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In this paper the stabilizing of non- premixed turbulent flame with a porous medium is studied experimentally. One of the approaches taken to stabilize the flame in high thermal capacity is the usage of the porous medium on the burner. A non-premixed burner with natural gas fuel is used. The First, tests are carried out for the conventional burner and then for the combined burner with the carbide ceramics porous medium. In the conventional burner effects of fuel and air velocity and equivalence ratio on flame length, flame lift off and the stability limit are discussed. Porous silicon carbide ceramics with pore densities of 10ppi, 20ppi and 30ppi are used in the combined burner. Experiments are done at 5cm, 10cm and 15cm distances of porous medium from the burner. The viewed flames in the combined burner are grouped into four regimes. In conventional burner flame in a rich mixture is formed and flame length raise with increasing equivalence ratio. The results show that make less in pore density of the medium increases the possibility of flame formation in the porous medium. Moreover it is observed the flame is formed in the porous medium in an average equivalence ratio of φ=0.63, which is almost the equivalence ratio which a immersed flame is formed in a premixed porous burne.

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Recently, tubular flames are considered due to their advantageous in geometry of the flame. The major importance of tubular flame is its uniform temperature distribution. Therefore, it may reduce thermal fluctuations along the combustion chamber. In this paper, a non-premixed tubular flame is simulated numerically under various operational conditions. A solver is developed in openFOAM and numerical results are validated against the experimental measurements. Also, temperature distribution and concentration of major species of the flame in the middle of the burner are investigated and compared using global and DRM22 as chemical kinetics. In addition, stability of the flame in air presence as oxidizer has been studied. Results show that by increasing oxygen mole fraction in oxidizer, the equivalence ratio of the steady tubular flame region decreases and the flame will be established uniformly in equivalence ratio near the extinction limit. If pure oxygen is used as oxidizer, flame temperature will be increase strongly and tubular flame can be stable for equivalence ratio between 0.1 and 0.2. Thereupon carbon dioxide from the flue gases is added to the oxidizer to control the flame temperature changes. Establishment of steady tubular flame in presence of carbon dioxide is simulated too. Results show that by decreasing oxygen mole fraction, the equivalence ratio of the steady tubular flame region increases and the stability zone becomes wider

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Biogas is a low-calorie fuel comprises 50-70% methane and 30-50% carbon dioxide, with small amounts of other particles. Combustion of low-calorie fuels often involves significant challenges related to flame stability in most burners. Combustion of porous media is an effective method of directing flame heat to the input mixture, which can increase flame stability. In most studies, biogas has been used in experimentaly work or numerical simulation with simple geometry. In this paper, researchers simulate a two-layer porous burner with biogas fuel, based on an experimental design, in two dimensions. They evaluate the effect of the burner geometry, which was not investigated in previous researches, on the temperature distribution and the radiation efficiency. The results show that reducing the amount of carbon dioxide increases the burner surface temperature. Additionally, changes in the interface of the porous layers, simulated in two conical and spherical forms in two converging and diverging states, cause changes in the place of flame, the maximum combustion temperature, the temperature of the burner surface, and the radiation efficiency. The maximum combustion temperature and the maximum burner surface temperature occur for the conical geometry in convergent mode. Increasing 10% of carbon dioxide in the biogas fuel reduces the radiation efficiency by 25% on average. The radiation efficiency of the divergent burner is more than the convergent mode, about 37% for conical geometry and about 25% for spherical geometry. The maximum radiation efficiency is achieved when the burner is divergent and the amount of carbon dioxide is 30%.