How do aircraft air conditioning components provide comfort gas?

The air source of the air-conditioning system can be divided into two categories, one is the hot air flow drawn from the aircraft system, which enters the cabin under the action of the air-conditioning components; the other is the ram air from the outside, which is mainly used to cool the air from the aircraft system. The gas introduced to the air conditioning unit is discharged directly after use.

For ram air, the air in the atmosphere enters the ram intake port from the ram air intake valve, and then flows through the primary air conditioning heat exchanger and the secondary air conditioning heat exchanger in turn. After cooling the hot air in the assembly, it enters the plenum chamber. Finally, it is discharged out of the machine through the diffuser.

For the airflow introduced from the aircraft system to the air conditioning module, the bleed air enters the air conditioning module through the module flow control and shut-off valve, first flows to the primary heat exchanger to reduce the temperature, and then flows through the ACM (air circulation machine) compressor to increase the temperature. The work ability of the atmospheric gas, after it comes out, the temperature of the secondary heat exchanger continues to decrease, and then the temperature is lowered again by the reheater, and the temperature is further lowered by the condenser to reach the dew point to separate the water. The dewatered gas flows back to the reheater, and flows into the ACM turbine after the temperature rises. After the turbine comes out, the gas enters the condenser again. After the temperature rises, it enters the cockpit and the mixing header through the one-way valve.

The air path of the ram air

The new configuration of the aircraft adopts the ram air system of the E-FLOW configuration, which is explained here with the E-FLOW configuration. The front SRADA (smart ram air intake valve actuator) is located in the upper side cover of the ram air intake valve, which can be accessed by opening the cover. The actuator is an electronically controlled electric type. SRADA receives the flap position signal and The resistance change signal of the ram air temperature sensor controls the ram air intake valve and the adjustment plate. The rear SRADA is located next to the ram air outlet pipe, receives the signal from the front SRADA, and works with the front SRADA to make the ram air temperature sensor (located at the outlet of the ACM compressor and the secondary on the piping between the stage heat exchangers) stabilized at 110 degrees.

SRADA changes the air flow into the ram intake port by changing the position of the front and rear adjustment plates, and activates the guide valve through the guide valve link to realize the opening and closing of the intake valve. When the aircraft is on the ground, the ram air intake valve is fully opened to prevent foreign objects such as ice cubes, stones and other foreign objects from entering the air intake and damaging the air conditioning components; when flying in the air, the ram air intake valve is fully closed, and the air conditioner/lead on the cockpit P5 panel There is a light indicating RAM DOOR FULL OPEN (ram intake valve fully open) on the air panel. Note that even if the ram intake valve is fully closed when the flap is not fully closed, the light is still on. At this time, the grille of the exhaust port is not fully closed. Turn the light until the flaps are fully retracted. A self-test on the PZTC (component zone temperature controller) can test whether there is a fault in the ram air system. If there is a fault, it will display the front SRADA, the rear SRAD or the ram air temperature sensor fault.

The ram air enters the primary heat exchanger and the secondary heat exchanger through the ram air inlet, and the ram cold air and the hot air in the air conditioning assembly conduct heat transfer in the heat exchanger to achieve the effect of cooling the air of the assembly, and the ram air after heat exchange Out of the machine from the diffuser.

ACM consists of compressor, turbine and impeller fan. The fan is located at the diffuser end of the secondary heat exchanger. When the aircraft is on the ground, due to the low relative speed between the air and the aircraft, a good stamping effect cannot be produced. Negative pressure is generated, and the outside air is sucked into the heat exchanger; when the aircraft is flying at high speed in the air, the fan does not work, the ram air enters the ram air inlet smoothly, and at the same time, the fan bypass one-way valve in the diffuser is opened, and the airflow It flows into the diffuser through the valve and is discharged out of the machine.

The air path of the bleed gas in the module

The bleed air source of the component is APU, engine and ground air source vehicle, and the gas enters the component through the flow control and shut-off valve to provide hot air for the air conditioner. The flow control and shut-off valve is an electro-pneumatic switch that controls the pressure and flow of gas entering the air conditioning module. The position of the module switch and the state of the aircraft-related system determine the opening of the valve.

When the component switch is in the OFF position, the control circuit must not switch the valve to the closed position; when the component switch is in the AUTO position, if the air conditioners on both sides are working normally, the valve will work in the low flow mode. If the aircraft is in the air, the flaps are closed and When the air conditioner on the other side does not work, the valve works in the high flow mode; when the component switch is in the HIGH position, the APU bleed air switch is in the ON position, and the APU working speed is higher than 95%, the valve works in the APU high flow mode.

The bleed air passes through the primary heat exchanger, ACM compressor, and secondary heat exchanger in turn, and then enters the reheater. The function of the exchanger is to cool the air entering for the first time to reduce the temperature of the gas entering the condenser. When the air comes out of the condenser and enters the reheater again, it has the effect of heating.

After the air enters the condenser, the temperature is further reduced, and the temperature reaches the dew point, so that the water becomes liquid, and the water is separated under the action of the high-pressure water separator to obtain a relatively dry gas. There are two water separators on both sides of the condenser. There are rotating blades at the inlet of the water separator, so that the air entering the water separator rotates. Under the action of centrifugal force, the water is separated and thrown to the inner cylinder wall, and further collected by the water collector. It is discharged to the water collection main pipe through the pipe, and finally discharged to the ram air intake to cool the ram air. If the drain pipe is blocked, it can flow directly to the air conditioning cabin through the bypass valve. The high-pressure air that has been removed from the water flows through the reheater again, and then enters the turbine, which drives the turbine to rotate at high speed.

In order to prevent the condenser from freezing and to control the outlet temperature of the assembly, the gas from the turbine enters the high pressure water separator assembly mixing header, which mixes the ACM turbine outlet cold gas with TCV and the gas from BTCV, TCV (temperature control valve) and BTCV (Backup temperature control valve) Controls hot gas flow from the assembly flow control and shut-off valve. TCV is an electronically controlled electric valve, and BTCV is an electronically controlled pneumatic valve. When the TCV fails, the BTCV enters the standby mode to control the outlet temperature of the components, and also plays a role in preventing the condenser from freezing. When the gas from the ACM flows through the condenser, it is heated to a certain extent, and the temperature continues to rise. Finally, it flows into the mixing header or the cockpit through the one-way valve, so that the air-conditioning components can produce cold air of suitable temperature.

In order to improve the reliability of the air conditioner and obtain the component outlet gas with a more suitable temperature, the following sensors are installed on the component components: component temperature sensor, component inlet pressure sensor, component flow sensor, and mixing header temperature sensor. Components are controlled more efficiently.

In order to avoid the overheating of the air conditioner, the air conditioner assembly is equipped with three overheating switches: compressor outlet overheating switch (390F), turbine outlet overheating switch (210F), and module outlet overheating switch (250F). When any overheating switch is overheated, the closing of the overheating switch will cause the flow control and shut-off valve of the component to close, the air conditioner on that side will stop working, and the PACK light on the P5 board, as well as the main warning sign and the main warning light will also be lit. If the PACK can be reset after the overheating condition disappears, it is likely that the heat exchanger is blocked or too dirty. If it cannot be reset, it is necessary to test the function of the compressor outlet overheat switch and the turbine outlet overheat switch.