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Please use this identifier to cite or link to this item: https://dspace.lboro.ac.uk/2134/10975

Title: A quasi-dimensional model for performance and emissions predictions in a dual fuel engine
Authors: Johnson, Stephen
Keywords: Dual fuel
Quasi-dimensional
Multi-zone
Combustion
Modelling
Modeling
Packet model
Turbulent entrainment model
Methane
Issue Date: 2012
Publisher: © Stephen Johnson
Abstract: A new quasi-dimensional, multi-zone model has been developed to describe the combustion processes occurring inside a dual fuel engine. A dual fuel engine is a compression ignition engine in which a homogeneous lean premixed charge of gaseous fuel and air is ignited by a pilot fuel spray. The atomisation and preparation of the pilot leads to the formation of multiple ignition centres from which turbulent flame fronts develop. The energy release in a dual fuel engine is therefore a combination of that from the combustion of the pilot fuel spray and lean premixed charge. Hence, the dual fuel combustion process is complex, combining elements of both conventional spark and compression ignition engines. The dual fuel engine is beneficial as it can achieve significant reductions in emissions of carbon dioxide (CO2), as well as reducing emissions of oxides of nitrogen (NOx) and particulate matter (PM). A review of the dual fuel engine modelling literature highlighted the current lack of understanding regarding the coupling between the combustion of the pilot and the premixed combustion of the gaseous charge. Thus, the objective of this research was to provide a new modelling approach to describe the energy release rate in a dual fuel engine. The model simulates the combustion processes occurring inside the cylinder during the closed part of the engine cycle. The pilot fuel spray is described using a packet model approach, which includes sub-models for spray development and mixing, swirl, spray wall impingement, ignition and combustion. Flame development is described using an original approach in which flame growth is coupled to the burning zones in the cylinder and is simulated using a turbulent entrainment model. Emissions of NOx and soot are also evaluated. Predicted in-cylinder pressures are in good agreement with experimental data obtained from a naturally aspirated, in-line, four-cylinder, direct injection diesel engine operating with methane (CH4) as the gaseous fuel. Furthermore, predicted energy release rates show excellent agreement with experimental data. Breakdowns of the energy release rate provide an excellent insight into the progression of combustion in a dual fuel engine. Trends for emissions of NOx and soot with gaseous substitution ratio are also presented. A sensitivity analysis provides an improved understanding of the underlying physical mechanisms influencing the performance and emissions of a dual fuel engine.
Description: This thesis is confidential until 1st August 2017. A Doctoral Thesis. Submitted in partial fulfilment of the requirements for the award of Doctor of Philosophy of Loughborough University.
Version: Closed Access
URI: https://dspace.lboro.ac.uk/2134/10975
Appears in Collections:Closed Access PhD Theses (Mechanical and Manufacturing Engineering)

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