TY  - UNPB
PB  - UCL (University College London)
A1  - Mahmood, Adnan
Y1  - 2023/04/28/
M1  - Doctoral
N2  - 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.
EP  - 372
AV  - public
ID  - discovery10168822
N1  - 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.
TI  - A multi-physics simulation approach to Investigating the underlying mechanisms of Low-Speed Pre-Ignition
UR  - https://discovery.ucl.ac.uk/id/eprint/10168822/
ER  -