[maineSS]

I going to try and get started here- been defeated 4 times so far as my post disappears into the Void after hitting "Submit Reply". I'm still digging for some data in my files, but for now I'll start at one end of this thing and work towards the other.

Nerys made a very good observation in post #163 of the "Removing Ethanol From Gasoline" thread when he said "this is not about energy content, this is about the Wrong fuel for the engine".

Now some "progressively" minded people might argue that he's got the wrong engine for the fuel, but the point is that energy content of a fuel does NOT always predict what is delivered in useful work from the engine.

Let's look at two highly tuned engines. One is a NASCAR level V8 producing 767 Hp at 14:1 compression on race gas. The specs are at tfxengine.com/NaturallyAspiratedCombustionData.html- you'll have to add www, as my post count is insufficient to link. I chose this engine because cylinder pressure, temp, A/F ratios, etc. are displayed by Engine Cycle Analysis equipment in real time on a real engine.

The other is a 105mm Tank Cannon- a highly developed example of the original IC engine- the gun. It has a similar overall thermal efficiency (~30%), and loses heat in similar ways. The energy distribution of a gun, (as taken from Hatcher's Notebook) is:

Projectile Energy- 30.9%
Heat & Kinetic Energy of Gas-40.7%
Heat to Barrel & Shell Case-28%

Projectile Friction is 7%, but was part of "Heat to Barrel" in the test. The energy distribution for a "typical" engine is:

Shaft Output- 24%
Exhaust-23%
Coolant-25%
Internal Friction-7%
Thermal Radiation-11%

Both of these engines have a 4" dia bore, but the fuel energy and overall performance are quite different. The ECA data show the NASCAR engine is developing 96 Hp in cyl #4 at 1812 Psi (11.4 tons on the piston). It's interesting to note that peak pressure is developed at 5-10 deg ATDC, not the theoretical "ideal" of 14-15 deg ATDC. Also note 35% of the A/F mixture is burned by TDC- doing negative work.

When you tap the firing pedal on the 105, chamber pressure rises to 60,000 Psi. Force on the projectile is 400 tons, and by the time it exits the muzzle, it's travelling over 4900 ft/sec. Projectile acceleration is 50,000 G's, and the energy release rate is 30 MegaJoules in .01 sec, which is over 4 million Hp.

Note I said "rate of energy release". Gun propellant is NOT a Super Fuel- it averages 8-10 times LESS energy per lb than gasoline. The energy in the 105mm charge is about 28,455 Btu- a little more than 1 lb of gasoline at the High Heat Value of 20,000 Btu/lb. Maybe this is what Albert Einstein had in mind when he remarked that we had harnessed only a tiny fraction of the energy present in gasoline. Really, when you compare the car to the cannon, you have to wonder- after 120 years of development, is this the BEST we can do with gasoline?

If you suspect there's more to internal combustion than heat values- your right. Nerys and Olympiades are absolutely right when they point out that HOW fuel burns in an engine is much more important. To be continued....