Percorrer por autor "Domingos, Diogo Soares"
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- Combustion Characteristics of Oxygen-Hydrogen MixturesPublication . Domingos, Diogo Soares; Magalhães, Leandro Barbosa; Silva, André Resende Rodrigues daThe search for more efficient rocket propulsion systems has driven the aerospace engineering industry to innovate combustion chambers to withstand extreme conditions, including high pressure and temperature (up to 20 MPa and 3300 K). However, testing and optimising these systems through trial-and-error techniques is inefficient and costly. In response, and with the increased availability of computational resources, there has been a massive shift towards the development of numerical codes that facilitate the simulation and investigation of combustion events in liquid rocket engines. This dissertation aims to contribute to that effort by developing a robust and flexible numerical combustion model that can analyse different kinetic mechanisms. The model employs an Arrhenius parametrisation to estimate reaction rates and Lindemann or Troe methods to represent fall-off behaviour in pressure-dependent reactions. Importantly, the model is formulated to operate exclusively with gaseous-phase combustion, assuming that all reactants and products are fully vaporised before participating in the reaction. The numerical solver draws upon the SUNDIALS suite in the form of the CVODE solver using the Backward Differentiation Formula method suitable for stiff problems. The use of this method requires a non-linear (Newton method) and a linear (scaled, preconditioned GMRES) methods to efficiently deal with the initial value problem. The model possesses the ability to simulate isobaric and adiabatic flow reactor configurations, which offer flexibility in dimensionless analysis of combustion performance. Given the central role of hydrogen in the operation of liquid rocket engines, this fuel is adopted as the primary focus throughout the dissertation. Due to the importance of hydrogen in the operation of liquid rocket engines, this fuel is considered through the dissertation. To confirm its reliability, the model was compared with an extensive experimentally available dataset of species concentration profiles and ignition delay times, specially concerning hydrogen-oxygen mixtures. The validation set has a wide range of conditions with pressure ranging from 0.3 to 15.7 atm, initial temperature ranging from 880 to 935 K, and initial equivalence ratio ranging from 0.27 to 1.0. The results show that the model can accurately predict the evolution of species concentrations over time, in agreement with the experimental data used for validation. Therefore, the model establishes a solid foundation for future developments, including reactive environments involving more complex species such as hydrocarbons. Additionally, the model can be further enhanced by incorporating turbulent combustion and high-pressure reactive flows, which are typical of combustion chambers in liquid rocket engines.