Fuel vaporization

[Anonymous]

Someone mentioned in a thread in The Lounge that gas would have to be heated to somewhere around 450 degrees to completely vaporize. (I forget the exact number) I assume this is at atmospheric pressure. I assume the temp would be lower under a vacuum. Is there an easy way to figure what the temp would be under a given vacuum?

 

[Anonymous]

I think you would have to know the Reid Vapor Pressure of each component in the fuel (hundreds!) and do the math from there.

 

[xctasy]

Unscientific scorners reply."Nature abours a vaccum".


The correct vaccum would only be obtained if the individual load of fuel was subjected to a small chamber which could be placed under a vaccum.

A 500 hp car would need to be able to place fuel( 27 cc per second, or 0.44 US gals per minute) into an 'ideal vaccum chamber'. Then it would have to be given a positive pressure in order to pass into the combustion chamber. Extra work would need to be done to do this, as vaccum pumps are very hard to keep working on a constant, reliable basis. It's much easier to pressurize than to evacute a chamber.

The details are somewhat cloudy to me, and I can't undestand how up to 165 to 195 pounds per square inch of peak combustion pressure could have a slug of negative pressurized vapour injected into the engine.

Pressure zones move from the heigher to the lower. You'd have to make a prechamber engine, or some kind of statified charge engine, and then blow up or heat the gas in a steep change in pressure. A frozen intake charge would pack more stuff into the engine, a prevapourized engine would loose power becasue there is less stuff in the combustion chamber.


A real head bender, DC!

 

[Anonymous]

up to 165 to 195 pounds per square inch of peak combustion pressure

Peak CRANKING pressure, maybe!
Peak combustion pressure is much higher...

 

[Lazy JW]

My 1941 John Deere Model "A" two-cylinder 321 cubic inch tractor has a pretty effective fuel vaporization system. This is certainly not a new concept. My old Johnny Popper was designed to run heavy, low-octane fuels such as kerosene, stove oil, and distillates (also known as "tractor fuel"). These fuels simply will not vaporize sufficiently without extra heat being added, so they designed the intake manifold to have the exhaust passages completely surrounding the intake tract. It is a one-piece casting. The compression ratio is kept quite low (4.45:1) to keep the detonation under control. This is a spark ignition engine.

Modern egines went away from heating the intakes because it reduces peak power output. My Johnny Popper doesn't idle very well on straight gasoline, it doesn't seem to like the high vaporization effect, but pulls nicely under load.
Joe

 

[Anonymous]

Preheating the fuel/air charge leans out the mixture and causes problems such as a loss of power and detonation.

BUT...

If you can heat to the point of having a fully vaporized charge, then everything changes. At least that's what I've read.

Under a fully vaporized charge, you are using much less fuel, depending on who's claims you read - 50 - 90 percent less. Under full vaporization the mixture burns instantaneously. No excess heat. No detonation. No loss of power. At least in theory. I'm gathering needs supplies to build a vaporization set-up, as well as a test motor. You don't think I'd risk blowing up my new motor?

Even with the lean of peak, its still apples and oranges, its not a vaporized charge.