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The flame displacement speeds in turbulent premixed flames have been measured directly by the CH double-pulsed planar laser-induced fluorescence (PLIF). The CH double-pulsed PLIF system consists of two independent conventional CH PLIF measurement systems, and laser beams from each laser system are lead to same optical pass using the difference of polarization. The highly time-resolved measurements are conducted in relatively high Reynolds number turbulent premixed flames on a swirl-stabilized combustor. Since the time interval of the successive CH PLIF can be selected to any optimum value for the purpose intended, both of the large scale dynamics and local displacement of the flame front can be discussed. By selecting an appropriate time interval (100µs~200µs), deformations of the flame front are captured clearly. Successive CH fluorescence images reveal the burning/generating process of the unburned mixtures or the handgrip structures in the burnt gas, which have been predicted by three-dimensional direct numerical simulations of turbulent premixed flames. To evaluate the local flame displacement speed directly from the successive CH images, a flame front identification and displacement vector evaluation schemes are developed. Direct measurements of the flame displacement speed are conducted by selecting a minute time interval (≈30µs) for different Reynolds number (Re λ = 63.1~115.0). Local flame displacement speeds coincide well for different Reynolds number cases, which suggests the correctness of the flamelet concept. Furthermore, comparisons of the mean flame displacement speed and the mean fluid velocity show that the convection in the turbulent flames will affect the flame displacement speed for high Reynolds number flames.

重 s of displaoement speed of the name fronts ， were conducted in rela 恒vely high Reyno旦 ds number turbulent premixed flames on a sWh1 −stabilized combustor ， By selecting appropriate time interval of successive CH PLIF ， movement of the fiarne front was captured clearly ． L亘 addition ， by applying ss − correlation method f ( )r successive CH images obtained with minute dme interval ， displacement speed of the loca田 ame element is measu 爬 d ， Wilere 止e 且ame 丘ont is dete ined 恥 m mixed − average of CH fiuorescence intensity in corresponding intem)gation regions ． Local 齟ame displacement speed iS of the o 【 der of 〆 and probabilily density fUnctions coinCide very well fbr all Reynolds number cases under the normalizadon