Automatic restart control system for axisymmetric mixed compression inlet.

The servosystem design of a high-response airflow bypass valving system for supersonic mixed-compression inlets or other industrial or aerospace pneumatic systems is described. The valve utilizes a multislotted plate to achieve flow area change with minimum stroke and mass of moving parts. The servosystem utilizes a hydraulic piston-in-cylinder actuator close-coupled to a two-stage electrohydraulic servovalve. Using electronic compensation the small-amplitude response of the system, modulating 14 percent of its full flow area, is flat within 0 to -3 dB to 110 Hz. (161 cm [to the second power] ). A mathematical model of the system is presented and analytical responses are compared with experimental data.

Results of experimental tests conducted on a supersonic, mixed-compression, axisymmetric inlet are presented. The inlet is designed for operation at Mach 2.5 with a turbofan engine (TF-30). The inlet was coupled to either a choked orifice plate or a long duct which had a variable-area choked exit plug. Closed-loop frequency responses of selected diffuser static pressures used in the terminal-shock control system are presented. Results are shown for Mach 2.5 conditions with the inlet coupled to either the choked orifice plate or the long duct. Inlet unstart-restart traces are also presented. High-response inlet bypass doors were used to generate an internal disturbance and also to achieve terminal-shock control.