Studies on Micro Structure and Dynamic Behavior of Stretch-Controlled Flames

对层流火焰进行了详细的化学动力学和多组分扩散的数值计算。扩散火焰、扁平预混火焰和球状火焰具有不同的拉伸率。在扩散火焰中，(1)存在两种熄灭类型：间歇熄灭和完全熄灭。(2)局部拉伸率最大的下游有轻微的消光现象。(3)局部拉伸率对消光有很大影响。(4)沿火焰面的对流流动改变了火焰的熄灭极限，在平坦预混火焰中，随着对流速度的增加，形成了对称的孪生火焰，放热率峰值出现在中心部位。(2)火焰的燃烧速度随拉伸速率的增大而增大，但燃烧速率随拉伸速率的增大而减小。研究了拉伸速率对3种氢气/空气火焰的燃烧速度的影响，即向外传播(OPF)、向内传播(IPF)和静止(SF)火焰传播的球形方向和火焰半径改变了拉伸速率。对于IPF，当量比大于0.7时，火焰速度变大。但是，对于规模较小的Φ来说，结果正好相反。OPF和IPF的变化正好相反。(2)SF的拉伸率为零，但燃烧速度范围较大。(3)燃烧速度不仅受拉伸率的影响，而且受Lewis数的影响，这是因为在不同的扩散系数下，燃烧速度的结果是相反的。

Numerical computations of laminar flames have been conducted taking into account detailed chemical kinetics and multi-component diffusion. Diffusion flames, flat premixed flames and spherical flames considered of different stretch rate.In the diffusion flames, (1) There are two types of extinction, the intermittent and the perfect extinction. (2) Extinction occurs slightly in down stream where local stretch rate is the largest. (3) The local stretch rate is much affect the extinction. (4) The convection flow along the flamelet changes the extinction limit.In the flat premixed flame, (1) Symmetrical twin flame is formed As the counter velocity increases, the peak of the heat release rate comes to the central part. (2) The burning velocity increases with increasing the stretch rate, but the burning rate decreases with increasing the stretch rate.The effects of the stretch rate are investigated on the burning velocity in three kind of hydrogen/air flames, that is, outwardly propagating (OPF), inwardly propagating (IPF) and stationary (SF) spherical Direction of the flame propagation and radius of the flame change the stretch rate.(1) The burning velocity is changed for the smaller radius than 5mm. For the IPF, the flame velocity becomes large for the equivalence ratio ¢ larger than 0.7. But, for the smaller Φ, the results is opposite. The change is opposite for the OPF and IPF. (2) The stretch rate of the SF is zero, but the burning velocity has a wide range. (3) The burning velocity is dominated by not only the stretch rate but also the Lewis number, because the burning velocity has the opposite results assuming different diffusivities.