Stricter Emissions Standards Prompt FMTV Engine Redesign.
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. "It's a system, rather than a single component.
The ACERT approach, McCandless said, makes sense for the FMTV program, because it minimizes the changes that are needed to install the engine in the vehicles. "I don't know what technology is more effective," he said. "But the ACERT technology allows you to make the least number of changes to the existing installation, from a space requirement, from a heat-rejection requirement, cooling-system requirement.
"We are trying to use technology to enable the truck manufacturer to have as few changes as possible from the current trucks," he said.
ACERT is a technology that is more conducive to the needs of the customer/user than other technologies such as EGR (exhaust gas recirculation), that will demand extra space for packaging and cooling, etc.," said David Elmes, general manager of defense operation at Perkins Ltd., a manufacturer of military engines, in the United Kingdom, that is now owned by Caterpillar. "ACERT will not need [a high] level of additional integration and therefore is better for the OEM [original equipment manufacturer] end user in terms of planning and vehicle design," Elmes said.
Caterpillar has provided ACERT-modified engines to Oshkosh Truck Corp., in Oshkosh, Wisconsin, and to Stewart & Stevenson Tactical Vehicle Systems, in Sealy, Texas. Both firms will be competing for the next FMTV procurement contract.
These modified engines, stressed McCandless, are not yet in production. Both competitors will install these engines on FMTV prototypes. "They are being configured for 2004," McCandless said.
Earlier versions of FMTV trucks were powered by Caterpillar 3116 engines (225 horsepower for the 2.5-ton trucks and 290 horsepower for the 5-ton trucks). The FMTV trucks currently in production at Stewart and Stevenson have 7.2-liter 3126B engines (275 horsepower for the 2.5-ton trucks and 330 horsepower for the 5-ton trucks).
The 3126B is in full-rate production. The future FMTV will have a 3126E, which will be compliant with the tougher 2004 emissions standards. The biggest difference between the B and the E versions is that the E will have an after-treatment muffler, said Bob Williams, Caterpillar's program manager for FMTV. "The engine manufacturer is required to provide that piece of equipment," he said. "As much as possible, we'll make it look the same and fit the same space as the current muffler, but it may be a little bit bigger."
The efforts to reduce emissions in the 3126 engine have focused on both nitrous oxides and particulate matter, said McCandless. "The challenge is to lower them both at the same time. If you lower one, the other has a tendency to rise."
The Army awarded both Stewart & Stevenson and Oshkosh Phase 1 contracts for the so-called FMTV competitive-rebuy program. During this phase, each company will make some modifications to existing FMTV trucks and will submit them to the Army for testing. Stewart & Stevenson received a $4.4 million contract and Oshkosh a $5.6 million contract, each for eight prototypes.
Stewart & Stevenson has been the FMTV prime contractor since 1991.
A Phase II production contract is scheduled to be awarded in March 2003. Whoever wins will receive a $2 billion award, for the production of 14,000 trucks and trailers over five years.
In addition to the FMTV, the 3126 engine is used in Freightliner and GM commercial trucks. Caterpillar makes 300 of these engines per day. Caterpillar's competitors in the 3126-equivalent engine market include Cummins Inc., Navistar and Detroit Diesel Corp.
A Caterpillar 3126 engine (350 horsepower) also was selected for the U.S. Army's light armored vehicle III (LAV), made by General Dynamics Corp. and General Motors of Canada. The Army is buying 2,100 LAV III vehicles as an interim combat platform. The service plans to provide the LAV IIIs to its newly-formed medium brigades. By 2015 or 2020, the Army's goal is to field a yet-to-be-designed Future Combat System (FCS).
Combat vehicles, by law, don't have to comply with emission requirements, so the 3126 engine in the LAV does not meet the EPA regulations.
Another military vehicle program exempt from the 2004 emissions standards is the Marine Corps' medium tactical vehicle replacement (MTVR) truck. That truck has a C-12 engine (425 horsepower), made by Caterpillar. The MTVR is an 8-ton platform built by Oshkosh. The engine is exempt from the EPA 2004 emissions requirements, because the production contract was signed before that regulation came into effect.
The 3126 engine was used in a hybrid-electric drive developed by United Defense LP, for the Army's M113 armored personnel vehicle. McCandless predicted that the FCS will have a hybrid-electric propulsion system. For that reason, he said, Caterpillar is trying to position itself to win that business. "We are working to become part of the Future Combat System," McCandless said. A hybrid diesel-electric drive uses a diesel engine, electric motors and electric generators to achieve nearly twice the fuel efficiency of conventional gasoline engine vehicle and significantly reduce exhaust emissions.
"But that is not the total answer" to the emissions problem, said McCandless. Hybrid systems are still in development and are much more expensive than conventional drives, he said.
The Diesel Technology Forum, an industry advocacy group in Herndon, Va., forecast that diesel engines, in the future, will use a combination of emission control options to reduce NOx, PM and HC emissions.
The use of engine design modifications--such as cooled exhaust gas recirculation (EGR), timing retard and higher injection pressures--has resulted in reductions of 80 percent to 90 percent in emissions from diesel engines over the last 20 years, said DTE
Cummins Inc., in Columbus, Ind., announced that it would meet the new EPA emissions standards using cooled EGR technology. "We extensively researched all technical solutions, and concluded that the only feasible technology for meeting the 2.5 gram [emissions] levels is with exhaust gas recirculation," said John Wall, Cummins vice president. "No other option provides the benefits of fuel economy, cost, responsiveness and overall performance, and in our view, no other currently available technology can achieve a 2.5 gram ... emissions level in this timeframe," Wall said in a company news release.
DTF is promoting several techniques for reducing emissions by on-road heavy-duty diesels:
* Cleaner Diesel Fuel: Diesel fuel sulfur reduction could enable the introduction of after-treatment technologies that can reduce emissions of PM and NOx.
* Fuel Delivery: Improvements to the design and application of electronic engine controls and enhancements to fuel-injection technology could allow engines to burn fuel more efficiently, and avoid the temperature spikes that increase NOx emissions.
* Managing Air Intake and Exhaust: Exhaust gas recirculation (EGR) is an established technology on gasoline-powered vehicles that may be effective for heavy-duty diesels.
* After-treatment Technologies: This involves the use of catalysts or particulate traps to convert or capture engine-out emissions before they leave the exhaust pipe. Traps are used to remove and eventually burn particulate emissions. Catalysts for diesel engines are mote complex than their counterparts in gasoline engines, but hold promise for reducing NOx and particulate emissions, said the DTF.
Oxidation catalysts on diesel engines promote the chemical oxidation of carbon monoxide and hydrocarbons from the exhaust.
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|Author:||Erwin, Sandra I.|
|Date:||Aug 1, 2001|
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