Evaluating combustion instability in a sub-scale combustion experiment with three scaling parameters
The work explores the use of a laboratory burner to characterize the combustion stability characteristics of a liquid rocket injector at scaled flow conditions. The specific objectives are (1) to match the injector scaled parameters: velocity ratio, momentum ratio, and equivalence ratio; and (2) to evaluate injector combustion stability in a low-pressure, single-element sub-scale combustor. This combustor used gaseous methane and oxygen and a swirl-coaxial injector. A propellant heating system was implemented to match the scaling parameters. The nominal condition, a velocity ratio of 0.646, a momentum ratio of 1.94, and an equivalence ratio of 1.33, produced a 2,350 Hz, 3T mode at 1.19% amplitude. Two dominant instability modes were characterized at the conditions tested, the effects of the scaling parameters studied, and several feed-line instabilities were observed.