Pulse Detonation Engines: The Future of Aviation

Adam

New Member
Isn't it funny that we are constantly coming up with new types of aircraft engines since the Wright Brothers, yet the engines in our cars are basically the same as the very first car!!
 

CK

Well-Known Member
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Isn't it funny that we are constantly coming up with new types of aircraft engines since the Wright Brothers, yet the engines in our cars are basically the same as the very first car!!

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yeah that is kinda funny, I never thought of it like that.
 

Center_Mid

Well-Known Member
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Isn't it funny that we are constantly coming up with new types of aircraft engines since the Wright Brothers, yet the engines in our cars are basically the same as the very first car!!

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Wasn't Honda or Toyota working on a better GA piston engine? Also, I'm no gearhead, but why is it that so few GA engines run on deisel fuel? Wouldn't deisel make sense from a cost perspective?
 

tonyw

Well-Known Member
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Wasn't Honda or Toyota working on a better GA piston engine? Also, I'm no gearhead, but why is it that so few GA engines run on deisel fuel? Wouldn't deisel make sense from a cost perspective?

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Isn't the Diamond twin diesel powered, with a ridiculously good burn rate? I think I saw somewhere that it cruises at 200+ knots while burning only about 10 gph. Wow.
 

averyrm

Well-Known Member
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Why has no one mentioned the Wankel.

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What's a Wankel?

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Why the Wankel rotory engine! Used in the Mazda rx-7 and rx-8 cars. Renesis
 

UAL747400

Well-Known Member
I know there is some kind of disadvantage to them but I dont rember what.

I think you get one hell of a vibration from them and the spining wieght, as I like to call it, stresses the shaft which eventually breaks.

Correct me if im wrong on that, but I do know though there is a disadvantage to them.

Tom
 

JHines

New Member
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Is he trying to define a 'scramjet'?

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A scramjet is a ramjet in which the combustion process takes place at supersonic velocity. Like a ramjet, it has no moving parts in the flowpath (well, at least no turbomachinery).

A PDE is like a pulse-jet which produces thrust through a series of repeated detonations of a fuel-air mixture.

Although it could be stand-alone like a scramjet, a PDE can also be used as a "replacement" for a gas turbine combustor. Because it the process is discontinuous and produces a pressure rise in the combustor, it has the potential to alllow more mechanical work to be recovered in the turbine for the same average material temperature (like a reciprocating engine).
 

JHines

New Member
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Correct me if im wrong on that, but I do know though there is a disadvantage to them.

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I've never heard of a vibration problem, but like all automotive coversions it is a major headache to produce a reliable propeller speed reduction device at a reasonable weight.
 

MikeD

Administrator
Staff member
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Why has no one mentioned the Wankel.

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What's a Wankel?

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A Wanker?
 

averyrm

Well-Known Member
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Correct me if im wrong on that, but I do know though there is a disadvantage to them.

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I've never heard of the vibration problem.

They usually burn a lot of gas, and pollute a lot more (the new engine in the rx-8 tries to fix a lot of that)

The other problem is you can't start one up, drive ten feet, and then shut it off. Sometimes the engine will freeze up because of, I think, carbon deposits at the sides of the rotors.

On the plus sides, they make a lot of power for the displacement, don't weigh a lot, and are small dimensionally.
 

ananoman

New Member
It will be interesting to see how the new diesel engines work out. There have been some used in the past. Packard built a diesel radial in the '30s that was used on a Bellanca to set some time/distance records, but I have heard that it was pretty rough running. The Germans also tried some in the '30s and '40s. The only major use of diesel aero engines I know of was on rigid airships.

The traditional problem with a diesel recip. is high weight and low power. Diesels are more fuel efficient due to their high compression ratios which extract more work from the fuel. Adding a turbocharger or supercharger only makes them more efficient. They also use excess air for cooling instead of excess fuel like gas engines. Diesel engines do not have a 'throttle' in a traditional sense. They vary power output by varying the amount of fuel injected into the cylinders, not by controlling the amount of air entering the engine.

Since they have very high compression ratios and corresponding high cylinder pressures, the engines must be more 'heavy duty' and are traditionally much heavier than a gas engine of similar power. They also usually operate at a lower rpm. BMW now has some high speed diesel car engines that, while less powerful than a similar gas engine, still make alot more power than a traditional diesel.

Much of the advantage of the diesel aircraft engine comes from simple fuel availability. In most of the world, general avation simply does not exist as we know it. Jet A is the only fuel available. In Europe diesel is also cheaper than gas due to taxes. This could easily change. I would think that a computer controlled gas engine with fuel injection and variable ignition timing could be made to run on high octane auto fuel, while being lighter and cheaper than a diesel. With FADEC they can easily run lean of peak for a measurable gain in fuel efficiency.
 
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