Combustion-Stability Rating of Impinging-Jet Injectors Using Scaling Techniques in a Subscale Chamber

Combustion instability rating is investigated numerically and experimentally in a subscale chamber with impinging-jet injectors. Air-injection test and simulation using scaling techniques are proposed to predict combustion instability in an actual full-scale combustion chamber of rocket engines. In the present approach, the flow rate is maintained or reduced to the level which is provided by the usual feeding system. From the test and simulation, damping factors are obtained as a function of a hydraulic parameter. Based on the data, instability map is derived. Two instability regions are presented and it is found that they coincide reasonably with the results from hot-fire tests. Accordingly, the proposed approach can be applied cost-effectively to stability rating of jet injectors when mixing of fuel and oxidizer jets is the dominant process in instability triggering.