Inhalation toxicity characterization of nanoparticle and carbonyl emission from conventional diesel and methanol/gasoline-diesel RCCI engine

Abstract

Engine-emitted nanoparticles pose a threat to respiratory health, prompting the exploration of solutions like low carbon alternative fuels (methanol) and reactivity-controlled compression ignition (RCCI) engines. However, employing methanol in RCCI engines releases carcinogenic carbonyl compounds. The present study aims to experimentally investigate nanoparticle and carbonyl emissions from conventional diesel (CDC), gasoline-diesel RCCI (GD-RCCI) and methanol-diesel RCCI (MD-RCCI) engines. This study focuses on predicting lung loading caused by emitted nanoparticles and the potential cancer risk associated with carbonyl compounds. The investigation explores the impact of engine load (lower and medium) and fuel premixing ratio (rp) on particle and carbonyl emissions in RCCI engines. Findings reveal that MD-RCCI reduces total particle number (TPN) emissions by 60% compared to CDC. Results indicate that the concentration of nucleation mode particles (NMPs) decreases as engine load increases, while accumulation mode particles (AMPs) increase for both CDC and MD-RCCI combustion modes. With an increase in rp, the NMPs in the MD-RCCI and GD-RCCI engines are increased. Furthermore, the emission of HCHO and CH3CHO decreases with an increase in engine load. As the rp increases, HCHO and CH3CHO increase significantly. The forecast for lung loading reveals that nanoparticles emitted by CDC show a 30 % higher lung load compared to MD-RCCI. Additionally, as engine load increases, lung loading due to particles increases in CDC and decreases in MD-RCCI. In all test conditions, RCCI combustion demonstrates lower lung retention compared to CDC engine. The lung loading of particles of MD-RCCI decreases significantly with an increase in premixing ratio for a constant load as compared to GD-RCCI. The MD-RCCI engine shows higher cancer risk potential as compared to CDC and GD-RCCI engines. Operating the MD-RCCI engine at medium loads is advantageous for environmental and human health considerations.