Introduction to A320 cabin air temperature control system

The air-conditioning system ensures a constant supply of fresh air and maintains a constant selected temperature in the three areas of the cockpit, front cabin and rear cabin, mainly by conditioning the air entering the interior of the cabin. The air entering the cabin is regulated by mixing cold air and bleed air to the right temperature. The more complicated part of the air-conditioning system is to obtain the cold air that adjusts the temperature and humidity.

How to get conditioned cold air with air conditioning equipment?

The working process from bleed air to cold air for temperature and humidity control:

1. Component flow control valve: The high-temperature and high-pressure air obtained from the system passes through the component flow control valve, and the component flow valve is automatically adjusted by the component controller's instruction to control the component flow valve.

If the module compressor overheats, eg 230°C (446°F) the module flow control valve closes pneumatically. NOTE: Some of the hot air coming downstream from the assembly flow control valve is sent to the hot air pressure regulating valve. Both component flow control valves automatically close during engine start and reopen 30 seconds after the first engine has been started.

2. Air conditioner assembly: The flow-controlled air from the assembly valve enters the air conditioner assembly (A320 has two air conditioner assemblies), then the air passes through several steps in the main assembly, and the bleed air passes through the main heat exchanger and then to the compressor . The air is cooled in the main heat exchanger and then passes through a heater, condenser and water separator, which is used to remove water molecules from the air from the turbine air.

Air is expanded in the turbine section. This makes the exhaust temperature of the turbine very low. The turbine drives the compressor and the cooling air fan to obtain cold air with temperature and humidity adjustment. There are two steps in which the hot air conducts heat exchange through the radiator. Around the exchanger is the cold air in the high altitude. There are two connected open cabins in the belly of the aircraft, and the cold air in the high altitude is introduced to cool the air. The module controller also controls the anti-icing valve, which automatically opens to prevent ice from forming in the module condenser. Once the module controller has completely failed, the anti-icing valve will pneumatically control the module outlet temperature (to the mixer) to 15°C (59°F).

3. Bypass valve: The bypass valve is electronically controlled to regulate the outlet temperature of the assembly by increasing the hot air. Ram air inlet and ram air outlet vanes are used to regulate air flow through the heat exchanger.

To increase cooling, the ram air vanes are opened larger and the bypass valve closed smaller. To increase the temperature, close the ram air vanes smaller and open the bypass valve larger. During takeoff and landing, the ram air inlet vanes are fully closed to prevent the entry of foreign objects.

4. Main component controller: The component controller is mainly used to control the component flow control valve and bypass valve. Each module controller can perform basic temperature and flow regulation for the corresponding module according to the required signals from the zone controller.

The component controller also controls the flow of air into and out of the radiator to achieve the cooling air of the corresponding temperature. Note that the two open hatches that control the air in and out of the radiator area are not allowed to open during takeoff and landing.

Summary: If this process is simplified, the parts other than the component controller can be combined into the air conditioning component, that is, the hot air gets the cold air with temperature and humidity regulation through the air conditioning component. The cold air obtained from the air conditioning system must be mixed with the bleed air accordingly before it can be transported.

Sent to the cabin for cabin temperature adjustment.

5. Mixer: The conditioned air from the two air conditioning units is mixed in the mixer and then sent to each cabin.

The mixer can also be used to distribute air from the other to the three cabins when one of the air conditioning components fails. If both components fail (failure or smoke), the mixer can temporarily introduce emergency ram air into the air conditioning system in place of the air coming out of the air conditioning components.

6. Emergency Ram Air: Provides outside air to the aircraft's ventilation air in an emergency.

7. Zone temperature: Cockpit, front cabin and rear cabin these three are called zone temperature. The air output from the mixer is divided into three parts and delivered to these three temperature zones.

8. Zone controller: Select the appropriate cabin temperature according to the temperature sensor and temperature selector, and then send the signal to the component controller for temperature adjustment. So temperature regulation is automatic.

In the A320, each controller includes a main computer and an electronically controlled independent auxiliary computer, which can be used as a backup when the main computer fails.

9. Adjust the air valve: It can mix the conditioned air and hot air from the mixer in a certain proportion to obtain the required temperature and transport it to the temperature of the area that needs to be adjusted.

Summary: The most basic principle of the air temperature adjustment system is to control the temperature of the air entering the cabin, that is, to adjust the corresponding mixing ratio of cold and hot air entering the cabin, so as to achieve a reasonable adjustment of the cabin temperature.