The use of Natural Gas Vehicles in underground facilities: Application to the PARIS-LA-DÉFENSE underground network
Résumé
Considering the current strong development of natural gas vehicles and their use in many underground infrastructures, this paper focuses on the corresponding risk induced in such situations. It consists in applying the analysis of the consequences of the huge and complex underground network of the La Défense business center, in the suburbs of Paris. The different types of natural gas vehicles were considered, compressed natural gas (CNG) and liquified natural gas vehicles (LNG).
Based on existing knowledge in risk analysis, the main dangerous phenomena that can occur for those vehicles, jet fire, vapor cloud explosion, and tank burst, were all considered and modeled for each technology. To evaluate the release source term, the very beginning for both jet fire and flammable cloud characterization, the classic gas release model was used while considering the pressure decrease in the tank to get the mass release time variation. This was mainly interested in estimating the resulting jet fire heat release rate and duration and the corresponding impact on the global heat release curve. As far as vapor cloud explosion (VCE) is concerned, the worst-case situation, more precisely the largest flammable mass is obtained in the first seconds following the release beginning. The specificity for VCE represents the tunnel confinement's influence on the pressure wave propagation. In such an environment, the commonly used multi-energy approach, based on semi-spherical wave propagation is inappropriate, reflexion phenomena should be introduced to provide a better prediction.
The consequence modeling shows that, for both technologies, the worst dangerous phenomena remain the tank burst, especially for LNG where the lethal effect may affect most of the people present in the tunnel, for CNG lethal effect should reach 30 m and more for the same tank burst scenario. This huge consequence highlights the importance of preventing its occurrence through the efficiency of dedicated safety measures but also fire prevention since such a tank burst is induced by a fire in the surrounding of the tank. For the jet fire case, the consequences are a global vehicle heat release rate increase, during the gas release, while this could influence the efficiency of the tunnel ventilation, this does not significantly modify the thermal consequences for people. Regarding the vapor cloud explosion, lethal overpressure would affect passengers of the few closest vehicles for LNG and users in an area of 4 to 20 m centered on the vehicle for CNG.
Domaines
Ingénierie de l'environnementOrigine | Fichiers produits par l'(les) auteur(s) |
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