Assessment of combustion behavior and catalytic converter deposits in a CI engine operated with MWCNT-enriched pongamia biodiesel: experimental study

Abstract Although biodiesel seems to be a promising alternative fuel for compression ignition (CI) engines, its use can cause deposit formation on the catalytic converter and impact engine durability. The effects of 30 ppm multi-walled carbon nanotube (MWCNT) dispersed Pongamia biodiesel blends (B10, B20 and B30) on combustion characteristics, engine performance and catalytic converter deposits on 500 h engine operation are investigated. In-cylinder pressure, heat release rate, ignition delay and combustion duration were used to assess combustion characteristics, and scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were applied to characterize the catalyst deposits. The fuel with the best overall performance was B20-MWCNT, with the highest fuel efficiency of 26.9% and the lowest fuel consumption of 0.25 kg/kW-h. The lowest ignition delay time (5.7°CA) and combustion duration (30.8°CA) were also achieved with B20-MWCNT. The B20-MWCNT exhibited the highest peak cylinder pressure (69.62 bar) and heat release rate (83.94 J/°CA) which demonstrated better combustion when considering the addition of MWCNT. SEM/EDS analysis showed that the fouling was less with fine and compact deposits with SEM compared to neat biodiesel. These results showed that B20-MWCNT has the best performance in terms of combustion and durability of the catalytic converter, which can be used as an efficient and sustainable fuel in CI engine.