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In the continuing development of a hydrogen fueled IC engine optimized for application to a generator set or hybrid vehicle, experiments were performed at Sandia National Laboratories on two engine configurations. The intent is to maximize thermal efficiency while complying with strict emissions standards. The initial investigation was conducted utilizing a spark ignited 0.491 liter single cylinder Onan engine and has progressed to a spark ignited 0.850 liter modified for single cylinder operation Perkins engine. Both combustion chamber geometries were “pancake” and achieved a compression ratio of 14:1. The engines were operated under premixed conditions. The results demonstrate that both engines can comply with the California Air Resources Board's proposed Equivalent Zero Emission Vehicle standards for NOx during operation at an equivalence ratio of 0.4.

Engine dynamometer testing of homogeneous charge, spark ignition lean burn engines fueled by natural gas, hydrogen/natural gas blends and neat hydrogen was conducted to determine if NOx emissions from blended fuel operation can be reduced below those generated from natural gas operation, approaching those due to a 100% hydrogen fueled engine. The preliminary tests were conducted at the University of Central Florida/Florida Solar Energy Center on an eight cylinder automotive engine. The results indicate that the hydrogen/natural gas fuel has the potential of meeting highly restrictive NOx levels. Sandia National Laboratories conducted follow-on, comparative tests using a single cylinder research engine. The Sandia results indicate that the proposed CARB EZEV standard for NOx can be met without exhaust gas aftertreatment using a 30% hydrogen (by volume) / 70% natural gas blend fuel in a constant speed/power, hybrid vehicle application which achieves 60 MPG gasoline equivalent efficiency.