Thermal Management System Architecture for Hydrogen-Powered Propulsion Technologies: Practices, Thematic Clusters, System Architectures, Future Challenges, and Opportunities

Abstract

The thermal management system architectures proposed for hydrogen-powered propulsion technologies are critically reviewed and assessed. The objectives of this paper are to determine the system-level shortcomings and to recognise the remaining challenges and research questions that need to be sorted out in order to enable this disruptive technology to be utilised by propulsion system manufacturers. Initially, a scientometrics based co-word analysis is conducted to identify the milestones for the literature review as well as to illustrate the connections between relevant ideas by considering the patterns of co-occurrence of words. Then, a historical review of the proposed embodiments and concepts dating back to 1995 is followed. Next, feasible thermal management system architectures are classified into three distinct classes and its components are discussed. These architectures are further extended and adapted for the application of hydrogen-powered fuel cells in aviation. This climaxes with the assessment of the available evidence to verify the reasons why no hydrogen-powered propulsion thermal management system architecture has yet been approved for commercial production. Finally, the remaining research challenges are identified through a systematic examination of the critical areas in thermal management systems for application to hydrogen-powered air vehicles’ engine cooling. The proposed solutions are discussed from weight, cost, complexity, and impact points of view by a system-level assessment of the critical areas in the field.

Fuels systems and components for future airliners fuelled with liquid hydrogen

“…Integral tanks use the fuselage structure to contain the fuel. This is advantageous in terms of aircraft design, since the tank can properly be designed to allow a better utilization of the fuselage volume [2]. Integral tanks are part of the airframe structure, which means that they must be designed to withstand fuselage stresses and loads, including that due to the fuel.…”

“…Liquid hydrogen must be stored at 20 ÷ 30 𝐾 at a pressure of 1 ÷ 3.5 𝑏𝑎𝑟; these conditions need to be maintained throughout the whole mission [2], and the boil-off phenomenon (hydrogen evaporation and leakages through permeation) must be minimized; this can be achieved by insulating the tanks. Insulation can be internal, namely, the insulating material is in direct contact with hydrogen, or external.…”

“…Another problem that arises in the hydrogen fuel system design is related to the fuel drain line. In some studies, the excess hydrogen is proposed to be drained and recirculated towards the aircraft tanks, where it is stored at cryogenic conditions [2]. In this configuration, the drained hydrogen needs to be cooled down and its pressure needs to be decreased, to reach conditions compatible with the liquid phase, and this introduces another heat exchange in the system.…”

“…To avoid these complications, the leakage from the fuel line and from the components (pumps, valves, etc.) should be minimized [2]. Secondary tanks for the storage of hydrogen in gaseous conditions could be necessary to have gaseous hydrogen available for the cold engine starting phase, when the heat exchangers are not able to properly increase the hydrogen temperature before it enters the combustion chamber.…”

“…Over the last decades, the continuous growth in the demand for air transport worldwide has led to a significant increase in CO2 emissions from aircraft. To minimize the negative impact of this growth on the environment, the Flight Path 2050, set by the Advisory Council for Aeronautics Research in Europe (ACARE), has defined the goal of achieving a 75% reduction in C02 emissions per passenger kilometer by 2050 [1,2]. In November 2021, among the ten European Partnerships approved by the EU to accelerate the green and digital transition, one has specifically been designed for aviation, namely, "The Clean Aviation", which aims to develop the next generation of ultra-efficient low-carbon aircraft [3].…”