitrogen discharge device. In this embodiment, liquid nitrogen discharging equipment includes nitrogen gas collection pipeline and nitrogen gas discharge tower 7, and the nitrogen gas that the liquid nitrogen heat exchanger flows out gets into nitrogen gas discharge tower 7 through nitrogen gas collection pipeline, and 7 bottoms in nitrogen gas discharge tower are provided with the dilution fan for to nitrogen gas exhaust tower forced draft, send nitrogen gas into the high altitude and discharge, prevent that the lower nitrogen gas of density from piling up on ground, endangering personnel's safety.

According to the liquid nitrogen evaporation refrigeration high-flow fresh air compensation system, the control module has the functions of air flow compensation control and temperature control, and comprises a PLC (programmable logic controller), a pitot tube 7, a differential pressure transmitter, a temperature sensor 8, a flowmeter and an upper computer, wherein the pitot tube 7 is arranged at the central position of the air outlet side of the axial flow variable frequency compensation fan 3 and is used for being matched with the differential pressure transmitter to realize real-time monitoring of air volume; the temperature sensor 8 is arranged on the air outlet side of the liquid nitrogen heat exchanger 4 and used for realizing real-time monitoring of the air temperature; the flowmeter is arranged on the liquid nitrogen inlet pipeline and used for realizing the real-time monitoring of the liquid nitrogen flow entering the liquid nitrogen heat exchanger.

In this embodiment, the PLC controller is configured to obtain signals of the pitot tube 7, the differential pressure transmitter, the temperature sensor 8, and the flow meter, and control the compensation fan 3, the liquid nitrogen switch valve, the liquid nitrogen regulating valve, the electromagnetic valve, the dilution fan, and the air valve 5. In addition, be provided with the ooff valve and the governing valve of adaptation in nitrogen gas collecting tube, shower and towards frost water discharge pipeline shanghai, the PLC controller still is used for realizing the control to these valves. In this embodiment, the PLC controller is preferably placed in a site where the PLC controller is located and is convenient for personnel to operate, the liquid crystal touch screen is configured as a human-computer interaction interface, and the PLC reserves a communication interface. According to the indication value of the temperature sensor 8 and the target temperature, the flow of liquid nitrogen is controlled by adjusting the opening of the regulating valve in real time, and then the temperature of the compensation air is controlled. In this embodiment, the plurality of liquid nitrogen heat exchangers 4 connected in series can be controlled independently or in a centralized manner, and during independent control, a temperature sensor 8 needs to be installed at the downstream of each heat exchanger to perform segmented control on the temperature of the compensation air.

In this embodiment, the host computer is used for realizing the setting and the state display of the test process parameter. The system can realize the startup and shutdown, the issuing of instructions such as target temperature and air quantity, and the display and storage of parameters such as air quantity, temperature and the rotating speed of a compensation fan through an upper computer.

Advantageously, in this embodiment, the control module has functions of local manual control and remote automatic control, and also has emergency treatment measures, and the liquid nitrogen regulating valve can be closed emergently through the emergency stop switch of the control box panel in an emergency state.

In one embodiment of the present application, in use, the operational flow is as follows:

a) before the test starts, the control module is powered on;

b) opening a liquid nitrogen inlet switch valve and a nitrogen gas discharge switch valve, and confirming that the regulating valve is in a closed state;

c) butt-jointing the liquid nitrogen tanker and a liquid nitrogen heat exchanger, and adjusting the liquid supply pressure of the liquid nitrogen tanker to about 4 Bar;

d) starting a nitrogen dilution fan;

e) opening the air valve;

f) setting a target value of the compensation air temperature, starting the compensation fan at a lower rotating speed, starting a compensation air temperature control function, and starting an air compensation system at a lower air volume;

g) after the temperature of the compensation air is basically stable, gradually increasing the rotating speed of the compensation fan until the flow and the temperature of the compensation air reach target values;

h) monitoring the compensation air flow, if the rotation speed of the compensation fan reaches the maximum value and the air flow is reduced, indicating that the liquid nitrogen heat exchanger is frosted seriously, and then carrying out defrosting operation:

