Performance and emission characteristics of a diesel engine employing straight vegetable oils from Vanuatu as fuels

Abstract

The performance characteristics of the engine and the emission levels with Copra Oil (CPO), Virgin Coconut (cocos nucifera) Oil (VCO), Tamanu (calaphyllum inopyllum) Oil (TMO), and Nangae (canarium indicum) Oil (NGO) are presented. The oils, obtained from naturally grown trees in Vanuatu, were tested as straight vegetable oils (SVOs) in a Diesel engine and the results are compared with those of neat diesel. The oils were converted to their fatty-acid-methyl-esters (FAMEs) using gas chromatography to determine their fatty acid compositions. The brake thermal efficiency with SVOs was found to be comparable to diesel. The structure of the alkyl chain and the carbon-to-hydrogen ratio were also studied. All the oils have Palmitic acid, Capric acid, Caprylic acid, and Oleic acid as the major fatty acids. The CPO and VCO have higher amounts of Oleic acid, which acts as an additive and breaks up the interaction between the major fatty acids at higher temperatures, reducing the viscosity. Emissions of CO2 were lower while those of CO, NOx, and SO2 were higher with SVOs compared to diesel. The results indicate that the local SVOs are good and inexpensive substitute fuels for Vanuatu that can help the country meet the UN’s sustainable development goals.