Zhengli Hua

Experimental and Numerical Studies on High-Pressure Composite Cylinders Subjected to Localized and Engulfing Fire

Vehicle fires may lead to on-board high-pressure composite cylinders experiencing a term of localized and engulfing fire. During this period, the composite cylinder would be degraded and even burst before pressure relief device (PRD) could be activated to release internal high-pressure gas. In this paper, experimental investigation for such cylinders subjected to localized and engulfing fire was conducted on an aluminum liner composite cylinder filled with hydrogen. A three-dimensional computational fluid dynamics (CFD) model is developed to study the key factors influencing PRD activation time. The effects of hydrogen and compressed natural gas (CNG) as filling media, cylinder pressure and localized fire exposure time are analyzed in detail. The experimental results showed that pressure and temperature of internal gas rose very slowly during the localized fire. In addition, Hydrogen and CNG as filling media with different pressures have weak influence on the activation time of thermally activated PRD (TPRD), but have significant effect on the activation time of pressure-activated PRD (PPRD). TPRD can respond more quickly to protect the hydrogen composite cylinder than PPRD. PRD activation time increases as the localized fire exposure time is extended.

Design fatigue life evaluation of high-pressure hydrogen storage vessels based on fracture mechanics:

Design fatigue life of high-pressure hydrogen storage vessels constructed of low alloy steels, austenitic stainless steels, and iron-based superalloy was analyzed based on facture mechanics in 45 MPa, 85 MPa, and 105 MPa hydrogen and air. Cylindrical model was used and the wall thickness of the model was calculated following five regulations including the High Pressure Gas Safety Institute of Japan (KHK) designated equipment inspection regulation, KHKS 0220, Chinese special equipment regulation (TSG) R0002, Chinese machinery industrial standard (JB) 4732, and ASME Sec. VIII, Div. 3. Design fatigue life for four typical model materials was also analyzed to discuss the effect of ultimate tensile strength, pressure, regulations and hydrogen sensitivity on the design fatigue life in hydrogen. It was discussed that hydrogen influence decreases with decreasing pressure or ultimate tensile strength. The design fatigue life data of the model materials under the conditions of pressure, ultimate tensile strength, KIH, fatigue crack growth rates, and regulations in both hydrogen and air were proposed quantitatively for materials selection for high-pressure hydrogen storage vessels.

Crack Growth Analysis of High-Pressure Equipment for Hydrogen Storage

Crack growth analysis (CGA) was applied to estimate the cycle life of the high-pressure hydrogen equipment constructed by the practical materials of 4340 (two heats), 4137, 4130X, A286, type 316 (solution-annealed (SA) and cold-worked (CW)), and type 304 (SA and CW) in 45, 85 and 105 MPa hydrogen and air. The wall thickness was calculated following five regulations of the High Pressure Gas Safety Institute of Japan (KHK) designated equipment rule, KHKS 0220, TSG R0002, JB4732, and ASME Sec. VIII, Div. 3. We also applied CGA for four typical model materials to discuss the effect of ultimate tensile strength (UTS), pressure and hydrogen sensitivity on the cycle life of the high-pressure hydrogen equipment. Leak before burst (LBB) was confirmed in all practical materials in hydrogen and air. The minimum KIC required for LBB of the model material with UTS of even 1500 MPa was 170 MPa·m0.5 in 105 MPa. Cycle life qualified 103 cycles for all practical materials in air. In 105 MPa hydrogen, the cycle life by KIH was much shorter than that in air for two heats of 4340 and 4137 sensitive to hydrogen gas embrittlement (HGE). The cycle life of type 304 (SA) sensitive to HGE was almost above 104 cycles in hydrogen, while the cycle life of type 316 (SA and CW) was not affected by hydrogen and that of A286 in hydrogen was near to that in air. It was discussed that the cycle life increased with decreasing pressure or UTS in hydrogen. This behavior was due to that KIH increased or fatigue crack growth (FCG) decreased with decreasing pressure or UTS. The cycle life data of the model materials under the conditions of the pressure, UTS, KIH, FCG and regulations in both hydrogen and air were proposed quantitatively for materials selection for high-pressure hydrogen storage.Copyright