Point Measurement Of Detonation Wave Propagation Using Ion Guage
Abstract
Accurate measurement of detonation wave velocity is important in the study of detonations. Detonation wave velocity is calculated by the ratio of distance between two transducers which the wave front travels over the propagation time. Conventional methods included transducers placed a few cm apart thereby yielding an average velocity of the wave. A gauge was developed in which the transducers were placed a few mm apart so that an effective point measurement of velocity can be determined. Different types of sensors used in determining the detonation wave velocity included pressure, flame and ion. Of the three, the ion sensor was chosen because of its simple and straightforward mechanical and electrical design, and compactness. A pair of ion gauges was built into a four-hole ceramic tube potted with epoxy into a steel plug. Solid copper wires were used as electrode pairs. The distance between the two gauges was around 5.2 mm thereby giving a point measurement. A non-stationary cross correlation technique was then used to determine the velocity and its uncertainty. The technique was tested in a 2-in. ID and 30-ft long stainless steel detonation tube. Five ion gauges were installed along the length of the tube. The results were compared against those obtained from pressure transducers spaced 60 in. apart.