Expansion Tube Operation with Thin Secondary Diaphragm

摘要

An experimental study of expansion tube operation was conducted by highlighting the interference due to the secondary diaphragm, which separates the shock and acceleration tubes, upon the shock wave transition past the separation. The in-tube processes were diagnosed by framing shadowgraphs and on-wall pressure measurements. Among commercially available diaphragm materials examined, only when using the thinnest Mylar diaphragm (3 μm in thickness), was the shock wave transition not accompanied by serious flow disturbance due to shock wave reflection or to pressure loss through the cloud of ruptured diaphragm fragments. Although cellophane diaphragm was more brittle and suitable for fragmentation, it had the mass penalty caused by its smaller tensile stress and commercial availability, thereby resulting in much larger disturbances.