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Aircraft Ventilation
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Aircraft Ventilation

Aircraft air conditioning system. aircraft ventilation.

 

Aircraft air-conditioning system is a life support system onboard and is designed to maintain the temperature and air pressure in the hermetically sealed cabin of the aircraft at a level to ensure the normal functioning of the passengers and crew. Sealed cab provides their design concept, the presence of seals on the hatches and doors, constant pressurization of SLE.

 

Tasks

 

The rise to a height of more than 3 km causes a person the appearance of signs of oxygen starvation. Raising more than 9 km in height facing aeroembolizmom (release of liquid gas bubbles of the body). At an altitude of more than 19 km boiling occurs subcutaneous fluid. The air temperature at a height of up to 11 km -60 ° C. In order to provide for the life of a normal mode in such extreme conditions, a variety of onboard life-support systems were created.

 

Principle of operation

 

The system works in the air, which is taken from compressors of operating aircraft engines. The temperature of such air reaches 500 ° C, the pressure is 1,6 MPa. In this case, the air is divided into an 2 stream. The first flow (the cold line), passing through the cooling system, is directed to the mixer. The second stream goes directly into the mixer. In the mixer, both flows are mixed, this air is sent to the hermachine. Also in airplanes, hot air is used as a component of an anti-icing system, it passes through pipes located under the skin of the aircraft and heats the surface to prevent ice build-up.

panel air jet

Control of the air on the dashboard

To cool the air, heat exchangers of the following types are used: turbo-refrigerators (TX), fuel-air radiators (TWR) and air-to-air radiators (VVR). In a complex air-conditioning system, several stages of air cooling, arranged in cascades, can be used. Each stage has its own automatic temperature controllers. For example, on the Tu-154 airplane, the selected air from the engines is cooled first in the TX and VVR located near the 3 engine, then is fed to the SLE and PIC, and in the SLE there are two secondary TXs and VVRs (located in the nose of the root part of the wing, for Blowing VVR in each wing there is a small air intake), cooling air to normal for breathing temperature.

The structure of the automatic temperature regulator (ART) includes a temperature dial, located in the cabin, the temperature sensor in the pipeline, the electronic block of automatic control and electrical systems executive (regulating valve in the pipeline). Most of the controls in the air conditioning system may not be equipped with an aircraft cabin temperature setting unit and operates automatically.

air jet pipe

Two rectangular heat exchanger (air-to-air radiator = WWR) silver

Supply cooled air in the cabin / cabin of the aircraft air-conditioning duct system may cause the formation of fog, which gradually dissipates when the system begins to operate in a stable mode. To eliminate this phenomenon in the design phase of the aircraft provide for special measures (collecting condensate drainage holes in the outboard air-conditioning system space).

In hermetic tanks, pressure is regulated taking into account special programs that differ in transport aircraft, heavy and maneuverable combat aircraft. For heavy aircraft at altitudes up to 2000 m, a zone of free ventilation is introduced, above - the zone of absolute constant pressure and the zone of excess pressure relative to a typical atmosphere. For maneuverable airplanes, in order to reduce the rate of pressure change in the hermachine in the performance of vertical maneuvers within 2-7 km, a zone of variable pressure was introduced. With the help of the pressure regulation machine, a strictly dosed discharge of excess air from the sealed cabin into the seaward space occurs. This machine on military aircraft has normal and combat modes of operation. When using the machine in combat mode inside the cabin, the pressure is sharply reduced - this technology is used to prevent the crew from receiving barotrauma during a sharp depressurization, for example, in the event of a shell attack by the projectile. Damage to the integrity of the cabin by machine gun and cannon fire when flying at high altitudes caused explosive decompression during the Second World War and the death of crews.

the ventilation system of the aircraft

Between packs Alcove chassis, bottom, is an outlet for venting air.

 

Air-conditioned air is supplied not only to the hermetic cabin, but also to the technical compartments where the electronic equipment is located, so that the normal temperature conditions of the units and units are maintained. On bombers that can carry nuclear weapons, SCR warms up completely all the unsealed air bomb, while maintaining the temperature above 0 ° C (guided nuclear missiles have internal heat stabilization). The presence of an auxiliary power unit on board the aircraft also implies the selection of air for conditioning the cabins and compartments from the APU.

In the event of an emergency, emergency shutters are available to quickly stop the ventilation of the cabin, in the event of a fire in the engine and the introduction of smoke into the cabin from the air ducts, which immediately shut off the three-way pipelines or taps that smoothly control the shutter in normal opening and closing mode. The emergency mode of the air conditioning system provides the electric motor only for closing in forced mode. Also, during emergency situations, a ventilation program operates from the high-speed head, which serves to ventilate the cabin in case of smoke. For this, the pilot needs to lower the aircraft's height to 4000 m, depressurize the cabin and turn on the ventilation system.

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