How can jet engines be more fuel efficient?

Question

Jet engines are becoming more fuel efficient but how? How can basicaly simple engine( by how it produces thrust) be altered to allow for greater range and power? Both turbofan with reheat and without.

Answer 1

The Jet Engine

1. Simply put it Sucks, Squeezes, Bangs and Blows – that is it!

2. The jet engine Sucks (or pulls) in large quantities of air. With modern high by-pass turbofan engines, they can easily ingest a fully-grown man standing several meters away from the inlet. http://www.youtube.com/watch?v=5jxcSY1AwrM

3. The engine then takes this air and compresses it or the Squeeze process.

4. At that point, the engine adds an ignition source with fuel and actually explodes the compressed air in the Bang process.

5. Finally, direction vanes force the exploded air out the back of the engine at high velocities creating an exhaust thrust vector – the Blow. Newton’s Third Law of Motion says; for every action, there is an equal and opposite reaction; therefore, by pushing the air out the back of the engine the object it is attached to (the wing or fuselage of the aircraft) moves forward. Like a swimmer pushing against a wall in a swimming pool with his feet, the jet develops thrust.



To increase the efficiency of this process the engine manufacturer can increase the efficiency of any of these individual steps. In an unrelated but relevant area, airframe designers can change the design of the wing and allow for a higher service ceiling. A jet engine is more efficient the higher it flies, in other words if manufacturers can design a wing that will allow the plane to fly at higher altitudes, the fuel flow (gallons per hour) the engine consumes will lower.



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Answer 2

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Answer 3

If you don't heat air you don't waste energy.



So the ideal jet would move air without heating it.



Or would cool air while moving it, beaming the excess energy back home to head Grandmas toes at night.



But there is another aspect. Direction of thrust. All current engines do not produce covalent flow. Thus at nozzle the jet plume to some degree separates and pushes in the wrong direction, as well as the right direction. Produce more covalent flow, and just like a laser, the energy levels needed to shine farther will dramatically drop. I know it sounds silly, but the next big answer might well have been found over 80 years ago in wind tunnel design.

Answer 4

By designing the fuel delivery system to obtain 100% complete atomization. There's still unburned fuel coming out of any engine. When you get 100% atomization and burning, you've achieved maximum efficiency as far as fuel goes. The next step is working on friction inside the engine and drag on the airframe. Then making the airplane immune to gravity. Then making the whole airplane lighter - including the engines. But that's all theory, not really achievable in real life.

Answer 5

Increasing the temperature gradient between the inside of the engine and the outside world improves efficiency, so many design improvements concentrate on this. The limiting factor is the structural strength of the materials used to build the engines, which declines with increasing temperature. Constant improvements in these materials and in engine designs allow the temperatures to be gradually increased over time, improving efficiency.



Another way of improving efficiency is by moving a large mass of air slowly, rather than a small mass of air quickly. Turbofans are the implementation of this concept, and they've improved efficiency greatly (and have reduced noise greatly as a side benefit).

Answer 6

Like what somebody else said, they can improve either the sucking, squeezing, banging, or blowing :P



Improvement in sucking can be done by improving the fan at the front. Nowadays, in the new engine designs, we've got massive diameter, variable/chord, composite, forward fans.

(Turboprops are essentially jet engines with a propeller, which is a very large diameter fan in front.

There has also been talk about a pusher-type turboprop that would be even more efficient, without as much a loss in speed as turboprops)



Improvement in squeezing is being done with multiple stage, multiple gearboxes, multiple spool compressor stages, and lighter stronger materials



Improvement in banging is being accomplished by designing combustor cans that are more efficient and burn cleaner, like on the GE GEnx. Hopefully, perhaps in the future, they'll come up with some kind of additive to allow the fuel to burn cleaner, or come up with a new fuel that offers more energy density--bang for your buck--than jet A.



Improvement in blowing is being done in about the same way as sucking. Better fans, lighter and stronger materials, lower friction shafts and gearboxes leading back to the rest of the engine, etc.

Answer 7

There are so many highly skilled engineers working on this constantly, tweaking and modifying the designs that exist it's extremely unlikely that the opinion of anyone who isn't working on it will have an appreciable effect.



The basics would be better combustion (less wasted fuel), better lubrication (less friction) or more efficient use of the power generated.

Answer 8

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Answer 9

The only way it's more fuel efficient is if they dont use them

Answer 10

chemistry

the combustion process can be altered to give a bigger bank for the buck

in simple terms

Answer 11

make the planes lighter?

Answer 12

afterburners so they don't wast arny