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SSC-Natick Press Release

U.S. Army Soldier Systems Center-Natick
Public Affairs Office
Kansas Street
Natick, MA 01760-5012

Contact: Chief, Public Affairs Office
(508) 233-5340

Date: June 6, 2005
No: 05-27

Capillary force fuels pocket stove

NATICK, Mass. -- Once you hear the slight puff and see the yellow flame mellow into a glowing blue, you know the capillary force vaporizer has gone into action.

The vaporizer is a breakthrough in burner technology being applied to the Modular Individual Water Heater, a jointly developed product of the Department of Defense Combat Feeding Directorate’s Equipment and Energy Technology Team at the U.S. Army Soldier Systems Center here, and Mountain Safety Research (MSR), a division of Cascade Designs, Inc. in Seattle, Wash.

Trioxane fuel bars had been the source for warfighters to heat water for beverages, dehydrated rations and personal hygiene, but there were drawbacks and production has been discontinued, said Leigh Knowlton, project officer.

“Soldiers had supply problems because they’re considered fuel and ordered separately from food. It will also evaporate if the seal is broken in storage and can give off noxious fumes when burned,” he said.

Knowlton said little has changed in the last 40 years in this area of warfighter sustainment. Current authorized equipment to heat water consists of a plastic canteen, steel cup, cup stand and cover. Absent the fuel bar, the alternative is the military’s squad stove, a commercial product that has an external fuel tank with a pump to build pressure and prime the stove.

“It’s heavy because of the bottle, has a lot of moving parts, it’s expensive, and it’s not about efficiency—it blasts out heat,” Knowlton said. “If you can use less fuel, that’s less fuel to carry.”

Meal, Ready-to-Eat (MRE) rations have a flameless heater for the entrée and upcoming pouches to make hot beverages, but there’s still a void for the dried foods found in the Long Range Patrol/Cold Weather Ration, which require 28-40 ounces of hot water for all the components. He said the situation will worsen if the canteen cup is phased out because of the increasing popularity of bladder hydration systems.

With no existing commercial stove or water heater that’s lightweight, compact, compatible with on-the-move hydration systems and meets the military’s requirement to burn JP-8 fuel, the capillary force vaporizer invented by Vapore, Inc. in Richmond, Calif., became the solution.

Three-part wick

About the size and shape of a pair of antacid tablets, the three-layer vaporizer held together by an impermeable exterior glaze has no moving parts and fits inside a cone-shaped stove where it converts liquid fuel into a pressurized gas. Knowlton said the vaporizer is durable as well, working for hundreds of hours before wearing out.

A coarse ceramic layer at the bottom is the feed wick that touches the fuel. In the middle is the boiler wick, a fine ceramic layer that generates high capillary pressure and vaporizes the fuel. On top is the orifice disk that conducts heat from the flame to the boiler wick and has one or more pinhole-sized openings to expel fuel vapor.

“Because there’s no pressurized tank, it’s potentially safer. If something goes wrong, it just goes out,” Knowlton said. “MSR is excited because this is their route to a revolutionary product.”

As configured in the current prototype, the stove is unpacked from its own commercial steel mug, but Knowlton said a sack may become available so it can be carried independently.

Starting it is as simple as holding the stove upside down for 30 seconds for priming, turning it upright and lighting the priming wick with an MRE match. Within 60 seconds, the capillary force vaporizer takes over, emitting a whooshing blue flame. A sliding steel lever with off, simmer and full settings regulates output.

The mug filled with water is placed on the stovetop pot support and windscreen. Knowlton said the commercial cup, which is designed to improve heat transfer efficiency, could be offered for the military version, or the system may be modified to accommodate canteen cups.

Another heat transfer system is the hot water coil, which was developed to easily heat water from hydration packs.

Once described as resembling an elephant stethoscope, a flexible plastic tube connects to the water bladder and feeds water to a metal heat exchanger that attaches onto the pot support and windscreen. A valve inside the heat exchanger releases hot water through another tube that can be directed into a dehydrated meal or beverage pouch.

With either method, a pint of water is heated in six to 10 minutes. The stove system has twice the energy efficiency of a squad stove, burns JP-8 and holds enough fuel in its tank to last for three days, Knowlton said.

Cold weather Army and Marine Corps units are likely early adopters, according to Knowlton, although all the services have shown interest. MSR plans on selling a white-gas version of the stove as part of their product line of outdoor recreational gear.

Combat Feeding and MSR built the stove under a cost-sharing contract, and the technology base could lead to more products.

“The vaporizer technology has interesting applications beyond stoves,” Knowlton said. “Vapore is leaning toward medical devices. But for military applications, it has potential for anything that needs a small amount of vaporized fuel, and that’s challenging to do with JP-8.”

Beverage chillers, personnel warmers, lanterns, generators for individual warfighter equipment and infrared markers are examples of small heat-driven devices for the military.

Knowlton said more research is going into the hot water coil and mug to increase their efficiency and reduce weight. The commercial stove will be ready next year, with the military version possibly being fielded in limited quantities before commercial sales.

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This page last updated on 23 January 2004.