|This article does not cite any references or sources. (January 2009)|
An intake, or especially for aircraft inlet, is an air intake for an engine. Because the modern internal combustion engine is in essence a powerful air pump, like the exhaust system on an engine, the intake must be carefully engineered and tuned to provide the greatest efficiency and power. An ideal intake system should increase the velocity of the air until it travels into the combustion chamber, while minimizing turbulence and restriction of flow.
Automobile engine intakes
A modern automobile air intake system has three main parts, an air filter, mass flow sensor, and throttle body. Some modern intake systems can be highly complex, and often include specially-designed intake manifolds to optimally distribute air and air/fuel mixture to each cylinder. Many cars today now include a silencer to minimize the noise entering the cabin. Silencers impede air flow and create turbulence which reduce total power, so performance enthusiasts often remove them.
All the above is usually accomplished by flow testing on a flow bench in the port design stage. Cars with turbochargers or superchargers which provide pressurized air to the engine usually have highly-refined intake systems to improve performance dramatically.
Production cars have specific-length air intakes to cause the air to vibrate and buffett[dubious ] at a specific frequency to assist air flow into the combustion chamber. Aftermarket companies for cars have introduced larger throttle bodies and air filters to decrease restriction of flow at the cost of changing the harmonics of the air intake for a small net increase in power or torque.
Porsche in the 1980s designed an intake system for their cars that changed the length of the intake system by alternating between a longer and shorter set of tubing using a butterfly valve, creating a small amount of positive pressure which increased overall performance of the engine. Audi began to use a similar system in some cars in the 1990s.
With the development of jet engines and the subsequent ability of aircraft to travel at supersonic speeds, it was necessary to design inlets for optimal air flow at any speed, which allowed the compressor stage to operate at its optimum flow speed of just-subsonic, regardless of the velocity of the ambient air at the mouth of the intake. These designs are highly complex due to the requirement to manage flow and shock front formation through the subsonic, transonic, and supersonic flight regimes. In aircraft design the air-intake is part of the fuselage or lies within a nacelle.