Study on viscosity and surface tension properties of biodiesel-diesel blends and their effects on spray parameters for CI engines

Biodiesels, prepared from different vegetable oils, have the potential to substitute the petro-diesel fuel in engines for global sustainability. In this work, the biodiesels of castor oil, neem oil and sunflower oil, have been produced in the laboratory by transesterification process and the properties of the prepared fuels are measured and compared against those of diesel. We have focused on the fuel properties that influence the spray formation in the engine cylinder following injection, viz. viscosity and surface tension, at various temperatures. The viscosity and surface tension properties are also measured for blends of diesel and biodiesels at different temperatures and blend ratios. Different correlation functions, both from the literature and newly developed, are used to evaluate the viscosity and surface tension of pure fuels and blends. The properties of the blends predicted from the correlations are compared against the measured values. The deviations in the predicted and measured values are statistically obtained to identify the most suitable correlation for the fuels under consideration. The effects of the variation in the properties of the pure and blended fuels on the spray characteristics, like mean drop diameter and spray cone angle, for compression ignition engines are studied using suitable correlations. The results are used to determine the preheating required in the biodiesel and blended fuels to achieve the identical spray parameters in the engine cylinder as with diesel fuel following injection.