Velocity measurements and turbulence statistics of a confined isothermal swirling flow

A two-component laser Doppler velocimeter was employed to measure the flow properties of a confined, isothermal, swirling flowfield in an axisymmetric sudden expansion research combustor. A free vortex swirler was used to stir the flow at the inlet of the combustor. Measurements of mean velocities, Reynolds normal and shear stresses, and triple products were carried out at axial distances ranging from 0.38H (step height) to 18H downstream of the swirler. Detailed experimental data are provided to help in the understanding of the behavior of swirling, recirculating, axisymmetric, and turbulent flows inside dump combustors. A balance of the turbulence energy equation has been performed in order to get a detailed insight into the turbulent shear layer behavior. The turbulent kinetic energy terms: production, diffusion, and convection terms were computed directly from the experimental data using central differences. The viscous dissipation term was obtained from the balance of the kinetic energy equation. The analysis of the data was successful in identifying the various areas of interest in the flowfield where different turbulent transport mechanisms dominate. In addition, the data from this study will be available for upgrading advanced numerical codes. The swirling flow streamlines data are compared with the simple dump flow and it is shown that swirl reduces the size of the corner recirculation region in addition to creating a central toroidial recirculation region. In summary, swirling enhances the production and distribution of turbulence energy in the combustor which, in turn, indicates thorough flow mixing and earlier flow recovery.

[1]  David G. Lilley,et al.  Flowfield modeling and diagnostics , 1985 .

[2]  N. Ninomiya.  Measurement of the Reynolds stress budgets in an axisymmetric free jet with the aid of three-dimensional particle tracking velocimetry , 1993 .

[3]  W. H. Stevenson,et al.  Investigation of turbulent transport in an axisymmetric sudden expansion , 1990 .

[4]  W. Jones,et al.  Calculation methods for reacting turbulent flows: A review , 1982 .

[5]  A. M. Mellor,et al.  Combustion Measurements in Air Breathing Propulsion Engines. Survey and Research Needs , 1976 .

[6]  A. Nejad,et al.  Velocity measurements in a research combustor part 1: Isothermal swirling flow , 1992 .

[7]  C. H. Priddin,et al.  Predictions of the flow field and local gas composition in gas turbine combustors , 1979 .

[8]  Near-field study of a turbulent freejet and velocity bias effects , 1996 .

[9]  Surya Pratap Vanka,et al.  Efficient computational tool for ramjet combustor research , 1988 .

[10]  David G. Lilley,et al.  Inlet Velocity Profile Effects on Turbulent Swirling Flow Predictions , 1994 .

[11]  K. L. Orloff,et al.  Reduction of Flow-Measurement Uncertainties in Laser Velocimeters with Nonorthogonal Channels , 1983 .

[12]  E. Kilik.  Influence of the blockage ratio on the efficiency of swirl generation with vane swirlers , 1985 .

[13]  S. Fujii,et al.  Swirling Jets with and without Combustion , 1981 .

[14]  Hunter Rouse,et al.  Jet diffusion in the region of flow establishment , 1967, Journal of Fluid Mechanics.

[15]  D. L. Davis,et al.  The design and combustion performance of practical swirlers for integral rocket/ramjets , 1983 .

[16]  A. Lefebvre.  Gas Turbine Combustion , 1983 .

[17]  J. M. Beér,et al.  Velocity and Static-Pressure Distributions in Swirling Air Jets Issuing From Annular and Divergent Nozzles , 1964 .

[18]  C. A. Martin,et al.  Aspects of the Design of Swirlers as used in Fuel Injectors for Gas Turbine Combustors , 1987 .

[19]  N. Kasagi,et al.  Three-dimensional particle-tracking velocimetry measurement of turbulence statistics and energy budget in a backward-facing step flow , 1995 .