Correlation of turbulent burning velocity for syngas/air mixtures at high pressure up to 1.0 MPa

•OH-PLIF measurement was conducted for syngas turbulent premixed flames at 1.0 MPa.•Flame front structure was compared for various syngas composition.•Combined effect of pressure and syngas composition was examined.•Different turbulence–flame interaction between syngas and CH4 was studied.•Correlation of turbulent burning velocities was obtained at high pressure.

Instantaneous flame front structures of the turbulent premixed flames of syngas/air and CH4/air mixtures were investigated using OH-PLIF technique at high pressure up to 1.0 MPa, through which the turbulent burning velocities were derived and correlated with the turbulence intensity. Results show that both syngas/air and CH4/air mixtures, ST/SL increases remarkably with the increase of u′/SL particularly in the weak turbulence region. For the syngas/air mixture, the intensity of flame front wrinkle is promoted with the increase of hydrogen fraction in the syngas due to the increased preferential diffusive-thermal instability. Compared to CH4/air mixture, the syngas flames possess much wrinkled flame front with much smaller fine cusps structure, and with increasing u′/SL, the rate of the increase of ST/SL for the syngas/air mixtures is more significant than that of CH4/air mixtures. This demonstrates that the increase of flame front area due to turbulence wrinkling is promoted by flame intrinsic instability for syngas/air mixtures. The values of ST/SL for all mixtures increase with the increase of pressure because of the decrease of flame thickness which promotes the hydrodynamic instability. A general correlation of turbulent burning velocity for the syngas/air and CH4/air mixtures was obtained in the form of ST/SL ∝ a[(P/P0)(u′/SL)]n.