Intake

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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.

Contents

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

Related Research Articles

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A jet engine is a type of reaction engine discharging a fast-moving jet that generates thrust by jet propulsion. While this broad definition can include rocket, water jet, and hybrid propulsion, the term jet engine typically refers to an internal combustion airbreathing jet engine such as a turbojet, turbofan, ramjet, or pulse jet. In general, jet engines are internal combustion engines.

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

A ramjet, or athodyd, is a form of airbreathing jet engine that uses the forward motion of the engine to produce thrust. Since it produces no thrust when stationary ramjet-powered vehicles require an assisted take-off like a rocket assist to accelerate it to a speed where it begins to produce thrust. Ramjets work most efficiently at supersonic speeds around Mach 3 and can operate up to speeds of Mach 6.

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

A carburetor or carburettor is a device that mixes air and fuel for internal combustion engines in an appropriate air–fuel ratio for combustion. The term is sometimes colloquially shortened to carb in the UK and North America or to carby in Australia.

<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.

<span class="mw-page-title-main">Pratt & Whitney J58</span> A high-speed jet engine

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.

Blowoff valve A pressure release system in turbocharged engines

A blowoff valve is a pressure release system present in most petrol turbocharged engines. Blowoff valves are used to reduce pressure in the intake system as the throttle is closed, thus preventing compressor surge.

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

In automotive engineering, an inlet manifold or intake manifold is the part of an engine that supplies the fuel/air mixture to the cylinders. The word manifold comes from the Old English word manigfeald and refers to the multiplying of one (pipe) into many.

Inlet cone

Inlet cones are a component of some supersonic aircraft and missiles. They are primarily used on ramjets, such as the D-21 Tagboard and Lockheed X-7. Some turbojet aircraft including the Su-7, MiG-21, English Electric Lightning, and SR-71 also use an inlet cone.

Manifold vacuum, or engine vacuum in an internal combustion engine is the difference in air pressure between the engine's intake manifold and Earth's atmosphere.

<span class="mw-page-title-main">Ram-air intake</span>

A ram-air intake is any intake design which uses the dynamic air pressure created by vehicle motion, or ram pressure, to increase the static air pressure inside of the intake manifold on an internal combustion engine, thus allowing a greater massflow through the engine and hence increasing engine power.

Carburetor, carburettor, carburator, carburettor heat is a system used in automobile and piston-powered light aircraft engines to prevent or clear carburetor icing. It consists of a moveable flap which draws hot air into the engine intake. The air is drawn from the heat stove, a metal plate around the exhaust manifold.

<span class="mw-page-title-main">Crankcase ventilation system</span> System to relieve pressure in a combustion engines crankcase

A crankcase ventilation system removes unwanted gases from the crankcase of an internal combustion engine. The system usually consists of a tube, a one-way valve and a vacuum source.

In turbocharged internal combustion engines, a boost controller is a device sometimes used to increase the boost pressure produced by the turbocharger. It achieves this by reducing the boost pressure seen by the wastegate.

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

A plenum chamber is a pressurised housing containing a fluid at positive pressure. One of its functions is to equalise pressure for more even distribution, compensating for irregular supply or demand. It is typically relatively large in volume and thus has relatively low velocity compared to the system's other components. In wind tunnels, rockets, and many flow applications, it is a chamber upstream on the fluid flow where the fluid initially resides. It can also work as an acoustic silencer.

<span class="mw-page-title-main">Components of jet engines</span> Brief description of components needed for jet engines

This article briefly describes the components and systems found in jet engines.

<span class="mw-page-title-main">Radiator (engine cooling)</span> Heat exchangers used for cooling internal combustion engines

Radiators are heat exchangers used for cooling internal combustion engines, mainly in automobiles but also in piston-engined aircraft, railway locomotives, motorcycles, stationary generating plant or any similar use of such an engine.

An airbreathing jet engine is a jet engine that ejects a propelling (reaction) jet of hot exhaust gases after first taking in atmospheric air, followed by compression, heating and expansion back to atmospheric pressure through a nozzle. Alternatively the reaction jet may include a cold jet of ducted bypass air which has been compressed by a fan before returning to atmospheric pressure through an additional nozzle. These engines are gas turbine engines. Engines using only ram for the compression process, and no turbomachinery, are the ramjet and pulsejet.

The Wright XRJ47 was an American ramjet engine developed in the 1950s to help propel the rocket-launched SM-64 Navaho supersonic intercontinental cruise missile. Although the design flight Mach Number was 2.75, a peak flight speed of Mach 3.0, at altitudes up to about 77000 ft, was envisaged. This very large ramjet had a number of design problems, including some difficulty in light-up. Development of the Navaho missile was cancelled along with the ramjet engine in 1957.

References

  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.