Experimental study on cryo-compressed hydrogen ignition and flame

• Published in: International journal of hydrogen energy Vol. 45; no. 7; pp. 5098 - 5109
• Main Authors: Kobayashi, Hiroaki, Muto, Daiki, Daimon, Yu, Umemura, Yutaka, Takesaki, Yuichiro, Maru, Yusuke, Yagishita, Tsuyoshi, Nonaka, Satoshi, Miyanabe, Kota
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 07-02-2020
• Subjects: High-pressurized hydrogen; Hydrogen flame; Liquid hydrogen; High-pressurized hydrogen; Liquid hydrogen; Hydrogen flame
• ISSN: 0360-3199; 1879-3487
• DOI: 10.1016/j.ijhydene.2019.12.091

This paper presents a hydrogen ignition experiment conducted to establish safety standards for high-pressure hydrogen handled at the hydrogen stations for fuel cell vehicles (FCV). In the experiment, cryogenic hydrogen pressurized to over 80 MPa was leaked from a pinhole nozzle, and the blast pressure at the ignition and the flame length during steady combustion were measured. The hydrogen supply equipment used in the experiment has a maximum flow rate of 100 kg/h, a maximum discharge pressure of 90 MPa, and a temperature adjustment range of 50 K–300 K. Four types of pinhole nozzles with different outlet diameters, viz. 0.2 mm, 0.4 mm, 0.7 mm, and 1.0 mm were used to leak the hydrogen. In the experiment, the effects of the pinhole nozzle diameter, hydrogen supply pressure and temperature, and an igniter location on the blast pressure and flame length were evaluated. The igniter being appropriately positioned, once a steady flame was formed, combustion continued even if the ignition source was turned off, which necessitated the stopping of hydrogen supply to extinguish the fire. As a result of the experiment, it was found that the blast pressure and the flame length can be expressed as the correlation equations of the hydrogen leakage flow rate. However, even if the leakage flow rate was the same, we found that the flame length increases with decreasing the hydrogen supply temperature. We presented a correlation equation for the cryo-compressed hydrogen flame length that is about 30% longer than the previously presented equations for 300 K hydrogen flame.
•Hazard of hydrogen fire increases as lowering hydrogen temperature.•Maximum overpressure is proportional to the leakage flow rate.•Due to temperature effects, the flame length becomes longer at lower temperatures.