Sensitivity study on a Reverse turbo-Brayton cryocooler for zero boil-off on an airborne liquid hydrogen tank

Abstract

Liquid hydrogen has been identified as a low-emission alternative to hydrocarbon fuel sources for aircraft. Although there has been a notable increase in the number of studies and technology readiness of liquid hydrogen technologies in the recent decade, there is still more research and development necessary to realize commercially viable hydrogen-fueled aviation. Achieving zero boil-off by using active cooling has been identified as a potential method of decreasing the mass and volume of a future liquid hydrogen fueled aircraft. However the lack of literature or data on the thermal performance and specific power of cryocoolers for this application makes it difficult to assess its feasibility. Therefore, a study was performed to develop a reverse turbo-Brayton cryocooler simulation tool, focused on the three heat exchangers of this cooler type. This paper presents the methodology for the development of this tool alongside a case study on a liquid hydrogen fuel tank for TU Delft's flying-V concept. From the case study it has been concluded that the considered RTBC design offers a reduction in the liquid hydrogen mass, however not significant enough to offset the cryocooler's own weight. An improved performance and specific power of the individual components would be required to achieve a net weight reduction.