What Is an Air Inlet?

An air inlet, an air duct, or an opening of a similar structure, which uses the aircraft to move forward to collect air and direct it to the engine or ventilator.

Air inlets can be divided into leading edge air inlets, funnel-shaped air inlets (or funnel-shaped air inlets), skin air inlets, internal air inlets, etc. according to their shape and location.

According to the air inlet, it works outside or inside the surface layer, and can be divided into a head air inlet (also known as a stamped air inlet) and a submerged air inlet. The latter can be divided into fully submerged and partially submerged.

The leading edge of the air inlet is relatively obtuse to avoid air flow separation at the inlet when taking off at low speed. The internal channels are mostly diffuse. At maximum speed or

Supersonic inlets pass through multiple weaker

Intake ducts are roughly divided into frontal and non-frontal air intakes depending on their position on the aircraft. Front air intake: The air intake is located at the head of the fuselage or engine nacelle, and the flow field in front of the air intake is not disturbed. Its advantage is simple structure. The biggest disadvantage of the front air intake on the fuselage head is that the fuselage head is not easy to place

Engine air intakes often freeze, preventing sufficient air flow from the intakes to maintain combustion. Air intakes are very susceptible to icing, as this icing can occur without the need for visible droplets. Therefore, the engine air intake may freeze in sunny and warm weather. The temperature range at which the intake port freezes varies with the type of engine (compared to piston and jet engines). However, in general, if the temperature of the air is below 10 ° C and the humidity is high, there may be icing at the air intake. ^[3]

Air inlet carburetor freezes

In the carburetor, the air will expand and the fuel will vaporize, which is prone to icing. If the humidity of the air sucked into the carburetor is high, the carburetor may freeze when its internal temperature is less than 22 ° C. The temperature drop in the carburetor is generally less than or equal to 20 ° C, but it may sometimes reach 400 ° C. In the presence of a certain amount of moisture in the air, if the temperature of the carburetor is lowered to 0 ° C and below, its internal passage will occur Freeze. Icing is most likely to occur at exhausts, throats, and throttles.

The carburetor heater is an anti-icing rather than a de-icing device, so its main function is to prevent icing. When the heater is turned on, the air is heated before entering the carburetor, keeping the temperature of the fuel and air mixture above 0 ° C. The heater may melt a small amount of snow and ice entering the air intake. Since the carburetor heater may adversely affect the performance of the aircraft, it must be used in accordance with the aircraft operating manual. ^[3]

Inlet fuel system

Water is easily soluble in fuel oil, so when humidity is high, fuel oil will absorb a certain amount of water. When the fuel absorbs more moisture and its temperature is less than or equal to the freezing temperature of water, the fuel system freezes occasionally. ^[3]

Air intake system

When the weather conditions are conducive to icing, that is, the presence of liquid water and the temperature at which icing can occur, icing may occur in the air intake system. However, the air intake system can also freeze in clean air, provided that the relative humidity of the air is high and the temperature is less than or equal to 10 ° C. ^[3]

Air inlet

The icing conditions of the inlet are similar to those of the carburetor: that is, the presence of supercooled water, or the humidity of the air is high and the temperature is higher than 0 ° C.

The pressure of the air entering the inlet is very low during the aircraft's run, take-off, and climb phases, so the temperature can be reduced to the extent that condensation or sublimation occurs. As a result, icing can occur in the intake duct, which narrows the duct and affects air entry. ^[3]

Air inlet deflector

When supercooled droplets form icing on the inlet deflector, the air flow into the engine will decrease. This causes the engine's thrust to drop, and in severe cases will cause the engine to stop. Once this kind of icing occurs, a very direct hazard is that the accumulated ice falling off the front of the compressor air inlet may be sucked into the engine and cause serious damage to the engine. ^[3]