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 chapter concerns 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 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 stoichiometric regime (Ф = 1). The two lean regimes of Ф = 0.7 and 0.8 are investigated only by calculations. 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.

Highlights

  • This chapter concerns the numerical simulation and the Particle Image Velocimetry (PIV) measurements on oxy-fuel burners with three separated jets

  • The development passes by new method of combustion in order to reduce pollutant emissions and fuel consumption, as well as by the improvement of flame stability [1, 2]

  • The existence of two zones of recirculation is observed with different directions of rotation, which explains the appearance of the negative velocity

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Summary

Introduction

This chapter concerns the numerical simulation and the PIV measurements on oxy-fuel burners with three separated jets. The development passes by new method of combustion in order to reduce pollutant emissions and fuel consumption, as well as by the improvement of flame stability [1, 2]. The substitution of air with pure oxygen leads to an increase in the laminar combustion rate up to 1300%, improves the thermal efficiency, increases the adiabatic flame temperature (2200 K for CH4-Air, 3090 K in oxy-combustion) reduce fuel consumption by 50% and, from an environmental point of view, reduce the formation of nitrogen oxides by up to 95% [4]. Few works, are investigated the effect of equivalence ratios (in lean regime) on characteristics of non-premixed oxy-methane flames from burner with separated jets. The aim of this contribution is to investigate numerically the effect of different equivalence ratio on the combustion characteristics of a diffusion methane oxy-flame in a stabilized separated burner.

Basic configuration of the burner
Numerical method
PIV measurements on burners with inclined jets
Velocity distribution and current lines
Temperature distribution
Radial profiles of longitudinal velocity and turbulence intensity
Longitudinal velocity field
Findings
Conclusion
Full Text
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