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Proceedings ArticleDOI

Flow Field Behind the Flame Holders in an Isothermal Model of an Afterburner - A Theoretical Study

01 Nov 2001-

AboutThe article was published on 2001-11-01. It has received None citation(s) till now. The article focuses on the topic(s): Afterburner. more

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Journal ArticleDOI
Abstract: Measurements of the velocity characteristics of near-wake flows were obtained with a direction-sensitive laser-Doppler anemometer The wakes were formed downstream of central disks of diameters 8·9, 12·5 and 14·2 mm which were located on the centreline of a 20·0 mm jet Detailed measurements were obtained with initial annular-jet velocities of from 9·4 to 39·5 m/s and include values of the axial and radial components of the mean velocity, the three normal stresses and the shear stress Probability density distributions and energy spectra were also measuredThe results show, for example, that the curvature of the annular jet increases with disk diameter and that the ratios of the maximum positive and negative centre-line velocities to the exit velocity increase with decreasing disk diameter and are essentially independent of the initial velocity The turbulent field is substantially anisotropic with a minimum turbulence intensity of around 30% in the recirculation region; the locations of zero shear stress and zero mean velocity gradient are not coincident The measured spectra reveal predominant frequencies in a small region of the outer-shear layer and in the vicinity of the jet exit; these discrete frequencies did not propagate downstream nor into the recirculation region

66 citations

Journal ArticleDOI
Abstract: An experimental and numerical investigation was conducted to study the turbulent velocities and stresses behind a two-dimensional bluff body. Simultaneous three-component laser-Doppler velocimeter (LDV) measurements were made in the isothermal incompressible turbulent flowfield downstream of a bluff body placed at midstream in a rectangular test section. Mean velocities and Reynolds stresses were measured at various axial positions. Spanwise velocity measurements indicated that the flow is three dimensional in the recirculation zone of the bluff body. Confidence in the accuracy of the data was gained by calculating the mass fluxes at each axial station. These were found to agree with each other to within ±3 percent. A parallel Computational Fluid Dynamics (CFD) study was initiated to gage the predictive accuracy of currently available CFD techniques. Three solutions were computed: a two-dimensional steady-state solution using the standard k-∈ model, a two-dimensional time-accurate solution using the standard k-∈ model, and a two-dimensional time-accurate solution using a Renormalized-Group (RNG) k-∈ turbulence model. The steady-state solution matched poorly with the data, severely underpredicting the Reynolds stresses in the recirculation zone. The time-accurate solutions captured the unsteady vortex shedding from the base of the bluff body, providing a source for the higher Reynolds stresses. The RNG k-∈ solution provided the best match to the data.

11 citations

Journal ArticleDOI
Abstract: A computational procedure is described for the calculation of isothermal flow fields of two-ring flame stabilizers in practical afterburners and also for the reacting flow parameters in a research afterburner. The predictions have been obtained using a finite volume solution procedure for the steady three-dimensional elliptic equations of fluid flow. The physical models include the κ-e turbulence model, eddy breakup model, two-step reaction model, droplet vaporization and combustion model, and six-flux radiation model. The presence of radial gutters and staggering the distance between two-ring gutters alter the afterburner flow patterns considerably, including the elimination of diffuser stall and flow separation losses near the diffuser. The predicted and measured emissions in the research afterburner geometry agree qualitatively. The effect of the fuel to air ratio and location of the fuel injector on the temperature and species concentration distribution are presented in detail.

3 citations