Experimental and Numerical Study of Swirling Diffusion Flame Provided by a Coaxial Burner: Effect of Inlet Velocity Ratio

Sawssen Chakchak,Hajar Zaidaoui,Ammar Hidouri,Toufik Boushaki,Mouldi Chrigui

doi:10.3390/fluids6040159

Abstract

This paper reports an experimental and numerical investigation of a methane-air diffusion flame stabilized over a swirler coaxial burner. The burner configuration consists of two tubes with a swirler placed in the annular part. The passage of the oxidant is ensured by the annular tube; however, the fuel is injected by the central jet through eight holes across the oxidizer flow. The experiments were conducted in a combustion chamber of 25 kW power and 48 × 48 × 100 cm3 dimensions. Numerical flow fields were compared with stereoscopic particle image velocimetry (stereo-PIV) fields for non-reacting and reacting cases. The turbulence was captured using the Reynolds averaged Navier-Stokes (RANS) approach, associated with the eddy dissipation combustion model (EDM) to resolve the turbulence/chemistry interaction. The simulations were performed using the Fluent CFD (Computational Fluid Dynamic) code. Comparison of the computed results and the experimental data showed that the RANS results were capable of predicting the swirling flow. The effect of the inlet velocity ratio on dynamic flow behavior, temperature distribution, species mass fraction and the pollutant emission were numerically studied. The results showed that the radial injection of fuel induces a partial premixing between reactants, which affects the flame behavior, in particular the flame stabilization. The increase in the velocity ratio (Rv) improves the turbulence and subsequently ameliorates the mixing. CO emissions caused by the temperature variation are also decreased due to the improvement of the inlet velocity ratio.

Highlights

Among the essential aims of combustion research is to increase the efficiency of combustion and minimize the production of pollutants
Comparison of the computed results and the experimental data showed that the Reynolds averaged Navier-Stokes (RANS) results were capable of predicting the swirling flow
An experimental and numerical investigation of swirling flow under non-reacting and reacting conditions provided by a coaxial burner with a radial injection of fuel was presented

Summary

Introduction

Among the essential aims of combustion research is to increase the efficiency of combustion and minimize the production of pollutants. Practical combustion systems such as combustion furnaces, diesel engines and rocket engines use non-premixed flames due to their safety and better flame stability compared to a premixed flame [1]. In this process, oxidant and fuel are injected separately into the flame to limit the flashback and explosion. Several studies have shown that turbulent diffusion flame fields play an important role in reducing atmospheric pollution and maintaining the stability of the flame, and the good performance of combustion systems [2,3,4]. The use of swirling flames can enhance the mixing of the reactant, generating a compact and intense flame, 4.0/)

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Results

Conclusion