As I understand it, Dr. Rudolph Diesel invented his high compression engine to take advantage of the mounds of coal dust piling up in the countryside.
Unfortunately the coaldust motor immediately broke; he had much better results using vegetable oil and petroleum distilates.
Question is, how is coal dust fed through a pipe and squirted out an injector at the height of top dead center?
Or was the dust simply poured into the intake manifold, like gasoline in a spark ignition engine?
I believe in Diesel’s original design the fuel was injected throughout most of the power stroke. I’ll try to find a cite.
It is well known that the diesel was developed to use coal dust. Apparently Diesel used air to convey the dust into the cylinder:
http://www.freeautoadvice.com/diesel/hist.html
As I understand it, later engines were built using coal dust introduced in emulsions with water or petrochemicals. I’m not sure if any of these engines exist today. However, power plants using coal today usually use powdered coal which is introduced by air into the combustion area. There are designs which combine fuels (coal dust and oil) and which use water to convey the coal dust into the furnace.
By the way, all diesels require injection of the fuel at high pressures. If the fuel is introduced during the compression stroke, the resulting pre-ignition will cause a severe loss of power and likely destroy the engine.
Coal dust diesel engines used a reservoir of pulverized coal which was what we might call “micronized” in the industry today (about 325-mesh fineness) which was metered into the intake system via a rotating mesh screen. Early ones used pressurized air, but later ones were tried with atmospheric air. The coal dust was not good at all for startup, so normal diesel oil was typically used, and when the cylinder got to temperature the coal dust would be used instead. However, I think there were a couple of designs which tried startup using entirely coal dust. I think Diesel’s designs used mainly metallurgical anthracite coal, which was not really a very good choice for this application - a high-volatile bituminous coal would have been much better. I mean, the metallurgical anthracite would be low in impurities and ash, but has a very high ignition temperature.
In Venezuela, there are experimental IC engines that run from Orimulsion (I’ve seen them), which is a bitumen-water emulsion that I’ve written about at-length. Wartsilia Diesel also did or is still doing research on Orimulsion engines as well. Coal-water slurry in IC engines is still looked at as a niche or experimental fuel, but not in what I would call any seriousness. It is used at the Mohave power plant, which is an 1800 MW plant near California that takes its coal from the Black Mesa mine via pipeline. However, California wants to shut it down by some pretty onerous environmental penalties in 2006, but how they are going to replace that 1800 MW of baseload power, no one in that area of California has really thought of…oh well. I guess they can just build a new plant at Four Corners, like they think they can.
I could write a book on on how coal is combusted in power plants. Well, I sort of did…
Una