Theses

Due to the environmental concerns, strict regulations and requirements enforced by legislative bodies, the aviation industry is actively looking to undertake a transition from kerosene fuelled aircraft to zero-emission aircraft. Numerous options have been evaluated to identify a suitable candidate to replace kerosene.

Hydrogen was identified as a potential candidate to replace and assist kerosene in future aircraft powered by cryogenic propulsion systems. Hydrogen is an abundant element which is found naturally in gas form. Gaseous hydrogen (at 700 Bar and atmospheric temperature) has around three times higher gravimetric energy density compared to kerosene (at atmospheric conditions) [1] [2] [3]. However, the volumetric energy density of gaseous hydrogen (at 700 Bar and atmospheric temperature) is lower than kerosene (at atmospheric conditions) [1] [2] [3]. To overcome this, hydrogen must be stored as a liquid at 20 K. In liquid form (at atmospheric conditions), the volumetric energy density of hydrogen is around four times lower than kerosene (at atmospheric conditions) [1] [2] [3]. This means that compared to kerosene, to travel the same distance with a hydrogen fuelled aircraft, around four times larger storage tanks are required.

The storage tanks must also be compatible to operate under cryogenic conditions. Moreover, sufficient insulation is required to prevent any heat entering the storage tanks leading to evaporation and loss of hydrogen. Finally, the tanks must be designed to prevent components apart from the fuel system encountering with hydrogen.