دانلود رایگان مقاله مطالعه عددی ویژگی های شعله اکسی در مشعلی با سه جت جدا

Abstract

Oxy-flames from burners with separated jets present attractive perspectives because the separation of reactants generates a better thermal efficiency and reduction of pollutant emissions. The principal idea is to confine the fuel jet by oxygen jets to favor the mixing in order to improve the flame stability. This paper investigates the effect of equivalence ratio on characteristics of a non-premixed oxy-methane flame from a burner with separated jets. The burner of 25 kW power is composed with three aligned jets, one central methane jet surrounded by two oxygen jets. The numerical simulation is carried out using Reynolds Average Navier-Stokes (RANS) technique with Realizable k-ε as a turbulence closure model. The eddy dissipation model is applied to take into account the turbulence-reaction interactions. The study is performed with different global equivalence ratios (0.7, 0.8 and 1). The validation of the numerical tools is done by comparison with experimental data of the stochiometric regime (Ф = 1). The two lean regimes of Ф = 0.7 and 0.8 are investigated only by calculations. The obtained results of the computational models with the experimental data are performed, and a good agreement is found. The velocity fields with different equivalence ratio are presented. It yields to increase of longitudinal and transverse velocity, promotes the fluctuation in interaction zone between fuel and oxygen also a better mixing quality and a decrease of the size of the recirculation zone.

5. Conclusion

The present study is a numerical investigation of development and structure of flow from an oxy-fuel flame generated by a burner constituted with three jets, jet central continued methane and surrounded by two oxygen jets. This work consists in mainly characterizing numerically the influence of the global equivalence ratios of 0.7, 0.8 and 1 on the behavior of the oxy-flames. Validations of computational models with experimental data of the designed stable case are performed, and a good agreement is found using Realizable k-e. The results of radial profiles of mean velocities, fluctuations and temperature are represented with varying global equivalence ratio. From an aerodynamics point of views, the global equivalence ratio modifies the mean longitudinal velocity of flow near to the burner but keep the mean flow velocity behavior in the central jet. The study of the turbulence intensity along the jet shows that the global equivalence ratio increases the velocities fluctuation intensity. The global equivalence ratio is very efficient to increase the turbulence intensity and in consequence the mixing of the fuel jet with the oxidant and the surrounding fluid.