CN113844678B - Fresh air control system and control method for airplane test - Google Patents
Fresh air control system and control method for airplane test Download PDFInfo
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- CN113844678B CN113844678B CN202111454908.6A CN202111454908A CN113844678B CN 113844678 B CN113844678 B CN 113844678B CN 202111454908 A CN202111454908 A CN 202111454908A CN 113844678 B CN113844678 B CN 113844678B
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- B64F—GROUND OR AIRCRAFT-CARRIER-DECK INSTALLATIONS SPECIALLY ADAPTED FOR USE IN CONNECTION WITH AIRCRAFT; DESIGNING, MANUFACTURING, ASSEMBLING, CLEANING, MAINTAINING OR REPAIRING AIRCRAFT, NOT OTHERWISE PROVIDED FOR; HANDLING, TRANSPORTING, TESTING OR INSPECTING AIRCRAFT COMPONENTS, NOT OTHERWISE PROVIDED FOR
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Abstract
The invention provides a fresh air control system and a fresh air control method for an airplane test, and relates to the technical field of airplane tests. Aircraft test new trend control system includes: the tonifying qi subsystem, the tonifying qi subsystem includes: the aircraft test fresh air control method comprises the following steps: s1, before the test starts, the control system is electrified; s2, butting a liquid nitrogen tank car and a liquid nitrogen heat exchanger; s3, starting a nitrogen dilution fan; s4, setting and regulating an air temperature target value; s5, keeping the balance of air supply and exhaust; s6, judging that the liquid nitrogen heat exchanger frosts and defrosts; s7, carrying out further test; s8, prompting and alarming when the liquid nitrogen tank car needs to be replaced; and S9, finishing the test. The invention solves the problem that the prior art can not meet the test requirement of an aircraft laboratory on the whole aircraft engine under the condition of extremely low temperature, and has the advantages of real-time flow monitoring and PID/Bang-Bang combined temperature control.
Description
Technical Field
The invention relates to the technical field of airplane testing, in particular to an airplane test fresh air control system and a control method.
Background
In order to fully exert the combat efficiency of weaponry, the environmental adaptability requirement and the evaluation index system of the military aircraft must be tested, so that the military aircraft can better adapt to various complex environments in China.
Especially, aircraft testing in extremely low temperature environments is essential. In a low-temperature environment, the front edges of wings and empennages of an airplane are easy to accumulate ice, so that the front edges of the wings and the empennages are deformed, the lift force of the airplane is reduced, the resistance is increased, the instrument distortion is caused by the ice accumulation of dynamic and static pressure holes of the airplane, the judgment of a pilot is influenced, and the airplane engine is possibly directly crashed after being influenced, so that the casualties are caused, and therefore, the starting test of the airplane engine under the extremely low temperature condition is the most important one in the airplane test. The requirements for low temperature factor evaluation in aircraft testing include: the reduction of material hardening and embrittlement, the prevention of shrinkage to varying degrees from material to material in response to temperature transients, and the different rates of expansion of the different components causing the components to seize one another, etc.
The airplane climate environment laboratory provides a simulation environment for the environmental adaptability research of various airplanes and equipment, and can simulate various natural environment working conditions such as low temperature, high temperature, damp heat, snowfall, freezing rain, solar irradiation and the like. Of all the test items for aircraft, the starting and working tests of engines under extreme climatic conditions (especially at extremely low temperatures) are one of the most important test 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 a climate environment laboratory, high-temperature tail gas of the aircraft engine is discharged out of the laboratory, and meanwhile low-temperature air equivalent to the discharge amount of an engine tail gas discharge system needs to be supplemented into the laboratory, so that the quality of the air in the laboratory is unchanged (or the indoor pressure is stable), the test temperature is stable, the safety of the test is ensured, and the method is realized through an air compensation system. Aiming at the blank of the prior art and the urgent need of the aircraft complete engine test in the aircraft laboratory at the extreme low temperature in China, the invention provides an aircraft test fresh air control system and a control method based on liquid nitrogen evaporation refrigeration so as to meet the start test of an aircraft engine.
Disclosure of Invention
The technical problem solved by the invention is as follows: the prior art can not meet the requirement of the aircraft laboratory in China on the test of the whole aircraft engine under the extremely low temperature condition.
