Coal Can Fly

Hardly anything new about that. Rudolf Diesel designed several engines to run on powdered coal.

Graham

Any none ever really worked. In fact, even the coal/oil surries for Indian locomotives never worked out. GE had about 20 different additives to keep the suspension and it _still_ didn't work.

Moreover, diesel is a little heavy and unreliable for commercial aviation.

Finally, at high altitudes you need gas turbines.

With a heat exchanger unrefined coal can power gas turbines.

Bret Cahill

The Luftwaffe got a diesel powered bomber to the US east coast and back from occupied Europe during WW2.

Graham

Alexander Lippisch designed a supersonic fighter plane intended to be powered by coal dust, but it was not built.

It's disputed whether that actually happened:

Do you know what commercial jet fuel is?

High octane kerosene(#1)

Does there exists high octane kerosene? I though octane number is measured (and is only valuable for) gas engines, measuring how difficult is do self ignite gasoline in high pressure and temperature. 'High Octane' (if it's analog existed for kerosene) wouldn't be valuable for jet engine. For diesel engines which use more or less kerosene other number - cetane number is used, which is more or less opposite to octane number. High cetane number diesel fuel is more valuable, but probably not for jet engines.

No.

Kerosene contains no octane (although there may conceivably be trace amounts)..

I think Bill was too subtle. Kerosene, Jet A, and diesel fuel are all very similar.

The Jumo series of diesel aircraft engines first entered service in 1932.

One of the latest developments in piston engines for light aircraft is the Thielert diesel, which runs on Jet A. This is an advantage because many existing smaller aircraft engines were originally designed for 80 octane leaded, and can develop mechanical problems if run exclusively on the 100 LL which is currently available at airports. It's enough of a problem that people have spent the money to produce supplemental type certificates, which allow (sometimes with certain changes) existing certified aircraft to legally run on auto fuel, and a fair number of airports now have an "auto gas" pump. There are other companies developing small aircraft diesels, Delta Hawk and Zoche come to mind, though I don't know if they have actually delivered any to customers. People have also run diesel cars on Jet A, though I have heard that the lubricity is not as good as #2 diesel, and can cause problems with some injectors.

Also, I understand NATO is moving toward a requirement that all vehicles of the participating armed forces be able to operate on either diesel or aviation kerosene.

So most jet fuel isn't very exotic, and diesel engines work fine in aircraft.

Tim Ward

Half right. It's a longer chain hydrocarbon like kerosene or diesel, but it's not "high octane". Detonation or preignition are not problems in diesels or turbines. The main issues for JP fuel are vapor pressure and cleanliness. You don't want your fuel to boil away, freeze up, clog, or wear some of the fiddly bits in the injection system.

My point was that JP and diesel are very similar, so diesel cannot be rejected out of hand as too heavy or unreliable for commercial aviation.

No, since there is no octane in kerosene. But around here the diesel fuel pump does have a cetane rating. I guess that would be a 'similar' rating of the fuel's "quality"?

daestrom

(and is only valuable

pressure and

jet engine.

pump does have a

You could make expensive E85 without the octane. It would still be high-octane.

Octane (C8H18) is the baseline for measuring Octane, a property of fuels for Otto engines.

It _has_ been done. During the second world war, when gasoline was hard to come by, many (most?) cars in Sweden were equipped with a coal gas generator, and the cars were able to run on the "generator gas" (mainly CO) those units produced. The generator units could even be fueled with firewood, in a pinch. The efficiency is very low, though. And somehow I doubt that modern, computerized cars will be as easy to convert as the simpler cars of the forties.

S.

More likely charcoal. The raw producer gas made from wood has a lot of moisture and volatile materials in it. From charcoal it is carbon monoxide and nitrogen, plus some hydrogen if water or steam injection is used.