Qinyuan LI, Bo YAN, Mingbo SUN, Jiajian ZHU, Yifu TIAN, Minggang WAN, Tiangang LUO, Yongchao SUN
DOI Number: XXX-YYY-ZZZ
Conference number: HiSST 2024-00149
Three-dimensional characterizations and evolution laws of the flame structure during combustion
destabilization in an axisymmetric supersonic combustor were investigated. The multi-view OH-PLIF
imaging system was used to visualize the instantaneous flame structures distributing at multiple
typical cross-sections of a fully transparent axisymmetric supersonic glass combustor. The high-speed
photography and pressure measurement systems were employed to assist in the analysis of the flame
structure evolution during combustion destabilization. The experiments were conducted with an
inflow speed of Mach 2.5 and a total temperature of 1800 K. The global equivalence ratios (GER)
were 0.12, 0.15, 0.21 and 0.26, respectively. It was found that a loop-shaped flame with a central
hole is an essential flame structure characterization in the axisymmetric supersonic combustor. The
flame loop mainly distributes near the cavity shear-layer, and the instantaneous structure fluctuates
over time. There is the most intense combustion and thickened flame near the cavity ramp. As GER
exceeds 0.21, an excessive enhanced combustion induces thermal choking. The flame propagates
upstream away from the cavity along the boundary-layer near the jet wake. It leads to a violent
reciprocal flame propagation, marking an unsteady combustion. The thermal choking initiates near
the ramp where the most intense combustion occurs. The local flame loop is significantly expanded,
filling almost the entire flow path. The loop-shaped flame structure downstream the combustor is
affected slightly due to a low-speed and thickened cavity shear-layer. In contrast, the flame structure
near the middle part of the combustor is disrupted severely. A diffused and fragmented flame loop
fluctuates violently over time. A large amount of fragmented flames spread into the core flow
occasionally.