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Long-haul and other heavy-duty trucks, presently almost entirely powered by diesel fuel, face challenges meeting worldwide needs for greatly reducing nitrogen oxide (NOx) emissions. Dual-fuel gasoline-alcohol engines could potentially provide a means to cost-effectively meet this need at large scale in the relatively near term. They could also provide reductions in greenhouse gas emissions. These spark ignition (SI) flexible fuel engines can provide operation over a wide fuel range from mainly gasoline use to 100% alcohol use. The alcohol can be ethanol or methanol. Use of stoichiometric operation and a three-way catalytic converter can reduce NOx by around 90% relative to emissions from diesel engines with state of the art exhaust treatment.

In high pressure hydrogen injection hot surface ignition engines under nearly all engine operating conditions combustion pressure vibration is generated just after ignition. As a result of many experimental investigations the true nature for the cause of this interesting phenomenon was found and are listed: (1) This phenomenon probably originates from the extremely high local rate of burning of the hydrogen-air mixture. (2) Accompaning the stronger combustion pressure vibration was an increase in engine vibration and noise with increase in NOx emission and higher piston temperature. (3) Longer ignition delay resulted in a steeper pressure-time diagram which resalted in a stronger combustion pressure vibration. (4) The phenomenon had negligible effect on engine performance. (5) The phenomenon can be prevented by premixing a ceratain quantity of hydrogen gas into the intake air stream. The result was a shortened ignition delay.

Internal combustion engines for plug-in hybrid heavy duty trucks, especially long haul trucks, could play an important role in facilitating use of battery power. Power from a low carbon electricity source could thereby be employed without an unattractive vehicle cost increase or range limitation. The ideal engine should be powered by a widely available affordable liquid fuel, should minimize air pollutant emissions, and should provide lower greenhouse gas emissions. Diesel engines could fall short in meeting these objectives, especially because of high emissions. In this paper we analyze the potential for a flex fuel gasoline-alcohol engine approach for a series hybrid powertrain. In this approach the engine would provide comparable (or possibly greater) efficiency than a diesel engine while also providing 90 around lower NOx emissions than present cleanest diesel engine vehicles. Ethanol or methanol would be employed to increase knock resistance.