Experimental study of the effect of hydrogenated catalytic biodiesel-Ethanol blends on combustion and soot formation process within an optical engine

Abstract

[EN] The utilization of Ethanol in compression ignition engines has demonstrated great potential for reducing greenhouse gas emissions and breaking the NOX-soot trade -off relationship. However, it is usually necessary to burn ethanol with high-reactivity fuels to address its problem of high resistance to autoignition and low power output, especially during cold-start or low-load conditions. However, this combustion of high-reactivity fuels can lead to high soot emissions. This paper examines the characteristics of in-cylinder soot formation throughout two-color pyrometry in an optical engine operated in partially premixed low-temperature combustion mode, focusing on hydrogenated catalytic biodiesel/ethanol/n-octanol blends with two different proportions (75%/ 15%/10% and 60%/30%/10% by volume) and varying injection strategies. The results indicate that both blends exhibit a typical two-stage heat release process, with the highest cylinder pressure, earliest soot onset and the highest integrated KL factor occurring at an injection timing of - 25 degrees CA. By slightly compensating for power output, a higher proportion of ethanol in the blends leads to a significant in-flame soot reduction and a more uniform soot distribution within the cylinder.