Analysis of combustion noise by changing inlet velocity in lean turbulent premixed flame

Undesirable effects of entropy wave, such as higher levels of NOx emission, combustion instability and generated noise, have been well known. However, the thermal and hydrodynamic conditions of the combustor can largely modify the extent of unfavorable influences by subsiding the strength of the generated hot spots. In this study, therefore, hot spot annihilation in a lean-premixed Ethylene combustor is numerically studied using the flamelet model and large eddy simulation. The effects of various thermal and hydrodynamic conditions, such as inlet inlet velocity on entropy waves in both thermally convective and adiabatic combustor, are investigated. The resultant acoustic noise, potentially generated by the entropy waves, is also compared among studied cases, which demonstrates the necessity of embedding the thermo-hydrodynamic effects on the entropy waves in low-order models of combustion instability prediction. The results show that increase in inlet velocity improves combustion efficiency, it aids entropy waves survival and may cause subsequent instability or higher emission production. The results of this study can be beneficial to operate a lean-premixed combustor precisely in conditions far from generation of noise, emission or instability