Experimental Study of Suction Flow Control Effectiveness in a Serpentine Intake

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The intakes of modern aircraft are subjected to ever-increasing demands in their performance. Particularly, they are expected to carry out diffusion with the highest isentropic efficiency while subjected to aggressive geometry requirements arising from stealth considerations. To avoid a penalty in engine performance, the flow through intake needs to be controlled using various methods of flow control. In this study, a serpentine intake is studied experimentally and its performance compared with and without boundary layer suction. The performance parameters used are nondimensional total pressure loss coefficient and standard total pressure distortion descriptors. The effect is observed on surface pressure distributions, and inferences are made regarding separation location and extent. A detailed measurement at the exit plane shows flow structures that draw attention to secondary flows within the duct. Suction is applied at three different locations, spanning different number of ports along each location, comprising of ten unique configurations. The mass flow rate of suction employed ranges from 1.1% to 6.7% of mass flow rate at the inlet of the intake. The effect is seen on exit total pressure recovery as well as circumferential and radial distortion parameters. This is examined in the context of the location of the suction ports and amount of suction mass flow, by the deviation in surface pressure distributions, as well as the separation characteristics from the baseline case. The results show that applying suction far upstream of the separation point together with a modest amount of suction downstream results in the best performance.