观察气体燃料从扩散燃烧逐步地改变成半预混燃烧的变化过程可以更加清楚地了解半预混燃烧燃烧，预混燃烧的特点。

The gradual change of gaseous fuel from diffusion combustion to semi premixed combustion is observed, and the characteristics of semi premixed combustion and premixed combustion can be more clearly understood.

燃料气与空气的混合物在燃烧焰面法线方向的速度分量大于该混合物的火焰传播速度，则火焰被推出火孔，开始离焰，直到火焰被吹跑造成火焰熄火——脱火。燃烧器发生脱火是不允许的。

The velocity component of the mixture of fuel gas and air in the normal direction of combustion flame is larger than that of the mixture, and the flame is pushed out of the fire hole and starts to le***e the flame until the flame is blown away, causing the flame to go out. It is not allowed to remove fire from the burner.

石油化学工业炉燃料气与空气混合物离开火孔速度一般都比较高，都超过其火焰传播速度。但是燃烧器在结构上都有相应的措施保证不发生脱火现象，使火焰稳定燃烧。

The mixture of fuel gas and air in the petrochemical furnace is generally higher than that of the flame, which is more than the flame propagation speed. But the structure of the burner has the corresponding measures to ensure that the flame is not degenerated and the flame can be burned steadily.