MODELLING OF SPRAYS IN INTERNAL COMBUSTION ENGINES; ENGINEERING, PHYSICAL AND
MATHEMATICAL APPROACHES
S.S. Sazhin
Sir Harry Ricardo Laboratories, School of Computing, Engineering and Mathematics,
University of Brighton, Brighton BN2 4GJ, U.K.
A complementary nature of engineering, physical and mathematical approaches to the modelling of sprays in
Diesel and gasoline internal combustion engines is discussed. Recently developed models, describing the
disintegration of liquid jets and the dynamics of vortex ring-like structures in Diesel and gasoline engine-like
conditions, described in [1,2], are reviewed. Analytical formulae for vortex ring translational velocities, predicted by
vortex ring models, are compared with the results of numerical solutions to the underlying equations and
experimental data.
Recently developed approaches to modelling multi-component biodiesel and Diesel fuel droplet heating and
evaporation are presented [3,4]. Temperature gradient, recirculation and species diffusion within the droplets are
taken into account. It is pointed out that there are serious problems with the application of the approach to the
modelling of heating and evaporation of realistic Diesel fuel droplets, based on the analysis of diffusion of
individual components. In our earlier papers [4,5], a new approach to the modelling of heating and evaporation of
multi-component droplets, suitable for the case when a large number of components are present in the droplets, was
suggested. This approach is based on the introduction of quasi-components, and the model was called the ‘quasidiscrete’ model.
A recently developed kinetic model, taking into account a combined effect of inelastic collisions between
molecules, a non-unity evaporation coefficient and the presence of three components in a mixture [6,7], is described.
The latter effect is important for the problem of heat and mass transfer in a mixture of Diesel fuel (approximated as
a mixture of n-dodecane and p-dipropylbenzene) and air (approximated by nitrogen). Results of functionality testing
of the kinetic algorithm, taking into account the contributions of three components, are presented. The effects of
inelastic collisions are taken into account [8]. Molecular dynamics (MD) simulation is used to study the evaporation
and condensation of n-dodecane (C12H26), the closest approximation to Diesel fuel. The interactions in chain-like
molecular structures are modelled using an optimised potential for liquid simulation (OPLS) [9]. The results of the
estimation of the evaporation/condensation coefficient are presented. This coefficient is used in the kinetic
modelling of n-dodecane droplet heating and evaporation.
The authors are grateful to the EPSRC (UK) (Project EP/J006793/1) for the financial support of this project.
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