Computational tools drive hydrogen-powered aircraft engines towards a greener future
The aviation sector accounts for over 2 % of global greenhouse gas emissions, and without significant interventions this level is projected to nearly quadruple by 2050. While innovations in electric aviation are on the rise, limitations in battery energy density and costs prevent these technologies from achieving the speed and payload capacities needed for long-haul flights. Future propulsion technologies leveraging hydrogen have the potential to significantly improve the efficiency and performance of traditional aircraft turbines. Unlike conventional engines, which rely on a constant-pressure combustion process, hydrogen-based pressure gain combustion (PGC) engines create a pressure rise within the combustor. This innovation enables superior fuel utilisation and delivers enhanced overall performance.
Utilising hydrogen as energy fuel
Undertaken with the support of the Marie Skłodowska-Curie Actions (MSCA) programme, the FLOWCID project proposed developing innovative computational tools and methods to address the key challenges of zero-emission pressure gain combustors and turbines. “We wanted to tackle two critical fluid dynamic challenges hindering compact propulsion concepts: flow separation caused by high-pressure gradients and unstarting where the airflow fails to move smoothly through the turbine, disrupting the engine's operation,” explains the MSCA research fellow Eusebio Valero. To address these challenges, FLOWCID employed advanced numerical simulations, mathematical analysis, and experimental validation. The objective was to understand and control flow dynamics in high-speed internal flows, such as those found in hydrogen-based pressure gain engines.
Key achievements
Valero and the host at Purdue, Paniagua, made important progress in advancing this technology. One major achievement was to improve computer models that simulate how air and gases move through high-speed internal flows. By refining these simulations, researchers could better predict and understand how turbulence and sudden changes in airflow, known as shocks, impact engine performance. This helps ensure the engines are designed to handle real-world conditions effectively. The project also focused on managing the enormous amounts of data produced by these simulations. Using innovative methods, the team identified key patterns in airflow behaviour, particularly around areas where problems like flow separation occur. “These findings provided critical insights into the root causes of inefficiencies and offered ideas for fixing them,” highlights Valero. Another key achievement was studying how small changes in engine design or operating conditions impact airflow. This allowed the team to develop strategies for improving performance, such as fine-tuning engine shapes or using techniques like injecting air at specific points to keep the flow steady and efficient.
Impact on aviation and beyond
The innovations of the FLOWCID project have significant environmental and socioeconomic implications. By refining high order computational tools and stability solvers, the project contributes to precise computational analysis of future propulsion systems, essential to realise zero-emission aviation, reducing dependency on fossil fuels and mitigating climate change. Importantly, project advancements in simulation and flow control methodologies extend beyond aviation. Building on its success, FLOWCID aims to build a comprehensive sensitivity map of physical flow features that influence complex aerodynamic behaviours and integrate machine learning to detect and optimise novel aerodynamic configurations. “We are confident that our continued efforts will further enhance flow control and design efficiency, positioning hydrogen-based advanced thermal engines as a viable alternative to traditional aircraft engines,” concludes Valero.
Keywords
FLOWCID, pressure gain engines, aviation, hydrogen, zero-emission, flow separation, unstarting