In order to solve the problems, the technical scheme of the invention is as follows:
an aircraft test fresh air control system comprising:
the tonifying qi subsystem, the tonifying qi subsystem includes: a compensation wind channel for inciting somebody to action outdoor air introduces aircraft climate laboratory, with the liquid nitrogen heat exchanger that is used for carrying out the cooling to outdoor air of compensation wind channel intercommunication, be used for sending into indoor supply air duct with low temperature air with being used for of liquid nitrogen heat exchanger intercommunication, supply air duct is located aircraft climate laboratory and communicates with aircraft climate laboratory, the control module that is located aircraft climate laboratory who has local manual control and long-range automatic control function concurrently, the temperature monitoring module of monitoring air supply temperature, the humidity monitoring module of monitoring air supply humidity, the wind speed monitoring module of monitoring air supply pressure differential, wherein:
the compensation air duct is internally provided with the following components in sequence from left to right: a filter screen used for filtering impurities in outdoor air, a variable frequency compensation fan communicated with the filter screen, a pitot tube communicated with the variable frequency compensation fan,
a nitrogen gas discharge tower for discharging nitrogen gas at high altitude is communicated with the upper part of the liquid nitrogen heat exchanger through a pipeline provided with a nitrogen gas discharge switch valve, a liquid nitrogen tank wagon for providing refrigeration liquid nitrogen is communicated with the lower part of the liquid nitrogen heat exchanger through a pipeline which is sequentially provided with an adjusting valve, a flowmeter and a liquid nitrogen liquid inlet switch valve,
the control module includes: the PLC controller is used for carrying out overall regulation and control on the control system and is connected with the PLC controller: a liquid crystal display screen for man-machine interaction, a PID controller for realizing fresh air temperature control by a PID feedforward method, a wireless networking submodule for controlling the system by networking,
the logic unit carried on the PLC controller is as follows: a monitoring submodule for acquiring fresh air data in the system through a temperature monitoring module, a humidity monitoring module and a wind speed monitoring module, a monitoring submodule for alarming through a liquid crystal display screen when the fresh air data does not accord with a set value, a temperature setting submodule for setting a compensation air temperature target value, a flowmeter operator module for calculating compensation air flow, a fresh air temperature control method judgment submodule adopting a Bang-Bang/PID fresh air temperature control strategy selection control method, a Bang-Bang fresh air temperature control submodule for realizing fresh air temperature control through the Bang-Bang control method,
the logic units carried on the PID controller are as follows: a fresh air supply flow control submodule used for taking the exhaust flow calculated by the flow calculation submodule as PID control feedforward to accurately control the flow of fresh air supply, a PID feedforward fresh air temperature control submodule used for realizing fresh air temperature control through a PID controller,
the temperature monitoring module includes: temperature sensors arranged at the inlet of the air compensation pipeline fan, the outlet of the liquid nitrogen heat exchanger and the inlet of the laboratory for compensating the air temperature,
the humidity monitoring module includes: humidity sensors arranged at the inlet of the air compensation pipeline fan and the inlet of the laboratory,
the wind speed monitoring module comprises: and the pressure difference sensors are arranged at the outlet of the air variable-frequency compensation fan and in the air supply pipeline.
Furthermore, a defrosting water discharge pipeline is arranged at the top of the liquid nitrogen heat exchanger, a defrosting water discharge pipeline is arranged at the bottom of the liquid nitrogen heat exchanger, a plurality of spray heads are arranged on the defrosting water discharge pipeline, an electromagnetic valve is arranged at the upper end of the defrosting water discharge pipeline, a defrosting water discharge valve is arranged on the defrosting water discharge pipeline, the defrosting water discharge pipeline is connected with a water pump for providing normal temperature water, a defrosting water storage tank is connected to a water inlet of the water pump, a heat preservation layer wraps the outside of the defrosting water storage tank, and the liquid nitrogen heat exchanger is cooled through the normal temperature water, so that the inner part of the liquid nitrogen heat exchanger can be prevented from being frozen.
Furthermore, an air valve is arranged in the air supply pipeline, and the air valve is favorable for controlling the air supply quantity.
Furthermore, one end of the bottom of the nitrogen discharging tower is communicated with a dilution fan, and diluted nitrogen can meet the high-altitude gas discharging standard, so that the environment is protected.
The invention also provides a control method of the fresh air control system for the aircraft test, which comprises the following steps:
s1, before the test starts, the control system is electrified, and a liquid nitrogen inlet switch valve and a nitrogen discharge switch valve are opened;
s2, butting the liquid nitrogen tanker with a liquid nitrogen heat exchanger, and adjusting the liquid supply pressure of the liquid nitrogen tanker to 4 Bar;
s3, starting a nitrogen dilution fan;
s4, connecting the mobile device of the tester with the system through the wireless networking submodule, and setting the target value of the compensated air temperature through the temperature setting submodule
The PLC controls the variable-frequency compensation fan to be started at a low rotating speed, and the temperature of fresh air at the outlet of the liquid nitrogen heat exchanger is acquired through the temperature sensor at the outlet of the liquid nitrogen heat exchanger
Finally, the fresh air temperature control method judgment submodule selects the Bang-Bang fresh air temperature control submodule or the PID feedforward fresh air temperature control submodule through the Bang-Bang/PID fresh air temperature control method to finishThe fresh air temperature is quickly regulated until the air supplementing temperature is stabilized to the target temperature;
s5, after the temperature of the compensation air is basically stable, gradually increasing the rotating speed of the frequency conversion compensation fan, and calculating the air supply flow target value through the air supply flow target value calculation method of the fresh air supply flow control submodule
And current laboratory exhaust flow
Comparing the air flow rate and the temperature to be used as PID control feedback, realizing the control of the air supply flow rate by adjusting the frequency of the variable frequency compensation fan, and setting an air supply flow rate target value by a step length of 5kg/s until the compensation air flow rate and the temperature reach the target values;
s6, the PLC collects and monitors the flow rate of the compensation air through the pressure difference sensor, the current frequency and the flow rate of the variable frequency compensation fan are judged, if the rotating speed of the variable frequency compensation fan reaches the maximum value and the flow rate of the air drops, the liquid nitrogen heat exchanger is seriously frosted, and then defrosting operation is carried out;
s7, if the liquid nitrogen heat exchanger works continuously for 30min, the liquid nitrogen heat exchanger is defrosted after the test is finished, if the total length of intermittent working time in a short time exceeds 30min, the frosting condition of the liquid nitrogen heat exchanger is checked after the test is finished, and the liquid nitrogen heat exchanger is defrosted timely;
s8, monitoring the nitrogen pressure and the nitrogen flow value in real time through the air speed sensor by the system, and when the pressure and the flow are lower than set values, prompting an alarm screen to flicker by a liquid crystal display screen and displaying that the liquid nitrogen volume is insufficient and the liquid nitrogen tank car needs to be replaced;
and S9, after the test is finished, closing the air replenishing subsystem.
