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Title: The behaviour of swirling flames under variable fuel composition
Author: Lewis, Jonathan
ISNI:       0000 0004 5351 0717
Awarding Body: Cardiff University
Current Institution: Cardiff University
Date of Award: 2014
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This thesis is concerned with the swirl stabilised combustion of gases with variable composition, primarily those derived from the gasification of carbonaceous material, and secondarily those that occur naturally, such as shale gas. During the course of this research the temporal composition of producer gas, derived from the gasification of biomass, was studied in order to ascertain the effect its variable fuel composition had on its combustion properties. Its variation was highly dependent on gasifier operation, and despite the stoichiometric air-to-fuel ratio and Wobbe Index of the fuel being consistent, high throat temperatures resulted in high hydrogen content and laminar flame speeds. Alterations in flame speed are linked to thermo-acoustic instabilities, flame extinction and damaging flame propagation. Acoustic response under combustion conditions was investigated, to determine how it altered over a flames stability range. Indicators of impending flame flashback and blowoff were found, which could be utilised to prevent such events from occurring in an appropriate control system, without the need for real time gas analysis. Flames with high hydrogen content display a propensity for flashback, especially in high turbulence burners, such as those found in gas turbines, where thermo-acoustics are also a significant problem. Variation in fuel composition, particularly in the proportion on hydrogen, exacerbates these problems. The diffusive injection effects of three gases on reacting flow structures were investigated as a method of improving the stability of pre-mixed flames. Carbon dioxide was found to improve flame stability, whilst reducing emissions during the combustion of syngas mixtures in a development gas turbine combustor. Monitoring acoustic response and diffusive injection are thus suggested as additional stabilisation methods for the combustion of gases with variable composition.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: TA Engineering (General). Civil engineering (General)