Spray characteristics of diesel and derivatives in direct injection diesel engines with varying injection pressures

Abstract

The combustion and emission characteristics of inedible oils and their derivatives are quite different from those of mineral diesel; in particular, inedible oils and their derivatives present higher molecular, relative density, and vaporization characteristics. These properties exert great impacts on the fuel spray as well as the interactions of this spray with air in the combustion chamber. Thus, examining spray characteristics, including spray cone angle, spray tip penetration, spray area, and fuel atomization, is necessary. The spray characteristics of fuel mainly depend on the fuel injection pressure, density, viscosity, ambient pressure, and temperature. Among these parameters, fuel injection pressure significantly affects the spray structure. In this study, experiments were conducted using diesel, jatropha oil methyl ester, karanja oil methyl ester, and two biodiesel blended fuels (JB20 and KB20)] as fuels in a diesel engine with different injection pressures. Optical techniques for spray visualization and image processing are very efficient tools for analyzing the spray parameters of the tested fuels. Macroscopic spray properties, such as spray tip penetration, spray cone angle, and spray area, were acquired from images captured by a high-speed video camera. The Sauter mean diameter and spray volume of all of the tested fuels were also estimated. Experimental results showed that the biodiesel blends demonstrate features different from those of diesel fuel. KB100 presented the highest spray tip penetration and spray area, followed by JB100 JB20, KB20 and diesel. Diesel fuel showed the best spray parameters, followed by JB20, KB20, KB100 and JB100. The tested fuels exhibited better spray characteristics at higher injection pressures than at lower ones.