A numerical simulation devoted to premixed methane-air low swirl stabilized flames obtained from a low swirl burner configuration is presented in this paper. A relatively wide range of methane-air equivalence ratios varying from 0.6 to 1.4 is considered. Several parameters identified as governing the flame structure, namely; velocity and temperature fields, methane (CH 4 ) distribution and (thermal) nitric oxide (NO) formation are analyzed and compared to experimental available results. Turbulence is taken into account using RANS (Reynolds Average Navier-Stokes) standard k-e model coupled to partially premixed model dedicated to combustion. Comparisons with literature results show satisfactory agreement for all studied flame parameters. It is particularly established that a compromise between maximum temperature and minimum (thermal) NO emissions can be ensured for low swirl burners with the flame maintained stable. Furthermore, several low swirl burners' characteristics are recovered. Keywords Turbulence Á Premixed combustion Á Methane-air Á Swirled flames Á Low swirl burner Á Equivalence ratio List of symbols D Burner nozzle diameter (50 mm) D h Hydraulic diameter (mm) F Body force (N) h t Total enthalpy (J kg -1 ) I Turbulent intensity (%) k Turbulent kinetic energy (m 2 s -2 ) k Chemical species k k 00 Eddy diffusivity (m 2 /s) P Static pressure (Pa) Pr Prandtl number R Burner radii fraction r Radial direction component (mm) Re Reynolds number S Swirl number Sch Schmidt number Sch t Turbulent Schmidt number T Temperature (K) u Velocity component (m/s) Vax Axial component velocity (m/s) Vs Tangential component velocity (m/s) V 0 Mean velocity inlet (m/s) x Axial direction component (mm) Y Mass fraction s Viscous force tensor (N m -1 ) e Turbulent kinetic energy dissipation (m 2 s -3 ) k Thermal conductivity (W/(m k)) q Density (kg m -3 ) m Kinematic viscosity (m 2 /s) V t Eddy viscosity (m 2 /s) a Valves inclination angle (°) l Viscosity (m 2 s) l t Turbulent viscosity (m 2 s) < Molecular diffusivity flux
This paper presents a three dimensional numerical simulation of premixed methane-air low swirl stabilized flames. The computational domain has a simple geometry describing a LBS (low swirl burner) with 50mm of nozzle diameter. RANS Standard κ -ε model to treat turbulence coupled with partially premixed combustion model are used. The purpose is to show the applicability limits and their capacities to predict governing flame parameters by varying swirl intensity and CH4 mass fraction at the inlet, which shows the optimum operating area of the burner in terms of generated energy and flame stability with a particular interest to thermal NOx apparitions. This work is compared and validated with experimental and LES numerical simulation works available in the literature. Results offered good similarity for all flame studied parameters. Swirl number was varied from 0.5 to 1.0 to ensure a wide operating range of the burner. From S=0.6, we observed the onset of recirculation zones, while for the inert flow the appearance of recirculation zones was observed for S=0.9. CH4 equivalence ratio was increased from 0.6 to 1.4. That showed apparition of zones with important NOx mass fraction due to the existence of zones with high temperature. Otherwise, the flow field wasn't disturbed in terms of recirculation zones apparitions who remained absent for all cases. Actual investigation works to find equilibrium between the maximum of generated temperature and the minimum of NOx emissions for swirled burners. Used models haven't showed applicability limits, results were clear and precise and offered a significantly gain in computing time and means.
This work presents a numerical simulation of premixed methaneair low swirl stabilized ame, the geometry describes a low swirl burner kind. Reynolds average NavierStokes standard κ−ε model for turbulence coupling to partially premixed model for combustion were used with varying methane equivalence ratio from 0.6 to 1.4. Parameters governing ame structure are investigated; velocity, temperature, CH4 distribution and thermal nitric oxide apparitions elds, results are compared and validated with experimental and large eddy simulation works cited in references, they oer good similarities for all ame parameters studied. Actual study works to nd equilibrium between the maximum of generated temperature and the minimum of thermal NO pollutant emissions for low swirl burners without neglecting the ame stabilization which must be maintained.
Load balancing is a primary consideration in Adhoc networks, due to scarcity of resources. Equitable distribution of the load reduces consumption of network resources and provides homogeneous traffic characteristics in the network, such as load per node or the time from end-to-end incurred on each path.In this paper we present an optimization of the reactive routing protocol AODV with load balancing. The goal is to provide a balanced distribution of traffic on different network nodes.
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