Closed-loop control of shock train in inlet-isolator with incident shocks

The close-loop control of the shock train location considering the effects of incident shocks has been investigated in a direct-connect wind tunnel. Under this condition, three algorithms for shock train location were investigated: pressure ratio method, static pressure summation method and backpressure method. The first method was found to be most suitable for the case with incident shocks and implemented experimentally within the closed-loop control. The backpressure method, which is identified to be a much better proxy for shock-train location in previous study, is found to be unsuitable when applied to the case with incident shocks, due to the less correlation with the shock train motion. A proportional-integral controller was designed and verified in a relative uniform flow condition, and then the applicability was explored to the cases with incident shocks. It was found that within the interaction region the shock train cannot follow the instruction well, because the inner close-loop of the shock train responds faster than the control system. Based on the distribution of the interaction region, an improved measure was proposed and examined experimentally.