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Multiphase fuel combustion in a swirl diffusion burner: an operational and performance study

Agwu, Ogbonnaya 2020. Multiphase fuel combustion in a swirl diffusion burner: an operational and performance study. PhD Thesis, Cardiff University.
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Meeting the ever-growing energy demands of the world while not sacrificing energy security/environmental sustainability by relying on a single fuel source means that combustion systems must demonstrate fuel flexibility. Currently, the gas turbine burns a wide range of fuels and fuel combinations. However, there seems to be a limit to an exploration of its fuel flexibility. Whereas there are numerous investigations into multiphase fuel combustion in other internal combustion engines like the diesel engine, there is a dearth of such studies for the gas turbine. Consequently, this thesis investigates the simultaneous combustion of practical liquid and gaseous fuels in a 20 kW swirl-stabilised gas turbine relevant combustor. The investigation involved developing a dual-phase fuel injection system capable of handling diesel/methane, diesel/syngas, biodiesel/methane, biodiesel/syngas and blends of methanol/glycerol co-combusted with methane. The effect of partly replacing the liquid fuel with a gaseous type fuel on combustion characteristics like flammability limits, flame stability, flame structure and exhaust emissions were studied for the diesel and biodiesel blends. The gas substitution ratio was based on heat energy contribution in such a manner that a certain percentage of a desired heat output is contributed by the gaseous fuel and the balance by the liquid fuel. The nature of non-reacting flows in the system, including air flow and liquid fuel spray was also investigated using CFD while experimental measurements were supported using numerical chemical kinetics modelling. Flame extinction tests proved that as gas substitution ratio increases, flammability limits decrease owing to changing non-reacting and reacting flow dynamics. Intermediate combustion species chemiluminescence imaging was key to the investigations and was used in evaluating reaction zone characteristics and flame stability. These parameters as well as exhaust emissions were assessed as test conditions were varied. It was important, for the methanol/glycerol blends, to establish the feasibility of its combustion without retrofitting the burner used for the other blends in order to prove its practicality. Thereafter, the influence of methane addition on flame structure and stability was investigated.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Engineering
Uncontrolled Keywords: multiphase combustion; swirl flames; alternative fuels; biodiesel; glycerol; flame stability.
Date of First Compliant Deposit: 11 December 2020
Last Modified: 19 Oct 2021 01:27

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