Chris Cosman wrote:

My question is, since diesel fuel is heavier than gas is the HP/pound

of fuel

still about the same?

The HP/lb depends not only on the fuel, but also on the engine.  Recall

thast

engine's can be rated by the BSFC.  That's HP / lb / hour.

If you want to talk about energy available per pound, that would be

Btu/lb.

Gasoline and diesel are roughly equivalent on a Btu/lb basis (both in

the range

of 18,000-19,000 Btu/lb), but since diesel is denser, diesel has more

Btu/gal

(128,400) than gasoline (115,000).  See:

http://afdc.nrel.gov/pdfs/fueltable.pdf

It's also easy to see that adding oxygenates (ethanol, methanol, or

MTBE) lowers

the energy per gallon of gasoline.  Less energy per gallon equals more

gallons

per hour for the same HP in a given engine.  Yet another reason to avoid

alcohol

when using mogas to fly.

Now if we could just find a safe way to carry pure hydrogen...  :-)

Russell Kent

Hydrogen is a pain. Nobody seems to really understand this, especially the
people promoting its use. I don't mean you Russell, I mean all of the
environmental groups which seem to totally ignore science. I agree that
hydrogen could be a clean fuel for stationary applications using fuel cells.
There is still the question of how to generate it efficiently, but that is a
different story. When I used to work with rocket engines and pumps we had
all kinds of problems with hydrogen. Here is a brief sampling:

1.) because of it's low molecular weight, it will escape through leaks that
would not even show up with a normal gas.

2.) It has a very wide flammability range meaning it will burn over a very
wide range of fuel air ratios. this makes it very dangerous for grandma to
pump into her sedan.

3.)storage is a nightmare. We had a huge spherical tank that was vacuum
insulated and was a never-ending source of problems. We called it "the death
star"

4.) when it burns, the flame is invisible to the naked eye. We had infrared
binoculars to look for the source of the fire. Beats the old method of
holding a broom out in front of you. If the broom bursts into flames, don't
go any closer (I'm not kidding!)

5.) energy density is atrocious. it only makes sense when you need the low
molecular weight for high specific impulse. A 747 running on hydrogen might
have room for 10 people.

Metal hydrides are too heavy for aircraft, and cars for that matter. I am
afraid that the clean hydrogen economy utopia is a paper exercise that
sounds good in theory. About the only bright spot is that hydrogen gas is
lighter than air, so any conflagration will rise up and away from the
ground, and it does tend to disperse rapidly.

For aircraft energy density (KJ/M^3 or BTU/ft^3) is key. Just add a little
carbon to hydrogen and miraculous things happen! It can be stored in any
good old gas can. It is safe for grandma to pump at the gas station.
Flammability range is much narrower. You can see the flame with the naked
eye. Energy density goes way up etc, etc, etc. But nobody is giving out
grant money to research the new hydro-carbon economy, oh wait, that is what
we already have! Add carbon and you have a nice liquid carrier for hydrogen.

The following should make Paul all aglow and I'm sure will cause the
pseudo-environmentalist left wing crazies no small amount of stomach acid:

http://www.discover.com/may_03/featoil.html

They are installing their first plant about 2 hours from my location. If
this works I predict we will be mining land fills in 20 years. These guys
are contributing more than all the dreadlock-wearing, drum-beating-loonies
combined, and OH MY GOD, there is a PROFIT involved.

Monty

 
The AirCraft Rotary Engine NewsLetter.  Powered by Linux.
ACRE NL web site. http://home.earthlink.net/~rotaryeng/            
Copyright 1998-2003 All world wide rights reserved.