Tough War Lessons Force Military Vehicle Programs To Consider Fuel Efficiency
Something must be done to reduce the dependence on battlefield fuel.
JP-8, the military’s fuel of choice, is used to power generators, rotary-wing aircraft and vehicles.
Of those three, vehicles may hold the best promise of savings. Commercial manufacturers have been working on ideas to reduce miles-per-gallon ratings for decades.
“With all the budget constraints and cuts, that’s the wise thing to do: leverage all the technologies that are matured on the commercial side and modify them appropriately to use them in the military,” said Mike Mekhiche, BAE Systems’ Electronic Solutions Sector power and energy management director.
Chris Yakes, vice president for advanced products at Oshkosh Corp., said in the past when it came to designing military vehicles, “It was always form following function.” Performance specifications took precedence and efficiencies “were thrown to the wayside.”
Fuel efficiency requirements are now making their way into the upcoming Joint Light Tactical Vehicle and Ground Combat Vehicle programs, Yakes noted.
About a dozen years ago, Oshkosh saw that this paradigm would change. “It became obvious what was going on in the commercial industry. It was going to catch up with us and the military was going to have to get more efficient.”
Tom Reinhart, an engineer at the Southwest Research Institute in San Antonio, Texas, said the commercial truck and vehicle industry has reached a turning point. For the past 20 years a consortium of commercial vehicle manufacturers at the institute has focused on meeting stringent Environmental Protection Agency standards on emissions. Military trucks only had to meet 1998 requirements, so their manufacturers had little reason to join.
“Over time, military engines and civilian engines have been diverging because of that,” he said.
But since those standards have mostly been met, the EPA along with the National Highway Traffic Safety Administration are turning their attention to improving fuel consumption.
A new consortium focusing on fuel efficiency is now being formed, and military truck makers may find some synergies there.
Hybrid engines, low resistance tires, computerized transmissions and aerodynamics are some of the ways civilian vehicle fleet manufacturers are using to reduce the amount of diesel being consumed. However, city buses, 18-wheelers, garbage trucks and inner-city delivery vehicles all have vastly different “duty cycles.” Adapting technologies used in the commercial or public sector to military standards is never a perfect fit, and it is hard to nail down exactly what a typical day in the life of a military vehicle might be, Reinhart said.
That is a factor when a service decides to invest in a particular fuel-saving technology.
“In the civilian world, if you’re buying a truck, you normally have a pretty good idea how you’re going to use it,” Reinhart said.
A hybrid engine uses the kinetic energy derived from braking and stores the power in batteries. Trucks that are hauling goods from Florida to Arizona on the relatively flat Interstate 10 would not find efficiencies in such technology. However, a city bus or a garbage truck, which makes numerous stops and starts, might.
“How you drive the vehicle has a huge effect,” Reinhart said.
“The same idea applies in the military world. It’s probably more difficult … because you might use a given type of vehicle in many different ways.”
The contrast can be seen in Iraq and Afghanistan. Iraq had relatively good sealed roads, and convoys could travel on them for hundreds of miles from supply bases in Kuwait. Afghanistan is famous for its mountains, where brakes are needed more often.
BAE has installed its HybriDrive propulsion system on 3,700 buses in dozens of cities, and logged more than 300 million fleet miles.
“Leveraging commercial technologies first of all gives you the maturity — the demonstrated performance — in the commercial environment,” Mekhiche said.
BAE is now branching out with a variant, the HybriDrive Parallel System, for delivery, sanitation, construction and utility vehicles. Fuel savings can be anywhere from 30 to 50 percent over traditional engines, although they are best when used in stop-and-go cycles, BAE fact sheets said.
“Our business unit works very closely with the military side to transfer and leverage all the work that has been occurring on the commercial side,” Mekhiche said. Some of the hybrid technology developed has made it into the M109A6, the upgraded Paladin howitzer, and there is interest within the company to employ it on the Army’s Ground Combat Vehicle, if that program moves forward.
“In some cases, the commercial environment is harsher than the military environment,” he noted.
A New York City transit bus not only undergoes the stop-and–go cycle, it suffers mechanical vibrations and shocks caused by potholes. A transit bus operates 15 to 17 hours a day nonstop, which is unheard of in military vehicles even in war time, he said.
“When we meet with our military customers and describe the duty cycles and requirements for a transit bus in New York, they basically smile because it is several folds harsher than what you would see in a combat environment or in a tactical vehicle,” he said.
However, the fact that the military does not have a typical duty cycle, or at least a predictable one, has given its acquisition personnel pause when it comes to hybrid engines, Reinhart said.
“You really don’t know for sure if that is what you’re going to be doing five years from now. That’s the struggle you’re always going to have in a military application,” he added.
And adapting commercially successful technologies to military use is never simple. Mekhiche noted that the form factors are different. The components should ideally be modularized so they can fit in a variety of vehicles. They must also meet military specifications to ensure the engines electro-magnetic properties don’t interfere with radio communications, he added.
