Effect of the injection pressure and orifice diameter on the spray characteristics of biodiesel

The purpose of this study was to analyze the influence of the injection pressure and orifice diameter on the spray characteristics of soybean biodiesel. The macroscopic spray characteristics of the spray tip penetration (STP) and spray cone angle (SCA) were tested with a high-speed camera system. The microscopic spray characteristics, such as the statistical size distribution, Sauter mean diameter (SMD), representative diameters and dispersion boundary, were obtained using a Malvern laser particle size analyzer (PSA). The test results showed that with an increasing injection pressure, the STP and the SCA of the biodiesel increased, but the curves of size-volume distribution and cumulative volume distribution of the atomized droplets shifted to smaller diameters. The SMD and representative diameters decreased, and the dispersion boundary was reduced. Moreover, with a decreasing orifice diameter, longer STP and smaller SCA values were observed. Similarly, the size distribution curves of the atomized biodiesel droplets shifted to smaller diameters. The SMD and representative diameters were reduced, and the relative size range of the atomized biodiesel droplets was enlarged. Higher injection pressures and smaller orifice diameters improved the biodiesel atomization; however, the smaller orifice diameters caused an inhomogeneous size distribution of the atomized biodiesel droplets.