3、下行风流中发火时风流的方向通风系统总风压的作用方向和火风压的作用方向不同时(即火灾是发生在下行风流里的时候),井下通风状态发生紊乱的情形,一般说,将具有另外一种性质,如图2—9所示。假定 c 是外部系统,a 是内部系统,b是旁侧分支风流。我们知道,在一条风路中有两个作用方向完全相反的压源时,风流的方向将和较大风压压源的作用方向一致。因此,当一个通风系统中存在三个不同的压源(最大的风压值 h_大、中等的风压值 h_中和最小的风压值 h_小)时,则可能出现两种不同的 3, the direction of the wind flow in the event of a fire in the downwind flow Direction of the total wind pressure in the ventilation system is different from the direction of the effect of the fire pressure (that is, when the fire occurs in the downwind flow), and the ventilation in the downhole state is disordered , Will have another property, as shown in Figure 2-9. Suppose c is an external system, a is the internal system, and b is the lateral branch windflow. We know that when there are two pressure sources in opposite directions in a wind tunnel, the direction of wind flow will be the same as that of the larger wind pressure source. Therefore, when there are three different pressure sources in a ventilation system (the maximum wind pressure value h_ is large, the medium wind pressure value h_ is the smallest and the small wind pressure value h_ is small), two different types of pressure sources may occur of