Preferably, the Bang-Bang/PID fresh air temperature control method in step S4 specifically includes the following steps:
s4-1, when
When the liquid nitrogen heat exchanger is started, the regulating valve of the liquid nitrogen heat exchanger is completely opened;
s4-2, when
When the liquid nitrogen heat exchanger is in use, the regulating valve of the liquid nitrogen heat exchanger is completely closed;
s4-3, when
And in time, the opening degree of the regulating valve of the liquid nitrogen heat exchanger is controlled by the PID controller, and the temperature control of the fresh air is completed.
Preferably, the method for calculating the target value of the make-up air flow in step S5 includes the following steps:
the air supply pipeline is divided into a plurality of circular sections
Block areas, wherein 1 measuring point is arranged in each block area, and the measuring point positions are obtained according to the following formula:
in the formula:
in order to supplement the air to the cross section radius of the pipeline,
is as follows
The distance between the measuring point of each area and the center of the cross section,
to divide the sectional area of the gas supply pipe by the number,
arranging a differential pressure sensor at each measuring point, and calculating the measuring points
Wind speed of wind
The calculation formula is as follows:
in the formula:
is the flow coefficient of the pitot tube (6),
for measuring points
The wind speed of the wind turbine is measured,
as measured by a differential pressure sensor
The dynamic pressure of the air flow in the air chamber,
for measuring points
The density of the gas stream at the point (c),
wherein the content of the first and second substances,
obtained by the following calculation formula:
in the formula: in
Is the absolute pressure of the local atmosphere,
for measuring points
At the temperature measured by the temperature sensor,
is an ideal gas state constant and is,
flow of make-up air
The calculation formula of (2) is as follows:
in the formula:
in order to supplement the air flow,
for measuring points
The wind speed of the wind turbine is measured,
for measuring points
The density of the gas stream at the point (c),
in order to supplement the air to the cross section radius of the pipeline,
the regulation and control of the air supply flow rate are beneficial to the air pressure regulation in the aircraft climate laboratory for dividing the number of the cross section areas of the air supply pipelines.
Preferably, the defrosting operation in step S6 includes the steps of:
s6-1, closing the compensation fan, the liquid nitrogen regulating valve and the air valve;
s6-2, opening an electromagnetic valve for providing defrosting water and a defrosting water discharge valve, and spraying normal temperature water to the liquid nitrogen heat exchanger for defrosting through a spray head on a defrosting water discharge pipeline;
s6-3, after spraying water at normal temperature for 20min, checking the defrosting condition through an access door;
and S6-4, after defrosting is finished, closing the electromagnetic valve for providing defrosting water and the defrosting water discharge valve, returning to the step S5, and restarting the air supply subsystem through the variable frequency compensation fan.
Further preferably, the step S9 of turning off the air supply subsystem includes the following steps:
s9-1, closing the variable frequency compensation fan and the liquid nitrogen regulating valve;
s9-2, stopping liquid supply by the liquid nitrogen tank wagon;
s9-3, closing the air valve;
s9-4, closing the nitrogen diluting fan after the nitrogen diluting fan continuously works for 10min so as to fully discharge nitrogen accumulated in the system;
s9-5, closing a liquid nitrogen inlet switch valve and a nitrogen discharge switch valve;
and S9-6, controlling the system to be powered down.
