So far, a single air shutter for fire protection has been studied for shutting off flame and smoke flowing through a corridor at a fire, and follows have been described in the preceding reports.
(1) The significance of an air shutter for fire protection and the economical method for its design (Report 1)
(2) The smoke leak ratio and the permissible time to take refuge safely (Report 2)
(3) The influence of side flow, out side disturbing flow to air shutter, which has ununiform velocity distribution on the air shutter flow (Report 3)
Now, as shown in the Report 1, the more the air shutters are installed at a corridor, the less the area of danger zone caused by a fire becomes, and the easier escapers can take refuge to the safety zone.
From the above, it is necessary to know the characteristics of push-pull flows of a plural type air shutter installed in a limited space as a corridor or a passage way.
Then, to begin with, the static pressure at the space among two air shutters is investigated experimentally with variation of the ratios of flow rate from the sorroundings, Q2, to the one from the push opening, Q1, and of the size ratios of the air shutter. As the result, it becomes clear that the static pressure at the inner space is negative and distributes uniformly. Furthemore, using Euler's number defined by dividing the static pressure by the dynamic pressure at the push opening, the Euler's number depends only flow ratio, Q2/Q1, and the ratio of distance, H/E, between push and pull opening to width of push opening. In the range of practical use of two air shutters (2.0 ≦ H/E ≦ 5.0, 2.0 ≦ Q2/Q1 ≦ 7.0), the relation between Euler's number, Eu , and H/E and Q2/Q1 can be expressed as following experimental equations.
(1) When the both external sides of two air shutters are open to the atomosphere.
Eu = 2.2(H/E )-2.0 (Q2/Q1)1.7 (1)
(2) When one of the sides is close.
Eu = 8.8(H/E )-2.0 (Q2/Q1)1.7 (2)
From the above equations, the static pressure at the space shut in a practical two air shutters can be estimated when the values of H/E, Q2/Q1 and the push flow velocity, υ1, are given.
In addition, the relation between the fact that the static pressure rises caused by thermal expantion of air at a practical fire and the negative static pressure caused by the two air shutters is referred to.
