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 airbreathing jet engine such as a turbojet, turbofan, ramjet, or pulse jet. In general, jet engines are internal combustion engines.
A gas turbine, also called a combustion turbine, is a type of continuous and internal combustion engine. The main elements common to all gas turbine engines are:
The turbofan or fanjet is a type of airbreathing jet engine that is widely used in aircraft propulsion. The word "turbofan" is a portmanteau of "turbine" and "fan": the turbo portion refers to a gas turbine engine which achieves mechanical energy from combustion, and the fan, a ducted fan that uses the mechanical energy from the gas turbine to accelerate air rearwards. Thus, whereas all the air taken in by a turbojet passes through the turbine, in a turbofan some of that air bypasses the turbine. 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, typically used in aircraft. It consists of a gas turbine with a propelling nozzle. The gas turbine has an air inlet, 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.
The CFM International CFM56 series is a French-American family of high-bypass turbofan aircraft engines made by CFM International (CFMI), with a thrust range of 18,500 to 34,000 lbf. CFMI is a 50–50 joint-owned company of Safran Aircraft Engines of France, and GE Aviation (GE) of the United States. Both companies are responsible for producing components and each has its own final assembly line. GE produces the high-pressure compressor, combustor, and high-pressure turbine, Safran manufactures the fan, gearbox, exhaust and the low-pressure turbine, and some components are made by Avio of Italy and Honeywell from the US. The engines are assembled by GE in Evendale, Ohio, and by Safran in Villaroche, France. The completed engines are marketed by CFMI. Despite initial export restrictions, it is the most common turbofan aircraft engine in the world, in four major variants.
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. Afterburning 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 very high 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 Pratt & Whitney J57 is an axial-flow turbojet engine developed by Pratt & Whitney in the early 1950s. The J57 was the first 10,000 lbf (45 kN) thrust class engine in the United States. The J57/JT3C was developed into the J75/JT4A turbojet, JT3D/TF33 turbofan, and PT5/T57 turboprop. The J57 and JT3C saw extensive use on fighter jets, jetliners, and bombers for many decades.
The General Electric LM6000 is a turboshaft aeroderivative gas turbine engine. The LM6000 is derived from the CF6-80C2 aircraft turbofan. It has additions and modifications designed to make it more suitable for marine propulsion, industrial power generation, and marine power generation use. These include an expanded turbine section to convert thrust into shaft power, supports and struts for mounting on a steel or concrete deck, and reworked controls packages for power generation. It has found wide use including peaking power plants, fast ferries and high speed cargo ship applications.
A combustor is a component or area of a gas turbine, ramjet, or scramjet engine where combustion takes place. It is also known as a burner, combustion chamber or flame holder. In a gas turbine engine, the combustor or combustion chamber is fed high pressure air by the compression system. The combustor then heats this air at constant pressure. After heating, air passes from the combustor through the nozzle guide vanes to the turbine. In the case of a ramjet or scramjet engines, the air is directly fed to the nozzle.
A compressor stall is a local disruption of the airflow in the compressor of a gas turbine or turbocharger. A stall that results in the complete disruption of the airflow through the compressor is referred to as a compressor surge. The severity of the phenomenon ranges from a momentary power drop barely registered by the engine instruments to a complete loss of compression in case of a surge, requiring adjustments in the fuel flow to recover normal operation.
The air turborocket is a form of combined-cycle jet engine. The basic layout includes a gas generator, which produces high pressure gas, that drives a turbine/compressor assembly which compresses atmospheric air into a combustion chamber. This mixture is then combusted before leaving the device through a nozzle and creating thrust.
This article briefly describes the components and systems found in jet engines.
The Teledyne CAE J402 is a small turbojet engine. Several variants have been developed to power unmanned air vehicles such as missiles and target drones. Developed in the 1970s for the Harpoon anti-ship missile, the J402 was the first jet engine to be designed as a "wooden round", meaning that the engine had to be able to sit for long periods without maintenance or inspection and work right away.
The Flader J55, also known as the 124 within the company, was a small turbojet engine notable for its use of a supersonic axial-flow compressor. Development started at Fredric Flader Inc. in 1947, with the first examples being delivered in 1949. However, these delivered far lower power than predicted. Improved models followed in early 1952 that met the performance requirements, but demonstrated very poor reliability. When small engines from other companies became available, the J55 project was cancelled in 1952.
An airbreathing jet engine is a jet engine that emits a jet of hot exhaust gases formed from air that is forced into the engine by several stages of centrifugal, axial or ram compression, which is then heated and expanded through a nozzle. They are typically gas turbine engines. The majority of the mass flow through an airbreathing jet engine is provided by air taken from outside of the engine and heated internally, using energy stored in the form of fuel.
The accessory drive is a gearbox that forms part of a gas turbine engine. Although not part of the engine's core, it drives the accessories, fuel pumps etc., that are otherwise essential for the operation of the engine or the aircraft on which it is mounted. Accessory drives on large engines handle between 400–500 hp.
Many variations of aircraft engine starting have been used since the Wright brothers made their first powered flight in 1903. The methods used have been designed for weight saving, simplicity of operation and reliability. Early piston engines were started by hand, with geared hand starting, electrical and cartridge-operated systems for larger engines being developed between the wars.
The General Electric GE9X is a high-bypass turbofan developed by GE Aviation exclusively for the Boeing 777X. It first ran on ground in April 2016 and first flew on March 13, 2018; it powered the 777-9's maiden flight in early 2020. It received its FAA type certificate on September 25. Derived from the General Electric GE90 with a larger fan, advanced materials like CMCs, and higher bypass and compression ratios, it should improve fuel efficiency by 10% over its predecessor. It is rated for 110,000 lbf (490 kN) of thrust.
A free-turbine turboshaft is a form of turboshaft or turboprop gas turbine engine where the power is extracted from the exhaust stream of a gas turbine by an independent turbine, downstream of the gas turbine and is not connected to the gas turbine. This is opposed to the power being extracted from the power spool via a gear box.
The General Electric Catalyst is a turboprop engine under development by GE Aviation. It was announced on 16 November 2015 and will power the Cessna Denali, it first ran on December 22, 2017, and should be certified in 2020. The 850 to 1,600 hp engine aims for 20% better efficiency than its competition thanks to a 16:1 overall pressure ratio, variable stator vanes, cooled turbine blades, 3D printed parts and FADEC.
