The airplane cargo fire is a severity disaster for the airplane in flight. The fire alarm system in cargo compartment plays an important part of the flight safety, which is a useful method to reduce the severity fight fire. However, the inflight altitude of airplane has been leading a low air pressure condition in the cargo, which should be affect the smoke spread and fire alarm process in the air cargo. In this paper, the smoke spread and fire alarm process has been investigated via numerical simulation. The various air pressure, fire source with different heat release rate and soot yield rate have been also discussed. During the simulation process, we can obtain the smoke spread, temperature distribution, and obscuration rate under the designed fire conditions. The fire alarms system response time of point-type smoke detector and line-type smoke detector (LSD) system have discussed under different fire scenarios and mounted location. The results indicate that the lower air pressure would accelerate the smoke speed velocity and bring the fire alarm time forward. The anti-interference property of LSD should be enhanced as the low air pressure influence and severe environment in the aircraft cargo. The results should offer the technical and scientific support for the cargo fire alarm system.

飞机起火是飞行中飞机的严重灾难。货舱中的火灾报警系统在飞行安全中起着重要的作用，这是减少严重起火的有用方法。然而，飞机的飞行高度一直导致货物中的气压较低，这将影响航空货物中的烟雾扩散和火灾报警过程。本文通过数值模拟研究了烟雾扩散和火灾报警过程。还讨论了各种空气压力，具有不同放热率和烟yield产生率的火源。在模拟过程中，我们可以在设计的火灾条件下获得烟雾扩散，温度分布和遮盖率。讨论了点型烟雾探测器和线型烟雾探测器（LSD）系统在不同火灾场景和安装位置下的火灾报警系统响应时间。结果表明，较低的气压会加快烟雾速度，并使火灾报警时间提前。LSD的抗干扰性应提高，因为航空货物中的气压影响较小且环境恶劣。研究结果应为货物火灾报警系统提供技术和科学支持。LSD的抗干扰性应提高，因为航空货物中的气压影响较小且环境恶劣。研究结果应为货物火灾报警系统提供技术和科学支持。LSD的抗干扰性应提高，因为航空货物中的气压影响较小且环境恶劣。研究结果应为货物火灾报警系统提供技术和科学支持。