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 H2 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 H2 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% H2 addition. The combustion duration is shortened for all H2 mixtures. Regarding engine performance, an important benefit in terms of brake thermal efficiency is noted for all H2 blends; it increases with increasing enrichment rate and reaches approximately 16% increase for the 50% H2 mixture relative to pure NG case. Moreover, enriching NG with H2 is an effective solution for reducing unburned hydrocarbons and carbon monoxide at moderate to high engine loads. However, for NOx emissions, the addition of H2 to NG is only attractive at low and moderate loads. In addition, over 80% engine load, NG enrichment with H2 generates knock, which rapidly reaches high intensities.