Research On Fully-Wrapped Carbon Fiber Reinforced Composite High-Pressure Hydrogen Storage Cylinder Subjected To Localized Fire

Hydrogen is considered as an important energy carrier as electricity because of its advantages such as source diversification, clean, high conversion efficiency, storability and transportability, etc. Development of hydrogen energy and hydrogen fuel cell vehicle (HFCV) has become a part of national strategy in the main vehicle production countries around the world, and also the key fundamental research content of the development plan of medium and long term science and technology in China. High-pressure hydrogen storage is the most popular storage method for HFCVs due to its advantages such as technical simplicity, low energy consumption for compressing hydrogen, fast filling-releasing rate, etc.As an important energy storage component of HFCV, safety performance of high-pressure hydrogen storage cylinder in an accident such as vehicle fire is a key for public acceptability and market promotion of HFCVs due to the high-pressure (30-70MPa) hydrogen and cylinder’s flammable carbon fiber/epoxy composites. The storage cylinder could burst before its pressure relief device (PRD) is activated under localized fire condition caused by accidental vehicle fire. At present, it is not clear for the fire resistance of hydrogen storage cylinders subjected to localized fire, and there is also no effective way to predict the cylinder’s failure at that situation. Related investigation should be carried out.Research on fully-wrapped carbon fiber reinforced composite high-pressure hydrogen storage cylinder subjected to localized fire is conducted, which is supported by the National High Technology Research and Development Program of China (863Program)"Safety guarantee technology and demonstration of high-pressure hydrogen storage, transport and refueling equipments"(No.2012AA051504). The main content and conclusions are shown as follows:(1) Studies on the key technology of localized fire test for high-pressure hydrogen storage cylinders are conducted, and thus relevant key technologies are mastered including self-cooling fast pressurization of filling gas, remote control of fire source extension, remote monitoring of cylinder’s heat response parameters, safety guarantee of test operator, etc. Through the studies, a localized fire test apparatus is developed. Furthermore, localized fire tests for hydrogen storage cylinders are conducted to obtain the heat responses and release characteristics of hydrogen and air as filling media, respectively. Finally, residual strength burst tests for the cylinders after fire tests are carried out to analyze the influence of hydrogen and air release on the residual strength of the cylinders. The difference in heat responses of hydrogen and air is small, while hydrogen release rate is much larger during the fire test. Due to the effect of released hydrogen deflagration, heat damage of the testing cylinder filled with hydrogen is more serious so that its residual strength is lower.(2) Based on the localized fire test results, a computational fluid dynamic (CFD) model is developed for simulating the cylinders subjected to localized fire caused by different fire sources, and the whole process of localized fire test. Heat transfer characteristics of the cylinders under localized fire condition are analyzed using this model to find out the effects of filling media, filling pressure, localized fire exposure time, localized fire impingement area on PRD activation time. Moreover, heat transfer characteristics of aluminum-liner (type III cylinder) and plastic-liner (type IV cylinder) fully-wrapped carbon fiber reinforced high-pressure hydrogen storage cylinders are compared to confirm the difference in the heat transfer performance of the cylinders exposed to localized fire. Because of the only difference of liner materials, average temperature and pressure rise rate of internal hydrogen of type III cylinder is higher than that of type IV cylinder under the same localized fire condition. When localized fire is far from the PRD located at the cylinder’s end-boss, temperature rise rate of hydrogen around the end-boss of type III cylinder is higher than that of type IV cylinder so that heat can transfer faster to the PRD.(3) Heat response data coupling transfer between the CFD model and finite element analysis model of the cylinder is realized, and thus a thermal loading analysis approach is developed to accurately transfer thermo-mechanical coupling boundary condition between the two models. Based on this analysis approach and mechanical property degradation models of the materials of cylinder’s aluminum-liner and carbon fiber/epoxy composite layers, a mechanical response analysis method for the cylinder under thermo-mechanical loadings is developed. The burst pressure degradation process of the cylinder along the localized fire exposure time is revealed through the calculation of cylinder’s burst pressure at each time of fire impingement. Then, an association relationship of cylinder burst pressure-internal gas pressure-localized fire exposure time is established to develop a prediction method of burst pressure and fire resistance time of the cylinder subjected to localized fire. Finally, the prediction method is validated by predicting the burst pressure and fire resistance time of a high-pressure hydrogen storage cylinder that was used for a localized fire burst test conducted by JARI.