Investigations on flame liftoff characteristics in liquid-kerosene fueled supersonic combustor equipped with thin strut

Abstract

The flame characteristics of liftoff and attachment in supersonic combustor fueled with liquid kerosene were investigated by the methods of numerical simulation and experiment. A thin strut was equipped in the center of the combustor acting as the flame holder, and the function of fuel injection was also achieved by the thin strut. In the experimental and numerical conditions, the Mach number in the inlet of the combustor is 2.8, with the stagnation state of Tt=1680 K, Pt=1.87 MPa. The flame images during the experiment process are captured by high speed camera, with the camera parameter of 8000 frames per second, and the pressure distributions in the combustor are also recorded by the pressure sensors. Results show that the flame structure could be divided into two statuses, namely flame liftoff status and flame attachment status, and both the equivalence ratio and the plasma jet ignitor could make an influence on the flame status. By analyzing the flow field characteristics obtained by numerical simulation, the formation mechanism of the flame liftoff phenomenon is discussed, and the flame status depends on both the fuel premixed process and flame propagation characteristics. Further, to investigate the influence of equivalence ratio on the flame liftoff characteristic, an experiment with a linearly increasing equivalence ratio from 0.3 to 0.76 is conducted. The hysteresis of flame liftoff distance is found in different equivalence ratio changing paths, and the path response characteristics are probed. The conclusions of this article is helpful for having an understanding of propagation process and revealing the combustion stabilization mechanism in the thin strut-equipped scramjet combustor.