Combustion characteristics of a direct-injection diesel engine fueled with Fischer-Tropsch diesel

Abstract

Fischer-Tropsch (F-T) diesel fuel is characterized by a high cetane number, a near-zero sulphur content and a very low aromatic level. On the basis of the recorded incylinder pressures and injector needle lifts, the combustion characteristics of an unmodified single-cylinder direct-injection diesel engine operating on F-T diesel fuel are analyzed and compared with those of conventional diesel fuel operation. The results show that F-T diesel fuel exhibits a slightly longer injection delay and injection duration, an average of 18.7% shorter ignition delay, and a comparable total combustion duration when compared to those of conventional diesel fuel. Meanwhile, F-T diesel fuel displays an average of 26.8% lower peak value of premixed burning rate and a higher peak value of diffusive burning rate. In addition, the F-T diesel engine has a slightly lower peak combustion pressure, a far lower rate of pressure rise, and a lower mechanical load and combustion noise than the conventional diesel engine. The brake specific fuel consumption is lower and the effective thermal efficiency is higher for F-T diesel fuel operation.