Investigation on combustion characteristics and emissions of diesel/hydrogen mixtures by using energy-share method in a diesel engine

Considering hydrogen as a clean alternative fuel for engines, this paper is to develop a procedure to add hydrogen in an intake manifold and to design an exhaust gas recirculation (EGR) system for a direct injection diesel engine. The cylinder gas pressure, air mass flow, fuel mass flow, and emissions (such as CO, CO ₂, HC, NO _X, and smoke) were measured under various engine loads and 0%-40% EGR ratios adjusting the hydrogen-energy-share ratio at 0%-20%, meaning that the energy of hydrogen replaced 0%-20% that of diesel fuel. The combustion characteristics such as cyclic variations, heat release rate, brake thermal efficiency, and specific fuel consumption (SFC) were determined. The results show that the variation coefficient values of indicated mean effective pressure (IMEP) are from 0.9% to 2.8%. The rate of decrease in the smoke emission is 37.6%, and that in the NO _X emission is 59.5% for a 60% load, 40% EGR ratio, and 20% added hydrogen.