Dynamic response characteristics of flame during condition transition in a cavity-based scramjet combustor

Experimental study is performed to investigate the dynamic response characteristics of the flame when global equivalence ratio increases suddenly during the condition transition in a cavity-based scramjet combustor. High -enthalpy supersonic flow enters the combustor on conditions that Mach number, stagnation temperature, and total pressure are 2.52, 1486 K, and 1.6 MPa, respectively. In this paper, more attention is paid to the charac-teristics of flame evolution after sudden increase of fuel injection pressure and combustion characteristic when the injection pressure gets stabilized again. Three flame modes after condition transition have been observed and analyzed according to the transient chemiluminescence image captured by high-speed photography. There are two kinds of stable flame modes after transition mission at a low injection pressure difference, which are mainly reflected in the distribution of flame and intensity of visible light. Whereas, once the injection pressure difference exceeds a critical value, intense periodic flame flashback phenomenon begins to appear in the combustor. It can clearly capture the back and forth motion of the flame in the combustor, along with the local blowout and reignition phenomenon. Furthermore, the dominant frequency of flame flashback decreases and contrast of combustion intensity becomes more obvious as the injection pressure difference increases.

Automated summary

An experimental study was conducted on the dynamic response characteristics of the flame in a cavity-based scramjet combustor during a sudden increase in global equivalence ratio during condition transition. Three flame modes were observed and analyzed using high-speed photography, showing that intense periodic flame flashback occurs when the injection pressure difference exceeds a critical value. The dominant frequency of flame flashback decreases and the contrast of combustion intensity becomes more obvious as the injection pressure difference increases.