Effects of hydrogen and methane addition on combustion characteristics, emissions, and performance of a CI engine

In this study, while a hydrogen + methane mixture in the gas phase (30% H2 + 70% CH4 in moles) is injected from an intake port by a gas injector, ignition is supplied with diesel fuel sprayed from a diesel injector. The energy content of the sprayed gas fuel is modified to constitute 0% (only diesel fuel), 15%, 40%, and 75% of the total fuel energy content. All tests are conducted at 1500 rpm stable engine speed and in full-load condition. The effects of energy content modification of hydrogen + methane gas fuel on engine performance, emissions, and combustion are observed. Both NOx and soot emissions are taken under control with 15% and 40% energy content rates in the gas fuel compared to the diesel-only condition. Although an increase is observed in CO and THC emissions with gas fuel addition compared to the diesel-only condition, an improvement is considered compared to the results obtained for only methane fuel usage with diesel fuel. Moreover, gas fuel mixtures reach a high value (75% energy content) as peak cylinder gas pressure decreases. A single-phase heat release was observed, and the diesel combustion characteristic of the engine was converted into gasoline combustion with the addition of 75% hydrogen + methane as the energy basis.