On the Stability and Characteristics of Biogas/Methane/Air Flames Fired by a Double Swirl Burner

CO 2 -diluted methane fuel is relevant to biogas combustion applications. Despite its poor heating value and low reactivity, which limit its practical applicability, biogas gains popularity as a renewable fuel. However, implementing it in combustion systems requires either modifying or replacing the existing burners. This study investigates the stability, temperature field, and pollutant emissions of CH 4 /CO 2 /air-premixed flames fired by a double-swirl burner. A CH 4 /air mixture of equivalence ratio, Φ out , was used in the outer stream, while a CH 4 /CO 2 /air mixture was supplied to the inner stream. The CO 2 mole fraction, x_CO_2 , in the inner fuel blend varied from 0 to 0.4 for various inner stream equivalence ratios, Φ in . The stability diagram of these flames was mapped in terms of Φ in verses x_CO_2 for a fixed Φ out . Based on the stability map, the inflame temperature field was investigated for six flames. Increasing the