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The localized fire test provided in the Global Technical Regulation for Hydrogen Fuel Cell Vehicles gives two separate test methods: the ‘generic installation test - Method 1′ and the ‘specific vehicle installation test - Method 2′. Vehicle manufacturers are required to apply either of the two methods. Focused on Method 2, the present study was conducted to determine the characteristics and validity of Method 2. Test results under identical burner flame temperature conditions and the effects of cylinder protection covers made of different materials were compared between Method 1 and Method 2.

To investigate the events that could arise when fighting fires in vehicles with carbon fiber reinforced plastic (CFRP) hydrogen storage cylinders, we conducted experiments to examine whether a hydrogen jet diffusion flame caused by activation of the pressure relief device (PRD) can be extinguished and how spraying water influences the cylinder and PRD. The experiments clarified that the hydrogen jet flame cannot be extinguished easily with water or dry powder extinguishers and that spraying water during activation of the PRD may result in closure of the PRD, but is useful for maintaining the strength of CFRP composite cylinders for vehicles.

If a compressed hydrogen tank for vehicles is filled with hydrogen gas more quickly, the gas temperature in the tank will increase. In this study, we conducted hydrogen gas filling tests using the TYPE 3 and TYPE 4 tanks. During the tests, we measured the temperature of the internal liner surface and investigated its relationship with the gas temperature in the tank. We found that the gas temperature in the upper portion of the TYPE 4 tank rose locally during filling and that the temperature of the internal liner surface near that area also rose, resulting in a temperature higher than the gas temperature at the center of the tank. To keep the maximum temperature in the tank below the designed temperature (85°C) during filling and examine the representative tank internal temperatures, it is important to examine filling methods that can suppress local rises of tank internal temperature.

Fuel cell vehicles represent a new system, and their safety has not yet been fully proved comparing with present automobile. Thorough safety evaluation is especially needed for the fuel system, which uses hydrogen as fuel, and the electric system, which uses a lot of electricity. The fuel cell stacks that are to be loaded on fuel cell vehicles generate electricity by reacting hydrogen and oxygen through electrolytic polymer membranes which is very thin. The safety of the fuel and electric systems should also be assessed for any abnormality that may be caused by electrolytic polymer membranes for any reasons. The purpose of our tests is to collect basic data to ultimately establish safety standards for fuel cell stacks. Methanol pool flame exposure tests were conducted on stationary use fuel cell stacks of two 200W to evaluate safety in the event of a fire.

Gas behavior during fast filling of a compressed gaseous hydrogen storage tank (Type 3, 35MPa) was simulated numerically to investigate in detail the resulting unsteady temperature distribution and its correlation with the storage tank conditions. The governing equations for the gas phase are the mass, momentum, and energy equations; these equations were discretized using the finite volume method (FVM) in three-dimensional space. The numerical results were carefully compared with the experiment results and have been validated. Consequently, the temperature distributions in space, the time histories of temperature at the measured points, and the filling time to the target pressure were all in good agreement. Furthermore, the unsteady gas and its thermal behavior were clearly visualized in three-dimensional space.

To investigate methods of conducting flame exposure tests (bonfire tests) on high-pressure hydrogen gas cylinders that are safe and have high accuracy across repeated tests, we used numerical simulation and experiments to analyze the feasibility of using substitutive gases for filling as well as the effects of the burners used as the fire source. Through a series of virtual experiments using substitutive gases, flame scales, and filling pressure as parameters, we examined the maximum internal pressure, the rate of pressure rise, and the starting time of Pressure Relief Device (PRD) activation. Because substitutive gas properties differ from those of hydrogen gas, we concluded that using substitutive gases would be inappropriate. In addition, we observed that when the flame scale was small, the cylinder's internal pressure before the thermal-activated PRD activation, the rate of pressure rise, and the starting time of PRD activation all increased rapidly.