A study on hydrogen supplementation in a compression ignition engine fuelled with diesel/biodiesel mixtures: Efficiency and emission trade-offs

The adoption of alternative fuels can boost energy security and minimize carbon emissions. Addressing the global climate change challenge, many countries have committed to net-zero targets. Achieving net-zero emissions necessitates decarbonizing every sector of the economy. Hydrogen, produced from renewable energy, poses minimal environmental risks, and expanding its production will aid in meeting net-zero goals. The present study investigates the impact of hydrogen induction with diesel and biodiesel (lemon and orange peel oils) in dual fuel operation to evaluate the engine performance and emissions characteristics. A single-cylinder, diesel engine was used for experimentation. The hydrogen flow rates of 4 litres per minute (L/min),6 L/min, and 8 L/min were used with diesel and biodiesel. A 32.12 % increase in Brake Thermal Efficiency (BTE) and a 22.89 % decrease in Brake Specific Energy Consumption (BSEC) were observed when using pure diesel combined with 6 L/min of hydrogen gas. The addition of hydrogen significantly reduced exhaust emissions. Being a carbon-free fuel, hydrogen does not directly contribute to the formation of carbon-related pollutants such as CO, HC, and PM. Furthermore, its high diffusivity and wide flammability range promote superior mixing with intake air, which enhances the homogeneity of the charge and facilitates more complete combustion. The introduction of hydrogen acts as a combustion enhancer, enabling leaner combustion with higher flame propagation rates and more efficient oxidation of the primary fuel. Diesel combined with 6 L/min of hydrogen resulted in minimal Carbon Monoxide (CO) and Hydrocarbons (HC) as well as lower Carbon Dioxide (CO₂) and smoke emissions. But the increase in cylinder temperature and pressures led to a rise in Nitrogen Oxides (NOx) emissions caused by hydrogen addition.