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.
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 operates in the air, which is taken from the compressor is running aircraft engines. The temperature of the air reaches 500 ° C, pressure - 1,6 MPa. The air flow is divided into 2. The first stream (cold line) passing through the cooling system is directed to the mixer. The second stream goes directly into the mixer. In the mixer the mixing of the two streams, the air is directed into the pressurized cabin. Also in the hot air jets are used as a component of the anti-icing system, it passes through the tubes located under the skin of the aircraft, and heats the surface to prevent ice build-up.
Control of the air on the dashboard
To cool the air using heat exchangers of the following types: turbo-cooler (TX), the fuel-air cooler (TBP) and air-to-air cooler (VVR). In a complex conditioning system can be used multiple stages of cooling air cascaded. Each stage has its own automatic temperature controller. For example, the Tu-154 bleed air from the engine is cooled first in TX and VVR located near 3-th engine is then supplied to the SCR and the PIC, and in foreign currency, there are two secondary TX and VVR (located in the toe of the wing root for VVR blowing in each wing has a small air intake), the cooling air for breathing to normal 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.
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).
The pressurized cabin pressure is adjusted according to the specific programs, which vary in transport aircraft, heavy and maneuverable combat aircraft. For heavy aircraft at altitudes up to 2000 m entered a zone of free ventilation above - the zone of the absolute constant pressure and excess pressure zone relative to a typical atmosphere. For maneuvering the aircraft to reduce the rate of change of pressure in the pressurized cabin while performing vertical maneuvers within 2-7 km, entered a zone of alternating pressure. With automatic adjustment pressure is strictly metered discharge of excess air in the pressurized cabin outboard space. This machine on military aircraft has a normal and battle modes. When using the machine in combat mode inside the cabin pressure decreases dramatically - such technology is applied in order to prevent getting the crew barotraumas at sharp depressurization, for example, in the case of destruction of the aircraft shell. Damage to the integrity of the cabin machine-gun fire when flying at high altitudes cause an explosive decompression during the Second World War and the death of the crew.
Between packs Alcove chassis, bottom, is an outlet for venting air.
Air conditioning is applied not only in the pressurized cabin, but in the technical compartments, where electronic equipment is located in order to maintain the normal operating temperature and block units. Bombers, which can carry nuclear weapons, SLE heats completely all leaky bombolyuk aircraft, maintaining the temperature at a level above 0 ° C (guided missiles with nuclear warheads have internal thermal stabilization). The presence on board the aircraft auxiliary power unit also implies the selection of air conditioning and cabin sections from the APU.
In the event of an emergency, for quick termination cab ventilation, a fire in the engine and applying the smoke into the cabin of the air ducts in foreign currency are emergency valve, which immediately cover the three-way pipes or taps that run smoothly in normal mode shutter for opening and closing. Emergency mode-conditioning system provides for work only at the closing of the electric motor in forced mode. Also during the emergency ventilation has a program of dynamic pressure, which serves to ventilate the cabin in the event of smoke. To do this you need to reduce the height of the pilot of the aircraft to 4000 m, depressurize the cabin and turn on the ventilation system.
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