Methane flame stability in a jet impinging onto a wall

Flame stability is analyzed for a methane flame in a jet impinging onto a wall. A wide range of equivalence ratio is considered and lean burn stability is emphasized. The effects of burner to plate distance (H/d), inlet velocity (U_in), inlet fuel concentrations (φ_in) and stagnation plate type on flame stability are discussed. The results show that a double solution region exists, that is, the flame may exhibit two different configurations in a certain range of operating conditions depending on which way the condition is approached (lean to rich or rich to lean). When the operating condition is in this region, the flame is unstable since an external disturbance may transform the flame shape from conical to flat flame or flat to conical flame. The double solution region is strongly influenced by the burner to plate separation distance and inlet velocity. Lower H/d or lower inlet velocity decreases the double solution region, i.e. the flame is relatively stable at lower H/d or lower inlet velocity. Instability in the double solution region may strongly affect the flame shapes. Therefore, the design of low Reynolds number heating devices, such as domestic gas burners, should take the double solution region into consideration, especially for those used in lean premixed flame applications.