Detecting shock arrival in expansion tubes and shock tunnels using high-frequency photodiodes

Autor: Christopher M. James, D. R. Wikner, Timothy J. McIntyre, D. Cox, L. Barltrop, A. Komonen
Rok vydání: 2021
Předmět:
Zdroj: Shock Waves. 31:399-411
ISSN: 1432-2153
0938-1287
DOI: 10.1007/s00193-021-01026-6
Popis: In expansion tube and shock tunnel facilities, freestream properties are generally inferred from the measurement of shock speeds using wall-mounted instrumentation. By measuring the shock arrival time at known locations along the facility wall, their spacing can be used to calculate the shock speed. These shock arrival measurements are generally taken using high-frequency pressure transducers. For operation at low pressures and shock speeds in excess of 10 km/s, the transducer rise time and its small voltage response to the passing shock wave can become the largest source of uncertainty in the found shock arrival time. In these situations, shock arrival can also be found optically by measuring the radiative emission of the passing shock wave using photomultiplier tubes or photodiodes, which can have rise times of much lower than a microsecond and potentially a larger voltage response to the passing shock wave. This paper presents a photodiode system that has been used to optically measure shock arrival in the X2 hypervelocity expansion tube at the University of Queensland. Experimental results show that for challenging low-density, high shock speed conditions, the photodiode system is able to measure shock arrival with a much larger signal-to-noise ratio than a comparable pressure transducer while operating with a similar or higher-frequency response. This behaviour makes the photodiode system an ideal sensor for detecting shock arrival in these situations.
Databáze: OpenAIRE
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