# Tag Info

25

Turbojets and turbofans are very similar indeed: both are turbine engines; both create thrust from jet exhaust; and both have a rotating implement in front that can be called a fan. Although in the case of the turbojet, it isn't called a fan but the compressor first stage. $\$ Junkers Jumo 109-004 So what is the difference? There are five types of ...

22

In a turbojet, all the air goes through the engine proper, through the combustion chamber and all the stages of compressor and post-combustion turbine blades. In a turbofan, some of the air is just pushed by a fan around the rest of the engine. This is the "bypass". As Harper points out, it's not fundamentally different from a turboprop or extracting ...

15

Completely different design philosophies They are both turbine engines, and that is where the similarity ends. In a turbojet, the compressor-burner-turbine package is optimized to make thrust. A turbofan engine is a type of turboshaft engine. These use a compressor-burner-turbine core, but use a secondary set of turbine blades to convert its thrust ...

5

The main way to convert a gas turbine to provide thrust rather than shaft horsepower is to attach a large fan or propeller in place of the previous load. For example, the GE CF6, which powers aircraft such as the 747, 767, and A330, has a gas turbine variant called the LM6000 that provides around 50 MW of power. If you want to provide thrust from the ...

5

To start the engine, the fan blades have to be spun up. This is typically handled by either blowing air through them from some outside source, and/or by using an APU to generate power to drive the shaft they're connected to. Once the engine is running, it sucks in enough air to keep going on its own.

4

Turboprops and turbojets - or, more broadly, jets - produce thrust in somewhat different ways. First of all, let's address the way thrust is produced. Per Newton's 2nd and 3rd laws, force equals acceleration times mass, and an action (accelerating the air) produces an opposite reaction. After canceling out the variables (the math is easy to find), thrust is ...

3

After reading all the answers I felt that none of them really explained the answer in a way understandable to a layperson, so I will attempt to do so. First of all, both types of engines will burn fuel to generate energy, which is ultimately used to accelerate a stream of air towards the rear of the aircraft to create thrust. They differ in the method by ...

3

A burning turbine consists of compressor stage, burning stage and gas turbine stage. Both compressor and turbine stages consist of sets of stator and rotor blades and the rotors are connected via shaft so part of the work the turbine generates can be used to compress the intake air. The output from the turbine stage is a high-velocity jet of hot air-fuel-...

3

Assuming that the net thrust of a turbojet is constant is not correct. It is assumed to be constant (for simplicity by the aircraft performance engineers and usually valid for low subsonic speeds), but in reality, the performance is not constant, and it also varies with altitude. This is best shown by a simple simulation of a turbojet engine. The following ...

3

The final turbojet-powered aircraft to carry passengers was an Aerotours Dominicano Boeing 707-020 (early name for the Boeing 720). Registration N8711E. Retired sometime between 1986 and 1996. The final turbojet-powered aircraft to carry cargo was an Airborne Express Caravelle 6R. Registration N902MW. Retired in 2002. Hope this answers your question!

3

$v_0$ is the airflow speed through the engine, not the airspeed. As per @Bianfable’s comment. How the engine works at standstill: the compressor sucks air into the inlet, it initiates the flow through the engine. Axial compressor blades similar to a propeller, centrifugal compressors by slinging air out towards the compressor outlet. Maximum thrust at ...

2

I suppose the F135-PW-400 powerplant on the F-35B does just that. A turbine engine is used to create high enthalpy gas which can either pass through a turbine to produce mechanical work or pass through a diffuser to accelerate it and create a reaction impulse. General Electric has designed power generation gas turbines which use the gas core from the GE ...

2

Most turbine engines designed to drive some sort of mechanical system such as a hydraulic pump and electrical generators are not designed to provide thrust because their fuel controller can only run it at one speed. In other words, there is no throttle. Also, the internal components may not be designed for that type of application. So while it is in theory ...

2

Thrust is created by accelerating a working mass in opposite direction. Net thrust is the difference between the impulse of the air flowing towards the engine and the combined impulse of burnt fuel and the air exiting the engine (and propeller, if one is fitted), derived by time. That impulse is the product of mass and speed. When flying faster, the entry ...

2

It is simply the rate at which fuel can be burned. For instance, the Saturn V's first stage carried 1.37 million kg of liquid oxygen (along with the kerosene fuel), which it burned in about 165 seconds. Imagine the size of the jet intake you'd need for a comparable amount of air.

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There are several effects which in combination make constant thrust a good approximation at subsonic speed. Thrust is created by accelerating a working mass in opposite direction. Net thrust is the difference between the impulse of the air flowing towards the engine and the combined impulse of burnt fuel and the air exiting the engine (and propeller, if one ...

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