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  • 1
    Electronic Resource
    Electronic Resource
    On the modelling of scalar and mass transport in combustor flows (1989)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 28 (1989), S. 861-877 
    Details
    ISSN: 0029-5981
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: The results of a numerical study of swirling and non-swirling combustor flows with and without density variations are presented. Constant-density arguments are used to justify closure assumptions invoked for the transport equations for turbulent momentum and scalar fluxes, which are written in terms of density-weighted variables. Comparisons are carried out with measurements obtained from three different axisymmetric model combustors. The three experiments cover recirculating flow, swirling flow and variable-density, swirling flow inside model combustors. Together, they offer wide ranging flow conditions to test the validity of the models. Results show that the Reynolds stress/flux models do a credible job of predicting constant-density, swirling and non-swirling combustor flows with passive scalar transport. However, their improvements over algebraic stress/flux models are marginal. The extension of the constant-density models to variable-density flow calculations shows that the models are equally valid for such flows. Therefore, the present results argue well for the adoption of constant-density models for variable-density flows until a successfully validated variable-density model is available.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nme.1620280410
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  • 2
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    A second-order modeling study of confined swirling flow (1991)
    Elsevier
    Details
    Publication Date: 1991-03-01
    Print ISSN: 0142-727X
    Electronic ISSN: 1879-2278
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Elsevier
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    PAPER CURRENT
  • 3
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    A numerical and experimental study of coaxial jets (1989)
    Elsevier
    Details
    Publication Date: 1989-09-01
    Print ISSN: 0142-727X
    Electronic ISSN: 1879-2278
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Published by Elsevier
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  • 4
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    Calculations of particle-laden flows by second-moment closures (1991)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A differential second-moment closure is applied to calculate nonswirling turbulent particle-laden jet flow. The closure is effected by extending constant-density single-phase turbulence models to the continuous (carrier) phase of two-phase flow. The dispersed (discrete) phase is treated by stochastic-Lagrangian technique. To reduce the effects of numerical (false) diffusion on the predicted results, a higher order differencing scheme, namely the flux-spline, is employed. In addition, an experimental study is conducted to provide data of good quality, especially near the inlet, for model assessment. The experiment consists of a confined coaxial jet flow of air with glass beads. The beads' diameter is 105 microns and is injected from the inner jet with a mass loading ratio of 0.9. The computed results are in good agreement with experimental data, especially for the carrier phase. However, the predicted turbulence fluctuations associated with the discrete phase are lower than the data at the downstream region of the flow field.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 91-0082
    Format: text
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  • 5
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    A comparison of three algebraic stress closures for combustor flow calculations (1985)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A comparison is made of the performance of two locally nonequilibrium and one equilibrium algebraic stress closures in calculating combustor flows. Effects of four different pressure-strain models on these closure models are also analyzed. The results show that the pressure-strain models have a much greater influence on the calculated mean velocity and turbulence field than the algebraic stress closures, and that the best mean strain model for the pressure-strain terms is that proposed by Launder, Reece and Rodi (1975). However, the equilibrium algebraic stress closure with the Rotta return-to-isotropy model (1951) for the pressure-strain terms gives as good a correlation with measurements as when the Launder et al. mean strain model is included in the pressure-strain model. Finally, comparison of the calculations with the standard k-epsilon closure results show that the algebraic stress closures are better suited for simple turbulent flow calculations.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: ASME PAPER 85-WA/FE-3
    Format: text
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  • 6
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    Calculation of turbulent three-dimensional jet-induced flow in a rectangular enclosure (1990)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The application of a flux-spline scheme to three-dimensional fluid flow is reported. A comparison is made of the performance of this scheme with that of the Power-law differencing scheme. The numerical results are compared with experimental data. For the problem considered in this study, the flux-spline scheme is more accurate than the Power-law. For a prescribed accuracy, the flux-spline scheme requires a far fewer number of grid points. Thus, it has the potential of providing a numerical error-free solution, especially for three-dimensional flows, without requiring an excessively fine grid.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 90-0684
    Format: text
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  • 7
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    Modeling of Fluctuating Mass Flux in Variable Density Flows (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The approach solves for both Reynolds and Favre averaged quantities and calculates the scalar pdf. Turbulent models used to close the governing equations are formulated to account for complex mixing and variable density effects. In addition, turbulent mass diffusivities are not assumed to be in constant proportion to turbulent momentum diffusivities. The governing equations are solved by a combination of finite-difference technique and Monte-Carlo simulation. Some preliminary results on simple variable density shear flows are presented. The differences between these results and those obtained using conventional models are discussed.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA. Lewis Research Center Combust. Fundamentals Res.; p 147-160
