Development of a new quantitative kinetic model for the analysis of heating and evaporation processes in complex hydrocarbon fuel droplets

This project was concerned with the development of a new quantitative kinetic model for the analysis of hydrocarbon fuel droplet heating and evaporation, suitable for practical engineering applications.

The work on the project was mainly focused on the following two areas:

Firstly, a new molecular dynamics algorithm for the simulation of complex hydrocarbon molecules, with particular focus on the evaporation process of liquid n-dodecane (C_12H_26), which is used as an approximation for Diesel fuel, was developed. The complexity of the n-dodecane molecules was reduced based on the consideration of a number of psuedoatoms, each representing the methyl (CH_3) or methylene (CH_2) groups. This research allowed investigators to understand the underlying physics of the evaporation process of these molecules and to estimate the values of the evaporation/ condensation coefficient of n-dodecane in a wide range of temperatures relevant to Diesel engines.

Secondly, a new numerical algorithm for the solution of the Boltzmann equation, taking into account inelastic collisions between complex molecules, was developed. In this algorithm, additional dimensions referring to inelastic collisions were taken into account alongside three other dimensions describing the translational motion of molecules as a whole. The conservation of the total energy before and after collisions was taken into account. A discrete number of combinations of the values of energy corresponding to the components of translational motions and internal motions of molecules after collisions was allowed and the probabilities of the realisation of these combinations were equal.

The results were applied to the kinetic modelling of the evaporation process of n-dodecane droplets in Diesel engine-like conditions.

This was a collaborative project between Dr Bing-Yang Cao (Tsinghua University, Beijing, P.R. China), whose expertise includes the development of numerical algorithms for molecular dynamics simulation, Dr Irina Shishkova (Moscow Power Engineering Institute, Russia), whose expertise is focused on the development of numerical codes for the solution of the Boltzmann equation, the PI, Professor Sergei Sazhin, whose expertise includes the development of new physical models of fuel droplet heating and evaporation with a view of applications to modelling the processes in internal combustion engines, Professor Morgan Heikal, the co-investigator of the project, advised the project members on the relevance of the models to automotive applications, and a research student, who was trained in new research methods, not widely known and/or used in the UK.

This project built upon previously funded EPSRC projects EP/C527089/1 and EP/E02243X/1, and the Royal Society Joint project with Russia, supporting the collaboration between the PI and Dr I. Shishkova.