COMPARATIVE STUDY OF MACROSCOPIC SPRAY PARAMETERS AND FUEL ATOMIZATION BEHAVIOUR OF STRAIGHT VEGETABLE OILS (JATROPHA), ITS BIODIESEL AND BLENDS

The combustion and emission characteristics of vegetable oils and derivatives arequitedifferentfrommineraldieselduetotheirrelativelyhighviscosity,density,andvaporisation characteristics. These properties affect the fuel spray and the interac-tion of the spray with air in the combustion chamber therefore it is important toanalyse the spray characteristics e. g. spray tip penetration, spray cone angle,sprayarea,andfuelatomization.Opticaltechniquesforsprayvisualizationandim-age processing are very efficient to analyse the comparative spray parameters forthese fuels. Present research investigates the effect of chamber pressure on spraycharacteristics of jatropha straight vegetable oils (J100) – blends (J5, J20), andjatropha biodiesel (JB100) – blends (JB5, JB20) vis-a-vis baseline data of mineraldiesel. Experimentswereperformedforall thesefuels/blendsinjectedin a constantvolumesprayvisualisationchamber(coldchamber)at fourdifferentchamberpres-sure (1, 4, 7, and 9 bar, respectively). It was found that J100 and JB100 have thehighest spray tip penetration, cone angle, and the spray area followed by J20, J5,mineral diesel and JB20, JB5, mineral diesel, respectively, however J20, J5 andJB20, JB5 have better atomization characteristicsas compared to J100 and JB100,respectively. Cone angle was higher for biodiesel blends as compared to straightvegetable oils blends at atmospheric pressure however as the chamber pressurewas increased to 9 bar, it became almost equal for both fuel types. Spray parame-ters are found to be excellent for mineral diesel followed by jatropha biodiesel andjatropha oil. It was found that atomization of fuel becomessuperiorwith increasingchamber pressure.