Experimental investigation of transverse acoustic instabilities

dc.contributor.advisor Lieuwen, Timothy C.
dc.contributor.author Smith, Travis Edward
dc.contributor.committeeMember Seitzman, Jerry M.
dc.contributor.committeeMember Menon, Suresh
dc.contributor.committeeMember Sun, Wenting
dc.contributor.committeeMember Ranjan, Devesh
dc.contributor.department Aerospace Engineering
dc.date.accessioned 2018-01-22T21:11:46Z
dc.date.available 2018-01-22T21:11:46Z
dc.date.created 2017-12
dc.date.issued 2017-11-09
dc.date.submitted December 2017
dc.date.updated 2018-01-22T21:11:46Z
dc.description.abstract This work presents 5 kHz stereo PIV and OH PLIF measurements as well as OH* and CH* chemiluminescence measurements of transversely forced swirl flames. The presence of transverse forcing on this naturally unstable flow both influences the natural instabilities, as well as amplifies disturbances that may not necessarily manifest themselves during natural oscillations. By manipulating the structure of the acoustic forcing field, both axisymmetric and helical modes are preferentially excited away from the frequency of natural instability. Additionally, forced and self-excited transverse acoustic instability studies to date have strong coupling between the transverse and axial acoustic fields near the flame. This is significant, as studies suggest that it is not the transverse disturbances themselves, but rather the induced axial acoustic disturbances, that control the bulk of the heat release response. The work first presents a method for spatially interpolating the phase locked r-z and r-θ planar velocity and flame position data, extracting the full three-dimensional structure of the helical disturbances. These helical disturbances are also decomposed into symmetric and antisymmetric disturbances about the jet core, showing the subsequent axial evolution (in magnitude and phase) of each of these underlying disturbances. Then experiments performed with essentially the same transverse acoustic wave field, but with and without axial acoustics, show that significant heat release oscillations are only excited in the former case. The results show that the axial disturbances at the nozzle exit are the dominant cause of the heat release oscillations. These observations support the theory that the key role of the transverse motions is to act as the “clock” for the instability, setting the frequency of the oscillations while having a negligible direct effect on the actual heat release fluctuations. They also show that transverse instabilities can be damped by either actively canceling the induced axial acoustics in the nozzle (rather than the much larger energy transverse combustor disturbances), or by passively tuning the nozzle impedance to drive an axial acoustic velocity node at the nozzle outlet.
dc.description.degree Ph.D.
dc.format.mimetype application/pdf
dc.identifier.uri http://hdl.handle.net/1853/59252
dc.language.iso en_US
dc.publisher Georgia Institute of Technology
dc.subject Combustion instabilities
dc.subject Swirl flame
dc.subject Transverse acoustics
dc.title Experimental investigation of transverse acoustic instabilities
dc.type Text
dc.type.genre Dissertation
dspace.entity.type Publication
local.contributor.advisor Lieuwen, Timothy C.
local.contributor.corporatename College of Engineering
local.contributor.corporatename Daniel Guggenheim School of Aerospace Engineering
local.relation.ispartofseries Doctor of Philosophy with a Major in Aerospace Engineering
relation.isAdvisorOfPublication b612098b-d0e6-4ea2-a8d5-92d6d02fe6c4
relation.isOrgUnitOfPublication 7c022d60-21d5-497c-b552-95e489a06569
relation.isOrgUnitOfPublication a348b767-ea7e-4789-af1f-1f1d5925fb65
relation.isSeriesOfPublication f6a932db-1cde-43b5-bcab-bf573da55ed6
thesis.degree.level Doctoral
Original bundle
Now showing 1 - 1 of 1
Thumbnail Image
32.59 MB
Adobe Portable Document Format
License bundle
Now showing 1 - 1 of 1
No Thumbnail Available
3.86 KB
Plain Text