The invention has the beneficial effects that:
(1) in the aspect of fresh air temperature control, the fresh air real-time temperature is compared with a compensation air temperature target value, the quick response of the fresh air temperature is completed selectively by a Bang-Bang control and PID feedforward method, the air supply flow is calculated, the air supply flow is compared with the gas emission amount of an airplane climate laboratory, the working efficiency of a variable frequency compensation fan is controlled, and the dynamic balance of the air pressure and the temperature in the airplane climate laboratory is completed, so that the invention has the advantages of high efficiency, quickness and self-regulation;
(2) the system can realize the temperature control of the compensation air at the temperature of minus 25 to minus 45 ℃ by controlling the refrigerating flow of the liquid nitrogen, and the control error is not more than plus or minus 2 ℃;
(3) the invention has high control precision, safety and environmental protection: 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;
(4) the invention has stable operation, safety and reliability: in order to solve the problem of frosting of the liquid nitrogen heat exchanger, defrosting water is adopted to ensure the temperature stability in the test process, and meanwhile, a plurality of tank cars are adopted to supply liquid simultaneously to ensure the uniform and stable liquid nitrogen supply in the starting process of the engine.
Drawings
FIG. 1 is a block diagram of the system of the present invention;
FIG. 2 is a schematic view of a make-up gas flow measurement;
FIG. 3 is a block diagram of a fresh air feed forward PID air make-up control;
FIG. 4 is a schematic diagram of Bang-Bang/PID fresh air temperature control;
FIG. 5 is a control module diagram;
FIG. 6 is a block diagram of a PLC controller logic unit;
FIG. 7 is a block diagram of the PID controller logic;
FIG. 8 is an overall flow chart of the present invention;
FIG. 9 is a detailed flowchart of the step S4 in FIG. 8;
FIG. 10 is a detailed flowchart of the step S6 in FIG. 8;
the device comprises a compensation air duct 1, a liquid nitrogen heat exchanger 2, an air supply pipeline 3, a filter screen 4, a variable frequency compensation fan 5, a pitot tube 6, a nitrogen gas discharge tower 7, a dilution fan 8, a regulating valve 9, a flow meter 10, a liquid nitrogen liquid inlet switch valve 11, a liquid nitrogen tank wagon 12, an air valve 13, a defrosting water discharge pipeline 14, an electromagnetic valve 15, a defrosting water storage tank 16, a defrosting water discharge pipeline 17, a defrosting water discharge valve 18, a nitrogen gas discharge switch valve 19 and a water pump 20.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention clearer, the present invention will be described in further detail with reference to the accompanying drawings, and it is apparent that the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. 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 invention.
The terminology used in the embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the examples of the present invention and the appended claims, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise, and "a plurality" typically includes at least two.
Example 1
This embodiment is an aircraft test new trend control system, includes:
a gas supply subsystem, as shown in fig. 1, comprising: a compensation wind channel 1 for introducing outdoor air into aircraft climate laboratory, liquid nitrogen heat exchanger 2 that is used for carrying out the cooling to outdoor air with 1 intercommunication in compensation wind channel, be used for sending into indoor supply air duct 3 with low temperature air with the liquid nitrogen heat exchanger 2 intercommunication, supply air duct 3 is located aircraft climate laboratory and communicates with aircraft climate laboratory, be equipped with blast gate 13 in the supply air duct 3, the control module who is located aircraft climate laboratory that has local manual control and long-range automatic control function concurrently, the temperature monitoring module of monitoring air supply temperature, the humidity monitoring module of monitoring air supply humidity, the wind speed monitoring module of monitoring air supply pressure differential, wherein:
the compensation air duct 1 is internally provided with the following components in sequence from left to right: a filter screen 4 used for filtering impurities in outdoor air, a variable frequency compensation fan 5 communicated with the filter screen 4, a pitot tube 6 communicated with the variable frequency compensation fan 5,
a nitrogen gas discharge tower 7 for discharging nitrogen gas from high altitude is communicated with the upper part of the liquid nitrogen heat exchanger 2 through a pipeline provided with a nitrogen gas discharge switch valve 19, one end of the bottom of the nitrogen gas discharge tower 7 is communicated with a dilution fan 8, the lower part of the liquid nitrogen heat exchanger 2 is communicated with a liquid nitrogen tank wagon 12 for providing refrigeration liquid nitrogen through a pipeline which is sequentially provided with an adjusting valve 9, a flowmeter 10 and a liquid nitrogen inlet switch valve 11, the top of the liquid nitrogen heat exchanger 2 is provided with a flushing water discharge pipeline 14, the bottom of the liquid nitrogen heat exchanger 2 is provided with a flushing water discharge pipeline 17, the flushing water discharge pipeline 14 is provided with five nozzles, the upper end of the flushing water discharge pipeline is provided with an electromagnetic valve 15, the flushing water discharge pipeline 17 is provided with a flushing water discharge valve 18, the flushing water discharge pipeline 14 is connected with a water pump 20 for providing normal temperature water, the water inlet of the water pump 20 is connected with a flushing water storage tank 16, and the exterior of the flushing water storage tank 16 is wrapped with a heat preservation layer,
