In this study

a sinusoidal wave sound field environment with adjustable frequency and amplitude was created by loudspeakers. By taking the premixed blunt-body flame of lean combustion of methane-hydrogen mixture as the research object

the combustion instability of the whole combustion system was characterized by flame transfer functions and the motion and evolution of flame front was described by CH-based autofluorescence image. The effects of hydrogen volume fraction(0

10%

20%) on flame combustion instability under different sound field frequencies and velocity fluctuations(sound field amplitudes) were studied. The results show that

the combustion characteristics are very sensitive to the fraction of hydrogen in the fuel mixture. With an increase in the hydrogen concentration

when the sound field frequency varies within 90～105 Hz

the amplitude of flame transfer functions reduces

the flame-vortex interactions become mitigation

and the combustion instability of the premixed flame becomes weaker; when the sound field frequency changes within 115～170 Hz

the amplitude of flame transfer functions increases

the flame length becomes shorter

and the combustion instability of the premixed flame becomes stronger. With the increase of velocity fluctuation

the flame-vortex interactions become stronger at 160 Hz. As the hydrogen volume fraction increases

the drawing and entrainment of flame flow field by vortex structure improves

the fluctuations of heat release during the combustion enlarges

the amplitude of flame transfer functions increases

and the combustion instability of the premixed flame becomes stronger. These results help to understand the mechanism of combustion dynamics of methane-hydrogen flame

and develop the theory for active control strategies.