Sloan, DG
1994
Aspects of Flame Stability in a Research Dump Combustor
Sturgess, G.J.; Hedman, P.O.; Sloan, D.G. and Shouse, D.T.
Transactions of the ASME, 1994 (in press). (Also presented at the ASME International Gas Turbine and Aeroengine Congress and Exposition, The Hague, Netherlands, June 1994. Funded by ACERC, Wright Patterson Air Force Base and Air Force Office of Scientific Research.
The lean blowout process is studied in a simplified, nominally diffusion flame, research combustor that incorporates the essential features of the combustor primary zone for an aircraft gas turbine engine. The research combustor is provided with extensive optical access. To investigate the blowout, a variety of diagnostic techniques are employed, including direct flame observation, laser-Doppler anemometry, spontaneous OH-imaging, thin-filament pyrometry, laser-induced fluorescence OH imaging, coherent anti-Stokes Raman spectroscopy, and computational fluid dynamics. Lean blowouts in the research combustor are related to well-stirred reactor blowout. A blowout sequence is found to be initiated by the loss of a key flame structure in the form of an attached pilot flame. The behavior of this attached flame is investigated. It is concluded that a major contribution to the existence of the attached flame is near-field, non-stationary radial transport of reactants directly into the recirculation zone, rather than by mean flow recirculation of hot products. "Lift" of the attached flame is the reason that lean blowout in the research combustor is related to well-stirred reactor blowout since it allows at least partial premixing of reactants to take place.
1991
Flame Stability and Lean Blowout
Sturgess, G.J.; Sloan, D.G.; Roquemore, W.M.; Reddy, V.K.; Schouse, D.; Lesmerises, A.L.; Ballal, D.R.; Heneghan, S.P.; Vangsness, M.D. and Hedman, P.O.
10th International Society of Air Breathing Engines, Nottingham, England, September 1991. Funded by US Air Force.
A progress report is presented on a comprehensive research program aimed at improving the design and analysis capabilities for flame stability and lean blowout in the combustors of aircraft gas turbine engines. The motivation and aims of the program are reviewed, and the unusual approach adopted to address the research issues is outlined. The supporting experimental program and the test vehicles involved are described, together with some major results obtained to date. The modeling techniques that are being explored are summarized. Their potential and limitations are highlighted. Although much work remains yet to be done, the progress made thus far gives rise to reasonable optimism for achieving the program objectives.
1986
Modeling of Swirl in Turbulent Flow Systems
Sloan, D.G.; Smith, P.J. and Smoot, L.D.
Progress Energy Combustion Science, 12, (3), 63?250, 1986. 188 pgs. Funded by US Department of Energy.
The standard k-e equations and other turbulence models are evaluated with respect to their applicability in swirling, recirculating flows. The turbulence models are formulated on the basis of two separate viewpoints. The first perspective assumes that an isotropic eddy viscosity and the modified Boussinesq hypothesis adequately describe the stress distributions, and that the source of predictive error is a consequence of the modeled terms in the k-e equations. Both stabilizing and destabilizing Richardson number corrections are incorporated to investigate this line of reasoning. A second viewpoint proposes that the eddy viscosity approach is inherently inadequate and that a redistribution of the stress magnitudes is necessary. Investigation of higher-order closure is pursued on the level of an algebraic stress closure. Various turbulence model predictions are compared with experimental data from a variety of isothermal, confined studies. Supportive swirl comparisons are also performed for a laminar flow case, as well as reacting flow cases. Parallel predictions or contributions from other sources are also consulted where appropriate. Predictive accuracy was found to be a partial function of inlet boundary conditions and numerical diffusion. Despite prediction sensitivity to inlet conditions and numerics, the data comparisons delineate the relative advantages and disadvantages of the various modifications. Possible research avenues in the area of computational modeling of strongly swirling, recirculating flows are reviewed and discussed.
Sloan, DG
1994
Aspects of Flame Stability in a Research Dump Combustor
Sturgess, G.J.; Hedman, P.O.; Sloan, D.G. and Shouse, D.T.
Transactions of the ASME, 1994 (in press). (Also presented at the ASME International Gas Turbine and Aeroengine Congress and Exposition, The Hague, Netherlands, June 1994. Funded by ACERC, Wright Patterson Air Force Base and Air Force Office of Scientific Research.
The lean blowout process is studied in a simplified, nominally diffusion flame, research combustor that incorporates the essential features of the combustor primary zone for an aircraft gas turbine engine. The research combustor is provided with extensive optical access. To investigate the blowout, a variety of diagnostic techniques are employed, including direct flame observation, laser-Doppler anemometry, spontaneous OH-imaging, thin-filament pyrometry, laser-induced fluorescence OH imaging, coherent anti-Stokes Raman spectroscopy, and computational fluid dynamics. Lean blowouts in the research combustor are related to well-stirred reactor blowout. A blowout sequence is found to be initiated by the loss of a key flame structure in the form of an attached pilot flame. The behavior of this attached flame is investigated. It is concluded that a major contribution to the existence of the attached flame is near-field, non-stationary radial transport of reactants directly into the recirculation zone, rather than by mean flow recirculation of hot products. "Lift" of the attached flame is the reason that lean blowout in the research combustor is related to well-stirred reactor blowout since it allows at least partial premixing of reactants to take place.
1991
Flame Stability and Lean Blowout
Sturgess, G.J.; Sloan, D.G.; Roquemore, W.M.; Reddy, V.K.; Schouse, D.; Lesmerises, A.L.; Ballal, D.R.; Heneghan, S.P.; Vangsness, M.D. and Hedman, P.O.
10th International Society of Air Breathing Engines, Nottingham, England, September 1991. Funded by US Air Force.
A progress report is presented on a comprehensive research program aimed at improving the design and analysis capabilities for flame stability and lean blowout in the combustors of aircraft gas turbine engines. The motivation and aims of the program are reviewed, and the unusual approach adopted to address the research issues is outlined. The supporting experimental program and the test vehicles involved are described, together with some major results obtained to date. The modeling techniques that are being explored are summarized. Their potential and limitations are highlighted. Although much work remains yet to be done, the progress made thus far gives rise to reasonable optimism for achieving the program objectives.
1986
Modeling of Swirl in Turbulent Flow Systems
Sloan, D.G.; Smith, P.J. and Smoot, L.D.
Progress Energy Combustion Science, 12, (3), 63?250, 1986. 188 pgs. Funded by US Department of Energy.
The standard k-e equations and other turbulence models are evaluated with respect to their applicability in swirling, recirculating flows. The turbulence models are formulated on the basis of two separate viewpoints. The first perspective assumes that an isotropic eddy viscosity and the modified Boussinesq hypothesis adequately describe the stress distributions, and that the source of predictive error is a consequence of the modeled terms in the k-e equations. Both stabilizing and destabilizing Richardson number corrections are incorporated to investigate this line of reasoning. A second viewpoint proposes that the eddy viscosity approach is inherently inadequate and that a redistribution of the stress magnitudes is necessary. Investigation of higher-order closure is pursued on the level of an algebraic stress closure. Various turbulence model predictions are compared with experimental data from a variety of isothermal, confined studies. Supportive swirl comparisons are also performed for a laminar flow case, as well as reacting flow cases. Parallel predictions or contributions from other sources are also consulted where appropriate. Predictive accuracy was found to be a partial function of inlet boundary conditions and numerical diffusion. Despite prediction sensitivity to inlet conditions and numerics, the data comparisons delineate the relative advantages and disadvantages of the various modifications. Possible research avenues in the area of computational modeling of strongly swirling, recirculating flows are reviewed and discussed.