Combustion characteristics of various biogas flames under reduced oxygen concentration conditions
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Distributed combustion is a promising method to obtain more uniform thermal field inside a combustor and reduced ultra-low pollutant emission levels at a combustor outlet. In this way, oxygen concentration in the oxidizer is reduced, resulting in a lower reaction rate. This study aims at investigating thermal field distributions and pollutant levels of various biogas flames under distributed combustion conditions. Combustion characteristics of biogas flames have numerically been investigated by a commercial code on distributed combustion conditions in terms of fuel flexibility, diluent temperature, and diluent composition. k-epsilon standard turbulence model, PDF/The Mixture Fraction combustion model and P-1 radiation model have been used during the predictions. The oxygen concentration in the oxidizer has been reduced to the oxygen concentration of 15% to investigate various types of biogas, different mixture temperature, and diluent composition. The results resulting from conventional conditions show that the predictions have been in good agreement with the existing measured temperature profiles in terms of values and trends. According to the further modellings obtained from distributed combustion conditions, it can be said that more uniform thermal field has been emerged inside the combustor as the oxygen concentration has been reduced. Therefore, it can be concluded that distributed combustion conditions have been achieved. It can also be determined that pollutant emission levels have been decreased to ultra-low levels as the oxygen concentration has been reduced in the oxidizer.