The US military is looking to bolster fuel efficiency by creating a so-called "super engine" that runs on one type of fuel and can power a number of vehicles, including ground transport, generators, and small unmanned aerial vehicles (UAVs).
The US Army Research Laboratory (ARL) has been working on this task since the Department of Defense established a Single Fuel Forward policy in the late 1980s. The policy supported the use of a kerosene-based fuel called JP-8 to reduce the logistical burden involved in transporting and supplying different sources of energy to vehicles in combat areas and other locations, according to the Army.
Over the years, researchers have faced compatibility issues between the different engines, the Army said. Its research began with the use of turbine engines, but has now moved on to exploring the use of combustion engines.
Two international contractors inspect a sample of JP-8 fuel in Kuwait in 2010. The Army hopes to use the fuel as the basis for a "super engine" that can power a number of ground and air vehicles, as well as generators using this fuel. (Source: US Army Sgt. David Reardon, 1st Sustainment Brigade Public Affairs, US Army)
Incompatibility issues are chiefly in engine lubrication, large variation in Cetane numbers -- or the measurement between the start of fuel injection and the start of engine ignition or combustion -- and the fact that none of the engines that use JP-8 are designed and calibrated for the fuel, said Dr. Chol-Bum Kweon, acting team lead of the Engines Team of ARL’s Vehicle Technology Directorate, in a press release.
The main reason for these issues is that there is not enough information readily available about the specific combustion characteristics associated with the use of JP-8 in intermittent combustion engines, Kweon added.
The opening of a new lab this summer, the ARL Combustion Research Laboratory, should help speed up this research, particularly with respect to fuel spray and combustion, two critical areas key to the creation of a JP-8 engine. According to Kweon:
Fuel spray liquid penetration, quenching, vaporization, and mixing characteristics must be precisely understood to properly design combustion chambers and fuel injection systems because a fundamental understanding of fuel spray and combustion is essential in optimizing combustion processes of JP-8 -- fueled engines to improve fuel efficiency, engine performance, and reliability.
ARL’s Combustion Research Laboratory is a state-of-the-art, high- temperature and high-pressure combustion chamber that contains a combination of high temperatures up to 1,000 Kelvin and high pressure up to 150 bar. These metrics can simulate the operations of a real engine, minus its fluid motion aspect. The lab gives scientists a realistic proving ground for, in particular, uninterrupted spray and combustion processes that allow for the study necessary to create a JP-8 fuel-injection engine.
In addition to supporting the development of a JP-8 engine, researchers will also use the lab to test the performance of heavy fuel injection systems for diesel, bio, and synthetic fuels, as well as assess the impact of fuel properties on spray and combustion processes on engine performance and efficiency.
Researchers also can determine the impact of older fuel-injection systems on engine performance and fuel efficiency, especially for the Army’s ground vehicles, and evaluate various iterations of JP-8 fuels being developed throughout the DoD, Kweon said, going on to explain: "This laboratory has a unique capability to assess the various JP-8 surrogate fuels and to compare the results with the combustion mechanisms developed by various universities and government lab or atories."
All of this work to develop a universal combustion mechanism for JP-8 supports a trend across the US military to create more energy efficiency, and find alternative and better sources and uses of fuel. Other efforts include the Navy’s development of a biofuel made of seawater; the Air Force’s use of vortex surfing -- or flying planes in tight formation so they can draft off each other -- to conserve fuel; as well as other Army projects such as developing more fuel-efficient electricity generators.
I agree that when considering weapons for a particular mission the overriding theme should be kills per dollar spent. With the way we fight all the low intensity/counterinsurgency ops going on; the cost per kill goes way up thanks to the 'precision weapons revolution'.
I am a big fan of the civil war Gen. W.T. Sherman. He had a simple philosophy: War is hell, so you make it as bad as you can; the faster the enemy surrenders, the faster you can make friends.
I say use the big, dumb, cheap bombs and accept the colateral damage. Overkill is OK. It is all the extra damage that makes the enemy reconsider his life choices.
But don't forget that we still have peer adversaries. China is not an honest actor and Putin would love nothing less than to go back to his Soviet roots. We still need the big ticket items to counter their advances.
Whatever cuts the military budget, I cool with. It seems so silly to spend billions on advanced tech that never gets used. Most combatants the USA faces are irregular/rebel/civilian militants with simple weapons.
Wind and solar definitely make boring targets. You just can't get the impressive secondary detonations that give you a warm fuzzy during BDA.
I was just speaking strictly form factors - Petroleum can be more readily distributed and concealed (admittedly a lot of effort) than the high output wind and solar technologies that I am aware of. Wind can't get away from having tall structures (or kites). Solar is highly reflective and requires a lot of area.
However, with the growing backlash against wind and solar partly because of these reasons, perhaps solutions will be found. I just believe it is more appropriate to have civilian/private R&D work these issue.
this is clear. I'm just looking for the logic behind it. To make an engine that is like one size fits all in my opinion not too realistic. I may be wrong !?
To be fair, I bet there's no more enticing target for a pilot than a fuel tank farm. The phrase "The ensuing fireball" would have to be a favorite of theirs. Blowing up solar arrays would be the same as dropping bombs on any piece of empty desert.
Solar and wind energy just do not give the same energy density that petroleum fuel has.
Fuel 'diversity' is the best policy as TJ notes. Nothing stops a modern military faster than lack of go-go juice.
Solar and wind for military applications is very misguided. The large arrays required to get adequate energy will make a good target when used downrange. I know that I would like our enemies to mark their locations as provacatively.
Military R&D budgets have been used too often to perform research on things that have no practical use on the battlefield. In my opinion, the military should not be looking into things unless they can be used in harm's way.
Sorry, but we have to draw a line somewhere and that seems a reasonable restriction for military R&D. Considering the defense cuts coming our way; I would hate to see some of our useful and fieldable war technology get budget pressure because of something that has little benefit to the mission.
Navy ships do a significant amount of re-fueling at sea, often from tankers, occasionally from carriers. Naval aircraft use JP5, which has a different specific gravity than diesel, plus different BTU/gal lubricity and burn characteristics. Aircraft are less tolerant of fuel differences than perhaps a diesel engine or a stationary Gas Turbine so having one single diesel-ish fuel is the best answer even though it is likely a compromise in some applications. U.S. environmental laws have regulated our diesel fuel to remove some desirable characteristics to the detriment of longevity of the engines burning it. This is notable when reviewing the stated standard overhaul period for engines used in the U.S. versus the same engine being used in Europe. I'd guess much of the research into diesel fuel is to find a way to restore some of those desirable characteristics.
Bob, not sure about the "Navy takes a different method" approach. I know of at least one class of naval ship (details classified) powered by diesel and gas turbine engines (diesel for cruise, GT for combat). The gas turbines in these vessels burn diesel, not kerosene, to simplify fuel storage, supply and delivery.
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