In this work, an experimental investigation was conducted to analyze dual fuel engine (DF) operation using biogas fuel under high load at constant percentage energy substitution rate (PES). The performance, the ignition delay and other combustion characteristics of engine operating in dual fuel mode (biogas/diesel) are compared to the conventional mode. The biogas, composed of 60% methane and 40% carbon dioxide, is the primary fuel which is blended with air in the engine inlet manifold, whereas the pilot fuel is diesel. The equivalence ratio (ɸ) was varied by changing air flow rate while the energy introduced into the engine remained constant for all the examined cases. Combustion analysis showed that with increasing ɸ, the ignition delay tends to become longer and the peak of heat release rate was increased. Furthermore, as the ϕ increased from 0.35 to 0.7, THC and CO emissions were reduced by 77% and 58% respectively. The NOx emissions decreased at 60% PES by 24% while the BTE was improved by 13%.
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 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.
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