as shown in fig. 5, the control module includes: the PLC controller is used for carrying out overall regulation and control on the control system and is connected with the PLC controller: a liquid crystal display screen for man-machine interaction, a PID controller for realizing fresh air temperature control by a PID feedforward method, a wireless networking submodule for controlling the system by networking,
as shown in fig. 6, the logic units mounted on the PLC controller are: a monitoring submodule for acquiring fresh air data in the system through a temperature monitoring module, a humidity monitoring module and a wind speed monitoring module, a monitoring submodule for alarming through a liquid crystal display screen when the fresh air data does not accord with a set value, a temperature setting submodule for setting a compensation air temperature target value, a flowmeter operator module for calculating compensation air flow, a fresh air temperature control method judgment submodule adopting a Bang-Bang/PID fresh air temperature control strategy selection control method, a Bang-Bang fresh air temperature control submodule for realizing fresh air temperature control through the Bang-Bang control method,
as shown in fig. 7, the logic units mounted on the PID controller are: a fresh air supply flow control submodule used for taking the exhaust flow calculated by the flow calculation submodule as PID control feedforward to accurately control the flow of fresh air supply, a PID feedforward fresh air temperature control submodule used for realizing fresh air temperature control through a PID controller,
the temperature monitoring module includes: temperature sensors which are arranged at the inlet of the air compensation pipeline fan, the outlet of the liquid nitrogen heat exchanger 2 and the inlet of the laboratory for compensating the air temperature,
the humidity monitoring module includes: humidity sensors arranged at the inlet of the air compensation pipeline fan and the inlet of the laboratory,
the wind speed monitoring module comprises: and the pressure difference sensors are arranged at the outlet of the air variable frequency compensation fan 5 and in the air supply pipeline 3.
Example 2
The embodiment is an aircraft test fresh air control method based on embodiment 1, and as shown in fig. 8, the method includes the following steps:
s1, before the test starts, the control system is electrified, and the liquid nitrogen liquid inlet switch valve 11 and the nitrogen gas discharge switch valve 19 are opened;
s2, butting the liquid nitrogen tanker 12 and the liquid nitrogen heat exchanger 2, and adjusting the liquid supply pressure of the liquid nitrogen tanker 12 to 4 Bar;
s3, starting the nitrogen dilution fan 8;
s4, connecting the mobile device of the tester with the system through the wireless networking submodule, and setting the target value of the compensated air temperature through the temperature setting submodule
The PLC controller controls the variable-frequency compensation fan 5 to be started at a low rotating speed, and the temperature of fresh air at the outlet of the liquid nitrogen heat exchanger 2 is acquired through the temperature sensor at the outlet of the liquid nitrogen heat exchanger 2
As shown in fig. 4, the last fresh air temperature control method determination submodule selects the Bang-Bang fresh air temperature control submodule or the PID feedforward fresh air temperature control submodule through the Bang-Bang/PID fresh air temperature control method to complete the rapid regulation and control of the fresh air temperature until the air supply temperature is stabilized to the target temperature, and as shown in fig. 9, the Bang-Bang/PID fresh air temperature control method specifically comprises the following steps:
s4-1, when
When the liquid nitrogen heat exchanger 2 is started, the regulating valve 9 is fully opened;
s4-2, when
While, the liquid nitrogen exchanges heatValve 9 is fully closed by valve 2;
s4-3, when
During the process, the opening degree of an adjusting valve 9 of the liquid nitrogen heat exchanger 2 is controlled by a PID controller, and the temperature control of the whole fresh air is completed;
s5, after the temperature of the compensation air is basically stable, gradually increasing the rotating speed of the frequency conversion compensation fan 5, and calculating the air supply flow target value by the air supply flow target value calculation method of the fresh air supply flow control submodule as shown in figure 3
And current laboratory exhaust flow
And comparing the signals to be used as PID control feedback, realizing the control of the air supply flow by adjusting the frequency of the variable-frequency compensation fan 5, setting an air supply flow target value by a step length of 5kg/s until the compensation air flow and the temperature reach the target values, wherein the air supply flow target value calculation method comprises the following steps:
as shown in fig. 2, the gas supply pipe is divided into circular sections
Block areas, wherein 1 measuring point is arranged in each block area, and the measuring point positions are obtained according to the following formula:
in the formula:
in order to supplement the air to the cross section radius of the pipeline,
is as follows
