Performance, combustion and emission characteristics of a direct injection VCR CI engine using a Jatropha curcas oil microemulsion: a comparative assessment with JCO B100, JCO B20 and petrodiesel

Abstract

A Jatropha curcas oil (JCO) based hybrid microemulsion fuel (MHBF) comprising pretreated JCO–1-butanol–ethanol was prepared. The fuel characteristics of the hybrid microemulsion fuel (MHBF) were determined as per standard tests methods recommended by ASTM and compared with JCO B20, JCO B100 and petroleum diesel. The performance, combustion and emission characteristics of MHBF were studied for the first time in a variable compression ratio (VCR) direct injection CI engine. The fuel properties of the MHBF formulation were comparable to that of JCO B100 (viscosity of 5.9 mm² s⁻¹, density 0.872 g cm⁻³ and higher heating value of 38.25 MJ kg⁻¹), while the cold flow properties were found to be superior than JCO B100 and JCO B20. In terms of engine performance, the brake specific fuel consumption (BSFC) of MHBF was comparable to B100 and B20 but higher than petrodiesel; while brake thermal efficiency (η_bte) was close to that of JCO B100 but slightly lower than petrodiesel at almost all load conditions. In terms of emission quality, MHBF was found to be superior to all other tested fuels under all conditions of loading. Most significantly it was observed that up to 80% NO_x reduction as compared to petrodiesel was achieved when operated at full load with the MHBF at the maximum compression ratio of 17.5. Obviously, this is a significant finding and a factor of motivation and investigation for future biofuel applications.