Review
Version 1
Preserved in Portico This version is not peer-reviewed
Multi-Scale Modelling of Fuel Droplet Heating and Evaporation in Combustion Engines
Version 1
: Received: 6 April 2022 / Approved: 8 April 2022 / Online: 8 April 2022 (03:17:40 CEST)
A peer-reviewed article of this Preprint also exists.
Xie, J. (2024). Approaches for describing processes of fuel droplet heating and evaporation in combustion engines. Fuel, 360, 130465. Xie, J. (2024). Approaches for describing processes of fuel droplet heating and evaporation in combustion engines. Fuel, 360, 130465.
Abstract
This review summarises the main numerical models of fuel droplet heating and evaporation (DHE) in combustion engines across the different scales by accessing the nano/micro, meso and macroscopic fluid elements. The phenomena of multi-physics, multi-scale and multi-phase fluid flow and heat transfer are fully investigated when the fuel droplet (dodecane) is heating and evaporated into a background gas (nitrogen) crossing the liquid-vapour (LV) interface, kinetic region (i.e., Knudsen layer) and the bulk regions of liquid and gas in terms of molecular dynamics (MD) simulations, kinetic theory modelling (i.e., direct numerical solutions of Boltzmann equations) and convectional fluid dynamics approach, respectively. The evaporation coefficient of fuel evaporating molecules and their velocity distributions at the LV interface derived from MD simulations formulate a new kinetic boundary condition (KBC). Moreover, a novel kinetic model considering the inelastic collision between fuel molecules alongside the new KBC enables us to describe the non-equilibrium gas dynamics of fuel vapour and gas mixture in Knudsen layer (KL). Heat and mass flux analysis of the fuel droplet under combustion engine conditions can be accurately assessed by implementing the inelastic collision between fuel molecules in KL and a temperature-dependent evaporation coefficient at the LV interface into DHE. The surface temperature of fuel droplet and its evaporation time, which play a significant role in resolving the ignition delay and hence the combustion phasing in engines, can also be well estimated. The multi-scale modelling of fuel DHE will make significantly potential input into the cleaner engine targeting the low-carbon emissions and enhance the capability of the existing computational fluid dynamics (CFD) solvers.
Keywords
fuel droplet; liquid-vapour interface; molecular dynamics; evaporation coefficient; Knudsen layer; kinetic theory modelling
Subject
Engineering, Mechanical Engineering
Copyright: This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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