Graduate Research Thesis Topics (For available projects for graduate work follow "Open Positions" link):
I. Soot Formation in Combustion
- Soot formation in atmospheric laminar diffusion flames (E)
- Soot formation at elevated pressures (E)
- Modelling of soot formation in laminar flames (S)
- Modelling of soot formation in gas turbine engines (S)
II. Combustion Characterisctics of Biofuels for Aviation and Ground Transportation
- Laminar flame structure (S, E)
- Extinction limits (S, E)
- NOx and soot formation (S, E)
- High-pressure combustion characteristics (S, E)
III. Turbulent Premixed Combustion
- Turbulent premixed flame structure (E)
- Lean-premixed flame structure (E)
- Lean flame stability (E)
- Turbulent premixed flame modelling (S)
IV. Thermal Oxidative Stability of Aviation Jet Fuels
- Oxidative stability of biofuels for aviation (E)
- Quantification of thermal oxidative stability of jet fuels (E)
- Modelling of thermal oxidation in jet fuel lines and injectors (S)
E: mainly experimental; S: numerical simulation
Current Research Focus:
Soot Formation in Combustion
A significant portion of atmospheric particulates arises from combustion of fuels in various engines and furnaces. In urban areas, mobile sources are major contributors to ambient particulate matter concentrations. The main constituent of the particulates generated by combustion is carbon. These carbonaceous particulates, which are produced from gas-phase combustion processes, are known as soot. The detrimental effect of soot particulates on human health is a current concern and various restrictions are being placed on particulate matter emissions from vehicles and other sources. From an operational point of view, soot formation is not desired in most devices in which the energy conversion is by combustion.
The non-homogeneous nature of turbulent diffusion flames makes it very difficult to isolate parameters that affect soot formation and oxidation. For this reason more easily controlled laboratory experiments are performed in shock tubes and laminar diffusion flames. Co-flow burner flames are axisymmetric and two-dimensional flames with good stability. Some of the important research work on soot formation and oxidation has been conducted on co-flow laminar diffusion flames.
The important parameters that influence the formation of soot in such flames are the parent fuel molecular structure, the flame temperature, the amount and nature of diluents either in the fuel or in the oxidizer, and the pressure.
Laminar co-flow diffusion flames are very sensitive to initial conditions and perturbations. Although co-flow flames are 2-D, there has been a considerable effort for modelling these flames with detail chemical kinetics and with skeletal kinetic mechanisms. These modelling efforts and comparisons among co-flow burners of similar geometries require consistent and well-defined initial conditions.
Our efforts have been focussed on unravelling the soot formation mechanism in combustion. A high-pressure combustion vessel was built and installed at UTIAS combustion laboratory, and experiments to study the influence of pressure on soot formation are in progress.
Turbulent Premixed Combustion
Turbulent premixed and partially premixed combustion is encountered in most practical combustion devices such as gas turbines, reciprocating engines, and industrial and domestic burners. In gas turbines, lean premixed combustion systems have an intrinsic attraction for controlling the combustion process and are the methods of choice. Fully premixed systems provide control over combustion chemistry, reaction kinetics, flame temperatures, and pollutant emissions. Premixed and partially premixed (stratified) charge concepts used in advanced direct injection spark ignition engines for light duty vehicles have the potential for substantial thermal efficiency improvements.
Experiments have shown that turbulence increases the flame propagation rates in premixed combustion. However, the physics behind this effect has not been fully understood yet. One of the leading reasons for this is that the turbulent flame propagation display phenomena that are not common in other turbulent flames. In turbulent premixed flames, interplay of turbulence, thermodynamics, and chemical kinetics leads to a highly complex and convoluted situation. As a result, theoretical models and computational studies are far from explaining the experimental observations.
To exploit the potential of lean premixed and partially premixed combustion concepts for practical devices, a better understanding of the underlying physics is essential. The longer term objectives of this project is to provide information and new knowledge in the area of turbulent premixed and partially premixed combustion that can be used as tools in design of next generation of gas turbines and other combustion systems.
