Active Control of Supersonic Inlet Unstart Using Vortex Generator Jets

An experimental study was conducted to investigate the effects of Wheeler Doublets (WDs), Vortex Generator Jets (VGJs), and their combination on supersonic inlet unstart. The final objective of the investigation was to achieve active control of unstart through the use of an unstart detection technique and the most effective of these actuators. Actuators were placed in the inner side wall of a floor-mounted inlet-isolator model in a Mach 5 flow. Unstart is initiated by increasing the back pressure by deflecting a flap at the downstream end of the isolator. Exclusive use of either WDs or VGJs was seen to have some effect on the back pressure but did not have a significant impact on delaying unstart. The combination of WDs and VGJs allowed the isolator’s back pressure to be raised steadily about 32% higher than the maximum mean pressure achieved by the baseline case as well as resulted in a reduction of isolator pressure unsteadiness of about 34%. The WDs+VGJs combination was successful because the presence of the WDs mitigated the unstart-inducing effect the VGJs had on the flow. Once the WDs+VGJs 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. An important part of the control scheme was the identification of a wall-pressure-signal precursor to unstart that reliably predicted unstart onset. Experimental tests of this control system resulted in the achievement of active control of supersonic inlet unstart at a 50% success rate. In addition, areas that could significantly increase the success rate for the current unstart control technique were found, such as better unstart detection techniques and faster acting valves. The investigation showed that once the inlet-isolator system had unstarted, re-start was not achieved by activating the WDs+VGJs.