    Format: application/pdf
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  • 8
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    Fuel Injector: Air swirl characterization aerothermal modeling, phase 2, volume 2 (1993)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A well integrated experimental/analytical investigation was conducted to provide benchmark quality data relevant to prefilming type airblast fuel nozzle and its interaction with combustor dome air swirler. The experimental investigation included a systematic study of both single-phase flows that involved single and twin co-axial jets with and without swirl. A two-component Phase Doppler Particle Analyzer (PDPA) equipment was used to document the interaction of single and co-axial air jets with glass beads that simulate nonevaporating spray and simultaneously avoid the complexities associated with fuel atomization processes and attendant issues about the specification of relevant boundary conditions. The interaction of jets with methanol spray produced by practical airblast nozzle was also documented in the spatial domain of practical interest. Model assessment activities included the use of three turbulence models (k-epsilon, algebraic second moment (ASM) and differential second moment (DSM)) for the carrier phase, deterministic or stochastic Lagrangian treatment of the dispersed phase, and advanced numerical schemes. Although qualitatively good comparison with data was obtained for most of the cases investigated, the model deficiencies in regard to modeled dissipation rate transport equation, single length scale, pressure-strain correlation, and other critical closure issues need to be resolved before one can achieve the degree of accuracy required to analytically design combustion systems.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-189193-VOL-2 , E-7593-VOL-2 , NAS 1.26:189193-VOL-2
    Format: application/pdf
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  • 9
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    Fuel injector: Air swirl characterization aerothermal modeling, phase 2, volume 1 (1993)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A well integrated experimental/analytical investigation was conducted to provide benchmark quality relevant to a prefilming type airblast fuel nozzle and its interaction with the combustor dome air swirler. The experimental investigation included a systematic study of both single-phase flows that involved single and twin co-axial jets with and without swirl. A two-component Phase Doppler Particle Analyzer (PDPA) was used to document the interaction of single and co-axial air jets with glass beads that simulate nonevaporating spray and simultaneously avoid the complexities associated with fuel atomization processes and attendant issues about the specification of relevant boundary conditions. The interaction of jets with methanol spray produced by practical airblast nozzle was also documented in the spatial domain of practical interest. Model assessment activities included the use of three turbulence models (k-epsilon, algebraic second moment (ASM), and differential second moment (DSM)) for the carrier phase, deterministic or stochastic Lagrangian treatment of the dispersed phase, and advanced numerical schemes. Although qualitatively good comparison with data was obtained for most of the cases investigated, the model deficiencies in regard to modeled dissipation rate transport equation, single length scale, pressure-strain correlation, and other critical closure issues need to be resolved before one can achieve the degree of accuracy required to analytically design combustion systems.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-189193-VOL-1 , E-7593-VOL-1 , NAS 1.26:189193-VOL-1
    Format: application/pdf
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  • 10
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    Flow interaction experiment. Volume 2: Aerothermal modeling, phase 2 (1993)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: An experimental and computational study is reported for the flow of a turbulent jet discharging into a rectangular enclosure. The experimental configurations consisting of primary jets only, annular jets only, and a combination of annular and primary jets are investigated to provide a better understanding of the flow field in an annular combustor. A laser Doppler velocimeter is used to measure mean velocity and Reynolds stress components. Major features of the flow field include recirculation, primary and annular jet interaction, and high turbulence. A significant result from this study is the effect the primary jets have on the flow field. The primary jets are seen to create statistically larger recirculation zones and higher turbulence levels. In addition, a technique called marker nephelometry is used to provide mean concentration values in the model combustor. Computations are performed using three levels of turbulence closures, namely k-epsilon model, algebraic second moment (ASM), and differential second moment (DSM) closure. Two different numerical schemes are applied. One is the lower-order power-law differencing scheme (PLDS) and the other is the higher-order flux-spline differencing scheme (FSDS). A comparison is made of the performance of these schemes. The numerical results are compared with experimental data. For the cases considered in this study, the FSDS is more accurate than the PLDS. For a prescribed accuracy, the flux-spline scheme requires a far fewer number of grid points. Thus, it has the potential for providing a numerical error-free solution, especially for three-dimensional flows, without requiring an excessively fine grid. Although qualitatively good comparison with data was obtained, the deficiencies regarding the modeled dissipation rate (epsilon) equation, pressure-strain correlation model, and the inlet epsilon profile and other critical closure issues need to be resolved before one can achieve the degree of accuracy required to analytically design combustion systems.
    Keywords: AIRCRAFT PROPULSION AND POWER
    Type: NASA-CR-189192-VOL-2 , E-8180-VOL-2 , EDR-16026 , NAS 1.26:189192-VOL-2
    Format: application/pdf
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