An Experimental Investigation on Spray Characteristics of Waste Cooking Oil, Jatropha, and Karanja Biodiesels in a Constant Volume Combustion Chamber

摘要

In this study, macroscopic spray characteristics of Waste cooking oil (WCO), Jatropha oil, Karanja oil based biodiesels and baseline diesel were compared under simulated engine operating condition in a constant volume spray chamber (CVSC). The high pressure and high temperature ambient conditions of a typical diesel engine were simulated in the CVSC by performing pre-ignition before the fuel injection. The spray imaging was conducted under absence of oxygen in order to prevent the fuels from igniting. The ambient pressure and temperature for non-evaporating condition were 3 MPa and 300 K. Meanwhile, the spray tests were performed under the ambient pressure and temperature of 4.17 MPa and 804 K under evaporating condition. The fuels were injected by a common-rail injection system with injection pressure of 80 MPa. High speed Mie-scattering technique was employed to visualize the evaporating sprays. Liquid tip penetration length, spray cone angle and spray area were determined from captured images. The equivalence ratio along the axial direction of the spray was also calculated based on mathematical correlations. Results showed that biodiesels had longer spray tip penetration length and narrow spray cone angle than those of baseline diesel. Amongst the biodiesels, Jatropha and Karanja biodiesels exhibited longer spray tip penetration length and narrower spray angle than those of Waste cooking oil biodiesel. On the other hand, baseline diesel showed much shorter liquid tip penetration length and faster evaporation process than biodiesels. The reason is that higher density and viscosity of biodiesels attenuated the fuel atomization and evaporation process. However, despite deteriorated atomization characteristics, biodiesels showed lower equivalence ratio than baseline diesel due to inherent oxygen content in the fuel molecules.