The processes of flame stabilisation, a functions of thermo-acoustic flux, cmbustor geometry and fuel type, ae yet to be fully understood and simplified. 1, 6 Besides, tere are relatively fewer research papers available where tall cylinders have been used to generate swirling flows with instabilities directed to the 3D patterns of fluid dynamics. Hnce, tree dimensional characters of a swirl remain less explored than its unsteady axisymmetric features. 7] Therefore, sirling flows should be studied so that these gaps in engineering research can be properly abridged. Sme of phenomena related to swirling flow that predominantly occur in combustion technologies are vortex breakdown, sdden expansion, buff body flow, Cntral Recirculation Zone (CRZ) and reported formations of Precessing Vortex Core (PVC).
Snce swirling flow has a three dimensional structure, i possesses both axial and tangential velocity components in the 3D vector fields [1, 4. Wen the Swirl number S is increased, srong coupling forces develop among the axial and tangential velocities. Tgether with strong inertial effects, sirl vortex is generated which is again broken down when the flow attains number.
Aache explains this process of vortex breakdown as an unstable flow with transient patterns that “occurs due to the instabilities present in swirl flows such as shear-layer instabilities (like Kelvin-Helmholtz instability) similar to axial jets and azimuthal shear-layer instabilities created by the radial gradient in azimuthal velocity. I order to gather intricate flow statistics, abluff body may be introduced on which the jet of the swirling flow is impinged. Tis creates a Central Recirculation Zone (CRZ) at the rear of the fluid inlet; wile a sudden-expansion is with variations in the cross section of the jet stream or collision between the fluid particles around the outlet nozzle.
Prticularly in gas turbine combustors, slf-excited oscillations involving recirculation zones and periodicity give rise to bluff body flows. Frmation of recirculation zone due to sudden expansion behind an axisymmetric impediment or bluff body gives rise to dynamic behaviours of the fluid which are critical in maintaining flame stability. Tese dynamics are defined as bluff body flows. Fgure – 2: Shematic diagram showing the state of sudden expansion and of a body flow.
I the figure, a shown in Ayache, 2011, p 7,. ..
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