Expansion tunnel performance with and without an electromagnetically opened tertiary diaphragm

A study was conducted to examine the effect of synchronization of an electromagnetically opened tertiary diaphragm with flow arrival at the diaphragm on the pitot pressure measured at the test section of an expansion tunnel. The effect of tertiary diaphragm pressure ratio (ratio of initial nozzle pressure to quiescent acceleration section pressure) on the pitot pressure time history is also determined. The inadequacy of a pressure transducer protection arrangement used in previous expansion tube and expansion tunnel tests was revealed.