Closed-loop flow control of an ultra-compact serpentine inlet based on nondimensional model

Ultra-compact serpentine inlet faces serve inlet-engine compatibility issues due to flow distortion. To ensure inlet-engine compatibility over a wide range of Mach number, novel active flow control techniques with the ability of being opened or adjusted as needed draw many attentions in recent years. In this paper, a feedback control system was developed based on the method of microjet blowing. The proposed system includes a pressure adjusting valve to adjust the control effort, a dynamic pressure sensor to sense the inlet distortion intensity, a signal processing instrument to calculate the Root-Mean-Squared (RMS) pressure, and a controller to implement feedback control. To achieve high quality closed-loop controls at dynamic conditions, a novel nondimensional feedback method was developed. The advantage of this nondimensional method was validated at both off-design and arbitrarily changing Mach number conditions. With a sectional PI control law, the RMS control error reduced more than 56% at arbitrary changing conditions. Works in this paper also showed that the dynamics of this nondimensional system can be simplified as a stable second-order overdamped system.