FOR IMMEDIATE RELEASE
October 16, 1996
LIVERMORE, Calif. -- An environmentally friendly way to operate heaters for home and industrial uses has received a patent at Sandia National Laboratories in Livermore, Calif.
Sandia's patented approach creates only 5 ppm of NOx (oxides of nitrogen), a pollutant that contributes to smog. Air-quality limits are about 20 ppm, said Jay Keller, a researcher at Sandia's Combustion Research Facility. Keller is a co-inventor of the device with fellow Sandia researchers Taz Bramlette and Pamela Barr. Besides low NOx, this clean combustion approach also emits very low amounts of carbon monoxide.
The invention arose from work at the Combustion Research Facility to understand and improve the performance of pulse combustion, an inherently efficient process that was first demonstrated in turbines shortly after the turn of the century. Pulse combustion is currently used in industrial systems, such as process heat boilers, and some residential furnaces and water heaters. Once it is sparked, pulse combustion is self-sustaining, drawing in gas in a pulsating pressure wave and automatically firing on the order of 100 times a second.
Anyone who has heard an older automobile make a "ka-bump, ka-bump" noise after the ignition is turned off has encountered a similar phenomenon, known as "dieseling," in which the engine continues to draw in combustion products, said Jim Alvarez, a Sandia pulse combustion technician.
Pulse combustion was also used in jet engines of the World War II German surface-to-surface V-1 buzz bomb. The pilotless bomb, also known as the doodlebug, was launched from the continent to England. It fell from the sky when its buzzing engine stopped.
Nowadays, some top-of-the-line domestic water heaters and furnaces using pulse combustion exhibit thermal efficiency of 96 percent, compared to 70 - 85 percent thermal efficiencies characteristic of conventional systems.
Working with an experimental, see-through burner, the Sandia team minimized emissions by mixing fuel and air prior to burning, and by keeping the fuel-air ratio lean. Their patented one-way valve design prevents the burning fuel from igniting this premixed fuel in a flame "flashback," Keller said.
"We wanted to make the burner as environmentally benign as we could make it," he said, "and we were able to do it safely."
Added co-inventor Barr, "The invention operates safely because it keeps the fuel and air separate until the valve opens. Both gases mix after they pass through the valve. Allowing the fuel and air to mix during the journey to the combustion chamber minimizes the local regions of fuel-rich combustion, which is a major source of pollutants."
The patented invention stems from a partnership that began at Sandia in 1982 between the U.S. Department of Energy and the Gas Research Institute, an industrial consortium. Experimental work and computer modeling efforts were completed at Sandia some three years ago. The U.S. patent, No. 5540583, was issued July 30, 1996.
Sandia is a multiprogram Department of Energy laboratory, operated by a subsidiary of Lockheed Martin Corp. With main facilities in Albuquerque, N.M., and Livermore, Calif., Sandia has major research and development responsibilities in national defense, energy, environmental technologies and economic competitiveness.
Media contact: Nancy Garcia, Sandia/California Public Affairs; (510) 294-2932, Nancy_Garcia@Sandia.gov
Technical contacts: Jay Keller, Combustion Research Facility; (510) 294-3316; Taz Bramlette, Environmental Systems Program Office, (510) 294-2299; Pamela Barr, Combustion Research Facility, (510) 294-2249
Licensing contact: Subra Subramanian, Site Development Center, (510) 294-2311Nancy Garcia, Nancy_Garcia@Sandia.gov
Last modified: June 12, 2001
Sandia National Laboratories is operated by Lockheed Martin Corp. for the U.S. Department of Energy.