%0 Thesis
%9 Doctoral
%A Mahmood, Adnan
%B Mechanical Engineering
%D 2023
%F discovery:10168822
%I UCL (University College London)
%P 372
%T A multi-physics simulation approach to Investigating the underlying mechanisms of Low-Speed Pre-Ignition
%U https://discovery.ucl.ac.uk/id/eprint/10168822/
%X As part of the effort to improve thermal efficiency, engines are being   significantly downsized. A common issue in gasoline engines which limits   thermal efficiency and is further exacerbated by downsizing, is low speed pre ignition (LSPI). This thesis uses a Multiphysics approach, initially using a   validated 1D engine performance model of a GTDI engine, to define realistic   boundary conditions. A strong emphasis on validating each simulation   methodology as much as possible is maintained at each stage.   A hydrodynamic model of the ring-liner and Lagrangian CFD model are used   to investigate the impact of engine oil fluid properties on the mass of oil   transported from the crevice volume to the combustion chamber. A heat   transfer and evaporation model of a single droplet inside an engine   environment was developed for alkanes of chain lengths representing the   extremes of the chain lengths present in engine oil. It was found the droplet   generally evaporates at a crank angle which is close to the point where LSPI   is observed. The hydrocarbon study ends with a CFD constant volume  simulation to understand why engine oil like hydrocarbons ignite in rig tests   but not in an engine.   This research then proceeds to develop a single particle detergent model in   an engine environment, to initially understand why ignition occurs when a   calcium Ca based detergent is present but not in the case of a magnesium Mg   detergent. It was found from simulation that the common theory of calcium   oxide CaO resulting from thermal degradation from the previous cycle then   reacting with Carbon dioxide CO2 late in the compression stroke is unlikely.   There is a stronger case for the CaO particle causing ignition as it is present   in fresh engine oil sprayed onto the liner. As predicted by the hydrocarbon   evaporation model the oil will cover and protect the CaO particle until late in   the compression stroke when the oil will evaporate, exposing the CaO particle   to CO2.
%Z Copyright © The Author 2022. Original content in this thesis is licensed under the terms of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) Licence (https://creativecommons.org/licenses/by-nc-nd/4.0/). Any third-party copyright material present remains the property of its respective owner(s) and is licensed under its existing terms. Access may initially be restricted at the author’s request.