Linsen Xiong

With the rapid increase in electric vehicle ownership, fire risks associated with electric vehicles in tunnels have attracted increasing attention. In this study, a numerical model of an electric vehicle fire in a two-lane tunnel with an arched ceiling was established using the Fire Dynamics Simulator. The effects of transverse and longitudinal fire source locations on smoke layer thickness and longitudinal temperature distribution were investigated. Smoke layer thickness was identified using the visibility discontinuity method, and theoretical models incorporating the geometrical characteristics of the arched ceiling were established. The results indicate that fire source location exerts a marked influence on smoke layer development and longitudinal temperature attenuation. The maximum smoke-layer-thickness ratio exceeded unity in all cases and was generally greater downstream than upstream of the fire source. During the quasi-steady stage, the ceiling-temperature rise exhibited exponential decay along the tunnel. Relative to the centerline fire condition, displacement of the fire source to the center of the right lane increased the magnitude of the downstream composite attenuation coefficient by 5.6–11.2%; a further displacement toward the sidewall increased it by 20.6–34.1%. Most predictions from the proposed longitudinal temperature model agreed with the comparison data within ±20%. These findings underscore the need to jointly account for transverse and longitudinal fire-source locations in smoke-control design and evacuation-safety assessment for arched road tunnels.

A mechanical structure of a fiber Fabry–Perot interferometric vibration sensor for monitoring oil and gas pipelines has been proposed, and design analysis research on performance improvement has been carried out. By designing a serpentine beam structure, the mechanical sensitivity of the sensor is enhanced. Meanwhile, by designing a vertically symmetrical gravity-sensing structure, the cross-axis sensitivity of the sensor is reduced. The results of simulation analysis show that the mechanical sensitivity of the proposed design structure is 89.20 μm/g, which is 32.44 times that of the conventional structure. Moreover, due to the design of low cross-axis sensitivity, the optical sensitivity of the vibration sensor will not be degraded because of its installation status on the pipeline. The proposed mechanical structure provides a design reference for the application of the fiber Fabry–Perot interferometric vibration sensor on oil and gas pipelines, and offers potential for the development of a high-performance comprehensive safety risk monitoring system for oil and gas pipelines.