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High pressure direct injection of natural gas and hydrogen fuel in a diesel engine Trusca, Bogdan


Emissions and performance of an HPDI single-cylinder diesel engine fueled by natural gas and by a mixture of hydrogen-natural were investigated. A DDC 1-71 engine with electronic controls was used. Natural gas or hydrogen-natural gas mixture was injected late in the compression stroke after a pilot quantity of a diesel was injected. Engine performance and emissions have been measured over a wide range of parameters: gas injection pressure, engine load, injection delay and mass flow percentages for the gaseous fuels. These results were compared with conventional diesel fueling. The purpose of this research was to investigate the potential for reducing the diesel exhaust emissions while maintaining high thermal efficiency. With HPDI of natural gas and hydrogen-natural gas, NOx emissions can be reduced to almost half of those with diesel fueling, by appropriately adjusting the injection timing. NOx concentration is observed to increase with gas injection pressure. For hydrogen-natural gas fueling, an increase of the hydrogen percentage produces an increase in NOx. This is attributed to the higher combustion temperature as the percentage of hydrogen increases. Thermal efficiency of HPDI of natural gas was greater than conventional diesel fueling at high loads but almost identical for medium and low loads. For HPDI of hydrogen-natural gas mixture the thermal efficiency is less than with natural gas fueling. The drop in thermal efficiency has not yet been explained. With hydrogen addition, the unburned hydrocarbons are greatly reduced, for almost all the engine loads. Carbon monoxide emission with HPDI was reduced for high and low loads.

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