Influence of carbon dioxide addition on hydrogen-enriched diesel-WPO Blends in CI engines

• Investigated CO₂ as a sustainable diluent in hydrogen-fuelled CI engine operating in dual fuel mode. • Tested nine fuel blends including diesel, hydrogen, and waste plastic oil (WPO) with CO₂ and H₂ supplementation. • CO₂ at 20 LPM with 10 LPM H₂ reduced NOx emissions by 60% and CO by 30% under full load. • Maximum thermal efficiency of 32% observed with pure diesel; slight reduction with WPO blends. • Exergy and exergo-economic analyses confirm improved combustion stability and sustainability. • CO₂ dilution proved effective in enhancing emission control and supporting fuel flexibility. Combustion engines are major contributors to environmental pollution. This study investigates carbon dioxide (CO₂) as a sustainable diluent in hydrogen-fueled engines to reduce emissions and improve combustion stability. A 4-stroke single-cylinder CI engine operating in dual fuel mode was tested with nine fuel blends, including diesel, hydrogen, and waste plastic oil (WPO), with CO₂ (10 LPM, 20 LPM) and hydrogen (10 LPM) supplementation. Engine performance was analyzed under varying loads (0.1 Nm to 20 Nm) by measuring fuel consumption, exhaust gas temperature, cylinder pressure, and emissions. Results showed that CO₂ at 20 LPM, combined with 10 LPM hydrogen, reduced NOx emissions by 60% and CO emissions by 30% under full load among other emission drops. Thermal efficiency peaked at 32% for pure diesel, with a slight decline for WPO blends. Exergy analysis highlighted CO₂ dilution’s benefits in combustion stability, emissions control, and fuel efficiency. The study also considers exergo-economic and sustainability aspects, reinforcing CO₂ dilution as a viable strategy for cleaner and more efficient combustion. These findings demonstrate the potential of CO₂ dilution in hydrogen-fueled and hybrid engines, aligning with global sustainability to reduce environmental impact while maintaining performance and fuel flexibility.