Evaporation and Self-Ignition at High Pressures and Evaporation Residue of a Palm-Methyl-Ester Droplet

Abstract

Evaporation and self-ignition experiments of a single suspended droplet of palm methyl ester (PME) were conducted at high pressures to obtain fundamental data related to spray combustion. Ambient temperature and pressure were varied from 473 to 873 K and from 0.10 to 4.0 MPa, respectively. Combustion experiments were also performed at room temperature and atmospheric pressure. The initial droplet diameter was regulated between 0.5 and 0.6 mm. In order to obtain reference data, fatty methyl esters (FAME) of PME components, light oil, n-decane, and n-hexadecane were employed as a test fuel. Temporal variation of droplet diameter was measured from sequential back-lit images recorded with a high-speed video camera. PME droplet evaporation at relatively-low temperatures slows down drastically on the latest stage of evaporation. It is supposed to be due to alteration of the unsaturated FAMEs in PME during evaporation. As the increase in the ambient pressure, the corrected evaporation lifetime of PEM droplet increases below 673 K in the ambient temperature, and decreases above 773 K. The slow evaporation does not occur during droplet combustion. The corrected combustion lifetime of PME droplet is almost equal to that of light oil droplet at atmospheric pressure. The self-ignition delay time of PME droplet is 1.5 times as long as that of light oil droplet at the ambient pressure of 2.0 MPa.