The Impact of Hydrogen Enrichment on Engine Performance and Exhaust Emissions in LPG-Hydrogen Blends

Abstract

This work explores how adding hydrogen to LPG affects the performance and emission behavior of a modified CLIO2 four-cylinder spark-ignition engine. The investigation considered three fuel compositions—pure LPG, a blend containing 30% hydrogen and 70% LPG, and a richer mixture with 60% hydrogen and 40% LPG—tested at engine speeds between 1000 and 3500 rpm. Using computational fluid dynamics (CFD) modeling, the study evaluated parameters such as brake torque (BT), brake-specific fuel consumption (BSFC), and the concentrations of nitrogen oxides (NOx) and carbon monoxide (CO) in the exhaust gases. The simulation outcomes indicated a clear improvement in engine performance with increasing hydrogen content. The 60% hydrogen blend achieved the highest torque, nearly 100 N·m at 2000–2500 rpm, corresponding to about a 25% gain compared with the baseline LPG operation. Enhanced fuel economy was also recorded for this blend, which reached a minimum BSFC of nearly 50 g/kWh at higher speeds. Although NOx formation rose at lower speeds with hydrogen addition, a declining trend was noted at elevated speeds. Furthermore, CO emissions markedly decreased as the hydrogen fraction increased, with the 60% hydrogen blend sustaining the lowest steady-state level (0.21%) relative to pure LPG (0.37%). Overall, hydrogen supplementation proved to be an effective strategy for boosting LPG engine efficiency while simultaneously mitigating pollutant emissions.