Development of a cryogenic low-pressure H₂ tank using an innovative lightweight sandwich construction

© SMWA Sachsen

Project description

Research into alternative propulsion systems makes a significant contribution to reducing aviation’s emissions of climate-damaging greenhouse gases. For example, cryogenic hydrogen (stored in a super-cold, liquid state at around -253°C) can be used to replace kerosene. A critical issue in its storage is boil-off, i.e. the mass of liquid hydrogen that is converted into gaseous hydrogen due to external heating. Inevitably, the boil-off rate depends on the heat transfer coefficient, i.e. the insulation of the tank. If this rate exceeds the propulsion system’s consumption rate – for example, whilst waiting for take-off clearance – the excess gaseous hydrogen must be released into the environment and is therefore ‘lost’. This therefore requires a tank structure that possesses both a low heat transfer coefficient and a low mass.

A sandwich structure is the obvious choice for this. The liquid hydrogen is stored in an inner tank. The sandwich core serves to support the inner tank against the outer tank, which is particularly necessary under high acceleration loads. Heat transfer via free convection can be prevented within the sandwich core by creating a vacuum, similar to a thermos flask. Furthermore, the voids in the core structure developed by our partner FoxCore can be used to channel media and, if necessary, to heat the tank. The outer tank is in turn connected to the aircraft structure and can, if required, also be insulated externally.

Project focus

The project focuses on four key areas of innovation:

• Development of a comprehensive fuel tank concept for a specific application in an aircraft

• Mechanical and thermal design and optimisation of the metallic sandwich structure

• Sizing of the fuel tank insulation and heating system to tailor the boil-off rate precisely to the powerplant’s energy requirements

Project partners:

• Struktur- und Werkstoffmechanikforschung gGmbH

• Fox Core GmbH

Project data

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Kontakt Forschung

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