An aircraft is a vehicle that is able to fly by gaining support from the air. It counters the force of gravity by using either static lift or the dynamic lift of an airfoil, or, in a few cases, direct downward thrust from its engines. Common examples of aircraft include airplanes, helicopters, airships, gliders, paramotors, and hot air balloons.
A jet engine is a type of reaction engine, discharging a fast-moving jet of heated gas that generates thrust by jet propulsion. While this broad definition may include rocket, water jet, and hybrid propulsion, the term jet engine typically refers to an internal combustion air-breathing jet engine such as a turbojet, turbofan, ramjet, pulse jet, or scramjet. In general, jet engines are internal combustion engines.
A ramjet is a form of airbreathing jet engine that requires forward motion of the engine to provide air for combustion. Ramjets work most efficiently at supersonic speeds around Mach 3 and can operate up to Mach 6.
A pulsejet engine is a type of jet engine in which combustion occurs in pulses. A pulsejet engine can be made with few or no moving parts, and is capable of running statically. The best known example may be the Argus As 109-014 used to propel Nazi Germany's V-1 flying bomb.
The turbofan or fanjet is a type of airbreathing jet engine that is widely used in aircraft propulsion. The word "turbofan" is a combination of the preceding generation engine technology of the turbojet, and a reference to the additional fan stage added. It consists of a gas turbine engine which achieves mechanical energy from combustion, and a ducted fan that uses the mechanical energy from the gas turbine to force air rearwards. Thus, whereas all the air taken in by a turbojet passes through the combustion chamber and turbines, in a turbofan some of that air bypasses these components. A turbofan thus can be thought of as a turbojet being used to drive a ducted fan, with both of these contributing to the thrust.
The turbojet is an airbreathing jet engine which is typically used in aircraft. It consists of a gas turbine with a propelling nozzle. The gas turbine has an air inlet which includes inlet guide vanes, a compressor, a combustion chamber, and a turbine. The compressed air from the compressor is heated by burning fuel in the combustion chamber and then allowed to expand through the turbine. The turbine exhaust is then expanded in the propelling nozzle where it is accelerated to high speed to provide thrust. Two engineers, Frank Whittle in the United Kingdom and Hans von Ohain in Germany, developed the concept independently into practical engines during the late 1930s.
An afterburner is an additional combustion component used on some jet engines, mostly those on military supersonic aircraft. Its purpose is to increase thrust, usually for supersonic flight, takeoff, and combat. The afterburning process injects additional fuel into a combustor in the jet pipe behind the turbine, "reheating" the exhaust gas. Afterburning significantly increases thrust as an alternative to using a bigger engine with its attendant weight penalty, but at the cost of increased fuel consumption which limits its use to short periods. This aircraft application of "reheat" contrasts with the meaning and implementation of "reheat" applicable to gas turbines driving electrical generators and which reduces fuel consumption.
The bypass ratio (BPR) of a turbofan engine is the ratio between the mass flow rate of the bypass stream to the mass flow rate entering the core. A 10:1 bypass ratio, for example, means that 10 kg of air passes through the bypass duct for every 1 kg of air passing through the core.
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.
The Yakovlev Yak-36, also known as Izdeliye V, is a Soviet technology demonstrator for a VTOL combat aircraft.
A propelling nozzle is a nozzle that converts the internal energy of a working gas into propulsive force; it is the nozzle, which forms a jet, that separates a gas turbine, or gas generator, from a jet engine.
In aeronautics, an environmental control system (ECS) of an aircraft is an essential component which provides air supply, thermal control and cabin pressurization for the crew and passengers. Additional functions include the cooling of avionics, smoke detection, and fire suppression.
The Learjet 25 is an American ten-seat, twin-engine, high-speed business jet aircraft manufactured by Learjet. It is a stretched version of the Learjet 24.
A jet engine performs by converting fuel into thrust. How well it performs is an indication of what proportion of its fuel goes to waste. It transfers heat from burning fuel to air passing through the engine. In doing so it produces thrust work when propelling a vehicle but a lot of the fuel is wasted and only appears as heat. Propulsion engineers aim to minimize the degradation of fuel energy into unusable thermal energy. Increased emphasis on performance improvements for commercial airliners came in the 1970s from the rising cost of fuel.
A variable cycle engine (VCE), also referred to as adaptive cycle engine (ACE), is an aircraft jet engine that is designed to operate efficiently under mixed flight conditions, such as subsonic, transonic and supersonic.
Specific thrust is the thrust per unit air mass flowrate of a jet engine and can be calculated by the ratio of net thrust/total intake airflow.
The Rolls-Royce/Snecma Olympus 593 was an Anglo-French turbojet with reheat, which powered the supersonic airliner Concorde. It was initially a joint project between Bristol Siddeley Engines Limited (BSEL) and Snecma, derived from the Bristol Siddeley Olympus 22R engine. Rolls-Royce Limited acquired BSEL in 1966 during development of the engine, making BSEL the Bristol Engine Division of Rolls-Royce.
This article briefly describes the components and systems found in jet engines.
An airbreathing jet engine is a jet engine in which the exhaust gas which supplies jet propulsion is atmospheric air, which is taken in, compressed, heated, and expanded back to atmospheric pressure through a propelling nozzle. Compression may be provided by a gas turbine, as in the original turbojet and newer turbofan, or arise solely from the ram pressure of the vehicle's velocity, as with the ramjet and pulsejet.
The familiar study of jet aircraft treats jet thrust with a "black box" description which only looks at what goes into the jet engine, air and fuel, and what comes out, exhaust gas and an unbalanced force. This force, called thrust, is the sum of the momentum difference between entry and exit and any unbalanced pressure force between entry and exit, as explained in "Thrust calculation".
