Emulsification of waste cooking oil biodiesel blend with hydrogen peroxide to assess tailpipe emissions and performance of a compression ignition engine

Hydrogen peroxide (H₂O₂) is an excellent oxidant carrier that finds its use in combustion and fuel applications. In the present study, H₂O₂ (30% assay) is used as an emulsifier in waste cooking oil biodiesel blend (B20) and the emissions and performance in a compression ignition engine are assessed. Along with the neat B20, three blends of B20 with 0.5%, 1%, and 1.5% H₂O₂ concentrations are used. Increasing the concentration of H₂O₂ beyond 1.5% resulted in vapor lock in the fuel pump leading to a loss in injection pressure. An increase in the exhaust gas temperature was recorded with the increase in H₂O₂ concentration due to improved fuel properties, like, cetane number, thermal conductivity, and microexplosions of fuel droplets. However, NO_x emissions decreased mainly due to the presence of the hydroperoxyl group from H₂O₂. Analysis of variance was also carried out to assess the statistical significance of H₂O₂ on the responses and is seen that the maximum impact of H₂O₂ was positively influencing brake thermal efficiency (BTE), brake-specific fuel consumption (BSFC), hydrocarbon (HC), and NO_x. Compared with the B20 blend, H₂O₂ emulsified fuel with a concentration of 1.5% showed a substantial reduction of 53.7%, 28.6%, 14.2%, and 16.2% in the average emissions of CO, HC, smoke, and NO_x, respectively. Similarly, 7.9% and 7.1% improvement in the BTE and BSFC is obtained. However, more studies are required to ascertain the NO_x reduction mechanism and address issues of fuel vaporization at higher concentrations of H₂O₂.