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CFD simulations in Vehicle Maintenance Shops

CFD modelling (FLUENT) was used in Invalid BibTex Entry! to analyze H2 leak scenarios inside a commercial maintenance/repair/service station. The study was based on a 5-passenger sedan with compressed H2 gas reservoir carrying capacity of 6 kg at 10,000 psi (689.5 bar) pressure. The HFCV was designed to comply with SAE J2578 and J2579 standards for H2 and fuel cells, which include provisions for safety systems onboard the vehicle. Such assumed mechanisms include the implementation of a hydrogen detector in each wheel well. Each detector was designed to signal a shut down and isolation H2 procedure upon detecting 1% H2. Another assumed mechanism includes the use of an on-board computer that is capable of shutting down H2 flow upon detecting a larger than 20 CFM leak (9.4 lt s-1) when the vehicle is dormant. In addition the HFCV was equipped with a valve that isolates H2 in the tank upon engine (fuel cell) shut down. This assumed isolation mechanism was designed to monitor and test for leaks upon vehicle shut down and prior to start up by the on-board computer. In the study most of the modelling scenarios were based on a 20 CFM leak from beneath the vehicle. This leak rate corresponded to a fuel cell power output of about 50 kW. For the considered maintenance facility and scenarios no modifications to the baseline structures were recommended. The high rates of ventilation would dilute the assumed 20-CFM leak and result in a flammable mixture only in close proximity to the vehicle. The potential for flammable mixtures forming at the ceiling of the facility was assessed. The time required for a hydrogen leak to result in 20% of LFL at the ceiling was determined for different vehicle leak rates. Options for improving the ventilation in the building were presented.


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Page last modified on December 05, 2008, at 10:09 AM