Abstract
A hybrid H2–air kinetic scheme of 11 species and 15 reactions is developed, which is capable of simulating the high-temperature air reaction flows and H2–O2 combustion flows respectively or simultaneously. Based on the Gupta scheme, the mole fraction varying with a Mach number at specific conditions is analyzed, and the weakly-ionized 7-species 7-reaction scheme is selected. The effect of nitrogenous species on the H2–O2 combustion is analyzed by a zero-dimensional simulation of steady-state and unsteady-state combustion under specified conditions, and the selected dominant nitrogenous reaction N + OH = NO + H is distinguished by the production rate of the nitrogenous species. The thermodynamic properties are verified by comparison using the NIST–JANAF database. The reaction rate coefficients of the dominant reaction of the hybrid kinetic scheme distinguished by a sensitivity analysis are corrected. The proposed kinetic scheme is validated by a zero-dimensional calculation of the ignition delay time and two-dimensional computational fluid dynamics (CFD) simulation with finite-rate chemistry on the shock-induced sub-detonative and super-detonative combustion. The ignition delay time of the hybrid kinetic scheme is almost in the middle between the Shang scheme and Jachimowski scheme, and all the calculated ignition delay times are acceptably greater than the experiments due to the errors of the experiments and numerical models. The clearly captured bow shock wave and combustion front using the hybrid kinetic scheme and Shang scheme are almost the same, which is strongly consistent with the schlieren image. In addition, a good agreement of the flow characteristics and mass fraction of the species along the stagnation line is also obtained, which indicates the accuracy and reasonableness of the hybrid kinetic scheme to simulate hybrid H2–air reactive flows.
Highlights
Attention has widely been paid to the performance of air-breathing hypersonic vehicles and their propulsion systems in recent years [1,2,3,4]
Ahybrid H2 –air kinetic scheme of 11 species and 15 reactions was developed, which is capable of simulating the high-temperature air reaction flows and H2 –O2 combustion flows respectively or simultaneously
The nitrogenous species of the combustion reactions were screened by the simulations of the steady-state and unsteady-state combustion and the dominant nitrogenous reaction with non-negligible reaction rates being selected
Summary
Attention has widely been paid to the performance of air-breathing hypersonic vehicles and their propulsion systems in recent years [1,2,3,4]. In the combustor of the propulsion system, generally powered by a scramjet engine, the oxidant for the injected fuel is practically the mixture of the products or intermediates of high-temperature air chemical reactions rather than the hypothetical non-reactive N2 –O2 mixture in previous investigations In this case, a hybrid kinetic scheme considering both high-temperature air reactions and combustion reactions is necessary to be modeled. Jachimowski [28] proposed a kinetic scheme of 13 species and 33 reactions validated by satisfactorily reproducing the experimental results for a range of conditions relevant to the scramjet combustion, which is widely used and further reduced by other researchers. CFD simulation of the shock-induced sub-detonative and super-detonative combustion comparing the structure of flow field and distribution of species with the Shang scheme and experiment data
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