Mathematical modeling of CNG refueling station

One of the most important parameter in design of a compressed natural gas refueling station is detailed modeling of fast filling process. In this work, a new mathematical model was developed to analyze the fast filling process at compressed natural gas refueling stations. This new model is unique because connecting pipes between reservoir tanks and on-board vehicle cylinder also were taken into account. To model the process, the equation of state, continuity, momentum and energy equations have been solved for different parts of the system. The results have been validated against the experimental data to investigate effects of connecting pipes. The mass flow rate numerical values are in agreement with the experimental values. The study carried out for both cascade and buffer storage systems. Variations of pressure and Mach number at different parts of the system, effects of the intial reservoir tank temperature on natural gas vehicle in-cylinder pressure and temperature are presented. The results show that pressure loss through pipes is very important and should be considered.