Both BAE and Oshkosh have developed hybrid engines that can produce exportable power. The HybriDrive Parallel System differs from than the electric HybriDrive engine designed for buses that rely mostly on regenerative braking for power. The parallel engine has combustion and electric modules. The vehicle draws power from the most efficient of the two.
Oshkosh’s ProPulse hybrid diesel-electric has already been installed on the Army’s HEMTT A3 and the Marine Corps’ Medium Tactical Vehicle Replacement. It provides 20 percent fuel savings and up to 120 kilowatts of exportable power.
The exportable power not only reduces the need for a heavy generator, but eliminates the need for a second truck to haul it there.
“Why not just put that in the vehicle? It cuts the logistics tail in half,” Yakes said.
Reinhart said there will never be a slam dunk when it comes to engines and fuel efficiency. The laws of physics eventually will catch up. So truck makers must look for other ways to find fuel savings.
There recently has been renewed interest in the rolling resistance in tires.
The Army Tank and Automotive Research, Development and Engineering Center has built two Humvee-sized ground vehicle demonstrators to test out some of the commercially available technologies. In one experiment, it installed low-resistance tires on the vehicles and found that it would result in 7 percent fuel savings.
If they were installed on the Army’s entire fleet of tactical wheeled vehicles, that would result in $45 million in fuel savings per year, Thomas Mathes, TARDEC executive director for product development, said in an in-house magazine article on the program.
“It would pay for itself in a year,” Mathes said.
Reinhart noted that low-resistance tires come with trade-offs. Seven percent fuel savings are possible and significant. But the tires, which are now being used in commercial fleets, may not be able to grip surfaces as well in off-road conditions. They also are not as durable as conventional tires and wear out quicker. Those savings may be wiped out of the tires need to be replaced more often, he noted.
TARDEC officials were not made available for comment.
The good news is that truck companies are pressuring tire manufacturers to come up with products that have both low resistance and increased durability. It is expensive and time consuming to swap out 18 tires on a tractor-trailer, Reinhart said.
As far as transmissions, there are potential ways to save fuel if drivers can find the “sweet spot” where the engine is in the proper gear and working at maximum efficiency.
Most military medium and heavy logistical trucks have manual transmissions. Commercial truck companies can install onboard computers and smart cruise control systems that force drivers to find the optimal gears. Some are GPS enabled so the truck self-adjusts when it sees that it is approaching a hill. The most sophisticated devices can even factor in the estimated weight of the payload to further refine performance.
“These are things the military could pretty readily implement,” Reinhart said.
Meanwhile, the Marine Corps is beginning to look at driver behavior as a means to reduce fuel consumption (See story here).
For passenger vehicles, weight and aerodynamics have always translated into better fuel efficiency. But neither has traditionally been a concern for military vehicles, Yakes said. Yet there are savings there, he added.
The military has been weighing down vehicles such as the Humvee with additional armor and equipment. Taking weight off to increase fuel efficiency has not been a primary objective. The Marine Corps, for example, wants a lighter Joint Light Tactical Wheeled Vehicle so it can be more easily transported.
Yet, anywhere a military vehicle can be made lighter helps the overall fuel efficiency, Yakes said.
Reinhart said there is a big difference in weight savings between a passenger vehicle and a truck. A car only needs to haul drivers and passengers, so making them lighter can result in significant fuel savings. But there is little benefit in making lighter trucks. The savings don’t add up to much.
“You can spend a lot of money trying to take weight off and not save fuel,” he said.
It is the same for military trucks and aerodynamics. That simply is not as great a factor since they don’t travel at high speeds, Reinhart said.
“Once you put a big box on the back of [a truck], then you’re kind of struggling, because you’re trying to push a big brick through the wind, but that is not always the case,” he said.
Oshkosh has put a good deal of effort into studying how air flows over its vehicles.
“Anytime you operate above 45 miles per hour, aerodynamics becomes a dominant factor in your fuel savings potential,” he said.
In the medium all-terrain vehicle and a new truck it is proposing for the JLTV program — the light all-terrain vehicle — it has found “a couple percent” savings by changing the way the air goes around and through them.
“We put a lot of emphasis on making sure the vehicle still does the functions that the vehicle was originally designed to do, and in some cases increase their capabilities, while also saving fuel,” Yakes said.
The new emphasis in the military on fuel savings — along with EPA standards that are mandating commercial truck manufacturers to meet stricter fuel efficiency guidelines — may bring the two worlds closer together.
The now defunct Southwest Research Institute administered consortium that tackled the emissions problem for 20 years did not have any military truck makers in its fold. Since they did not need to meet emissions standards, they had no motivation to join.
They are welcome in the new Clean High-Efficiency Diesel Engine VI consortium that kicked off in November, Reinhart said. Members pay an annual fee and direct the institute on where they want to invest the pooled research dollars.
Yakes said: “The government is doing a good job of bringing these lessons learned [in Iraq and Afghanistan] into new requirements. They’re tough requirements in many cases. It’s not that they are insurmountable. It’s just that they are tough requirements to meet. They are challenging industry,” Yates said.
Topics: Land Forces