| Resumo : |
This study investigated the influence of the global equivalence ratio on the supersonic combustion of hydrogen with atmospheric air, aiming to contribute to the development of technologies related to hypersonic propulsion under the PROPHIPER 14-X Project. Experiments were carried out in the T1 Shock Tunnel (IEAv) using a combustor model equipped with pressure sensors and non-intrusive optical diagnostic devices. The equivalence ratio was varied by controlling the hydrogen injection pressure, with helium employed as an inert gas for comparison. The collected data were analyzed through chamber pressure variations, Schlieren visualization, and natural emission detection of OH* radicals, enabling the assessment of pressure distribution as well as the identification of shock waves and thermal gradients without directly interfering in the flow. The results demonstrated that variations in the equivalence ratio significantly influenced the pressure profiles within the combustion chamber, and regions of greater stability were identified at specific intervals. The detection of OH* radicals confirmed the occurrence of combustion in the supersonic regime, while pressure variation in the chamber helped define the optimal equivalence ratio range by relating combustion performance to injection conditions. The comparison of tests employing hydrogen versus helium revealed marked differences in pressure and temperature parameters, reinforcing the importance of precise equivalence ratio control for supersonic combustion efficiency. The Schlieren technique enabled the observation of interactions between shock waves and the fuel-oxidizer mixture, offering information about flame anchoring mechanisms and the dynamic behavior of the flow in supersonic regimes. It was verified that increasing the hydrogen injection pressure improved combustion efficiency up to a certain limit, beyond which instability intensified, possibly due to "thermal choking". It was concluded that accurate control of the equivalence ratio is essential for maximizing the efficiency and stability of SCRamjet combustion, providing support for future experimental campaigns and for the refinement of the engineering model linked to the 14-X Project. Finally, it is suggested that further studies address additional variables, such as combustor geometry, fuel type, and flow conditions, aiming to deepen the understanding of supersonic combustion mechanisms and to broaden the practical applications of this technology in hypersonic air-breathing propulsion systems. |