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. Cetane
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 cus-tomer/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 Mc-Candless, 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 DTF.
Cummins Inc., in Columbus, Ind., announced that it would meet the
new EPA emissions standards using cool-ed 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:
Oxidation catalysts on diesel engines promote the chemical oxidation
of carbon monoxide and hydrocarbons from the exhaust.