A typical commercial jet engine takes in 1. The mechanism by which a jet engine sucks in the air is largely a part of the compression stage. In many engines the compressor is responsible for both sucking in the air and compressing it.
Some engines have an additional fan that is not part of the compressor to draw additional air into the system. The fan is the leftmost component of the engine illustrated above. The compressor is shown in the above image just to the left of the fire in the combustion chamber and to the right of the fan. The compression fans are driven from the turbine by a shaft the turbine is in turn driven by the air that is leaving the engine. Compressors can achieve compression ratios in excess of , which means that the pressure of the air at the end of the compressor is over 40 times that of the air that enters the compressor.
At full power the blades of a typical commercial jet compressor rotate at mph kph and take in lb kg of air per second. Now we will discuss how the compressor actually compresses the air.
As can be seen in the image above, the green fans that compose the compressor gradually get smaller and smaller, as does the cavity through which the air must travel. The air must continue moving to the right, toward the combustion chambers of the engine, since the fans are spinning and pushing the air in that direction.
The result is a given amount of air moving from a larger space to a smaller one, and thus increasing in pressure. BANG In the combustion chamber, fuel is mixed with air to produce the bang, which is responsible for the expansion that forces the air into the turbine.
Inside the typical commercial jet engine, the fuel burns in the combustion chamber at up to degrees Celsius. The temperature at which metals in this part of the engine start to melt is degrees Celsius, so advanced cooling techniques must be used. The combustion chamber has the difficult task of burning large quantities of fuel, supplied through fuel spray nozzles, with extensive volumes of air, supplied by the compressor, and releasing the resulting heat in such a manner that the air is expanded and accelerated to give a smooth stream of uniformly heated gas.
To do so, they impart a moderate increase in the mass velocity to the combustion products for the large mass of air drawn through the engine in a given time. But turbojet and ramjet engines, which meet more demanding supersonic flight requirements, are less fuel-efficient. Various types of jet engines have been developed to deliver the required thrust and engine performance for a wide range of flight speeds and altitudes. Air-breathing turbojet, turbofan and ramjet engines operate according to similar principles in the sense that they raise the inducted air pressure before combustion and expand the high-energy gases before they leave, in a nozzle or exhaust system.
In turbojet engines, the inducted air goes through a compressor to increase its pressure before entering the combustor, then through a turbine before accelerating in the exhaust nozzle.
The ramjet engine, though, has no moving parts; it produces a ram pressure rise from decelerating the high-speed inducted air in the inlet diffuser. The ramjet engine can only operate at high supersonic velocities and therefore requires another launching device, such as a rocket or turbojet engine, to accelerate it to the required speed. Above a certain altitude the atmospheric density diminishes and jet propulsion is only possible for rocket engines that carry their own oxygen.
Rocket motors use either solid or liquid fuels. Solid rockets are the oldest types, and their bodies contain the combustion chamber and the solid fuel mixed with oxidizer. When the fuel is ignited the gaseous products of combustion are accelerated through the nozzle to produce thrust. In liquid rockets, the fuel and oxygen are stored in separate tanks and fed at controlled rates to the combustion chamber. Sign up for our email newsletter.
This concentrated energy is the thrust which propels the airplane. The reaction takes place with extreme speed and the turbines in most modern jet engines spin over 10, times a minute. What is in fuel mixture which causes this powerful reaction? Jet fuel is technically known as aviation turbine fuel, or ATF.
While initial jet engine experiments used steam power and early piston engines ran on gasoline. ATF is usually clear or light yellow. It consists of a mixture of hydrocarbons, and for safety reasons is processed with international specifications and standards. In commercial aviation, most jet engines use fuels known as Jet A and Jet A Most general aviation airplanes using turbine engines use a compound called Jet B, a performance type which is specifically designed for cold weather.
However, they are inefficient, and jet fuel is expensive. Turboprop airplanes are a combination of modern engineering and innovative use of lightweight materials. If the turboprop is considered a transition aircraft between piston-driven airplanes and jets, why are airplanes containing them still flown? Turboprops are becoming rarer, but they are still seen on regional airlines and general aviation aircraft.
They are favored by many pilots because they are generally less automated and much more efficient on shorter journeys. For example, it makes sense to fire up a jet engine to fly from Maine to Nevada, but a shorter hop from Colorado to New Mexico is more efficiently served on less fuel. Turboprops are more typically the airplane of choice in these circumstances. Matthew A. Johnston has over 23 years of experience serving various roles in education and is currently serving as the President of California Aeronautical University.
He is proud of his collaboration with airlines, aviation businesses and individual aviation professionals who are working with him to develop California Aeronautical University as a leader in educating aviation professionals. Hi my name is andrew meadows great article.
A different ratio than cars which planes are on. Are there a lot of job opportunities once school is finished, and can a mechanic from canada go to the United states to work? Thank you so much for your comment, Andrew. We are glad you enjoyed the article! There are many various job opportunities available upon graduation, and CAU offers graduate services to assist with job placement for all of our degree programs! Save my name, email, and website in this browser for the next time I comment.
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