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Showing 1 to 20 of 23 for “"Lewis number"”.
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Modelling of microgravity ignition phenomena
… $\theta$ is the activation energy and Le is Lewis number. For flame balls, the heat loss mechanism necessary for stable solutions is the radiation from burnt gas. If heat loss is less than quenching value, there are two stationary solutions, but the small branch solution is always unstable to …
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Effects Of Transport Properties And Flame Unsteadiness On Nitrogen Oxides Emissions From Laminar Hydrogen Jet Diffusion Flames
… of this research is to determine how the fuel Lewis number and the flow unsteadiness play a combined role in maximum flame temperature and affect NOx emission from jet diffusion flame. The fuel Lewis number is varied by increasing/decreasing the mole fraction of diluents in the fuel stream. …
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The stabilization and extinction of a microjet diffusion flame
… limit of complete combustion for unity Lewis number flames in jets of arbitrary strength. The solution is then attempted for the case of non-unity Lewis number Burke-Schumann flames in weak jets (micro-jets). Finally, the solution associated with non-unity Lewis number micro-flames with …
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Modelling of premixed laminar flame propagating in channels
… diffusive effects even for quite large Froud numbers in regard to the appearance of inversion. The variation of Lewis number has no essential effect on the planar flame shape formation when flame propagates downward. Lowering Lewis number can significantly decrease the critical conditions of …
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An investigation of transcritical effects for fuel injection and mixing applications
… are assessed as well. The results suggest that Lewis number is the relevant parameter to single droplet evaporation in a non-convective environment. In particular, the data indicates that the transient and quasi-steady evaporation rates vary exponentially with Lewis number. The …
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Thermal radiation and slip effects on mhd stagnation point flow of nanofluid over a shrinking sheet
… with respect to the involved parameters such as Lewis number, magnetic parameter, radiation parameter, Brownian motion, thermophoresis parameter, velocity and thermal slip parameters. The governing partial differential equations are transformed into nonlinear ordinary differential equation by a …
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Edge-Flames and Combustion at the Microscale
… influence that expands the range of Damkohler numbers for which instabilities occur for small Lewis numbers and affects the quenching limits of edge-flames with a Lewis number of unity. The thermal coupling between the combustion field and conductive burner walls in externally-heated, …
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MHD stagnation flow of nanofluid past a permeable shrinking surface with various conditions
… suction parameter, shrinking parameter, Prandtl number, Biot number and Lewis number. Using a similarity transformation, the governing partial differential equations are transformed into nonlinear ordinary differential equations and the numerical solutions are solved by bvp4c in Matlab software. …
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Investigation on weakly curved counterflow diffusion flames at infinitely fast chemistry
… reaction model at infinite Damkohler number and constant density is considered. This simplified model is then used to study the distribution of fuel and oxidizer mass fractions, shape of the reaction sheet, and the temperature field. The temperature of the reaction sheet for the unity …
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Sensitivity analysis on steady bionanofluid boundary layer flow
… among the independent variables, local Sherwood number is most sensitive to the Lewis number whereas the bioconvection Péclet and Schmidt numbers are the key drive parameters to the local density of motile microorganism. The theoretical study that comes with numerical results serve as an initial …
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Stagnation-point flow past a vertical stretching or shrinking sheets in a nanofluid with slip effect
… of various emerging parameters such as Prandtl number, Pr, Lewis number, Le, the stretching/shrinking parameter, 6 , Brwonian motion parameter,No,Thermophoresis parameter, Nt, shear stress, r,, , heat flux, q. and mass flux, q.. are investigated graphically on the skin friction coefficient, C, , …
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Propagation of spherically expanding premixed flames
… thickness at that instant in time. Effect of the Lewis number on the behavior of the flame is examined in the unconfined scenario. Also, the effect of stretch rate on local density weighted flame displacement speeds is studied, which indicates toward the consistent definition of the flame …
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Propagation of premixed flames in confined channels
… through the entire channel. Effect of the Lewis number on the time taken for the flame to propagate the channel is examined. A non-linear analytical model that treats the flame as a discontinuity is also used to compare with the obtained numerical solution. This model requires only solving …
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Computational analysis of magnetohydrodynamics boundary layer flow of nanofluid over a stretching sheet in the presence of heat generation or absorption and chemical reaction
… methods. The effects of different parameters, Lewis number, Eckert number, stretching, chemical reaction, local Reynolds number, Prandtl number, constant, heat source, Brownian motion, and Thermophoresis are analysed and compared. The numerical results for velocity, temperature, skin friction …
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Stationary edge flames in a wedge with hydrodynamic variable-density interaction
… speed and transverse strain rate and response to Lewis number variations. The details of the computational method will be discussed, including the underlying finite element method, the generation of boundary data, and the continuation of the flame through regions of varying transverse strain. This …
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Reduced-Order Models for the Prediction of Unsteady Heat Release in Acoustically Forced Combustion
… dimensionless quantities such as the Damk\"ohler number and several newly defined parameters. The plug-flow reactor (PFR) is applied to a laminar, burner stabilized flame, using a number of established approaches, but with new attention to developing simple albeit accurate expressions governing …
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Studies of Mixing Processes in Gases and Effects on Combustion and Stability
… and the variations of the Prandtl and Lewis numbers.</p> <p>The Lewis number and Prandtl numbers may vary significantly through the mixing layer. Neutral phase speeds and growth rates for spatial stability are also shown to be effected by the molecular weights and physical …
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A new theory of premixed flames in near-stoichiometric mixtures
… conditions, provided an effective Lewis number is introduced. On the other hand, for a flame in a nonuniform flow, the dynamics depend significantly on the mass diffusivities as well as mixture strength. In particular, we have analyzed the structure of flame in stagnation point flow …
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Dynamic stability, blowoff, and flame characteristics of oxy-fuel combustion
… in oxy-combustion, demonstrated by the effect of Lewis number with a value greater than one for flame temperatures under 1900 K. Most of this work focuses on experimental results from premixed flames in a 50 kW axi-symmetric swirl-stabilized combustor. Combustion instabilities, upon which much …
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Numerical Modelling of LOX Droplet Combustion in Hydrogen under Micro-gravity Conditions
… The new solver considers the non-unity Lewis number constraint for each species required for this laminar combustion involving 100% hydrogen concentration. The new solution predicts flame temperatures more accurately than the traditional reactingFoam solver, which produces incorrect …
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