Colloquium: Nicolas Renauld (ASM)

Double-walled vessels are recognized as an effective storage solution for liquid hydrogen (LH2) due to their superior thermal insulation. Similar to a thermos flask, the vacuum space between the inner cryogenic vessel and the outer vacuum shell prevents convective heat transfer, which would otherwise result in the rapid boil-off of the stored LH2. A critical component of this technology is the inner support structure which supports the inner vessel within the outer vacuum shell. It must be robust enough to handle operational loads and potential crash events specific to aviation applications, prevent excessive thermo-mechanical stresses caused by the contracting inner vessel, and minimize heat transfer through conduction. Despite its importance, there is a noticeable lack of comprehensive designs and research addressing this component, particularly in the context of aviation. The primary objective of this thesis is to develop a design methodology for creating effective inner support structures for double-walled vessel technology. The research is grounded in a practical context through a collaboration with AeroDelft, a student team at TU Delft currently retrofitting a Sling 4 aircraft for hydrogen-powered electric flight. As part of the next milestone in their Project Phoenix, AeroDelft aims to store 6 kg of LH2 in a double-walled vessel to meet the mission's requirements. To begin, functional, operational, and constraint requirements were established for the inner support structure. A baseline design for the inner vessel and outer shell was then developed. Subsequently, four distinct inner support structure concepts were introduced, each with its own design intents and key considerations. These concepts were subjected to various analyses, including modal, thermo-mechanical, crash loads, and heat leakage, to assess their viability and ability to meet essential functional requirements. To determine the most performative design(s), the concepts were evaluated and compared based on the following performance metrics: gravimetric efficiency, heat leakage, safety, and feasibility of manufacturing and assembly. The analyses demonstrated that all four design concepts meet the essential functional requirements, providing a solid foundation for further development or potential prototyping. While the focus was on a vessel designed for a small aircraft, the methodology and design insights are applicable to larger systems. Hence, this research contributes to advancing cryogenic storage solutions for hydrogen-powered aviation.

Supervisor: Dr.ir. JMJF (Julien) van Campen