Magazine article National Defense

Stricter Emissions Standards Prompt FMTV Engine Redesign

Magazine article National Defense

Stricter Emissions Standards Prompt FMTV Engine Redesign

Article excerpt

The U.S. Army's future 2.5-ton and 5-ton tactical trucks will have to comply with tougher diesel-emissions standards, which the U.S. Environmental Protection Agency has set for on-highway vehicles, beginning in 2004.

Even though the deadline for the stricter emissions standard is three years away, military engine makers already have adopted new technologies that, they hope, will make future engines less polluting and also easy to install in Army trucks.

That is an important consideration for the family of medium tactical vehicles (FMTV) program, because the Army does not plan a significant redesign of the truck. A future buy of 14,000 FMTV trucks, however, will require new diesel engines in order to comply with more stringent emissions standards. The FMTV engine is made by Caterpillar Inc., in Peoria, Ill.

Diesel engines rely on compression, rather than a spark, to ignite a mixture of air and diesel fuel. The mixture of air and fuel constantly changes to respond to the demands or load placed on an engine.

The emissions standards for heavy-duty trucks and buses--manufactured in 2004 or later--mandate that emissions be cut to less than half of the current standards. For the next FMTV procurement contract, expected in 2004, those engines will have to comply with the same emissions requirements as commercial engines.

The regulations are intended to reduce emissions of nitrous oxides (NOx), total hydrocarbons (THC), carbon monoxide (CO) and particulate matter (PM). Nitrous oxides and particulate matter are the biggest concerns for diesel-engine makers. Diesels have relatively low levels of carbon monoxide and hydrocarbons.

Diesels consume up to 40 percent less fuel than comparable gasoline engines and release about half as much carbon dioxide. But diesel-engine exhaust contains higher levels of soot particles and NOx than gasoline engines.

Engine manufacturers expect to achieve lower diesel emissions through techniques such as engine design, fuel and lubrication formulations and exhaust after-treatment.

The evaluation of diesel-engine emissions is based on two sets of criteria: emissions of greenhouse gas emissions and EPA air-quality standards--NOx, sulfur dioxide (SO2), coarse particulate matter (PM-10; smaller than 10 micrometers in diameter) and fine particulates (PM 2.5; particles smaller than 2.5 micrometers in diameter).

Emissions of carbon-based greenhouse gases are of increasing concern, because scientists have concluded that they affect global climate and temperature patterns.

The use of low-sulfur diesel fuel is one strategy designed to reduce emissions, experts said. Other options include raising the cetane number in diesel fuel to improve the combustion process. Cerane is a colorless, oily hydrocarbon found in petroleum.

New lubricants that reduce friction also can help lower emissions. Exhaust after-treatment is another technique which uses catalytic converters and particulate traps to control emissions after the combustion process.

DaimlerChrysler, in recent years, has funded work on so-called "designer diesel." According to the company's in-house magazine, engineers have made virtually sulfur-free liquid diesel fuel out of natural gas. The company expects that the application of synthetic fuels will open up new possibilities for engine designs that consume less fuel.

For the Army FMTV program, Caterpillar chose to modify the engine using technologies that are low risk, said Walter E. McCandless, engine product manager. To meet the 2004 emissions requirements, Caterpillar is using a technique called ACERT (advanced combustion emission reduction technology).

"ACERT is not just advanced fuel injection. It's a combination of fuel injection, turbo-charging, after-treatment, having the appropriate piston technologies, so you can take advantage of the advances in fuel injection," McCandless said in an interview. …

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