New techniques in turbofan engines

The new generation of engines have been developed versions of the foregoing. It uses new materials and frequently adds new elements, but the general concept remains the same. It is still the combustion of jet fuel in the combustion chamber that is ultimately used as a drive source, but more modernized techniques will be applied, and the development of better materials does not stop here. The benefits of these engines are mainly: weight reduction, lower fuel consumption and lower emissions of harmful gases.

Traditional turbofan

In a traditional turbofan air coming into the engine via the fan. The rotating fan accelerates the air. The bulk of the air goes to the compressor inside and a small amount will go around the core of the motor. This road is important for the cooling of the motor. In the combustion chamber, kerosene is injected. This is ignited by the combination of air at high pressure, which enters through the compressor.
The hot air will now rotate the turbines. These are connected via a central shaft with the fan. The exhaust of the engine accelerates the exhaust gases still more. As a result, there is a difference in speed between the ambient air and the exhaust gases. This difference implies the thrust. The thrust of the engine benefits not only from the combustion of kerosene through which the hot air turns the turbines. A part of the thrust also comes from the rotating fans that have the same function as a propeller.

High bypass ratio

Bypass ratio
Bypass ratio can be defined as the ratio of the air that does not pass through core of the turbofan engine in front of the amount of air that it runs through the motor. A high bypass ratio means that the amount of air is much larger goes around the core than the amount of air that passes through the core.
Specific explanation
The high bypass ratio has several advantages. Especially first pass less air through the core so less fuel is injected and therefore lower consumption. With a high bypass ratio engines are often equipped with a larger fan with more blades in order to enhance the propeller effect. Furthermore, a high bypass ratio engine produces less noise, which increases the comfort of the passengers. The noise reduction comes because the flow of cold air around the outlet has a dampening effect. The outlet pressure is also lower, which also makes for a reduction. The great strength of these engines will have to turn these less at full strength which as a secondary effect also reduces noise. The air in the by-pass also allows for a better cooling of the motor. A well-cooled engine has better combustion which lower emissions of harmful gases in the hand works.


For parts of aircraft engines is usually looking for materials that are both light and strong. This seems at first sight might be a contradiction, but in some cases it is anything but. For a long time, titanium is a metal that is frequently used. The latest developments in composites, there are better materials to use. The composite used in the fan blades of the GEnx engine GE is lighter, stronger and less impact to fatigue than titanium. Other elements of this new engine are made of composites which makes a lot of weight.
Manufacturers are increasingly using composites to manufacture from various parts of their planes. A disadvantage is that composites are replaceable harder than metals. For example, in the fuselage of an aircraft is to restore the more difficult when it is made of a composite in front of aluminum. In contrast, however, that people experimenting with composites that would repair minor damage on its own.

"Geared" turbofan

In these engines is a computer-controlled gearbox provided which ensures that the fan and high and low pressure compressor rotating at a different speed. The fan is driven slower than normal turbofan engines, which ensures a very high bypass ratio. For example, the Pratt & Whitney PW1000G has a bypass ratio of 12: 1. Both compressors run faster than the fan and compressor can consist of fewer parts. Since weight is saved.
The driving of both the fan and the compressors at their optimum speeds, makes for a more efficient combustion. This allows fuel consumption and emissions of harmful gases are reduced. The very high bypass ratio engines are also quieter. The addition of the gear box also has disadvantages. The really big fan creates more drag, which then again is detrimental to fuel consumption. The maneuverability of the unit would therefore be affected. Adding the gearbox and additional drive shafts for the compressor and the fan could impair the reliability of the engine. It should be noted that by reducing the size of the compressors, the reliability then rises again.
The weight loss by reducing the size of the compressor is canceled out by the addition of the gearbox. There, energy is lost through the heating of the gearbox. This has very little impact on the performance of the engine.