From old board -- Gaseous VS liquid fuel

[John]

This is copied over from the old board so I can answer it here:

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I guess I can't really add anything to the debate about whether the fuel is or should be fully vaporized but can someone tell me if burning a gas (say propane) gets more MPG than gasoline. I know that propane has a lower energy density than gasoline but if vaporization is that much better, then propane should still get more MPG. So, does propane get more MPG?

Martin.

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Not really. Propane burns cleaner then gasoline as gasoline is now normaly used. The mileage is about the same or a little less for propane, but performance can be improved for either fuel. If gasoline is totaly gaseous and when enough oxygen is provided for a clean burn then gasoline will give many more MPG than propane. The problems with using totaly gaseous gasoline are greater heat (burnt valves), and explosion and fire danger. I'm sure that the heat problem could be handled, but the explosion and fire danger is so great that no manufacturer wants to touch it.

John

[richard]

gasoline to burn REAL good ned to be .5 micron or less.

[Brian]

What's this? For once we agree on something? Nah.

Propane does indeed burn cleaner in the real world as it gets closer to complete combustion than gasoline does. Here's the equation for complete combustion of propane with air:

(C3H8)+ 5(O2+3.76 N2)--> 3(CO2)+ 4(H2O)+ 18.8(N2)

You can see the only byproducts of combustion given complete combustion of propane are carbon dioxide, water, and nitrogen. The exact same byproducts, but in different quantities, result from the complete combustion of octane:

(C8H18)+ 12.5(O2+3.76N2)--> 8(CO2)+ 9(H2O)+ 47(N2)

Unfortunately all the stabilizers, additives, etc. they add to gasoline make it a lot "dirtier" fuel to burn. Gasoline isn't pure octane either. The exact chemical composition of gasoline is tough to track down as the seasonal changes made to aid in vaporization effect the composition of the fuel. Neither propane nor gasoline completely combust, but propane gets closer to it so it doesn indeed burn cleaner than gasoline.

90% combustion of gasoline will yield more carbon monoxide and unburned hydrocarbons than 95% combustion of propane will. More of the propane is burnt, so it burns cleaner.

[(unknown)]

E-man here.  My password may not be working just yet.

In the 1950's there was one fellow willing to take on the mechanical challenges associated with using a very lean fuel mixture.  His name was Russell Bourke, and he developed a very ingenious engine that ran on a 1000 to 1 air/fuel ratio.  His first commercially available engine came out in 1954.  The basic layout was an opposed two cylinder engine having pistons arranged on opposite ends of a straight rod connected by a Scotch yoke drive mechanism in the center.

The exhaust temp was cool enough to put your hand near due to the almost complete combustion of fuel (including the hydrogen which favors an oxygen rich environment and high heat).  Also, the fuel burned so quickly, driven by the hydrogen flame propagation, that the end of the piston stroke during expansion was actually a refrigeration cycle which cooled the  spent gasses before exhausting them.  The combustion "event" is very much like a sharp detonation and only the in-line piston design saves the engine from becoming a pile of aluminum sand. The traditional Bourke engine has no flywheel and reaches ungodly rpm's.  The torque vs. rpm plotted curve looks similar to that of a turbine.

It's a real treat to study Bourke's engine if you've never been introduced.  They are still being produced by enthusiasts; here's a url: http://bourke-engine.com/index1.htm

 
E-man
 
 

[John]

No argument here! All the additives do hinder truly clean and complete combustion. All combustion has some byproduct, so "clean" really is a relative term.

John

[Bach On]

But don't I remember reading that propane doesn't supply as much horsepower as gasoline per cubic centimeter? Or did I hallucinate that?

Bach On

[Wolfie1]

That's right Mr On

If it is claimed that a gasoline engine can be converted to 100+ MPG through just vaporization of the fuel, a propane fueled engine should be able to get close to that number. So where is this super efficient engine?

Martin.

[Brian]

The oil companies have it under a sheet in their garages!!

[Brian]

True!! Propane does generate less power when compared to the burning the same amount of gasoline.

Ethanol is the way to go anyway. Burning ethanol greatly reduces emissions while making us free from our dependance on crude oil. It also allows you to increase the compression of the engine to 15 or 16 to 1 which increases efficiency.

Ethanol is fairly easy to come by as well. While you will get roughly the same fuel economy and about the same power when not pulling a load when compared to gasoline, the increase in compression and efficiency actually maintains the fuel economy at a constant level while towing, etc. I wish my truck did that....

Diesel engines are more efficient than current gasoline engines in that they run a higher compression ratio, but if it were possible to increase the compression of a gasoline engine (Otto cycle) the efficiency would be greater than that of a diesel engine operating at the same compression ratio. The Otto cycle is simply a more efficient process.'

You would lower emissions, maintain fuel economy, and generate the same amount of power, all without any crude oil!!  

[Bach On]

"The oil companies have it under a sheet in their garages!"

Please know: I'm not taking pot shots at this particular comment. But I've seen and heard charges like this for years from a number of sources. I wonder if everybody thinks this is really true?

If they are true, how could it be proven?

Seems like a patent would have been filed for the engine. Then it seems like the inventor's name would be listed. Somebody could then contact the inventor and ask. I suspect that has not been done. Or if the patent was sold, does the patent office maintain the current owners of a patent? Sure would make for an interesting research project.

I wouldn't put this tactic by the oil companies, but I doubt we can really prove it.

Bach On

[Brian]

LOL, All I've ever heard is rumors as well. In my humble opinion, the oil companies are bad, but not as bad as the cigarette companies!!!

"What the American public doesn't know is what makes them the American public"