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Compressed natural gas (CNG) currently is used as an alternative fuel for internal combustion engines in motor vehicles. This paper presents results of an analysis of leaks from a model isolated section of CNG fuel system. Discharge of CNG was modeled as vent flow of a real gas hydrocarbon mixture through an orifice from a reservoir with finite volume. Pressures typically used in CNG fuel systems result in choked flow for gas venting directly to atmosphere, producing an under-expanded, momentum-dominated, turbulent free jet with well defined velocity and concentration fields. This paper presents results of analyses of reservoir pressure decay, and vent flow and concentrations fields for CNG venting from a pressurized reservoir into the atmosphere. A combination of empirically-derived analytical relationships and detailed two-dimensional high resolution computational fluid dynamic modeling was used to determine the velocity and concentrations fields of the resulting CNG jet.

The fueling of hydrogen vehicles in three minutes enabling ranges above 500 km offers a significant advantage over other types of electric powertrain vehicles. SAE J2601, published in 2010, offers the first and only worldwide guideline to standardize fueling methodology. Due to the properties of hydrogen and compressed storage, each type and geometry tank heats up differently. Therefore, a hydrogen fueling methodology needs to take into account the range of storage anticipated from all automakers. This paper will describe a simulation tool developed in order to be able to assist in the development of a fueling procedure for General Motors Company; SAE J2601 team and the validation thereof. A reduced numerical simulation model has been developed that simulates the thermal response of a compressed gas storage tank operated under transient conditions.