Residue-Based Biodiesel: Experimental Investigation into Engine Combustion and Emission Formation

Abstract

Utilization of biofuels in autoignition engines is important but it is an exciting challenge to invent technologies that will harness the unique chemico-physical characteristics of these novel fuels. This study aims to investigate combustion phases (e.g., start of combustion and autoignition duration) along with emission characteristics of a residue-based biodiesel in autoignition engines. The fuel has been successfully derived from residue of a cooking-oil production process and two blends (B10 and B20, referring to 10 and 20% in volume of the biodiesel in the biodiesel–diesel mixture, respectively) along with fossil diesel (B0) were tested in a common-rail single-cylinder engine operating under a range of speeds (1,400, 1,800, and 2,400 revolutions per minute), loads (25–100%), and injection timing conditions (16–24° before top dead center). Combustion phases were extensively analyzed employing different approaches including in-cylinder pressure derivatives, heat release rate, and engine vibration signals, while particle and NOx formation, two major issues of autoignition engines, are also investigated. Equivalent timing between local maximum and minimum values of in-cylinder pressure derivative observed for B0, B10, and B20 [1.5° of crank angle (DCA) approximately] may suggest a minimal effect of blending ratio on autoignition duration, albeit the start of combustion occurs earlier for B10 and B20 (1–2 DCA) with respect to B0. Particle concentration of B20 decreases up to 30% compared with that of its fossil counterpart, and this is one of the major benefits of utilizing biodiesel in autoignition engines.