Optical study of a light diaphragm rupture process in an expansion tube

Wegener, Margaret; Sutcliffe, Mark; Morgan, Richard G.

doi:10.1007/s001930050003

Cited by 26 publications

(14 citation statements)

References 9 publications

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“…al. [21] by capturing images of the diaphragm as the shock wave impacted, and subsequently passed through it. Wegener discovered that upon impact by the travelling shock wave the diaphragm shears along its periphery and is pushed downstream as a planar disk, blocking the test flow.…”

Section: Diaphragm Fragmentationmentioning

confidence: 99%

“…A reflected shock can also be seen on this figure and will be discussed in depth in Section 1.3.2. [21] The fragments remaining in the flow continue to be accelerated down the expansion tube to hypersonic speeds where they may impact with pressure sensors and other instrumentation. This impact causes damage to and significantly increases the noise in the data acquired by the impacted instrumentation [18,22].…”

Section: Diaphragm Fragmentationmentioning

confidence: 99%

“…The thin film diaphragm has a finite burst time; due to this the first part of the test gas is stagnated and the primary shock wave is initially reflected back off the diaphragm upon impact, creating a reflected shock which travels against the flow [21]. Figure 9 displays the timedisplacement results from a 2D expansion tube simulation using a total variation diminishing scheme, conducted by Kage, K et al [15].…”

Section: Reflected Shockmentioning

confidence: 99%

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Feasibility analysis of a rapid opening valve as a thin film diaphragm replacement for expansion tubes

Wilson¹

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AcknowledgmentsI would first like to thank my supervisor, Doctor David Gildfind, whose willingness to consistently make time to meet and discuss progress and problems has been greatly appreciated. Your passion and professionalism are traits I hope I can emulate throughout my engineering career.I also want to thank my father, Lewis, for applying his extensive knowledge in entomology to issues such as valve sealing and piston decelerating methods; my mother and brother for their unwavering faith in my ability; and my sister for showing me that unabashed passion is the only way to approach your chosen field.Finally, I want to thank my room-mates and friends who listened and discussed my project throughout the year and distracted me when I needed a break. PAGE: III AbstractThe objective of this thesis was to assess the feasibility of replacing the thin film diaphragm on the University of Queensland's X2 expansion tube facility with a valve system. The aim of developing this system is to avoid issues associated with the use of the thin film diaphragm, while still producing acceptable test flows. To ensure the test flows are still acceptable, the valve must open in less than 0.5ms, as defined by Burgess [1]. The critical issue introduced by the utilization of a thin film diaphragm is that, upon impact by the shock, the thin film diaphragm is broken into fragments. These fragments can be accelerated into the test section by the flow where they may impact and damage instrumentation. There have been multiple attempts to avoid the diaphragm fragmentation issue. These attempts were compiled and assessed and it was concluded that none satisfactorily avoided the issues introduced by the thin film diaphragm without potentially significantly deviating the expansion tube test flow. To successfully replace the thin film diaphragm, a system which completely clears the expansion tube bore, rapidly, and with minimal disturbance to the surrounding gas, while maintaining a low leakage seal is required. An investigation showed that a gate valve best fulfilled this criterion. A gate valve consists of a flat plate of metal with a hole in it, termed the 'knife'. To open the valve, the knife is moved such that the hole aligns with the expansion tube bore. The gate valve should be accelerated and decelerated pneumatically, while being sealed using a PTFE encapsulated X-ring pressed against the face of the knife. To achieve the required opening time without knife failure due to excessive stresses, the knife length before the hole should be increased to allow the knife to be accelerated at a lower rate for a longer period of time before the hole begins to clear the expansion tube bore. Similarly, the length of the hole in the knife should be increased so the knife can be decelerated over a longer distance. Analytical equations to approximate knife, connecting rod and piston failure were developed and shown to be conservative using Finite Element Analysis. These equations were then utilised in an iterative, parametrised Python code which both...

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Section: Diaphragm Fragmentationmentioning

confidence: 99%

Section: Diaphragm Fragmentationmentioning

confidence: 99%

Section: Reflected Shockmentioning

confidence: 99%

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Feasibility analysis of a rapid opening valve as a thin film diaphragm replacement for expansion tubes

Wilson¹

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“…These codes generally use an inertia model which to takes into account the effects of the diaphragm being accelerated by the flow for a short distance after it ruptures. Such models have been well refined and are effective, however there is still a degree of uncertainty surrounding how and when the diaphragm breaks down which means that these codes are never completely accurate [1,17].…”

Section: Mirels Effect 216mentioning

confidence: 99%

“…Through analysis of how far the lines had moved over the time interval between photographs, the velocity of the oxygen molecules and therefore the air jet could be determined [21]. This study only concerned low velocity subsonic flows, however RELIEF 17 techniques have been used to characterize flows up to Mach 4, and the extension of the technique for use in the hypersonic regime looks very promising [22].…”

Section: Planar Laser Induced Fluorescence Velocimetry 221mentioning

confidence: 99%

A new method of measuring shock expansion tube test flow velocities

Crombie¹

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[Email address] ii AcknowledgementsThere are several individuals without whom the completion of this body of work would not have been possible. These people should not go without acknowledgement.Firstly, thanks must go to Tim Cullen for being one the people who conducted testing in the University of Queensland's X2 shock Expansion Tube facility on my behalf.Secondly Christopher James, who also conducted experiments and was very generous with his time in helping me to understand the results.Thirdly, The University of Queensland and the department of hypersonics who made their facilities available for experimentation along with a significant manufacturing budget to produce all the required instruments. AbstractShock expansion tubes are an important tool in the field of hypersonic research. However, these facilities possess a major weakness in the fact there is a great deal of uncertainty associated with the properties of the test flows that they produce.In an attempt to better characterise these properties, an instrument which was capable of measuring the velocity of the test flows produced by shock expansion tubes was to be designed and tested. This instrument would consist of two pitot probes which would be mounted in a shock tube at different locations to detect the arrival of the test gas. Based on the time difference between the arrival of this gas at each probe, its velocity could be calculated.Two probes were designed and manufactured for the testing of this concept in the University of Queensland's X2 shock expansion tube. The design, shown in the image to the right, was created with consideration given to the facts that the probe had to; be structurally capable of withstanding the hypersonic flow environment, protect the pressure transducer from this harsh environment, respond rapidly to changes in pitot pressure, be able to take measurements through the thickest boundary layers, create the smallest disturbance to the test flow possible, and record data which was not adversely affected by noise.This design was tested in the X2, which was configured to produce two high enthalpy test flows with velocities of 9468.1m/s and 9656.5m/s.Over the two experiments, the probes measured the velocity of the two test flows to within 3% of the current best estimates, although determining the arrival time of the test gas at each probe was difficult and there was large potential for error. The data recorded by the two probes was also sufficiently noise free and the instruments responded rapidly to any changes in pitot pressure.There was also no evidence that the probes were significantly disrupting the test flow, however further testing was required to confirm this. In summary, the design was a success and further testing was warranted to confirm these results and develop the concept further.iv

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