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[Digg] 200+ MPG Gun engine? - Adventures in Engineering — LiveJournal
The wanderings of a modern ronin.

Ben Cantrick
  Date: 2006-05-04 00:52
  Subject:   [Digg] 200+ MPG Gun engine?
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http://pesn.com/2006/05/02/9500266_Gun_Engine/

http://peswiki.com/index.php/Directory:Gun_Engine

The Gun engine works by harnessing detonation (fuel explosions) instead of the normal rapid burning of fuel (deflagaration) that our current engines use. Detonation is a LOT more energetic than deflagaration. So energetic, in fact, that it destroys car engines (usually by blowing apart the pistons inside the engine) when it occurs. The fact that the guy's prototype, while 92% efficient, destroyed its own crankshaft while running shows you how powerful detonation really is. The fact that his pistons haven't blown up certainly shows some promise, though.

In any event, color me skeptical. I have no problem believing that there's a much better way to do things than the current 30-35% efficient gasoline engines in all our cars. (Which happens, ironically, because we run our engines far too cool. The temperature differential puts the upper bound on the efficiency of an internal combustion engine.) But 220 MPG seems like fantasy. Though, I suppose, if my Civic can get 45 MPG now, and this guy's claims of quadruple efficiency are actually true, 150 MPG might be possible. Well, this will just have to be one place where I'll just have to hope my skepticism is unfounded...
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  User: nickhalfasleep
  Date: 2006-05-04 02:57 (UTC)
  Subject:   (no subject)
"It harnesses the power of detonation".

So how is detonation not combustion, and how is this different than the combustion in existing engines?

I'm not a chemist, but I think he's making "detonation" out to be something unusual, while it's just combustion. There are certainly a wide variety of fuel / air mixtures to play around with, but it is my basic understanding that it is a rapid combustion in modern car engines which is the same thing in terms of physical behavior as a "detonation".

If "detonation" were more powerful than existing combustion methods, I'm darn sure compression engines above diesel would have been more widely described in engine technology. In railroading locomotives I've heard nothing about it, ever, and they have always been willing to try really big, heavy engines if they delivered a ton of power (the dual-cylinder Fairbanks Morse opposed piston engines come to mind, also used in American Diesel-Electric submarines).

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Ben Cantrick
  User: mackys
  Date: 2006-05-04 03:09 (UTC)
  Subject:   (no subject)
So how is detonation not combustion, and how is this different than the combustion in existing engines?

Combustion is when the flame front travels (reasonably) smoothly outward from the spark plug and thus provides a smoother push downward on the piston.

Detonation is when the mixture gets under so much pressure or is so hot that many flame fronts occur simultaniously and the mixture explodes in all directions simultaniously.

In railroading locomotives I've heard nothing about it, ever, and they have always been willing to try really big, heavy engines if they delivered a ton of power

That's a good question. And as I said, I'm skeptical of the claims of this inventor.

One possible explanation I can think of is that that the railroads were welded to diesel fuel. According to one comment in the Digg post, diesel doesn't detonate at nearly the shock loads that gasoline does. You can harness diesel detonation fairly easily, but gasoline detonation tends to pulverize even the strongest alloys when used in a conventional piston/rod/crank design. Maybe locomotive designers never even considered a gasoline detonation engine design.
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  User: nickhalfasleep
  Date: 2006-05-04 03:14 (UTC)
  Subject:   (no subject)
Ah, okay, I see the difference. So he's trying to make a diesel engine that runs on gasoline. So it is harnessing a bomb. Seems like a really difficult materials problem.

I think even if diesel has a lower shock load, it is so widely used in situations where a strong physical and economical, that itwould be difficult to surpass diesel in an energy-per-dollar ratio.

I still want my Mr. Fusion.
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  User: (Anonymous)
  Date: 2011-04-11 20:01 (UTC)
  Subject:   He solved the "bomb" problem
"Any engineer will tell you that detonation in an engine is a bad thing and should be avoided otherwise destruction of the engine is a question of time. That’s because abnormal combustion, actually explosion, is taking place inside the combustion chamber and creates pressures about fourteen times normal combustion pressure and a temperature increase that can create hot spots, causing the inlet mixture to pre-ignite, leading to burnt pistons.

A Canadian physicist and inventor Kazimierz Holubowicz puzzled over the low efficiency of the reciprocating engine operating under normal combustion conditions because he knew that the energy released by fuel exploding, is very much more than under normal combustion. The obvious problem was how to build an engine that would allow fuel to explode (detonate) without the engine exploding!

He came up with a design that uses a second free floating piston in a very long cylinder. Basically the detonating fuel in the upper cylinder forces the free piston downward compressing air trapped in the space between the cylinders which act as a cushion. The free piston oscillates as the main piston is driven downwards turning the crankshaft. The exhaust in the upper cylinder expending most of its energy is relatively cool at 140 deg F and steam products of combustion condense to dissolve harmful SOx and NOx products allowing simple treatment and disposal".
(source: http://tinyurl.com/62thbqn )

There is also a site devoted to Mr. Holubowicz inventions: http://gun-engine.pl/
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osmium_ocelot: Linna
  User: osmium_ocelot
  Date: 2006-05-04 11:56 (UTC)
  Subject:   (no subject)
Keyword:Linna
"You can harness diesel detonation fairly easily, but gasoline detonation tends to pulverize even the strongest alloys when used in a conventional piston/rod/crank design."

one wonders if you could harness this energy with a piston/fluid/drive design. In addition to doing the work, the fluid would act as a shock absorber and lessen the stress on the piston head. There's a waterwheel design (invented I can't remember when) that is something like 90 odd percent efficent at transfering energy. Still used in water turbines today.

:::shrugs::: But I really don't know anything and I'm speculating out my ass.

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