Session: 01-01 Advanced Concepts I

Paper Number: 78214

78214 - Hydrogen Thermal-Powered Aircraft Combustion and Propulsion System 

Reduction of CO₂ emissions is a priority for every energy and transport system, especially for aviation. A goal has been set for the aviation industry to cut emissions to a carbon-neutral footprint by 2050. One target aircraft is the narrow-body aircrafts, which comprise a significant portion of overall aviation transportation.  This type of aircraft is expected to remain common and is a central focus of this proposed paper. While aviation traffic is expected to double by 2035, aircraft size is expected to remain similar because of mass requirements, future geoeconomics growth, and customer demands. This means that narrow-body (B737 and A320 today) subsonic aircrafts will likely be used for most passenger air-miles by 2050. Stakeholders (aircraft and engine manufacturers, airliners, etc.) agree that there are multiple avenues to achieve the CO₂ reduction goal.

The current path, driven by the International Civil Aviation Organization (ICAO), relies on the use of sustainable aviation fuel (SAF). SAF improves the CO₂ cradle-to-grave analysis by reducing the amount of CO₂ output, but still produces engine emissions with CO₂ and other hazardous components. NASA is considering fully electrified or hybrid thermal/electrified aircraft as a second CO₂ reduction strategy. An advantage of that path is its potential for net zero harmful emissions, but this approach is restricted because scaling up would add significant weight. Today, typical battery energy per mass is 20Wh/kg. For hydrogen fuel, it is 33,300Wh/kg, which means battery-powered narrow-body aircraft would be too heavy (compared to the thermal aircraft that requires 42MW input power for takeoff).  A third path for non-harmful emissions that has gained significant momentum recently is that of the thermal-powered hydrogen aircraft, which is the primary focus of this proposal. Either as a hybrid thermal/electric engine or as a thermal gas turbine engine, liquid-stored hydrogen fuel is a strong candidate for zero harmful emissions while still providing the requisite performance, range, and power needs. Limiting issues of hydrogen fuel include the level of NO_x emission when not premixed and the need for novel infrastructure to support large-scale H₂ deployment. NASA also announced in 2021 a partnership with the Federal Aviation Administration (FAA) and industry partners to demonstrate new technologies for high-power and hybrid-electric propulsion systems. This partnership includes the initiative “Sustainable Aviation Fuel Grand Challenge” to scale-up the use of SAF. In complement to that path, it is required to focus on the hydrogen thermal-powered aircraft and developing a technical approach to contribute overcoming critical existing technological and scientific gaps, while mitigating identified perceived or known risks.

The present article focused on discussing injection and combustor technologies enabling to eliminate CO₂ emissions, develop NO_x reduction and mitigation technologies, and examine a concept to fully eliminate NO_x. To achieve these goals, it is important to provide key estimates that support the methods and technologies developed and explored into this paper. This is conducted here for a typical current aircraft that will be retrofitted and considered. Once the design space and performance requirements are introduced, a compact low emission combustor including all components is discussed to operate with hydrogen swirled combustion for a conceptualized aircraft.

Presenting Author: Paul P. Palies UTSI

Presenting Author Biography: Dr. Paul Palies is Associate Professor at UTSI and the founding director of the Combustion and Propulsion for Aviation Research Center (C-PARC) at UTSI. His research is in reacting fluid dynamics with specializations in aeronautical propulsion research and physics of premixed swirling flames. He developed an expertise in combustion dynamics applied to laboratory scale combustors and jet engines with a demonstrated experience in acoustics, combustion and fluid dynamics. His published work has focused on understanding key physics and passive control strategies in this context as demonstrated by a patent, a book and several widely cited articles. He graduated from Ecole Centrale Paris in aerospace and from University of Paris XI in mechanics-physics. He has broad-band fundamentals knowledge in sciences and engineering. He holds a doctorate in combustion from Ecole Centrale Paris. His doctoral thesis investigated combustion dynamics mechanism identification, prediction and passive control for swirl-stabilized flames with theoretical, experimental and numerical methods. He was senior research scientist at the research center of United Technologies Corporation developing passive control strategy and modeling capabilities to support Pratt and Whitney's commercial combustors program. He is a reviewer for ASME IGTI, The Proceedings of the Combustion Institute, AIAA SciTech and Propulsion and Energy forums, Combustion and Flame, the Combustion Science and Technology Journal and the International Journal of Spray and Combustion Dynamics. He is Senior Member of AIAA and Member of the Propellants and Combustion AIAA Technical Committee. He has been appointed USNC/TAM AIAA Professional Society representative.

Authors:

Paul P. Palies UTSI