Combined high pressure and low temperature viscosity measurement of biodiesel

In this work, we report the measurement of the viscosity of biodiesel derived from sunflower oil and biodiesel blend with mineral diesel under combined conditions of high pressure and subambient temperature. Using a thermostatically controlled falling sinker-type viscometer, dynamic viscosity measurements were made at pressures up to 153 MPa, which are typical of those found in common-rail automotive diesel engines, and temperatures down to 0 °C. Reproducible and reliable viscosity data was obtained from sinker fall times. Calibration of the viscometer was based on n-dodecane. Biodiesel viscosities were found to increase exponentially with both rising pressure and reducing temperature. When combined with mineral diesel as a B20 blend, the viscosity was found to be less than for B100 for all temperatures considered. Both pressure and thermal freezing were found to also occur with increasing pressure and lowering temperature.