This paper studied the concentration distribution of gas extinguishing agent numerically in high velocity flow field. Civil aircraft power plant compartment has been a difficult area for its high velocity flow field formed after fire happens. Focusing on this issue, certain results, such as mass flow rate of agent gas, total mass of agent and extinguishing efficiency were presented. A typical apparatus of fire extinguishing system was set up, and its fire-fighting efficiency was evaluated. Critical ratio of mass flow rate and flow velocity, gas discharge time and locations of gas sample tubes were recommended. The results and data can provide a practical way in fire extinguishing system evaluation in civil aircraft power plant compartment.
In order to study the temperature field (TF) distribution and material flow (MF) in the friction stir welding process, the finite element model of friction stir welding (FSW) was established to simulate the welding process. The temperature field results showed that the temperature on the advancing side (AS) was higher than the retreating side (RS). The temperature field has an important influence on the material flow, so the material flow in the plunging stage and welding stage is simulated numerically to study the material flow trajectory in different stages. The results show that the material distribution is more uniform due to the long time in the plunging stage, and the amount of material flow in the plunging stage is larger than that in the welding stage. In the welding stage, it is found that the shoulder can promote the material flow. After analyzing the displacement of tracking particles in the welding stage, it is found that the displacement of particles on the AS is significantly higher than that on the axis and the RS.
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