EXPERIMENTAL INVESTIGATION ON THE REGIMES OF HYDROCARBON SUPERSONIC COMBUSTION

Numerical simulations of high-fidelity aerospace engines are usually based on the rapid chemical reaction flame surface assumption, that is, the characteristic scale of supersonic combustion reaction is smaller than the turbulent Kolmogorov scale. This model method has good simulation results for hydrogen fuel, but further research is needed for hydrocarbon fuels such as ethylene. Limited by the extreme environment special nonintrusive measurement techniques, experimental investigations on the discrimination of supersonic combustion flame mode have not been presented in literature. The applicability of the supersonic combustion flame surface model and understandings of the regimes of supersonic combustion restricts the development of high fidelity numerical simulation methods. Based on the in house designed MHz endoscope optical fiber sensor, experiments are designed to study the regimes of supersonic combustion of a dual-mode scramjet combustor. The minimum Shannon entropy of the chemiluminescence signal is used to define the characteristic time of supersonic combustion. The flow characteristic time of supersonic combustion is estimated according to the theoretical method and the incoming flow conditions. Combined with the partition combustion theory, the partition situation of hydrocarbon fuel combustion in a dual-mode scramjet is analyzed. Through combustion zoning and comparison with Taylor scale .The data presented in this paper suggests the supersonic combustion in the vortex framelet regime in a typical flight envelope (Re\cong 50000; Da∈1.80-2.60, B zone), suggesting the strong influence of turbulence,With different sizes relative to the Taylor scale, vortex structures corresponding to different scales dominate the process. In addition, parametric evaluation on the influence of equivalence ratio, flux ratio and Mach number during a simulated acceleration is presented in this paper. The experiment found that the combustion gradually increased with the increase of the equivalence ratio within a certain range, and the enhancement effect was obviously stronger than that of the flux ratio; the change of the flux ratio would cause the combustion to bifurcate; the change of the incoming Mach number was important for The effect of combustion is more obvious, and it also shows that the effect mechanism of incoming flow is an important direction for future research on turbulent combustion theory.