重力对扩散射流火焰动态特性的影响

本文探讨重力对扩散射流火焰动态特性的影响规律。结果表明，火焰闪烁现象是一种浮力诱导不稳定性，在浮力消失或反向重力场中，不存在这种不稳定性现象，闪烁频率与燃料射流速度无直接关系，但涡的大小随燃料射流速度的增大而增大。存在触发火焰闪烁的临界高度，闪烁频率与重力成平方根关系式。反向重力情况下，也存在浮力稳定型平面火焰，它反映了浮力与火焰的耦合作用。

EFFECTS OF GRAVITY ON THE DYNAMIC BEHAVIOR OF JET DIFFUSION FLAMES

Effects of gravity on dynamic behavior of jet diffusion flames are described in detail in this paper by the use of the direct numerical simulation incorporating flamesheet model. The results show that the flame flickering is a buoyancy-induced outer instability. Without the buoyancy interaction, the flames in reversed gravity and microgravity do not flicker. The flame flickering frequency is insensitive to flow rate. However, the size of the vortice structure is increasing with increasing the fuel jet velocity. The results further confirm that there is a critical height to induce the flame flicker, and the square-root dependence of the frequency on gravitational acceleration is supported by the results. In the reversed gravity, the buoyancy-stabilized laminar flat flame observed in premixed flame is also existed in the jet diffusion flames. It is the direct result of the balance of the buoyancy and flame jet momentum.