Blar i NTNU Open på forfatter "Worth, Nicholas"
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Flame transfer functions and dynamics of a closely confined premixed bluff body stabilized flame with swirl
Nygård, Håkon Tormodsen; Worth, Nicholas (Journal article; Peer reviewed, 2021)The flame transfer function (FTF) and flame dynamics of a highly swirled, closely confined, premixed flame is studied over a wide range of equivalence ratios and bulk velocities at a fixed perturbation level at the dump ... -
Heat release rate response of azimuthal thermoacoustic instabilities in a pressurized annular combustor with methane/hydrogen flames
Ahn, Byeonguk; Indlekofer, Thomas; Dawson, James; Worth, Nicholas (Journal article; Peer reviewed, 2022)In this study, the heat release rate (HRR) response during self-excited azimuthal thermoacoustic instabilities in a pressurized annular combustor is investigated for hydrogen/methane blended flames. The equivalence ratio ... -
In the wake of turbulence: A study on the effects of freestream turbulence on the flow around simple and complex geometries
Li, Leon (Doctoral theses at NTNU;2022:155, Doctoral thesis, 2022)With the growing demand of global energy consumption and a need to reduce pollution caused by energy production from fossil fuels, renewable sources of energy are becoming increasingly necessary for the future sustainable ... -
The inter-scale energy budget in a von Kármán mixing flow
Knutsen, Anna Nina; Baj, Pawel; Lawson, John M; Bodenschatz, Eberhard; Dawson, James; Worth, Nicholas (Peer reviewed; Journal article, 2020)A detailed assessment of the inter-scale energy budget of the turbulent flow in a von Kármán mixing tank has been performed based on two extensive experimental data sets. Measurements were performed at a Taylor microscale ... -
Large eddy simulation of CH4-air and C2H4-air combustion in a model annular gas turbine combustor
Zettervall, Niklas; Worth, Nicholas; Mazur, Marek; Dawson, James; Fureby, Christer (Journal article; Peer reviewed, 2018)Combustion instabilities are one of the major challenges in developing and operating propulsion and power generating gas-turbine engines. More specifically, techniques for managing the increasingly stringent emissions ... -
Large volume scanning laser induced fluorescence measurement of a bluff-body stabilised flame in an annular combustor
Govender, Dirren; Wiseman, Samuel; Dawson, James; Worth, Nicholas (Journal article; Peer reviewed, 2022)This study outlines a variant of three-dimensional OH planar laser-induced fluorescence and its application in characterising a single bluff body stabilised flame inside a 12 burner annular combustor. In this variant of ... -
Near-field response of an axisymmetric jet to transverse acoustic forcing
Dhiren, Mistry; Hanssen-Bauer, Øyvind Waage; Worth, Nicholas; Dawson, James R. (Chapter, 2016)Reacting flows in annular enclosures, such as combustion chambers in gas turbine engines, are subject to acoustic waves that inevitably interact with the primary flow [1]. In this study we consider a simplified case of a ... -
The response of an axisymmetric jet placed at various positions in a standing wave
Æsøy, Eirik; Aguilar, Jose; Worth, Nicholas; Dawson, James (Peer reviewed; Journal article, 2021)The hydrodynamic response of an axisymmetric jet placed at various positions in a standing wave oriented normally to the jet is investigated. At the velocity and pressure nodes the axisymmetric (m=0) and first azimuthal ... -
Scaling and prediction of transfer functions in lean premixed H2/CH4-flames
Æsøy, Eirik; Aguilar, Jose; Wiseman, Samuel; Bothien, Mirko R.; Worth, Nicholas; Dawson, James (Journal article, 2020)Features of the flame transfer function (FTF) are characterized for turbulent, non-swirled, bluff body stabilized “M” flames for different hydrogen and methane blends including pure hydrogen flames. An increase in the ... -
Self-excited longitudinal and azimuthal modes in a pressurised annular combustor
