Chemical and quality performance of biodiesel and petrol blends

Abstract

The development of an appropriate fuel to run on a petrol compression ignition engine conceptualises a low temperature combustion strategy, which faces challenges. With the high intake temperatures, low lubricity and need for a high compression ratio for this engine, the use of a petrol-biodiesel blend as a fuel addresses such issues. This study evaluates the characteristics of fuel quality and performance of blended fuels with biodiesel additives (5%, 15%, and 25%) to petrol (95%, 85%, and 75%) compared to 100% petrol and biodiesel. Biodiesel was produced from waste sunflower and palm oils. The fuel properties of the blends were assessed with respect to acid number, density, distillation, cetane number, metal contents, oxidation stability, viscosity, and water content. Results showed that the blended fuels met standard specifications and possessed improved fuel quality compared to pure petrol. Comparing the biodiesel-petrol blends with pure biodiesel, the values of these fuel properties were lowered except for oxidation stability which was enhanced. The two types of biodiesel fuel blends portrayed different fuel qualities, where sunflower biodiesel-petrol blends had more energy content and lower acid number, while palm biodiesel-petrol blends had exceptional thermal stability and characteristics of a better cold start. The high degree of unsaturation characterising sunflower biodiesel resulted in increased carbon residues, reduced cetane number and subsequent poor cold start. An increase in petrol percentage in the blends reduced concentrations of calcium and magnesium significantly and hindered the absorption of moisture content.