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Journal Article

A Study on Sealing Behavior of Rubber O-Ring in High Pressure Hydrogen Gas

Rubber O-rings installed in hydrogen tanks for fuel cell electric vehicles are repeatedly exposed to high pressure hydrogen gas. Exposure to high pressure gas sometimes causes cracks as a result of blistering after decompression. The degree of blister damage is influenced by material, environmental conditions such as decompression rate, and sealing shape such as squeeze ratio. Focusing on environmental conditions out of these influential factors, in this study, a high pressure hydrogen durability tester which exposes rubber O-rings repeatedly to high pressure hydrogen gas at arbitrary test conditions was developed. Using this tester, the influence of hydrogen pressure and temperature on blister damage and permeability was investigated for sealing materials used conventionally for high pressure equipment.
Technical Paper

Dynamic Simulation Software for Prediction of Hydrogen Temperature and Pressure during Fueling Process

In this study, in order to relax the pre-cooling regulations at hydrogen fueling stations, we develop a software algorithm to simulate an actual hydrogen fueling process to Fuel Cell Vehicle (FCV) tanks. The simulation model in the software consists of the same filling equipment found at an actual hydrogen fueling station. Additionally, the same supply conditions (pre-cooling temperature, pressure and mass flow rate) as at a hydrogen fueling station were set to the simulation model. Based on the supply conditions, the software simulates the temperature and pressure of hydrogen in each part of filling equipment. In order to verify the accuracy of the software, we compare the temperature and pressure simulated at each stage of the filling process with experimental data. We show that by using the software it is possible to accurately calculate the hydrogen temperature and pressure at each point during the fueling process.
Technical Paper

Effects of Hydrogen Concentration on Stoichiometric H2/CH4/Air Premixed Turbulent Flames

Outwardly propagating stoichiometric flames of H2/CH4/air were studied in a constant volume fan-stirred combustion chamber in order to investigate the effects of hydrogen concentration on the turbulent burning velocities. The experiments were conducted at mixture temperature of 350 K and mixture pressure of 0.10 MPa. The mole fraction of hydrogen in the binary fuel was varied from 0 to 1.0 for turbulence intensities equal to 1.23, 1.64 and 2.46 m/s. Laminar flames of the mixtures were first investigated to obtain the unstretched laminar burning velocities and the associated Markstein numbers. The unstretched laminar burning velocity increased non-linearly with increase in hydrogen fraction. The Markstein number and the effective Lewis number of the mixtures varied non-monotonically with hydrogen mole fraction. The Markstein number was used to investigate the influence of thermo-diffusive effects on the turbulent burning velocity.
Technical Paper

Turbulent Burning Velocity of Lean Hydrogen Mixtures

The present study is performed to examine experimentally the turbulent burning velocity characteristics of lean hydrogen mixtures with attention to the local burning velocity. The special mixtures, having nearly the same laminar burning velocity with different equivalence ratios Ф=0.3~0.9, are prepared. The measured turbulent burning velocities at the same turbulence intensity show to large increase as Ф decreases until about 0.5. Those, however, do not show such large increase when Ф becomes lower than about 0.5. This phenomenon is discussed by the estimated mean local burning velocity taking account of preferential diffusion, tomograms of turbulent flames and estimated Markstein number.