The distance between the measuring point of each area and the center of the cross section,
to divide the sectional area of the gas supply pipe by the number,
arranging a differential pressure sensor at each measuring point, and calculating the measuring points
Wind speed of wind
The calculation formula is as follows:
in the formula:
is the flow coefficient of the pitot tube (6),
for measuring points
The wind speed of the wind turbine is measured,
as measured by a differential pressure sensor
The dynamic pressure of the air flow in the air chamber,
for measuring points
The density of the gas stream at the point (c),
wherein the content of the first and second substances,
obtained by the following calculation formula:
in the formula: in
Is the absolute pressure of the local atmosphere,
for measuring points
At the temperature measured by the temperature sensor,
is an ideal gas state constant and is,
flow of make-up air
The calculation formula of (2) is as follows:
in the formula:
in order to supplement the air flow,
for measuring points
The wind speed of the wind turbine is measured,
for measuring points
The density of the gas stream at the point (c),
in order to supplement the air to the cross section radius of the pipeline,
the number of the gas supplementing pipeline section areas is divided;
s6, the PLC collects and monitors the compensation air flow through the pressure difference sensor, the current frequency and the current flow of the frequency conversion compensation fan 5 are judged, if the rotating speed of the frequency conversion compensation fan 5 reaches the maximum value and the air flow drops, the liquid nitrogen heat exchanger 2 is seriously frosted, and at the moment, defrosting work is required to be carried out, and as shown in figure 10, the defrosting work comprises the following steps:
s6-1, closing the compensation fan, the liquid nitrogen regulating valve 9 and the air valve 13;
s6-2, opening the electromagnetic valve 15 for providing defrosting water and the defrosting water discharge valve 18, and spraying normal temperature water to the liquid nitrogen heat exchanger 2 through a spray head on the defrosting water discharge pipeline 14 to defrost;
s6-3, after spraying water at normal temperature for 20min, checking the defrosting condition through an access door;
s6-4, after defrosting is finished, closing the electromagnetic valve 15 for providing defrosting water and the defrosting water discharge valve 18, returning to the step S5, and restarting the air supplementing subsystem through the variable frequency compensation fan 5;
s7, if the liquid nitrogen heat exchanger 2 continuously works for 30min, the liquid nitrogen heat exchanger 2 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 liquid nitrogen heat exchanger 2 is checked after the test is finished, and the liquid nitrogen heat exchanger 2 is defrosted timely;
s8, monitoring the nitrogen pressure and the nitrogen flow value in real time through the air speed sensor by the system, when the pressure and the flow are lower than set values, prompting the alarm screen to flash by the liquid crystal display screen, and displaying that the liquid nitrogen quantity is insufficient and the liquid nitrogen tank car 12 needs to be replaced;
s9, after the experiment is finished, the air replenishing subsystem is closed, and the method comprises the following steps:
s9-1, closing the variable frequency compensation fan 5 and the liquid nitrogen regulating valve 9,
s9-2, stopping liquid supply of the liquid nitrogen tank wagon 12,
s9-3, closing the air valve 13,
s9-4, closing the nitrogen diluting fan 8 after continuously working for 10min to fully discharge the nitrogen accumulated in the system,
s9-5, closing the liquid nitrogen inlet switch valve 11 and the nitrogen discharge switch valve 19,
and S9-6, controlling the system to be powered down.
Claims (8)
1. The utility model provides an aircraft test new trend control system which characterized in that includes:
a gas-replenishment subsystem, the gas-replenishment subsystem comprising: a compensation wind channel (1) for introducing aircraft climate laboratory with outdoor air, with compensation wind channel (1) intercommunication be used for carrying out the liquid nitrogen heat exchanger (2) that cool down to outdoor air, with being used for of liquid nitrogen heat exchanger (2) intercommunication send into indoor supply air duct (3) with low temperature air, supply air duct (3) be located aircraft climate laboratory and with aircraft climate laboratory intercommunication, have local manual control and long-range automatic control function's the control module that is located aircraft climate laboratory concurrently, the temperature monitoring module of monitoring air supply temperature, the humidity monitoring module of monitoring air supply humidity, the wind speed monitoring module of monitoring air supply pressure differential, wherein:
the compensation air duct (1) is internally provided with the following components in sequence from left to right: a filter screen (4) used for filtering impurities in outdoor air, a variable frequency compensation fan (5) communicated with the filter screen (4), a pitot tube (6) communicated with the variable frequency compensation fan (5),
a nitrogen gas discharge tower (7) for discharging nitrogen gas at high altitude is communicated with the upper part of the liquid nitrogen heat exchanger (2) through a pipeline provided with a nitrogen gas discharge switch valve (19), a liquid nitrogen tank wagon (12) for providing refrigeration liquid nitrogen is communicated with the lower part of the liquid nitrogen heat exchanger (2) through a pipeline which is sequentially provided with an adjusting valve (9), a flowmeter (10) and a liquid nitrogen inlet switch valve (11),
