A fuel control unit (FCU) is a control system for gas turbine engines.
A fuel control unit (FCU) is a control system for gas turbine engines.
Gas turbine engines are primarily controlled by the amount of fuel supplied to the combustion chambers. With this in mind we can say that, the very simplest fuel control for a turbine engine is a fuel valve operated by the pilot. Many pre-production models of early turbojet engines featured just that, but it was soon found that this kind of control was difficult and dangerous in actual use. Closing the valve too quickly while trying to reduce power output could cause a lean die-out, where the airflow through the engine blows the flame out of the combustion chamber and extinguishes it. Adding fuel too quickly to increase power can damage the turbines due to excessive heat, or the sudden rise in combustion chamber pressure may cause a compressor stall. Another danger of too much fuel is a rich blow-out, where soaking the fire with fuel displaces the oxygen and lowers the temperature enough to extinguish the flame. The excess fuel may then be heated on the hot tailpipe and ignite, possibly causing damage to the aircraft. [1] For an aircraft engine, changes in airspeed or altitude cause changes in air speed and density through the engine, which would then have to be manually adjusted for by the pilot.
A fuel control unit attempts to solve those problems by acting as an intermediary between the operator's controls and the fuel valve. The operator has a power lever which only controls the engine's potential, not the actual fuel flow. The fuel control unit acts as a computer to determine the amount of fuel needed to deliver the power requested by the operator.
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 gas turbine or gas turbine engine is a type of continuous flow internal combustion engine. The main parts common to all gas turbine engines form the power-producing part and are, in the direction of flow:
A turbofan or fanjet is a type of airbreathing jet engine that is widely used in aircraft propulsion. The word "turbofan" is a combination of references to the preceding generation engine technology of the turbojet and the additional fan stage. 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 air-start system is a power source used to provide the initial rotation to start large diesel engines and gas turbines.
The Brayton cycle, also known as the Joule cycle, is a thermodynamic cycle that describes the operation of certain heat engines that have air or some other gas as their working fluid. It is characterized by isentropic compression and expansion, and isobaric heat addition and rejection, though practical engines have adiabatic rather than isentropic steps.
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.
In aviation, a flameout is the run-down of a jet engine or other turbine engine due to the extinguishment of the flame in its combustor. The loss of flame can have a variety of causes, such as fuel starvation, excessive altitude, compressor stall, foreign object damage deriving from birds, hail, or volcanic ash, severe precipitation, mechanical failure, or very low ambient temperatures.
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.
A compressor map is a chart which shows the performance of a turbomachinery compressor. This type of compressor is used in gas turbine engines, for supercharging reciprocating engines and for industrial processes, where it is known as a dynamic compressor. A map is created from compressor rig test results or predicted by a special computer program. Alternatively the map of a similar compressor can be suitably scaled. This article is an overview of compressor maps and their different applications and also has detailed explanations of maps for a fan and intermediate and high-pressure compressors from a three-shaft aero-engine as specific examples.
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.
The Heinkel HeS 40(HeS - Heinkel Strahltriebwerke) was an experimental constant-volume jet engine designed by Adoph Müller's team at Heinkel starting some time in 1940 or 41. It was based on the mechanical layout of the HeS 30, but replaced the conventional flame cans with oversized ones including large poppet valves that sealed off the chambers during firing. Constant-volume combustion, similar to the Otto cycle used in most piston engines, is considerably more fuel efficient than the constant-pressure combustion used in a typical jet engine.
The Gluhareff Pressure Jet is a type of jet engine that, like a valveless pulse jet, has no moving parts. It was invented by Eugene Michael Gluhareff, a Russian-American engineer who envisioned it as a power plant for personal helicopters and compact aircraft such as microlights.
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.
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 Pirna 014 was an axial turbojet designed in East Germany in the mid- to late 1950s by former Junkers engineers, who were repatriated to East Germany in 1954 after being held in custody in the Soviet Union following World War II.
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. Geared hand starting, electrical and cartridge-operated systems for larger engines were developed between the First and Second World Wars.
An internal combustion engine is a heat engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal combustion engine, the expansion of the high-temperature and high-pressure gases produced by combustion applies direct force to some component of the engine. The force is typically applied to pistons, turbine blades, a rotor, or a nozzle. This force moves the component over a distance. This process transforms chemical energy into kinetic energy which is used to propel, move or power whatever the engine is attached to.
Aircraft engine performance refers to factors including thrust or shaft power for fuel consumed, weight, cost, outside dimensions and life. It includes meeting regulated environmental limits which apply to emissions of noise and chemical pollutants, and regulated safety aspects which require a design that can safely tolerate environmental hazards such as birds, rain, hail and icing conditions. It is the end product that an engine company sells.