Fabrizio BORGNA, Roberta FUSARO, Davide FERRETTO, Guido SACCONE, Nicole VIOLA
DOI Number: N/A
Conference number: HiSST-2025-309
An advanced multi-fidelity combustion modelling strategy aimed at accurately estimating non-carbon emissions from a hypersonic vehicle is proposed. Specifically, the air-breathing hypersonic case study CS3 (@Mach-5) from the European MORE&LESS project is employed for detailed combustion modelling and subsequent emissions analyses. This vehicle, functioning up to Mach 5.5, is equipped with two distinct air-breathing propulsion systems that operate sequentially during the mission: an Air Turbo Rocket (ATR) for Mach 0–5.5 operations and a Dual Mode Ramjet (DMR) for Mach 4–5.5 operations, both powered by a cryogenic hydrogen feedline. The evaluation of water vapor (H₂O) and nitrogen oxides (NOₓ) emissions is conducted for both propulsion systems through the detailed modelling of their combustion processes. The proposed multi-layer modeling approach integrates several simulation strategies to capture the intricate dynamics of combustion under varying operational conditions. Notably, the proposed modelling approaches leverage a single simulation suite, i.e. Cantera, to address the combustion phenomena. The versatility and robustness of Cantera enable simulations that balance incremental improvements in evaluation accuracy with computational complexity and processing time, ensuring that the trade-offs between model fidelity and computational efficiency are optimally managed. For the ATR propulsion system, the combustion process has been investigated using two complementary modelling levels. The first approach analyzes the combustion under the assumption of chemical equilibrium within the combustion chamber, providing steady-state thermodynamic properties and combustion gas compositions. This is complemented by time-dependent chemical-kinetic simulations conducted in a 0D Perfectly Stirred Reactor (PSR) integrated into a preliminary reactor network model, which allows for the evaluation of transient phenomena and a more precise determination of the exhaust gas composition. For the DMR propulsion system, similar modelling strategies have been adopted, with the addition of a refined 1D free flame propagation simulation. This additional layer of analysis enables a deeper insight into the flame dynamics and reaction kinetics that prevail at higher Mach numbers. By systematically comparing the emission outputs from the various modelling layers, the research identifies possible scaling laws among the emission trends at different levels of reliability. Finally, based on the emission results characterized by the highest accuracy, novel low fidelity analytical formulations for NOₓ emission indexes estimation are derived. Results indicate that the ATR produces lower NOₓ emissions compared to the DMR, in accordance with expectations based on the differing propulsion technologies. Nonetheless, both emission levels remain within acceptable limits for their respective Mach operational ranges. Similarly, the quantity of water vapor released aligns closely with the required combustion efficiency.