Investigation of natural gas enrichment with high hydrogen participation in dual fuel diesel engine

Abstract

This study explores the impact of natural gas (NG) enrichment with high H 2 concentrations (20, 30, 40 and 50 by v %) on combustion characteristics, engine performance, exhaust emissions and knock in a compression ignition engine running in dual fuel (DF) mode. Results indicated that H 2 addition to NG contributes to enhance gaseous fuel combustion that corresponds to an increased heat release rate (HRR) during the premixed phase of gaseous fuel that also causes an increase in the pressure peak, particularly at high loads. The maximum pressure peak and HRR correspond to 50% H 2 addition. The combustion duration is shortened for all H 2 mixtures. Regarding engine performance, an important benefit in terms of brake thermal efficiency is noted for all H 2 blends; it increases with increasing enrichment rate and reaches approximately 16% increase for the 50% H 2 mixture relative to pure NG case. Moreover, enriching NG with H 2 is an effective solution for reducing unburned hydrocarbons and carbon monoxide at moderate to high engine loads. However, for NO x emissions, the addition of H 2 to NG is only attractive at low and moderate loads. In addition, over 80% engine load, NG enrichment with H 2 generates knock, which rapidly reaches high intensities.