A Study on the Charge-Discharge Cycle of a Compressed Hydrogen Tank for Automobiles

Environmental pollution, global warming, and depletion of fossil fuels compel radical changes in automotive engine technologies in directions that offer both the potential for achieving near-zero emissions of pollutants and greenhouse gases and a diversification of the transport fuel system away from its present exclusive dependence on fossil fuels. Hydrogen-fueled vehicles can be an environment-friendly alternative. Composite high-pressure tanks can be used for storage of hydrogen gas on board road vehicles. Durability and safety of the fuel tanks are the important concerns involved. In this paper a numerical model is developed for the analysis of the cyclic fast charging and discharging process of a high-pressure hydrogen gas tank to determine the effect on tank wall temperature. The flow is considered as compressible, viscous, unsteady and turbulent. Axisymmetric, time-dependent, Navier-Stokes equations were solved with the two-equation realizable k-ε turbulent model for turbulent momentum closure. Redlich-Kwong real gas equation was used for density computations. The numerical model is of relevance to the design of high-pressure tanks for durability and safety, primarily with regard to the wall configuration.