Mazur, Marek; Kwah, Yi Hao; Indlekofer, Thomas; Dawson, James; Worth, Nicholas (Peer reviewed; Journal article, 2020)A new laboratory scale pressurised annular combustion experiment is introduced and used to generate selfexcited longitudinal and azimuthal instabilities. The experiments are operated at mean pressuresranging from approximately ... -
Study of wind turbine wake aerodynamics through the application of motion tracking techniques
Bjørnsgaard, Jenny Marie (Master thesis, 2016)In this master thesis an optical tracking system used to evaluate the 3D motion of an object in space has been studied. The aim of the study was to reconstruct the path of a rotating plank, and evaluate the accuracy of ... -
Study of wind turbine wake aerodynamics through vortex flow visualization
Gjesdal, Erik Lie (Master thesis, 2017)In this master thesis, a flow visualization experiment and a blade tracking experiment have been conducted. The aim of the thesis has been to assess the performance of the new blade tow tank rig at the Fluid Mechanics Lab ... -
Suppression of self-excited thermoacoustic instabilities by convective-acoustic interference
Æsøy, Eirik; Jankee, Girish Kumarsing; Yadala, Srikar; Worth, Nicholas; Dawson, James (Peer reviewed; Journal article, 2022)In this paper we demonstrate direct suppression of self-excited thermoacoustic instabilities over a range of operating conditions using targeted convective-acoustic interference. Premixed hydrogen enriched methane-air ... -
Symmetry breaking modelling for azimuthal combustion dynamics
Ghirardo, Giulio; Nygård, Håkon Tormodsen; Cuquel, Alexis; Worth, Nicholas (Peer reviewed; Journal article, 2020)Annular combustors can exhibit azimuthal thermoacoustic instabilities, which can rotate as a spinning wave at the speed of sound in the azimuthal direction, oscillate as a standing wave with pressure nodes fixed in space, ... -
Tailoring the gain and phase of the flame transfer function through targeted convective-acoustic interference
Æsøy, Eirik; Nygård, Håkon Tormodsen; Worth, Nicholas; Dawson, James Richard (Peer reviewed; Journal article, 2022)This paper investigates how targeted interference between two well characterized sources of hydrodynamic disturbances can modify the response of premixed bluff body stabilised flames with and without swirl. We introduce ... -
Thermoacoustic oscillations in a can-annular model combustor with asymmetries in the can-to-can coupling
Buschmann, Philip Erik; Worth, Nicholas; Moeck, Jonas (Peer reviewed; Journal article, 2022)Can-annular combustors are equipped with a set of nominally identical cans, circumferentially arranged around the shaft. Adjacent cans are coupled acoustically via a small gap at the downstream end, where the circular ... -
Three-Dimensional Measurement of Azimuthally Forced Flames in an Annular Combustor
Govender, Dirren (Doctoral theses at NTNU;2023:56, Doctoral thesis, 2023)This thesis aims to better understand thermoacoustic instabilities in annular combustors. Thermoacoustic instabilities are a topic of interest since it is a challenge to operate gas turbines in a lean regime that reduces ... -
Transient Thermo-Acoustic Responses of Methane/Hydrogen Flames in a Pressurized Annular Combustor
Ahn, Byeonguk; Indlekofer, Thomas; Dawson, James; Worth, Nicholas (Peer reviewed; Journal article, 2022)The present article experimentally investigates the triggering and transient growth of azimuthal instabilities in a pressurized laboratory-scale annular combustor featuring 12 methane/hydrogen flames, as the equivalence ... -
Vortex dynamics of a jet at the pressure node in a standing wave
Worth, Nicholas; Mistry, Dhiren; Berk, Tim; Dawson, James (Journal article; Peer reviewed, 2020)In this paper we investigate the vortex structure and dynamics formed in the near field of a turbulent axisymmetric jet subjected to transverse acoustic forcing. Full three-dimensional phase-averaged velocity measurements ...