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Dassault Super Mystere showing entry to engine intake duct Airforce Museum Berlin-Gatow 135.JPG
Dassault Super Mystère showing entry to engine intake duct

An intake (also inlet) is an opening, structure or system through which a fluid is admitted to a space or machine as a consequence of a pressure differential between the outside and the inside. The pressure difference may be generated on the inside by a mechanism, or on the outside by ram pressure or hydrostatic pressure. Flow rate through the intake depends on pressure difference, fluid properties, and intake geometry.


Intake refers to an opening, or area, together with its defining edge profile which has an associated entry loss, that captures pipe flow from a reservoir or storage tank. [1] Intake refers to the capture area definition and attached ducting to an aircraft gas turbine engine [2] or ramjet engine and, as such, an intake is followed by a compressor or combustion chamber. It may instead be referred to as a diffuser. [3] For an automobile engine the components through which the air flows to the engine cylinders, are collectively known as an intake system [4] and may include the inlet port and valve. [5] An intake for a hydroelectric power plant is the capture area in a reservoir which feeds a pressure pipe, or penstock, or into an open canal. [6]

Automobile engine intakes

Automotive intake assembly showing pink air filter, plastic ducting with sensors, metal throttle body and plastic manifold with plenum and runners Mustang-v6-roush-intake.jpg
Automotive intake assembly showing pink air filter, plastic ducting with sensors, metal throttle body and plastic manifold with plenum and runners

Early automobile intake systems were simple air inlets connected directly to carburetors. The first air filter was implemented on the 1915 Packard Twin Six.[ citation needed ]

The 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.[ citation needed ] Silencers impede airflow and create turbulence which reduce total power, so performance enthusiasts often remove them.[ citation needed ]

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.[ citation needed ]

Production cars have specific-length air intakes to cause the air to vibrate and buffet[ dubious ] at a specific frequency to assist airflow into the combustion chamber.[ citation needed ] 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.[ citation needed ]

Aircraft intakes

Aircraft using piston engines use intake systems similar to automobiles.

With the development of jet engines and the subsequent ability of aircraft to travel at supersonic speeds, it was necessary to design inlets to provide the flow required by the engine over a wide operating envelope and to provide air with a high-pressure recovery and low distortion. These designs became more complex as aircraft speeds increased to Mach 3.0 and Mach 3.2, design points for the XB-70 and SR-71 respectively. The inlet is part of the fuselage or part of the nacelle.

Aircraft with a maximum speed greater than about Mach 2 use intakes with variable geometry to achieve good pressure recovery from take-off to maximum speed. [7]

See also

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<span class="mw-page-title-main">Ramjet</span> Atmospheric jet engine designed to operate at supersonic speeds

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<span class="mw-page-title-main">Carburetor</span> Component of internal combustion engines which mixes air and fuel in a controlled ratio

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<span class="mw-page-title-main">Scramjet</span> Jet engine where combustion takes place in supersonic airflow

A scramjet is a variant of a ramjet airbreathing jet engine in which combustion takes place in supersonic airflow. As in ramjets, a scramjet relies on high vehicle speed to compress the incoming air forcefully before combustion, but whereas a ramjet decelerates the air to subsonic velocities before combustion using shock cones, a scramjet has no shock cone and slows the airflow using shockwaves produced by its ignition source in place of a shock cone. This allows the scramjet to operate efficiently at extremely high speeds.

Aircraft engine controls

Aircraft engine controls provide a means for the pilot to control and monitor the operation of the aircraft's powerplant. This article describes controls used with a basic internal-combustion engine driving a propeller. Some optional or more advanced configurations are described at the end of the article. Jet turbine engines use different operating principles and have their own sets of controls and sensors.

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The Pratt & Whitney J58 is an American jet engine that powered the Lockheed A-12, and subsequently the YF-12 and the SR-71 aircraft. It was an afterburning turbojet engine with a unique compressor bleed to the afterburner that gave increased thrust at high speeds. Because of the wide speed range of the aircraft, the engine needed two modes of operation to take it from stationary on the ground to 2,000 mph (3,200 km/h) at altitude. It was a conventional afterburning turbojet for take-off and acceleration to Mach 2 and then used permanent compressor bleed to the afterburner above Mach 2. The way the engine worked at cruise led it to be described as "acting like a turboramjet". It has also been described as a turboramjet based on incorrect statements describing the turbomachinery as being completely bypassed.

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<span class="mw-page-title-main">Inlet manifold</span> Automotive technology

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A throttle is the mechanism by which fluid flow is managed by constriction or obstruction.

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  1. Massey, Bernard Stanford (1979). Mechanics Of Fluids (4th ed.). Van Nostrand Reinhold. p. 201. ISBN   0-442-30245-2.
  2. Seddon, J.; Goldsmith, E.L. (1999). Intake Aerodynamics (2nd ed.). Blackwell Science. ISBN   0-632-04963-4.
  3. Bader, F.; Bunt, E.A. (February 1960). Ramjet Technology Thermodynamics Of Ramjet Flow Processes. Silver Spring, Maryland, US: Johns Hopkins University, Applied Physics Laboratory. p. 75. Document TG 370-2.
  4. Knowles, Don; Erjavec, Jack (1998). Automotive Engine Performance (2nd ed.). US: Today's Technician. p. 200. ISBN   9780827385191.
  5. Heywood, John B. (1988). Internal Combustion Engine Fundamentals. McGraw-Hill Education. p. 54. ISBN   0-07-028637-X.
  6. Muller, Richard (1921). Hydroelectrical Engineering. New York: G. E. Stechert & Co. p. 142.
  7. Gunston, Bill (2006). The Development Of Jet And Turbine Engines (4th ed.). ISBN   0-7509-4477-3.