'Coal car' by GM offers future fuel alternative

It's like no other Caddie you've ever seen. This particular car, a 1977 front-wheel-drive Eldorado, burns coal, not diesel fuel or gasoline. It has a turbine beneath the hood, and you can smell the coal ash as you drive down the road.

''We've done a lot of running with the coal-burning car,'' declares Albert H. Bell III, a General Motors executive engineer in charge of the advanced product and manufacturing engineering staff. The ''coal car'' project, begun in 1978, was in response to the energy squeeze at the time and the expectation that the days of fossil-fueled vehicles were soon to end.

Even though the car is now on the back burner, so to speak, the technology behind the car is very much in the file at the General Motors Technical Laboratories here in suburban Warren, Mich.

Richard J. Stettler, the man who headed up the coal-car project, describes the system: ''What the charcoal-burning stoves of World War II did was run a gasifier and then take that gas and burn it in a regular piston engine. What we wanted to do was put the coal right into the gas stream of the engine and thus get rid of the gasifier. We take the coal into the pressurized combustion chamber with air where it is ignited.''

After a spin around the GM Technical Center, Mr. Stettler at the wheel, the engineer turns and says: ''You take the wheel.''

We change places and are all set to go. ''Just turn the key and it comes up to idle by itself,'' Mr. Stettler explains. There is no starter motor to run as in a liquid-fueled automobile. I turn the key and let go, the engine springs to life, and we're ready to move.

''This instrument tells us the speed of the gasifier,'' Mr. Stettler continues, pointing to a dial on the dashboard. ''It's now at 35,000 r.p.m.'' Whirrr! ''And this tells us what the output shaft is running - about 850 r.p.m. - for the gearbox that goes to the wheels.''

The car picks up speed slowly, but he explains why.

''We made a modification in the pump to give us a little better delivery and more even flow. When we did that we cut down the capacity. Now we don't have a big enough pump to give us the acceleration.''

Then he apologizes, saying: ''Everything isn't exactly what we'd like it to be for a turbine. We're using all the components that you'd normally have in a regular piston car. The transmission, torque converter, etc. are the best match we could get. If we had a choice, we'd take a little different torque converter and the clutch would be different as well.''

But, he reminds, ''This was a feasibility study only.''

The secret to the car's feasibility is the small size of the coal: 3 microns compared with 57 to 75 microns not too many years ago. To provide some perspective, today's micronized coal is about half the size of powdered sugar and talcum powder. ''It takes a lot less time to burn and a great deal of the ash and other impurities have been removed because it has been made so small,'' Mr. Bell reports.

You can feel the car shift gears as the smell of coal ash filters into the car. ''Until we can get the ash down, we can't do much to get rid of the odor,'' he explains.

''There is also a little hydrocarbon (HC) that you can smell with the ash although the HC is unusually low and we could meet the standards today for HC and carbon monoxide. The nitrogen oxide would be too high because of the high nitrogen in the fuel. And, of course, the particulates would be too high because we have the ash.''

The engine peaks at about 63,000 r.p.m., Mr. Stettler reports. The ''fuel tank'' holds some 60 pounds of coal, enough for 80 or 90 miles., he says. The car works on heat units and wouldn't know the difference between diesel fuel and coal.

Powdered coal is a very safe fuel, declares Mr. Stettler. ''You can hold it over a candle ,'' he adds, ''and it won't ignite. Hauling gasoline around is one of the things that has bothered us for a long time.''

The whine of the turbine is loud and would never ''make it'' on the road as is. But the comfort for the motorist is the knowledge that even if the gasoline and diesel pumps ran out of fuel, this is one more alternative to keeping the vehicle fleet on the move.

While such coal-burning technology may be a long way from automotive use on the road, it could be applied to trains. ''I think this is one of the first places where we'll see this technology,'' asserts Mr. Bell. Both the Association of American Railroads and the American Railway Association tried in the late 1940s and '50s to burn powdered coal, but the project failed.

Because the powder wasn't small enough and had a lot of ash - coals can easily have 15 percent ash, says Mr. Stettler - the ash would melt and deposit on the turbine blades while the sulfur would attacked the high-temperature materials.

The railroads then went to big combusters as they tried to separate the ash before they put it into the engine. ''It did not prove feasible,'' reports Mr. Stettler. The railroads own about 25 percent of all the coal in the United States. If they could find a successful way to burn it, they probably would do so.

The Japanese also are doing work in this area, as well as for stationary-power applications, such as utility plants. Japan produces only about 80 million tons of coal a year but uses about 350 million tons. There is, however, a lot of coal in Australia and China.

As for propelling an automobile in the '90s and beyond, the GM coal car is one more way to go. Maybe.