SAMULET_Project_2_Combustion Systems for Low Environmental Impact
Lead Research Organisation:
University of Cambridge
Department Name: Engineering
Abstract
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Organisations
Publications
Balusamy S
(2015)
Nonlinear dynamics of a self-excited thermoacoustic system subjected to acoustic forcing
in Proceedings of the Combustion Institute
Balusamy S
(2017)
Extracting flame describing functions in the presence of self-excited thermoacoustic oscillations
in Proceedings of the Combustion Institute
Balusamy S
(2017)
Extracting flame describing functions in the presence of self-excited thermoacoustic oscillations
in Proceedings of the Combustion Institute
Cavaliere D
(2013)
A Comparison of the Blow-Off Behaviour of Swirl-Stabilized Premixed, Non-Premixed and Spray Flames
in Flow, Turbulence and Combustion
Dawson J
(2015)
The effect of baffles on self-excited azimuthal modes in an annular combustor
in Proceedings of the Combustion Institute
Dawson J
(2011)
Visualization of blow-off events in bluff-body stabilized turbulent premixed flames
in Proceedings of the Combustion Institute
Dawson J
(2014)
Flame dynamics and unsteady heat release rate of self-excited azimuthal modes in an annular combustor
in Combustion and Flame
| Description | The project consisted of four subprojects: I. Studies in a high pressure and temperature, full scale facility to investigate the behaviour of flames generated from prototype fuel spray nozzles during external acoustic forcing; II. Studies in a high pressure and temperature, full scale facility to obtain measurements of particulate matter, both during operation of realistic fuel spray nozzles operated under elevated pressures and temperatures; III. Laboratory scale studies of flame stability IV. Laboratory scale studies of an annular combustor Key findings I. The approach for the unsteady operation was to build a siren on the downstream end of the combustor, which generated a 15% change in mass flow rate at frequencies up to 600 Hz. The concept was successful, and has generated flame transfer functions over a range of operating conditions of air fuel ratio and splits between mains and pilot fuel. The operation has also unveiled previously not observed self-excited oscillations, which have been associated with turbulent-noise amplified entropy spots in the combustor. These in turn create higher velocity fluctuations, which affect the overall behaviour of the system. II. The measurement of particulate matter in the combustor has revealed so far an absence of volatiles in the exhaust, and a typical distribution in the sub-micron range. III. (i) The size of the recirculation zone is important for stability for all types of flames studied (premixed, non-premixed, spray). (ii) The blow-off event is a relatively slow phenomenon, which lasts a time that is long relative to the residence time in the combustor, allowing hence the possibility of control. (iii) A single correlation for the blow-off condition works reasonably well for all flames studied. (iv) The blow-off of interacting flames, of the type often seen in annular combustion systems, occurs at slightly different conditions but lasts significantly longer than the blow-off of isolated, single flames. IV. The behaviour of flames in an annular combustor vary significantly during operation, with acoustic waves rotating in either direction, and sometimes remaining stationary. The direction of rotation is affected by the direction of flame swirl. |
| Exploitation Route | I. The research at high pressures and temperatures was closely monitored by the industrial partners, Rolls-Royce, as the research involves their fuel injectors. Based on the present research, Rolls-Royce has changed their approach to the investigation of combustion instabilities. III. A computation code with the blow-off correlation has been delivered to Rolls-Royce. Preliminary use for a different geometry than the ones used for its validation has produced reasonable results so far, hence establishing its usefulness for design. IV. The work on the annular combustor is continuing and used to validate models in thermoacoustics. I. The results join one of the 4-5 studies over the past decade performed at high pressure and temperature conditions, with the added benefit of high speed imaging measurements to aid the interpretation. The database is currently being collated, and hopefully eventually disseminated via publication of the results, along with numerical models. III. The work has been published in the archival literature and presented in national workshops and international conferences. A follow-up project on blow-off control has been initiated. |
| Sectors | Aerospace, Defence and Marine,Energy |