Combustion Oscillation Analysis of Premixed Flames at Elevated Pressures

A new analytical time lag flame model based on Bloxidge's flame model was introduced, which calculates the combustion oscillation of premixed flame to take into account the distribution of heat release rate and flame speed that was calculated by analytical formulas dependent on pressure, temperature, fuel-to-air ratio and velocity. The transfer matrix technique using the new flame model was applied to the calculation of acoustic resonance characteristics. To verify the model, combustion oscillation experiments were performed for methane-air premixed flames stabilized by a swirl burner at elevated pressures in a range of 0.6-0.9MPa. The fluctuating pressure had a maximum peak at a specific value of fτ_f, where f is the resonance frequency and τ_f is the passing time of premixed gas through the flame zone. The analytical model could simulate the dependency of the fluctuating pressure local peak on the fuel-to-air ratio and the static pressure.