A review on production and implementation of hydrogen as a green fuel in internal combustion engines

Huge and continuously growing non-renewable energy consumption due to human daily activities is accountable for the fossil fuel source crisis in recent decades. The growing concern about the emissions from internal combustion engines also impels the development of new energy sources to replace or reduce conventional nonrenewable energy usage. In this context, hydrogen is found to be a promising solution in internal combustion engines to address these issues. The novelty of this review is to provide an overview of the use of hydrogen as internal combustion fuel, covering the operations in both spark-ignition (SI) and compression-ignition (CI) engines. Majority of the studies had shown that hydrogen enrichment fuels marked incredible engine performance in terms of thermal efficiency, fuel consumption and energy consumption. In addition, reductions in exhaust emissions such as smoke, soot, HC, CO, CO2 and NOx can be achieved in both SI and CI engines with proper operating conditions. Moreover, outstanding combustion behaviours were observed in both internal combustion engines with the application of hydrogen fuel. These enhancements were mainly attributed to the physicochemical properties of hydrogen, which exhibits higher calorific value and rapid flaming speed as discussed in this paper. To summarize, hydrogen utilisation in the IC and SI engines aided improvements in engine performance, exhaust emissions, and combustion behaviours under appropriate operating conditions and minor engine modifications such as ignition system and iridium spark plug for SI engines.