Effect of Inlet Pressure on Flow Characteristics in Cavity-Based Flameholder under Subatmospheric Pressure

Cavity-based flameholder is expected to be applied for ramjets or afterburners, which could work efficiently in the high-altitude space with low pressure. The detailed fluid structure helps to understand the flame stability principle of the flameholder. The fluid structure in the center section and side section of the cavity-based flameholder is experimentally measured at the inlet pressure of 0.04–0.10 MPa, Mach number of 0.1, and temperature of 300 K. Results indicate that the inlet pressure has a significant effect on the fluid-structure in the cavity. The bluff body affects the generation of the vortex in the cavity. As the inlet pressure decreases from 0.10 MPa to 0.04 MPa, the classical dual-vortex maintains excellent stability in the side section of the cavity. Whereas the single-vortex in the center section gradually becomes incomplete with the inlet pressure varying from 0.10 MPa to 0.06 MPa, and it disappears at 0.04 MPa. The reason is that with the reduction of inlet pressure, the density decreases as well, and the proportion of the mass flow rate attracted to the low-pressure area downstream of the bluff body increases, which leads to the vortex being gradually pulled and destroyed.