For the understanding of ball-like flame behavior in counterflow field, transient three-dimensional computations with thermal-diffusion model were conducted for a low-Lewis number mixture near lean limit. Three types of flame behaviors were confirmed: stable spherical ball-like flame (spherical BLF) in A ≤ 0.010, stable non-spherical ball-like flame (non-spherical BLF) in 0.01 < A < 0.089 and splitting ball-like flame (splitting BLF) in A ≥ 0.089, where A is ordinary stretch rate normalized with laminar burning velocity S_L and thermal diffusivity α. Analysis of flame structure for non-spherical BLF located its center at the stagnation point showed that the maximum temperature on the stagnation plane was higher than that on the counterflow axis because of the small difference between the flame curvatures on the stagnation plane and that on the counterflow axis. With the increase of stretch rate, the maximum temperature of the non-spherical BLF on the stagnation plane increased and the position of maximum temperature got away from the stagnation point. The maximum temperature on the counterflow axis decreased and the position of maximum temperature got closer to the stagnation point. Existence of unburned fuel was also confirmed near the stagnation point at A = 0.085. Thus, net fuel velocity was newly introduced to evaluate the effect of the unburned fuel diffusion. The profile of the net fuel velocity revealed two peaks in the case of A < 0.050 and four peaks in the case of A > 0.050. In the case A > 0.050, the inner two peaks were found to be due to the diffusion of unburned fuel to the outward direction. The analyses on the peak positions showed that the flame splitting occurs when the positions of the inner two peaks of the net fuel velocity are located outside of the reference flame ball radius.

为了理解逆流场中球状火焰的行为，对稀薄极限附近的低刘易斯数混合物进行了热扩散模型的瞬态三维计算。三种类型的火焰行为被证实：稳定球形球状火焰（球形BLF）在甲 在0.01 <≤0.010，稳定的非球面球状火焰（非球形BLF）甲<0.089和分裂球状火焰（分裂BLF）在甲 ≥0.089，其中A是具有层流燃烧速度归一普通拉伸率小号_大号和热扩散率α。对非球形BLF中心位于停滞点的火焰结构的分析表明，由于停滞平面上的火焰曲率与炉膛上的火焰曲率之间的差异较小，停滞面上的最高温度高于逆流轴上的最高温度。逆流轴。随着拉伸速率的增加，非球形BLF在滞止面上的最高温度升高，并且最高温度的位置远离滞止点。逆流轴上的最高温度降低，最高温度的位置更接近停滞点。在A的停滞点附近也确认存在未燃烧的燃料 = 0.085。因此，新引入了净燃料速度以评估未燃烧燃料扩散的影响。净燃料速度的曲线在A <0.050的情况下显示两个峰值，在A > 0.050的情况下显示四个峰值。在A＞ 0.050的情况下，发现内部的两个峰值是由于未燃烧的燃料向外侧扩散所致。对峰值位置的分析表明，当净燃料速度的内部两个峰值的位置位于参考火焰球半径之外时，会发生火焰分裂。