Diaphragm-type Shock Tube for High Shock Speeds

Abstract

DIAPHRAGM-TYPE shock tubes have been widely used in studies of gases at high temperatures^1,2. Their particular virtue is that they produce a reasonably homogeneous sample of test gas, with known properties, in the region between the shock wave and the interface zone. But one disadvantage is that the speed of the shock wave produced, and hence the temperature in the gas sample, is limited by the temperature of the driver gas. Substantial efforts have been made to increase driver gas temperatures. Among these, heating by an arc discharge has produced shock Mach numbers of approximately 40 (ref. 3), while heating by free piston compression⁴ has yielded values of approximately 30. It has been realized for some years that shock wave heating, using the double diaphragm technique^5,6, afforded a means of improving the performance of shock tubes. Model experiments are reported here which show that this principle can be used, in conjunction with a free piston driver, to achieve shock Mach numbers of 50.