This project aims to investigate the applicability of a theoretical model for vortex rings, developed by Kaplanski and Rudi (2005), to the analysis of vortex rings observed in direct injection gasoline engines. The investigators will also carry out a feasibility study on the further modification of this model, taking into account the effects of multiphase flow. They will also undertake further experimental investigation of vortex rings in these engines with particular emphasis on the essential parameter values required in order to develop the theoretical model. The project will examine the theoretical predictions of vortex ring properties against the values of typical parameters for gasoline engines which will allow a detailed comparison between the predictions of the model and experimental results to be made. Finally, the team will investigate the feasibility of developing a vortex ring model, capable of predicting the properties of vortex rings in gasoline engines.

This proposal is 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 will be 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, will be developed. The complexity of the n-dodecane molecules will be reduced based on the consideration of a number of psuedoatoms, each representing the methyl (CH_3) or methylene (CH_2) groups. This research will allow us 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, will be developed. In this algorithm, additional dimensions referring to inelastic collisions will be 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 will be 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 will be allowed and the probabilities of the realisation of these combinations will be equal. The results will be applied to the kinetic modelling of the evaporation process of n-dodecane droplets in Diesel engine-like conditions. This will be 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, who will advise the project members on the relevance of the models to automotive applications, and a research student, who will be trained in new research methods, not widely known and/or used in the UK. This project will build 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.

This proposal is concerned with the development of new mathematical models for transient Diesel fuel jets, taking into account their instabilities and acceleration, in a form suitable for implementation into computational fluid dynamics (CFD) codes. The distinction between convective, absolute and global instabilities and the effects of cavitation on the formation of Diesel fuel sprays will be taken into account. The latter effects are expected to appear via the modification of the boundary conditions for jets at the exit of the nozzle. Effects of boundary disturbances on the breakup of the jet will be studied experiementally using a three dimensional laser vibrometer. The jet acceleration is expected to lead to partial stabilisation of the jet. The effects of jet acceleration and jet instabilities will be used to develop a new stochastic model for the primary spray breakup in a form suitable for implementation into CFD codes. This stochastic model will be implemented into a customised in-house version of the KIVA-2 CFD code. This code will be used for modelling fluid dynamics, heat transfer and combustion processes in Diesel engines. The results of the modelling will be validated against in-house experimental data. This will open the way to implement new models to other CFD codes, including commercial ones.

This proposal is concerned with the development of a new hybrid quantum mechanics/ molecular dynamics (QM/MD) model for the simulation of complex hydrocarbon molecules and the application of this model to the simulation of n-dodecane and a mixture of n-dodecane and dipropylbenzene molecules in Diesel engine-like conditions. The solution of the time independent Schrodinger equation will allow us to obtain the equilibrium geometry of a molecule or an ensemble of molecules, and to calculate the potential energy for any position of atoms and electrons in the system. This approach will give us the potential energy of interacting molecules as a function of their geometry. Comparison of this energy for interacting individual C and H atoms and molecules with the interaction energy calculated by the conventional MD approach (taking into account the internal degrees of freedom of molecules, used in our current EPSRC project EP/H001603/1) for the same inter-atomic distances will allow us to analyse the differences in the QM and classical potentials. It is anticipated that our results will be used to calculate the corrections for the potentials used in the classical MD calculations. The new hybrid model will be used for the analysis of the dynamics of n-dodecane molecules in liquid and gas phases and at the liquid/gas interface, using techniques developed during the work on EPSRC project EP/H001603/1. It is anticipated that at this stage we will be able to establish the range of applicability of the conventional MD approach. A new approximate method of taking into account the QM corrections to the classical results will be developed. Also, the previously developed kinetic model, taking into account the presence of two components (fuel vapour and air) in the kinetic region will be generalised to take into account the presence of the three components (two species of fuel and one of air) there. These new models will be applied to the analysis of Diesel fuel droplet heating and evaporation in realistic engine conditions. In contrast to the previously developed models, the kinetic effects will be taken into account alongside the effects of temperature gradient and recirculation inside droplets and the effects of the moving boundary during the evaporation process. We are not aware of any previous research in this area. This will be a collaborative project involving visiting researchers Professor Vladimir M. Gun'ko (Chuiko Institute of Surface Chemistry of the National Academy of Sciences of Ukraine, Kiev, Ukraine) who is an internationally recognised expert in interfacial phenomena, Dr Bing-Yang Cao (Tsinghua University, Beijing, P.R. China), whose expertise includes the development of numerical algorithms for molecular dynamics simulation and 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. It will be led by 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. The Co-investigator Professor Morgan Heikal will advise the project members on the relevance of the models to automotive applications. A Research Fellow will also be included in the project. This project will build upon the currently funded EPSRC project EP/H001603/1, supporting the collaboration between the PI, Dr B-Y. Cao and Dr I. Shishkova, and previously funded EPSRC projects EP/C527089/1 and EP/E02243X/1, and a Royal Society Joint project with Russia, supporting the collaboration between the PI and Dr I. Shishkova.

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