| Due to the super dynamic characteristics,the military strategic position of supersonic combustion scramjet is very high.Based on this,a lot of research on supersonic combustion has been carried out in recent years in the world.The simulation of supersonic combustion is confronted with the dual difficulties of turbulence and chemical reaction dynamics.Therefore,the study on the chemical reaction mechanism of aviation kerosene is an important research direction of supersonic combustion.Based on the research of domestic RP-3 kerosene,this paper has cleared the kerosene is mainly composed of alkanes,aromatic and cycloalkane,using dodecane to substitute the alkane component,using paraxylene or ethyl-benzene to substitute the aromatic component,using three-methyl-cyclohexane or propyl-cyclohexane to replace the naphthenic hydrocarbon component,and finally proposing four different combinations of RP-3 aviation kerosene alternative fuels by permutation.In this paper,the chemical reaction mechanism was consisted of the macromolecular mechanism and the small molecule core mechanism which is called USC-II.For dodecane,paraxylene,ethyl-benzene and three-methyl-cyclohexane which have complete combustion mechanism,the macromolecular mechanisms were extracted by means,while the macromolecular mechanism of propyl cyclohexane was calculated through Gaussian.Finally,the comparison of simulation with the experimental results proves that the mechanism of the substitution which is composed of dodecane,ethyl benzene and propyl cyclohexane is suiTab..Before the application of the mechanism in the supersonic combustion simulation,to balance the computational cost of CFD simulation,this paper uses the ReaxRed package to reduce the detailed mechanism by DGR and CSP fistly,obtaining a simplified mechanism composed of 85 components and 346 steps elementary reaction,and then uses the method of main path analysis to simplify the macromolecular mechanisms to obtain a more simplified mechanism which consists of 65 components and 264 steps elementary reaction.After that,the ReaxRed program is used again to simplify the small molecule core mechanism,and finally a simplified mechanism of 43 components and 97 steps elementary reaction was obtained.The applicability of the simplified mechanism was verified.In this paper,using the simplified mechanism to study on the combustion process of kerosene in a dual combustor ramjet engine,compared with the scramjet combustion flow field simulation results of the general reaction,finding that the combustion process is more reasonable with the simplified mechanism.On the basis of these,the influence of the subsonic combustion chamber outlet gas parameters on the combustion flow field in the supersonic combustion chamber was studied and the results show that when the subsonic combustion chamber outlet gas temperature is increased,it is favorable to the combustion heat release in the scramjet combustor.While the gas Ma is increased,the combustion effect in the supersonic combustion chamber becomes worse. |
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