the control module includes: the PLC controller is used for carrying out overall regulation and control on the control system, and is connected with the PLC controller: a liquid crystal display screen for man-machine interaction, a PID controller for realizing fresh air temperature control by a PID feedforward method, a wireless networking submodule for controlling the system by networking,
the logic unit carried on the PLC controller is as follows: a monitoring submodule for acquiring fresh air data in the system through a temperature monitoring module, a humidity monitoring module and a wind speed monitoring module, a monitoring submodule for alarming through the liquid crystal display screen when the fresh air data does not accord with a set value, a temperature setting submodule for setting a compensation air temperature target value, a flow meter operator module for calculating compensation air flow, a fresh air temperature control method judgment submodule adopting a Bang-Bang/PID fresh air temperature control strategy selection control method, a Bang-Bang fresh air temperature control submodule for realizing fresh air temperature control through the Bang-Bang control method,
the logic unit carried on the PID controller is as follows: a fresh air supply flow control submodule used for taking the exhaust flow calculated by the flow meter operator module as PID control feedforward to accurately control the fresh air supply flow, a PID feedforward fresh air temperature control submodule used for realizing fresh air temperature control through a PID controller,
the temperature monitoring module includes: temperature sensors which are arranged at the inlet of the air compensation pipeline fan, the outlet of the liquid nitrogen heat exchanger (2) and the inlet of the laboratory for compensating the air temperature,
the humidity monitoring module includes: humidity sensors arranged at the inlet of the air compensation pipeline fan and the inlet of the laboratory,
the wind speed monitoring module comprises: differential pressure sensors arranged at the outlet of the air frequency conversion compensation fan (5) and in the air supply pipeline (3),
air supplement flow target value calculation method of fresh air supplement flow control submodule
And current laboratory exhaust flow
And comparing the signals to be used as PID control feedback, realizing the control of the air supply flow by adjusting the frequency of the variable-frequency compensation fan (5), setting an air supply flow target value by a step length of 5kg/s until the compensation air flow and the temperature reach the target value, wherein the air supply flow target value calculation method comprises the following steps:
the air supply pipeline is divided into a plurality of circular sections
Block areas, wherein 1 measuring point is arranged in each block area, and the measuring point positions are obtained according to the following formula:
in the formula:
in order to supplement the air to the cross section radius of the pipeline,
is as follows
The distance between the measuring point of each area and the center of the cross section,
to divide the sectional area of the gas supply pipe by the number,
arranging a differential pressure sensor at each measuring point, and calculating the measuring points
Wind speed of wind
The calculation formula is as follows:
in the formula:
is the flow coefficient of the pitot tube (6),
for measuring points
The wind speed of the wind turbine is measured,
as measured by a differential pressure sensor
The dynamic pressure of the air flow in the air chamber,
for measuring points
The density of the gas stream at the point (c),
wherein the content of the first and second substances,
obtained by the following calculation formula:
in the formula: in
Is the absolute pressure of the local atmosphere,
for measuring points
At the temperature measured by the temperature sensor,
is an ideal gas state constant and is,
flow of make-up air
The calculation formula of (2) is as follows:
in the formula:
in order to supplement the air flow,
for measuring points
The wind speed of the wind turbine is measured,
for measuring points
The density of the gas stream at the point (c),
in order to supplement the air to the cross section radius of the pipeline,
the number of the sectional areas of the air supply pipeline is divided.
2. An aircraft test fresh air control system according to claim 1, characterized in that a defrosting water discharging pipeline (14) is arranged at the top of the liquid nitrogen heat exchanger (2), a defrosting water discharging pipeline (17) is arranged at the bottom of the liquid nitrogen heat exchanger (2), a plurality of spray heads are arranged on the defrosting water discharging pipeline (14), the upper end of the defrosting water discharging pipeline is provided with an electromagnetic valve (15), a defrosting water discharging valve (18) is arranged on the defrosting water discharging pipeline (17), a water pump (20) for providing normal temperature water is connected to the defrosting water discharging pipeline (14), a defrosting water storage tank (16) is connected to the water inlet of the water pump (20), and the exterior of the defrosting water storage tank (16) is wrapped with an insulating layer.
3. An aircraft test fresh air control system as claimed in claim 1, wherein an air valve (13) is arranged in the supply duct (3).
4. An aircraft test fresh air control system as claimed in claim 1, wherein one end of the bottom of the nitrogen gas discharge tower (7) is communicated with a dilution fan (8).
