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Research in the application of nonthermal plasma technology to remove NOx from combustion flue gas is dominated by the oxidation of NO to NO2 and HNO3 (nitric acid), undesirable end products for mobile engine applications. An alternative approach is to react the NO with atomic nitrogen injected into the gas stream to reduce the NO into nitrogen and oxygen. The atomic nitrogen is generated by flowing nitrogen through multiple electrically excited, high-speed jet nozzles. The technology functions well in the sooty and wet conditions characteristic of diesel engines. A prototype system has been built and successfully demonstrated on a diesel engine exhaust slipstream at Caterpillar Inc.

A 20 watt thermophotovoltaic (TPV) battery substitute system is being developed that will provide higher storage capacity and lower weight than the batteries currently used for many military missions. It can also be instantaneous recharged by refueling with propane. The TPV battery substitute incorporates several advanced design features. These include: an evacuated and sealed enclosure for the emitter and photovoltaic (PV) cells to minimize unwanted convection heat transfer from the emitter to the PV cells; a selective tungsten emitter with a well matched gallium antimonide PV cell receiver, spectral control optical filters to recycle non-convertible radiant energy, and a silicon carbide thermal recuperator to recover thermal energy from the exhaust gases. The design of the system and fabrication of the components are discussed.

Early research in the application of nonthermal plasma technology to reduce NOx in combustion emissions established that the chemistry resulting from the direct excitation of exhaust gas streams is dominated by oxidation of NO to NO2 and nitric acid, undesirable end products for mobile systems. An alternative to direct plasma generation in diesel exhaust has now been demonstrated to shift this exhaust NOx chemistry from oxidation toward reduction to nitrogen and oxygen. The new approach reacts NO with atomic nitrogen injected into the exhaust stream through multiple electrically excited high-speed nitrogen jets. Chemical reduction of more than half of the NO in diesel exhaust has so far been demonstrated, with only minimal production of N2O. The technology functions well in the sooty and wet conditions characteristic of diesel exhaust. A system is presently being built for testing and evaluation on exhaust slipstreams at a Caterpillar Inc. test facility.