Using hythane as a fuel in a 6-cylinder stoichiometric natural-gas engine

Combination of right EGR rates with turbocharging has been identified as a promising way to increase the maximum load and efficiency of heavy duty spark-ignited natural gas engines. With stoichiometric conditions a three way catalyst can be used which means that regulated emissions can be kept at very low levels. However dilution limit is limited in these types of engines because of the lower burnings rate of natural gas with higher EGR rates. One way to extend the dilution limit of a natural gas engine is to run the engine with Hythane (natural gas + some percentage hydrogen). Previously benefits of hydrogen addition to a Lean Burn natural-gas fueled engine was investigated [1] however a complete study for stoichiometric operation was not performed. This paper presents measurements made on a heavy duty 6-cylinder natural gas engine. Three different experiments were designed and tested to investigate first of all if the engine encounters too severe knocking problems, second how and why, Hythane affect the running and finally how lean limit and dilution limit will be improved. The experiments were performed successfully and the results showed no significant differences between natural gas and Hythane in terms of efficiency and emissions when engine operates stoichiometric.