This research explores the feasibility of operating a small-scale internal combustion engine using hydrogen-rich gas produced through an onboard water electrolysis system. The generated gas, commonly referred to as HHO (a stoichiometric mixture of hydrogen and oxygen), is obtained by electrochemically splitting water using an alkaline electrolyte-based setup powered by an external electrical source. The produced hydrogen–oxygen mixture is directly supplied to a modified 100 cc four-stroke spark ignition engine, replacing conventional hydrocarbon-based fuel. To enable this operation, significant modifications were made to the carburetor and intake manifold to ensure controlled gaseous fuel delivery, proper mixing with intake air, and stable combustion conditions. Hydrogen's unique combustion characteristics—such as very low ignition energy, high flame propagation speed, and wide flammability range—require careful control of air–fuel ratios and ignition timing. Experimental results indicate that the engine can operate successfully under hydrogen-rich conditions, demonstrating the technical feasibility of onboard hydrogen generation for small engine applications. The exhaust emissions show a major reduction in carbon-based pollutants, with water vapor being the dominant byproduct. However, the system's overall performance is strongly influenced by electrolysis efficiency, electrical energy consumption, gas production rate, and thermal stability of the engine. Key limitations identified include high power demand for electrolysis, risk of backfire, heat accumulation in intake components, and the need for precise flow control mechanisms. Despite these challenges, the study demonstrates that onboard hydrogen generation can serve as a transitional clean-energy solution for internal combustion engines in small-scale applications.
Rohela et al. (2026) studied this question.