Cylindrical hydrogen pressure vessel
Topic(s) : Special Sessions
Co-authors :
Ulrich BLASS (GERMANY), Thomas VINAY NAGARAJ (GERMANY)Abstract :
Due to the low volumetric energy density of hydrogen (1.3 kWh/l at 700 bar and 20°C) compared to fossil fuels like gasoline (8.8 kWh/l), optimizing the use of space for hydrogen tanks is essential. However, conventionally wound pressure vessels are very inflexible in terms of their geometric dimensions. Additionally, any change in geometry requires the redesign of the liner (a barrier in the pressure vessel to prevent hydrogen permeation and manufacturing support). Therefore, a new design of cylindrical pressure vessels has been developed and patented at Leibniz-Institut für Verbundwerkstoffe, where both the length and diameter can be chosen almost arbitrarily. Due to the possibility to produce pressure vessels with very small diameter, the developed design is also suitable for hydrogen pipelines.
The new developed design is made of purely axial and circumferential oriented carbon fibre reinforced plastic (CFRP) layers. The loads in the pressure vessel are transferred layer by layer to a metallic dome. This layer wise load transfer leads to a uniform load introduction to the metallic dome. In order to ensure that the pressure vessel can withstand the burst pressure of 1575 bar, which is required in the automotive industry, a detailed optimization of the load transfer area is necessary. For a basic understanding of the general load transfer mechanism an analytical model has been developed. Furthermore, a parametric finite element (FE) model has been developed to investigate the occurring load transfer mechanisms in more detail. A parameter study has been carried out using the FE model to investigate the relationships between the geometrical parameters and the stresses that occur in the CFRP layers. In order to validate the Finite Element model several experimental investigations have been performed. To examine the load transition from CFRP to the metallic dome in detail, pressure-measuring films were placed between the CFRP and the metallic parts during the tests. This allows to determine the stress distribution in the contact area of the different materials. The results of the experimental investigation show a good agreement to the simulations.
In addition to the design of the pressure vessel a novel production process has been developed which makes it possible to produce the vessel with a purely axial and circumferential fibre orientation. Several pressure vessels have been produced and burst pressure tests have been performed. During those tests, the targeted burst pressure of more than 1575 bar has been achieved.
The new developed design is made of purely axial and circumferential oriented carbon fibre reinforced plastic (CFRP) layers. The loads in the pressure vessel are transferred layer by layer to a metallic dome. This layer wise load transfer leads to a uniform load introduction to the metallic dome. In order to ensure that the pressure vessel can withstand the burst pressure of 1575 bar, which is required in the automotive industry, a detailed optimization of the load transfer area is necessary. For a basic understanding of the general load transfer mechanism an analytical model has been developed. Furthermore, a parametric finite element (FE) model has been developed to investigate the occurring load transfer mechanisms in more detail. A parameter study has been carried out using the FE model to investigate the relationships between the geometrical parameters and the stresses that occur in the CFRP layers. In order to validate the Finite Element model several experimental investigations have been performed. To examine the load transition from CFRP to the metallic dome in detail, pressure-measuring films were placed between the CFRP and the metallic parts during the tests. This allows to determine the stress distribution in the contact area of the different materials. The results of the experimental investigation show a good agreement to the simulations.
In addition to the design of the pressure vessel a novel production process has been developed which makes it possible to produce the vessel with a purely axial and circumferential fibre orientation. Several pressure vessels have been produced and burst pressure tests have been performed. During those tests, the targeted burst pressure of more than 1575 bar has been achieved.