Performance and emissions of biodiesel engine with hydrogen peroxide emulsification and cerium oxide (CeO₂) nanoparticle additives

The use of biodiesel in a compression ignition (CI) engine has shown to be a promising alternative to conventional diesel owing to its ability to substantially reduce carbon and hydrocarbon emissions. However, an increase in the NOx due to the additional oxygen content from the fuel has led to different fuel pretreatment and exhaust gas after-treatment methods to curb emissions. Hydrogen peroxide (H₂O₂) has been recently investigated as an oxidant and emulsifier in biodiesel blends for CI engines. Although combustion improvement leading to reduced HC and CO emissions are reported, contrasting findings are found in the literature on the effect of NOx. Similarly, CeO₂ nanoparticles have demonstrated its capability in NOx abatement and hence this paper aims to assess the combined effect of H₂O₂ concentration and CeO₂ nanoparticles on the performance and exhaust emissions using B20 fuel. Three different concentrations of H₂O₂ (0.5%, 1%, and 1.5%) along with two levels of CeO₂ nanoparticle concentrations (40, 80 ppm) are investigated. Maximum brake thermal efficiency (BTE) is observed at 75% load and 1.5% H₂O₂ concentration with an average improvement of 1.2% in BTE over neat B20. The average reduction in CO and HC emissions for 1.5% H₂O₂ emulsification over neat B20 is 56–60% and 41–48% respectively. For the H₂O₂ concentration of 0.5%, 1%, and 1.5%, the average decrease in NOx compared to B20 fuel is 5.6%, 16.1%, and 22.7% respectively. Increasing the nanoparticle concentration from 40 ppm to 80 ppm also decreases emissions and improves BTE but its impact is significantly lower compared to the effect of H₂O₂ emulsification. Increasing H₂O₂ concentration in fuel blend improves the micro explosions leading to better mixing of fuel and air promoting better combustion. This resulted in the reduction of CO, HC, and NOx emissions as H₂O₂ is an active carrier of O₂ and •OH radicals which has a more dominant effect in improving combustion and reducing emissions.