Exhaust gasses being tested to stretch fuel in big trucks

It looks just like any other long-haul, diesel-powered truck on the road today. Yet it uses a lot fuel and could save billions of gallons of the precious fluid in the future.

Thermo Electron Corporation of Waltham, Mass., is testing an exhaust-gas-regenerator system on a heavyweight Mack truck in the Boston area and soon will be running it for the second time in the Pocono Mountains of Pennsylvania. Mack, a subcontractor in the project, is headquartered in Allentown, on the edge of the Poconos.

If ultimately picked up by the US trucking industry, the truck could save up to 100,000 barrels of crude oil a day. Although not suited to the automobile, it could also be used on long-distance buses as well. Like the turbine, it requires a sustained speed over long distances for best performance.

What the system does is tap the exhaust gases in the vehicle for better mileage on the road.

The so-called "bottomong-cycle system" uses a vapor generator instead of an exhaust muffler, plus a water-cooled condenser, regenerator, and turbine-wheel gearox. The high-temperature exhaust gas from the diesel egine vaporizes the working fluid in the system. Then the vaporized fluid expands through the turbine and provides more shaft power to the engine power train.

After partly cooling the vapor in the regenerator, vapor de-superheating and condensing occurs in the condenser. The feed pump then pumps the condensed working fluid through the liquid side of the regenerator before it once again enters the vapor generator, completing the cycle.

"Our goal is a 15 percent improvement in mileage in long-haul trucking," asserts Luco DiNanno, an engineer with Thermo Electron. So far the results are encouraging, he adds.

The potential for saving fuel is large. The US trucking industry, for instance, now carries some 2 billion tons of freight a year, with most of the work done by big diesel-powered units. In 1976 there were 1,124,000 Class 5 and 6 trucks on the road, with about one-third of them involved in long-distance hauling.

Figuring an average 4.8 miles per gallon for 92,000 miles a year, they burned 6.9 billion gallons of fuel.

A 15 percent improvement in m.p.g. would save more than 1 billion gallons of fuel, but that's not all. The saving to the trucking industry would have amounted to $600 million to $700 million a year.

It takes 2.38 barrels of crude oil to make one barrel of diesel fuel.

If these numbers were extrapolated to 1980, with about 490,000 heavy long-haul trucks on the road, the saving in diesel fuel could amount to 1.43 billion gallons and $830 million.

Short-haul vehicles also are seen as prime candidates for the system.

The Thermo Electron test truck has been averaging 5.7 miles per gallon on a 165-mile loop in suburban Boston, according to Mr. DiNanno, with the latest runs approaching 6 m.p.g.

Next month the vehicle will run over a roller-coaster route in the Poconos.

In 1981 the company hopes to test the system in a small fleet of trucks, but "this won't be done till the present hardware has shown satisfactory reliability and maintainability," Mr. DiNanno says. So far the record is good.

If successful, the system could be in use in many long-haul truck fleets by the mid- and late 1980s.

"Given reasonable resources and support to complete system refinements, improvements, and testing over the course of the next coupe of years," the engineer says, "we expect to have an efficient system design of proven reliability ready for limited production."

The company expects to be one of the producers of the system to industry.

Thermo Electron is also testing a system to fuel large stationary diesel engines directly with coal instead of petroleum. With the cooperation of Sulzer Brothers Ltd. of Switzerland, a test engine has already been operating successfully with coal-derived liquid fuels, using a slurry of 70 percent residual oil and 30 percent powdered coal.

Ultimately, the two companies expect to run the engine on coal alone.

A few years ago Thermo Electron worked under contract with Ford Motor Company on small steam-powered engines for potential use in automobiles. The program is no longer active.

United States funding of the Mack truck bottoming-cycle system so far is just over $6 million. The cost to commercialize the system, however, is estimated at