267 research outputs found
Kinetic and MD modelling of automotive fuel droplets heating and evaporation: recent results
[EN] Recent results of the investigation of kinetic and molecular dynamics (MD) models for automotive fuel droplet heating
and evaporation are summarised. The kinetic model is based on the consideration of the kinetic region in the close
vicinity of the surface of the heated and evaporating droplets, where the motion of molecules is described in terms
of the Boltzmann equations for vapour components and air, and the hydrodynamic region away from this surface.
The effects of finite thermal conductivity and species diffusivity inside the droplets and inelastic collisions in the
kinetic region are taken into account. A new self-consistent kinetic model for heating and evaporation of Diesel
fuel droplets is briefly described. The values of temperature and vapour densities at the outer boundary of the
kinetic region are inferred from the requirement that both heat flux and mass flux of vapour components in the
kinetic and hydrodynamic regions in the vicinity of the interface between these regions are equal. At first, the
heat and mass fluxes in the hydrodynamic region are calculated based on the values of temperature and vapour
density at the surface of the droplet. Then the values of temperature and vapour density at the outer boundary of
the kinetic region, obtained following this procedure, are used to calculate the corrected values of hydrodynamic
heat and species mass fluxes. The latter in their turn lead to new corrected values of temperature and vapour
density at the outer boundary of the kinetic region. It is shown that this process quickly converges and leads to
self-consistent values for both heat and mass fluxes. Boundary conditions at the surface of the droplet for kinetic
calculations are inferred from the MD calculations. These calculations are based on the observation that methyl
(CH3) or methylene (CH2) groups in n-dodecane (approximation of Diesel fuel) molecules can be regarded as
separate atom-like structures in a relatively simple United Atom Model. Some results of the application of quantum
chemical methods to the estimation of the evaporation/condensation coefficient are discussed.The authors are grateful to the EPSRC (UK) (grants EP/K005758/1, EP/K020528/1 and EP/M002608/1), the Royal Society (UK) (grant IE 160014) and the Russian Foundation for Basic Research (grant No. 17-08-01274) for their financial support.Sazhin, S.; Shishkova, I. (2017). Kinetic and MD modelling of automotive fuel droplets heating and evaporation: recent results. En Ilass Europe. 28th european conference on Liquid Atomization and Spray Systems. Editorial Universitat Politècnica de València. 1076-7082. https://doi.org/10.4995/ILASS2017.2017.4593OCS1076708
New approaches to hydrodynamic modelling of heating and evaporation of droplets and liquid films
Modelling of heating, evaporation and ignition of fuel droplets: combined analytical, asymptotic and numerical analysis
Modelling of droplet heating and evaporation: recent results and unsolved problems
Recent results of the investigation of biodiesel and Diesel fuel droplet heating and evaporation, presented in monograph [1] and the most recent original papers [2-6], are summarised. The results of calculations of heating and evaporation of biodiesel fuel droplets, taking into account the contributions of all components, using the discrete components models with finite and infinitely large species diffusivities, and assuming that biodiesel fuel can be treated as a one component fuel, are discussed. It is pointed out that there are serious problems with the application of the discrete components model, based on the analysis of diffusion of individual components, to the modelling of heating and evaporation of realistic Diesel fuel droplets. The generalised multi-dimensional quasi-discrete model and its application to realistic Diesel and gasoline fuel droplets are presented, following [2,4]. New approaches to modelling droplet heating and evaporation, based on kinetic and molecular dynamics models, are briefly summarised following [5,6]. The most important unsolved problems are identified
Computational Fluid Dynamics: a tool for engineering research?
The importance of Computational Fluid Dynamics codes in modelling of the processes in various engineering systems including those realted to irrigation and drainage is well recognized
Modelling of sprays using computational fluid dynamics codes
Abstract: Recently developed approaches to droplet and spray modelling in computational fluid dynamics (CFD) codes are reviewed. It is emphasized that the modelling of spray primary break-up needs to take into account the transient nature of sprays, while the modelling of droplet heating and evaporation needs to take into account a number of factors, including recirculation and finite thermal conductivity of liquid, semi-transparency of droplets and the kinetic effects. This modelling needs to take place in realistic three-dimensional enclosures, which makes it essential to find a compromise between the accuracy of the models and their CPU efficiency
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