Improving Engine Efficiency Using Hydrogen-Assisted Combustion: Experimental Testing and Machine-Learning Prediction

Abstract

This study investigates the performance enhancement and emission reduction potential of a gasoline internal combustion engine using on-demand hydrogen (HHO) enrichment generated through alkaline electrolysis. Unlike studies relying on compressed hydrogen storage, the proposed system produces hydrogen in real time and injects it into the intake manifold, eliminating storage risks and reducing system complexity. Experimental testing was conducted on a 2.4-L spark-ignition engine using a chassis dynamometer and OBD-II data acquisition. Engine operation was evaluated under two conditions: baseline gasoline mode and hydrogen-assisted gasoline mode. Key performance metrics included power output, torque, fuel consumption, air–fuel ratio (AFR), and exhaust emissions (CO₂, CO, HC, and NOx). Results showed that hydrogen enrichment significantly improved combustion characteristics. Maximum power increased from 99.47 hp to 121.47 hp (+22.14%), and maximum torque rose from 96.34 ft-lb to 131.90 ft-lb (+36.9%). At steady-state cruising, fuel consumption decreased from 8.56 L/h to 7.23 L/h (−15.53%), with AFR shifting from 15.1:1 to 15.5:1, confirming lean-burn operation. Emissions of CO₂, CO, HC, and NOx decreased due to faster flame propagation and more complete oxidation.

To complement the experimental results, regression modeling and an artificial neural network (ANN) soft sensor were developed to predict engine power and fuel rate based on hydrogen flow rate and RPM. The regression model achieved an R² of 0.999 for fuel prediction, while the ANN achieved an R² of 0.959 for power prediction, demonstrating strong predictive capability and applicability for real-time decision support. The findings demonstrate that hydrogen enrichment is a technically and economically viable approach to improving engine efficiency and reducing emissions, offering an immediate transitional pathway toward sustainable mobility without requiring major engine modifications.