1) closing the compensation fan, the liquid nitrogen regulating valve and the air valve;

2) opening a water defrosting water supply electromagnetic valve and a defrosting water discharge valve, and spraying normal-temperature water to the heat exchanger for defrosting;

3) the defrosting can be basically completely realized by spraying for 20min, and the defrosting condition can be checked through an access door;

4) after defrosting is finished, closing the water supply electromagnetic valve and the defrosting water discharge valve, and restarting the air compensation system from the step e);

i) if the liquid nitrogen heat exchanger continuously works for 30min, the heat exchanger is defrosted after the test is finished, if the total length of the intermittent working time in a short time exceeds 30min, the frosting condition of the heat exchanger is checked after the test is finished, and the heat exchanger is defrosted in due time;

j) after the test is completed, the air compensation system is closed:

1) closing the compensation fan and the liquid nitrogen regulating valve,

2) Stopping liquid supply of the liquid nitrogen tank wagon;

3) closing the air valve;

4) the nitrogen diluting fan is closed after continuously working for 10min so as to fully discharge nitrogen accumulated in the system;

5) closing the liquid nitrogen inlet switch valve and the nitrogen gas discharge switch valve;

6) the control module is powered off.

The liquid nitrogen evaporative refrigeration large-flow fresh air compensation system can directly cool normal-temperature air to the extremely-50 ℃ low temperature by utilizing the liquid nitrogen evaporative cooling effect, and air in a laboratory discharged by the operation of an aircraft engine can be compensated in a closed climate laboratory. The method and the device can be applied to the starting test of the civil aircraft engine in a large comprehensive climate laboratory at the extreme low temperature, and particularly can meet the requirement of the starting test of the aircraft engine with smaller emission of an engine tail gas emission system. The air cooling device can directly cool outdoor air of 50kg/s to 50 ℃ below zero and then send the outdoor air into a laboratory so as to compensate the air in the laboratory exhausted by the running of an aircraft engine in the extreme low-temperature environment of the laboratory, and ensure the test condition and the test safety.

The liquid nitrogen evaporation refrigeration large-flow fresh air compensation system further has the following advantages:

low cost, redundancy, reliability are high: the liquid nitrogen heat exchanger, the compensation fan and part of the control module are arranged outside the laboratory, the limitation of the placement area is small, and the space selectivity is large; each component can be repeatedly utilized, and can be repeatedly used by one-time investment; the air inlet duct has low cost, is easy to disassemble and can be recycled;

the configuration is flexible: the liquid nitrogen heat exchangers are arranged in parallel, can be additionally or additionally installed or uninstalled according to different test requirements, and meanwhile, the compensation fan can be a large-flow and high-power fan and the frequency can be adjusted according to the volume of compensation air;

the control precision is high, and is safe and environment-friendly: liquid nitrogen is used as a refrigerant, about 250kw of cold energy is provided by 1kg/s of liquid nitrogen, the liquid nitrogen supply flow and the running frequency of the axial flow variable frequency fan can be calculated according to the cold energy, the compensation air flow and the temperature are ensured to be accurately and controllably in a certain range, and meanwhile, nitrogen generated by evaporation of the liquid nitrogen is concentrated and discharged nearby high altitude, so that the harm to personnel and the environment is avoided, and the device is safe and environment-friendly;

the operation is stable, safe and reliable: in order to solve the problem of frosting of the liquid nitrogen heat exchanger, water is adopted for defrosting, and the temperature stability in the test process is ensured; and meanwhile, a plurality of tank cars are adopted to supply liquid simultaneously, so that the uniform and stable supply of liquid nitrogen in the starting process of the engine is ensured.

The above description is only for the specific embodiments of the present application, but the scope of the present application is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present application should be covered within the scope of the present application. Therefore, the protection scope of the present application shall be subject to the protection scope of the claims.