The development of a new, optimized fuel is a process in which diverse fuel properties have to be taken into consideration. For the inclusion of candidates that have yet to be synthesized, a fully predictive model relying on nothing but the molecular structure is mandatory for each relevant property. These relevant properties include the tribological properties. This is because most high-pressure injection systems rely on the tribological properties of the fuel itself for lubrication. In this work the focus is on the viscosity and lubricity of fuels. The former provides a hydrodynamic film for the separation of contacting surfaces, while the latter protects the surface in case of an insufficient hydrodynamic film.
This work begins with an overview of the complexity and diversity of different phenomena present in the boundary lubrication of fuel-lubricated systems ranging from nano- to macro-scale. Laboratory characterization techniques relevant to these various scales are discussed. Subsequently this work investigates the correlation between lubricity and wetting properties via contact angle analysis and adsorption theory. A quantitative structure property relationship model (QSPR) based on Conductor-like Screening Model for Real Solvents (COSMO- RS) is then presented. This model can be used as a tool for screening the lubricity of fuel compounds. In the last chapter, chemical and analytical techniques are adopted to describe the underlying lubricity mechanisms of esters of levulinic acid in comparison to similar compounds.