Rapid valve opening technique for supersonic blowdown tunnel

摘要

In supersonic blowdown tunnels with limited air storage, there is a desire to bring the tunnel to its oper_ating condition as fast as possible. However, if the starting process is too fast, large, dangerous oscillations may occur. A computer-based controller was developed which is able to start a supersonic wind tunnel very quickly without any overshoot of the stagnation pressure. The control system consists of a pressure transducer, a multifunction PC board and an automatic valve. An ideal valve opening profile for a partic_ular test is developed based on test data. The profile is stored in the system memory before a test and the multifunction board sends an analog output to the automatic valve during an actual test. After several tests and corrective interpolations, the pressure disturbances in the plenum chamber are typically reduced to one percent of the stagnation pressure.