Experimental Investigation of Diesel Engine Characteristics Fueled with Cerium Oxide Nanoparticle-Doped Toluene-Diesel Blends

Multi-component alternative fuel blends have the potential to improve diesel engine performance and combustion while reducing harmful exhaust emissions. In this study, the effects of toluene and cerium oxide (CeO2) nanoparticles added to diesel fuel on engine performance, combustion, and emissions were experimentally investigated. The experiments were conducted on a single-cylinder diesel research engine at a constant engine speed of 1800 rpm and at four different engine loads: 10.98, 16.48, 21.97, and 27.46 Nm. Commercial diesel fuel was employed as the reference fuel, whereas the alternative fuels comprised a T10D90 blend containing 10 vol. % toluene and T10D90C40, T10D90C80, and T10D90C120 blends, containing 40, 80, and 120 ppm CeO2 nanoparticles, respectively. The effects of the fuels were evaluated in terms of in-cylinder pressure, heat release rate (HRR), indicated thermal efficiency (ITE), brake specific fuel consumption (BSFC), exhaust gas temperature (EGT), indicated mean effective pressure (IMEP), coefficient of variation of IMEP (COVIMEP), maximum pressure rise rate (MPRR), combustion phase (CA50), carbon monoxide (CO), hydrocarbon (HC), and nitrogen oxide (NOx) emissions. The findings revealed that adding 10% toluene by volume to diesel fuel prolonged the ignition delay due to the low cetane number, delayed the CA50, and reduced the ITE while increasing BSFC and CO, HC, and NOx emissions. In contrast, CeO2 nanoparticles improved combustion particularly at medium and high engine loads—through their catalytic effect, thereby increasing in-cylinder pressure, HRR, and ITE, reducing BSFC and CA50, and largely mitigating the adverse effects of toluene addition. In particular, the T10D90C120 fuel containing 120 ppm CeO2 demonstrated the most significant improvement among the additive-containing fuels, delivering an ITE value of 35.95% at a load of 21.97 Nm. Overall, CeO2 nanoparticles effectively improved the combustion characteristics of diesel–toluene blends.