To measure Flame Transfer Functions of a swirl-premixed burner and investigate its flame dy-namic response to acoustic excitation,experimental studies were conducted on the combustion characteristics of methane/air and methane/hydrogen/air mixtures with hydrogen volume concentrations ranging from 10%to 60%.Acoustic excitation was applied using dual loudspeakers at frequencies ranging from 20 Hz to 400 Hz.The heat re-lease rate was measured using a photomultiplier tube to capture the spontaneous CH* fluorescence signal from the flame.The air velocity fluctuation at the flame front was measured using a dual-microphone method,and the pressure fluctuation signal was acquired downstream of the combustion chamber using dynamic pressure sensors.Besides,flame photographs were recorded using a digital camera.The experimental results indicate that after hy-drogen addition,the flame morphology transitioned from an expanded,large flame to a concentrated,short flame.The temporal average structures are significantly changed under low-frequency excitation.The Flame Transfer Functions under different conditions exhibit high-gain peaks and low-response valleys,displaying both low-pass and band-pass characteristics with a passband frequency ranging from 80 Hz to 200 Hz and a linearly decreasing phase.Specifically,flames with high hydrogen content have multiple high-gain peaks at higher frequencies,re-flecting the instability of hydrogen-enriched flames.
Acoustic excitationSwirl flameHydrogen-blended fuelCombustion instabilityFlame transfer functionFlame dynamic response
NETL
NSTL
万方数据
