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Fuels are subjected to extreme conditions inside a fuel injector. In modern common rail diesel engines, fuel temperatures can reach 150°C and pressures can exceed 2500 bar inside the rail. Under such conditions the fluid physical properties of the fuel can differ substantially from ambient pressure and temperature and can impact the spray behavior and characteristics. Moreover, experimental determination of the fuel physical properties at these extreme conditions can be very difficult. Previously it has been shown that for pure components, all atom molecular simulations offer a reliable means to calculate the key physical properties (including transport properties, e.g., viscosity) at FIE representative conditions. In this study we extend the approach to calculate these properties of binary mixtures using atomistic molecular simulations.

The effects of lubricant oil and fuel properties on low speed pre-ignition (LSPI) occurrence in boosted S.I. engines were experimentally evaluated with multi-cylinder engine and de-correlated oil and fuel matrices. Further, the auto-ignitability of fuel spray droplets and evaporated homogeneous fuel/oil mixtures were evaluated in a combustion bomb and pressure differential scanning calorimetry (PDSC) tests to analyze the fundamental ignition process. The work investigated the effect of engine conditions, fuel volatility and various lubricant additives on LSPI occurrence. The results support the validity of aspects of the LSPI mechanism hypothesis based on the phenomenon of droplets of lubricant oil/fuel mixture (caused by adhesion of fuel spray on the liner wall) flying into the chamber and autoigniting before spark ignition.