Percorrer por autor "Martins, Daniel Ribeiro"
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- Oxygen/Hydrogen Combustion under Supercritical Conditions: A Numerical StudyPublication . Martins, Daniel Ribeiro; Silva, André Resende Rodrigues da; Magalhães, Leandro BarbosaThe pursuit of enhanced propulsion system performance has driven the development of combustion technologies operating at increasingly higher pressures. Such conditions tipically exceed the thermodynamic critical thresholds of the propellants, giving rise to complex transcritical and supercritical flow regimes. The oxygen/hydrogen propellant combination has been extensively and successfully employed in liquid rocket propulsion, and, in the context of global decarbonization objectives, the clean, high-energy characteristics of hydrogen make it a promising candidate for future propulsion applications extending beyond rocketry. The modeling of shear coaxial injection of oxygen and hydrogen under supercritical conditions is addressed through a steady-state axisymmetric Favre-averaged Navier-Stokes formulation, with combustion treated using the Eddy-Dissipation-Concept model in conjunction with a detailed kinetic mechanism consisting of eight species and nineteen elementary reactions. The near-field region of the injector constitutes the primary focus of this work, as it is within this zone that the mixing efficiency is established, ultimately governing the overall combustion and engine performance. The simulations are carried out piecewise to ensure consistency thorugh all the simulation process. Firstly, non-reacting simulations are performed, incorporating both ideal- and real-gas models. After that, reacting simulations are performed in order to validate the developed numerical model against experimental data. Two main innovative contributions distinguish the present study from previous works on O2/H2 coaxial injection. The first concerns computational efficiency, achieved through a substantial reduction of the chamber length to the minimum extent necessary to ensure that the outlet boundary conditions do not affect the near-field region. In addition, the omission of the low-velocity recirculation zone located above the injector head was implemented to further reduce computational cost. The second innovation involves the inclusion of heattransfer effects in both the injector and chamber walls. In particular, the influence of the isothermal walls configuration on the injector is analyzed in light of the thermal disintegration mechanism of the inner jet, previously identified in the literature for cold-flow conditions under supercritical regimes. The numerical results demonstrated the capability of the developed framework to accurately model cryogenic O2/H2 injection and combustion under supercritical conditions. The non-reacting simulations established a robust numerical foundation and captured the key flow features, including the dense oxygen core and the surrounding high-velocity hydrogen stream. The incorporation of real-gas effects proved essential, as the ideal-gas assumption led to significant deviations in core length and mixing behavior. In the reacting regime, the real-gas model reproduced the experimental axial temperature profile and flame structure with good accuracy, outperforming the ideal-gas formulation and yielding results comparable to those reported in the literature, thereby confirming its suitability for high-pressure combustion modeling.