Abstract
In order to guide the optimization design of the pipeline network of the aircraft-fixed gas fire extinguishing system and improve its fire extinguishing performance, FLUENT software was used to simulate the influence of pipeline parameters such as diameter, length, and roughness on the release characteristics of the fire extinguishing agent. It can be found that the extinguishing agent can be divided into liquid and vapor extinguishing agents in the fire extinguishing pipeline system during the release. The spatial distribution and proportion of the liquid and vapor extinguishing agents are asymmetric. Results show that the peak value of the pressure drop rate (dPmax) has a good quadratic function relationship with the pipeline diameter (D) and the functional relationship is dPmax=−22.224+2.782D+0.089D2, which means that the peak value increased significantly with the increase in the pipeline diameter. Moreover, when the pipeline diameter is 25 mm, the average pressure drop rate of the vessel is about 35.02 MPa/s, which is 5.97 times the value of the average pressure drop rate when the pipeline diameter is 10 mm. With the increase in the pipeline diameter, the release time decreases significantly, the mass flow rate increases obviously, while the gasification ratio decreases rapidly at first and then increases slightly. The pipeline length also has a significant influence on the release characteristics of the extinguishing agent. With the increase in the pipeline length, the release time and the gasification ratio increase linearly, while the mass flow rate decreases linearly. Compared with the pipeline diameter and pipeline length, the influence of the pipeline roughness on the release characteristics of the extinguishing agent is weak. With the increase in the pipeline roughness, the release time and the gasification ratio of the extinguishing agent increases slowly, while the mass flow rate decreases slowly.
Highlights
An inflight fire can lead to disastrous consequences within a very short time
In order to study the influence of the pipeline diameter on the flow and release characteristics of the Halon 1301 agent, the diameters of the Pipe 1 and Pipe 2 shown in Figure 3 were both set to 10 mm, 15 mm, 20 mm and 25 mm respectively, which is for the contrast test with the same filling status of the extinguishing bottle
It can be seen from the figure that, with the increase in the pipeline diameter, the gasification ratio of the extinguishing agent released through the pipeline decreased at first and increased
Summary
An inflight fire can lead to disastrous consequences within a very short time. in order to ensure fire safety, the fire extinguishing system has become an essential fixed firefighting facility on an aircraft [1]. A homogeneous model to numerically calculate the pressure drop and the flow rate of the extinguishing agent was established by Elliott et al [15] to analyze the characteristics of the transient flow of the Halon 1301 agent in the pipeline. Using FLUENT software, Kim et al [17] numerically studied the flow characteristics of the Halon 1301 agent in the pipeline of the aircraft extinguishing system. Since the flow of nitrogen-pressurized Halon 1301 agent in the pipeline was a gas– liquid dispersed bubble flow with less than 0.01 inches bubble diameters [8], the mixture model is used to simulate the gas–liquid two-phase flow in this study. The turbulence model is the realizable k-ε model and the near-wall region adopts a scalable wall function approach
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