Transient Phenomena in Annular Combustors
type: CreativeWork
description: This thesis presents a detailed assessment of the transient phenomena related to the operation of annular gas turbine combustors, namely ignition and blow-off. The experiments were conducted on complex multi-burner geometries, close to realistic combustors, to provide a wide data set including stability limits, flame regimes and physical mechanisms of ignition and extinction. The first part of the investigation focused on the lean blow-off (LBO). Experiments were carried out on a premixed annular combustor, comprising a variable number of injectors, obtaining flame regime diagrams and stability curves for the system. Highspeed imaging (5 kHz) of OH* chemiluminescence revealed the peculiar flame shapes and behaviours that can be observed for different mixture velocities and equivalence ratios. Close to extinction, a pattern of blow-off and detachment of the flame was observed, due to flame-to-flame interactions, which was never reported for single burner systems. Further, a linear 5-burner combustor was built to investigate whether the same flame characteristics could be observed in a simpler and cheaper configuration. Laser diagnostics was employed, in the form of low-speed (10 Hz) CH2O planar laser induced fluorescence (PLIF). An analysis of the CH2O layer showed that the change in flame shape with the equivalence ratio was associated with the build up of formaldehyde in the side recirculation zone. The pattern of blow-off and detachment close to LBO could be explained with CH2O accumulating in the inner recirculation zone of a single burner causing the flame to lift, while restabilisation was triggered by flame pockets being convected from an adjacent flame to reignite the partially burnt products. In the linear configuration a non-premixed mode was also tested, resulting in a shorter flame with different characteristics, that showed a pattern of blow-off/reignition, instead of flame lift-off. A comparison between these multi-burner configurations and single burne…
abstract: This thesis presents a detailed assessment of the transient phenomena related to the operation of annular gas turbine combustors, namely ignition and blow-off. The experiments were conducted on complex multi-burner geometries, close to realistic combustors, to provide a wide data set including stability limits, flame regimes and physical mechanisms of ignition and extinction. The first part of the investigation focused on the lean blow-off (LBO). Experiments were carried out on a premixed annular combustor, comprising a variable number of injectors, obtaining flame regime diagrams and stability curves for the system. Highspeed imaging (5 kHz) of OH* chemiluminescence revealed the peculiar flame shapes and behaviours that can be observed for different mixture velocities and equivalence ratios. Close to extinction, a pattern of blow-off and detachment of the flame was observed, due to flame-to-flame interactions, which was never reported for single burner systems. Further, a linear 5-burner combustor was built to investigate whether the same flame characteristics could be observed in a simpler and cheaper configuration. Laser diagnostics was employed, in the form of low-speed (10 Hz) CH2O planar laser induced fluorescence (PLIF). An analysis of the CH2O layer showed that the change in flame shape with the equivalence ratio was associated with the build up of formaldehyde in the side recirculation zone. The pattern of blow-off and detachment close to LBO could be explained with CH2O accumulating in the inner recirculation zone of a single burner causing the flame to lift, while restabilisation was triggered by flame pockets being convected from an adjacent flame to reignite the partially burnt products. In the linear configuration a non-premixed mode was also tested, resulting in a shorter flame with different characteristics, that showed a pattern of blow-off/reignition, instead of flame lift-off. A comparison between these multi-burner configurations and single burne…
author: Ciardiello, Roberto
language: eng
keywords: Combustion, Annular combustor, Ignition, Blow-off
license: https://apollo8-f-pro.lib.cam.ac.uk/bitstreams/ca5bdbfa-b8d9-44ce-b86d-a578252a8858/download
license: https://www.rioxx.net/licenses/all-rights-reserved/
date published: 2021-05-01
date modified: 2026-07-22T22:24:18Z
provider: Cambridge University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Cambridge

PropertyValue
property ID: DOI
value: 10.17863/CAM.70267