Modeling the Dispersion of Leaks from LNG Buses in Maintenance Garages

The planned conversion of Seattle Metro Transit's bus operation to LNG necessitated modifying bus maintenance garages in order to assure fire-safety in the event of a leak from a vehicular LNG fuel system. The modification approach developed involved characterizing the probable worst-case leak from the bus' on-board LNG fuel system, and assuring that the building's ventilating system would keep the leak diluted to a concentration below the lower flammability limit. Leak dispersion behavior was modeled using computational fluid dynamics (CFD), and by a simple volumetric model suitable for PC spreadsheet. Comparison between the two models indicated that the volumetric model is a reasonably accurate means for estimating ventilation requirements.