Control of Supersonic Inlet-Isolator Unstart Using Active and Passive Vortex Generators

An experimental study was conducted to investigate the effects of ramp-type vortex generators in a Wheeler doublet configuration, vortex generator jets, and their combination on a supersonic inlet unstart and to achieve active control of inlet unstart. Actuators were placed on the inner side walls of a floor-mounted inlet-isolator model in a Mach 5 flow. Unstart was initiated in the inlet-isolator model by raising a flap at the downstream end of the isolator, which increased the back pressure. The combination of the passive Wheeler doublets and vortex generator jets allowed the isolator's back pressure to be raised about 32% higher than the maximum mean pressure achieved by the baseline case as well as resulted in a 34% reduction in the isolator rms pressure fluctuations. The Wheeler doublet plus vortex generator jet combination was successful because the presence of the Wheeler doublets mitigated the unstart-inducing effect the vortex generator jets had on the flow, when used separately. Once the Wheeler doublet plus vortex generator jet combination had proven to be the most effective actuator, an unstart detection technique and control logic were developed to form a closed-loop control scheme aimed at preventing unstart. Experimental tests of this closed-loop control system demonstrated successful control of supersonic inlet unstart with about a 50% success rate.