Measurement and prediction of high-pressure viscosities of biodiesel fuels

Nowadays common rail injection systems use high pressures to pump the fuel, even if at these conditions the liquid viscosity increases substantially over atmospheric levels. For the proper operation of these injection systems the knowledge of fuels high-pressure viscosities becomes crucial to optimize the engine performance. This work reports new experimental data of high-pressure viscosities for three biodiesels (soybean, rapeseed and their binary mixture) measured at temperatures from 293.15 K to 393.15 K and pressures from atmospheric up to 140 MPa, and proposes a correlation capable of describing the experimental data. The predictions results are excellent for the biodiesels studied, presenting overall average relative deviations (OARD) of only 3.9% in the entire ranges of pressures and temperatures studied. This correlation was also extended to describe the viscosities of biodiesels mixtures with diesel with an OARD of just 3.3%.