An effort to enhance hydrogen energy share in a compression ignition engine under dual-fuel mode using low temperature combustion strategies

A limited hydrogen (H2) energy share due to knocking is the major hurdle for effective utilization of H2 in compression ignition (CI) engines under dual-fuel operation. The present study aims at improvement of H2 energy share in a 7.4 kW direct injection CI engine under dual-fuel mode with two low temperature combustion (LTC) strategies; (i) retarded pilot fuel injection timing and (ii) water injection. Experiments were carried out under conventional strategies of diesel dual-fuel mode (DDM) and B20 dual-fuel mode (BDM); and LTC strategies of retarded injection timing dual-fuel mode (RDM) and water injected dual-fuel mode (WDM). The results explored that the H2 energy share increased significantly from 18% with conventional DDM to 24, and 36% with RDM, and WDM respectively. The energy efficiency increased with increasing H2 energy share under dual-fuel operation; however, for a particular energy share of 18% H2, it decreased from 34.8% with DDM to 33.7% with BDM, 32.7% with WDM and 29.9% with RDM. At 18% H2 energy share, oxides of nitrogen emission decreased by 37% with RDM and 32% with WDM as compared to conventional DDM due to reduction of in-cylinder temperature, while it increased slightly about 5% with BDM. It is emerged from the study that water injection technique is the viable option among all other strategies to enhance the H2 energy share in the engine with a slight penalty of increase in smoke, hydrocarbon, and carbon monoxide emissions.