The Use of Canola Oil, n-Hexane, and Ethanol Mixtures in a Diesel Engine

Environmental protection and the depletion of nonrenewable energy sources necessitate the search for the replacement of, among others, diesel fuel (Df) in diesel engines with renewable fuel without major structural changes. For this reason, vegetable oils are of interest as a possible fuel for this type of engine. Unfortunately, the physicochemical properties of vegetable oils differ significantly from Df. In addition to the boiling and freezing points, these properties include viscosity, density, and surface tension as well as wetting properties. For this reason, an attempt was made to modify these properties by adding n-hexane (Hex) and ethanol (Et) to canola oil (Co). The viscosity, density, surface tension, and wetting properties of Hex and Et are significantly different from those for Co. For the determination of the influence of Hex and Et on these properties of Co, the Co and Hex (10% and 15% w/w) mixtures and Co-Hex (10% and 15% w/w)-Et (0-5% w/w) mixtures were studied. The wetting properties of the studied mixtures were tested by the advancing contact angle measurements on polytetrafluoroethylene (PTFE), polymethyl methacrylate (PMMA), and engine valve. The obtained results suggest that there is a synergetic effect in lowering the surface tension and density of Co with the addition of Hex and Et, and the high Co viscosity is significantly reduced by the addition of Hex and Et. Co viscosity at 15% Hex and 5% Et concentrations are similar to Df. Based on the obtained results of the physicochemical properties of the mixtures studied, the engine tests were carried out on a chassis dynamometer. In the engine tests, it was found that for the mixture of 85% Co, 13% Hex, and 2% Et, the mean indicated pressures were higher than the mean indicated pressure for Df at engine speeds of 2000 rpm, 2500 rpm, 3500 rpm, and 4000 rpm. The reason for the increase in the mean indicated pressure for the mixtures of 85% Co, 13% Hex, and 2% Et should be seen in the shift of the indicator graph towards the top dead position of the piston and further. This way, the range of positive work in the open indicator chart is increased. In mixtures with Et and Co, the onset of combustion occurred later than for other fuels. This phenomenon is related to the fact that the autoignition delay angle for these fuels has increased. The use of Hex and Et as an additive to Co allows the use of refined Co (straight vegetable oil—SVO) to supply diesel engines of various types, also those equipped with a common rail injection system. The use of unrefined canola oil converted to ester is most advantageous in terms of energy. The physicochemical properties of mixtures of canola oil, Hex, and Et are similar to diesel. This allows for the use of Co as fuel in a much wider range of ambient temperatures than before. Such fuel may be produced and applied directly on a farm producing rapeseed.