5. An aircraft test fresh air control method based on the aircraft test fresh air control system of any one of claims 1 to 4 is characterized by comprising the following steps:
s1, before the test starts, the control system is electrified, and a liquid nitrogen liquid inlet switch valve (11) and a nitrogen gas discharge switch valve (19) are opened;
s2, butting the liquid nitrogen tank wagon (12) and the liquid nitrogen heat exchanger (2), and adjusting the liquid supply pressure of the liquid nitrogen tank wagon (12) to 4 Bar;
s3, starting a nitrogen dilution fan (8);
s4, connecting the mobile device of the tester with the system through the wireless networking submodule, and setting the target value of the compensated air temperature through the temperature setting submodule
The PLC controller controls the variable-frequency compensation fan (5) to start at a low rotating speed and exchanges heat through liquid nitrogenThe temperature sensor at the outlet of the device (2) acquires the fresh air temperature at the outlet of the liquid nitrogen heat exchanger (2)
Finally, the fresh air temperature control method judgment submodule selects a Bang-Bang fresh air temperature control submodule or a PID feedforward fresh air temperature control submodule through a Bang-Bang/PID fresh air temperature control method to finish the rapid regulation and control of the fresh air temperature until the air supply temperature is stabilized to the target temperature;
s5, after the temperature of the compensation air is basically stable, gradually increasing the rotating speed of the frequency conversion compensation fan (5), and calculating the air supply flow target value by the air supply flow target value calculation method of the fresh air supply flow control submodule
And current laboratory exhaust flow
And comparing the signals to be used as PID control feedback, realizing the control of the air supply flow by adjusting the frequency of the variable-frequency compensation fan (5), setting an air supply flow target value by a step length of 5kg/s until the compensation air flow and the temperature reach the target value, wherein the air supply flow target value calculation method comprises the following steps:
the air supply pipeline is divided into a plurality of circular sections
Block areas, wherein 1 measuring point is arranged in each block area, and the measuring point positions are obtained according to the following formula:
in the formula:
in order to supplement the air to the cross section radius of the pipeline,
is as follows
The distance between the measuring point of each area and the center of the cross section,
to divide the sectional area of the gas supply pipe by the number,
arranging a differential pressure sensor at each measuring point, and calculating the measuring points
Wind speed of wind
The calculation formula is as follows:
in the formula:
is the flow coefficient of the pitot tube (6),
for measuring points
The wind speed of the wind turbine is measured,
as measured by a differential pressure sensor
The dynamic pressure of the air flow in the air chamber,
for measuring points
The density of the gas stream at the point (c),
wherein the content of the first and second substances,
obtained by the following calculation formula:
in the formula: in
Is the absolute pressure of the local atmosphere,
for measuring points
At the temperature measured by the temperature sensor,
is an ideal gas state constant and is,
flow of make-up air
The calculation formula of (2) is as follows:
in the formula:
in order to supplement the air flow,
for measuring points
The wind speed of the wind turbine is measured,
for measuring points
The density of the gas stream at the point (c),
in order to supplement the air to the cross section radius of the pipeline,
the number of the gas supplementing pipeline section areas is divided;
s6, the PLC collects and monitors the flow rate of the compensation air through the differential pressure sensor, the current frequency and the current flow rate of the variable frequency compensation fan (5) are judged, if the rotating speed of the variable frequency compensation fan (5) reaches the maximum value and the flow rate of the air drops, the liquid nitrogen heat exchanger (2) is seriously frosted, and then defrosting operation is carried out;
s7, if the liquid nitrogen heat exchanger (2) works continuously for 30min, the liquid nitrogen heat exchanger (2) is defrosted after the test is finished, if the intermittent working time in a short time is longer than 30min, the frosting condition of the liquid nitrogen heat exchanger (2) is checked after the test is finished, and the liquid nitrogen heat exchanger (2) is defrosted timely;
s8, the system monitors the nitrogen pressure and the nitrogen flow value in real time through the wind speed sensor, when the pressure and the flow are lower than set values, the liquid crystal display screen prompts the alarm screen to flash, and the liquid nitrogen tank car (12) is required to be replaced when the liquid nitrogen amount is insufficient;
and S9, after the test is finished, closing the air replenishing subsystem.
6. An aircraft test fresh air control method according to claim 5, wherein the Bang-Bang/PID fresh air temperature control method in the step S4 specifically comprises the following steps:
s4-1, when
When the liquid nitrogen heat exchanger (2) is started, the regulating valve (9) is completely opened;
s4-2, when
When the liquid nitrogen heat exchanger (2) is in use, the regulating valve (9) is completely closed;
s4-3, when
During the process, the opening degree of an adjusting valve (9) of the liquid nitrogen heat exchanger (2) is controlled through a PID controller, and the temperature control of the fresh air is completed.
7. An aircraft test fresh air control method as claimed in claim 5, wherein the defrosting operation in the step S6 comprises the following steps:
s6-1, closing a compensation fan, a liquid nitrogen regulating valve (9) and an air valve (13);
s6-2, opening an electromagnetic valve (15) for providing defrosting water and a defrosting water discharge valve (18), and spraying normal temperature water to the liquid nitrogen heat exchanger (2) through a spray head on a defrosting water discharge pipeline (14) to defrost;
s6-3, after spraying water at normal temperature for 20min, checking the defrosting condition through an access door;
s6-4, after defrosting is finished, closing the electromagnetic valve (15) for providing defrosting water and the defrosting water discharge valve (18), returning to the step S5, and restarting the air supply subsystem through the variable frequency compensation fan (5).
8. An aircraft test fresh air control method as claimed in claim 5, wherein the step of turning off the air supply subsystem in the step S9 comprises the steps of:
s9-1, closing the variable frequency compensation fan (5) and the liquid nitrogen regulating valve (9);
s9-2, stopping liquid supply by the liquid nitrogen tanker (12);
s9-3, closing the air valve (13);
s9-4, closing the nitrogen diluting fan (8) after continuously working for 10min to fully discharge nitrogen accumulated in the system;
s9-5, closing a liquid nitrogen liquid inlet switch valve (11) and a nitrogen gas discharge switch valve (19);
and S9-6, controlling the system to be powered down.
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