[This article was first published in Army Sustainment Professional Bulletin, which was then called Army Logistician, volume 2, number 6 (November–December 1970), page 40. The text, including any biographical note, is reproduced as faithfully as possible to enable searchability. To view any images and charts in the article, refer to the issue itself, available on DVIDS and the bulletin’s archives at asu.army.mil/alog/.]
A MILITARY VEHICLE that can go further on less gasoline and cuts down on air pollution by giving off fewer exhaust fumes may become a reality by 1975.
At least, that is what the scientists at the U.S. Army Tank-Automotive Command (USATACOM) at Warren, Michigan, hope to accomplish with their new combustion system concept that not only sharply reduces harmful gas emissions but provides increased fuel economy.
The breakthrough in air pollution control has resulted from the precise control of combustion within the cylinder itself and not through the use of “add-on” pollution-control devices.
Essentially, the process, labeled “Hybrid” by USATACOM, combines the unthrottled, efficient operation of a diesel engine with the soft, controlled combustion in the spark ignition engine. Unlike the conventional spark ignition engine that uses a carburetor to deliver the proper air-fuel mixture to the cylinders, the hybrid features a fuel-injection system similar to that used on a diesel engine.
Fuel injectors at each cylinder inject precisely the amount of fuel needed to operate the engine at any given horsepower output requirement. This results in a cleaner air-fuel mixture and lower exhaust emissions at low and intermediate engine loads than can be achieved with the same engine equipped with a carburetor.
To date, the hybrid combustion principle has been applied exclusively to the Army’s 1/4-ton M151 jeep, which is powered with a 4-cylinder engine displacing 141 cubic inches. Tests indicate that with this process pollution control already meets or approaches proposed Federal exhaust emission standards for the year 1975. The tests further show that the process cuts fuel costs 20 to 40 percent.
USATACOM laboratory engineers point out that there is nothing radically different about the engine. They say it really is a combination of the conventional gasoline engine used in automobiles and the diesel engine found in highway trucks.
The engineers also refer to it as a “stratified charge” engine. This simply means that the engine burns the fuel at the location where it has the best mixture of air and fuel to give the most efficient combustion and therefore cuts down on a number of pollutants.
The engine is a little more expensive than a conventional gasoline engine because it uses a direct fuel injector. However, the net cost increase of a little under $100 per engine is substantially less than that of current engines with exhaust emission controls.
Advancements now under development could further reduce pollution from this engine to meet proposed 1980 goals. With unleaded fuel and a catalytic reactor, however, emissions can already be reduced to the proposed 1980 levels without further advances in combustion control.
Hybrid engine research, which has been underway at USATACOM for more than an decade, has as its goal not only the development of an engine that will emit fewer air pollutants but also one that can operate on many fuels, including gasoline and kerosene.
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