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Oxygen-Enriched Combustion

Oxygen-Enriched Diesel Combustion

Oxygen-enriched air (OEA) has the potential to offer a number of advantages for combustion in engines, including cold start operation, combustion control, increased power density, and increased fuel conversion efficiency. Oxygen-enriched combustion allows for higher combustion temperatures than can be achieved with atmospheric air, and hence engines that rely on heat transfer (e.g., Stirling engines) see immediate benefits from oxygen enrichment. Previous studies have shown that compression-ignition (i.e., diesel) engines also stand to benefit from oxygen-enriched combustion, although these studies have shown fairly modest gains in efficiency and power density when parasitic losses for generation of the OEA are considered. However, there is a potential for larger performance gains with careful integration and tuning of the air separation equipment and diesel engine. Membranes (either polymeric or mixed conducting ceramic) are the preferred method for air separation at the flow rates required for the U.S. Army's 100-kW generator, the focus of this effort. We have incorporated a model for membrane separation and a detailed diesel engine cycle simulation to study the oxygen-enriched diesel engine from a system perspective. Engine tuning parameters (e.g., injection timing) and membrane module parameters (e.g., permeate recovery) have been optimized together. Having completed these design calculations and some preliminary scoping experiments, we are now preparing to design and build a fully integrated, oxygen-enriched diesel combustion system.