Combustion, performance, and selective catalytic reduction of NOx for a diesel engine operated with combined tri fuel (H₂, CH₄, and conventional diesel)

In this study, the effect of tri fuel (ULSD, H₂, and CH₄) operation under real exhaust gas conditions with different gaseous fuel compositions on the combustion characteristics, engine emissions, and selective catalytic reduction (SCR) after treatment was examined at low, medium, and high engine loads. Pt/Al₂O₃-SCR reactor was used and operated at different exhaust gas temperatures. Results revealed that at low load, the two gaseous fuels (H₂ and CH₄) have the same trend on combustion proccess, where both reduce the in-cylinder pressure and rate of heat release. At the high engine load there was a considerable influence appeared as an increase of the premixed combustion phase and a significant decrease of the total combustion duration. In terms of emissions, it was observed that at high engine load, fuels with high CH₄ content tend to reduce NOx formation, whereas, fuels with high H₂ content tend to reduce PM formation, moreover, combustion of tri fuel with 50:50 fuel mixture resulted in lower BSFC compared to the other ratios and hence, the best engine efficiency. The hydrocarbon-SCR catalyst has shown satisfactory performance in NOx reduction under real diesel exhaust gas in a temperature window of 180–280 °C for all engine loads.