Improvement of a free piston driver for a high-enthalpy shock tunnel

Itoh, Katsuhiro; Ueda, Shuichi; Komuro, Tomoyuki; Sato, K.; Takahashi, Masahiro; Matsubara, Hiroshi; Tanno, Hideyuki; Muramoto, H.

doi:10.1007/s001930050115

Cited by 71 publications

(23 citation statements)

References 5 publications

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“…Itoh et al [5] define a useful piston 'over-drive' parameter, β, in terms of the actual piston speed at the moment of diaphragm rupture, u rupt , and the piston speed theoretically required (ignoring discrete wave processes) to exactly compensate for driver gas loss to the driven tube, U ref :…”

Section: Free-piston Driver Operating Conditionsmentioning

confidence: 99%

Free-piston driver performance characterisation using experimental shock speeds through helium

2015

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Tuned free-piston driver operation involves configuring the driver to produce a relatively steady blast of driver gas over the critical time scales of the experiment. For the purposes of flow condition development and parametric studies, it is useful to establish some average working values of the driver pressure and temperature for a given driver operating condition. However, in practise, these averaged values need to produce sufficiently accurate estimates of performance. In this study, two tuned driver conditions in the X2 expansion tube have been used to generate shock waves through a helium test gas. The measured shock speeds have then been used to calculate the effective driver gas pressure and temperature after diaphragm rupture. Since the driver gas is typically helium, or a mixture of helium and argon, and the test gas is also helium, ideal gas assumptions can be made without significant loss of accuracy. The technique is applicable to tuned free-piston drivers with a simple area change, as well as those using orifice plates. It is shown that this technique can be quickly used to establish average working driver gas properties which produce very good estimates of actual driven shock speed, across a wide range of operating conditions. The use of orifice plates to control piston dynamics at high driver gas sound speeds is also discussed in the paper, and a simple technique for calculating the restriction required to modify an established safe condition for use with lighter gases, such as pure helium, is presented.

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Section: Free-piston Driver Operating Conditionsmentioning

confidence: 99%

Free-piston driver performance characterisation using experimental shock speeds through helium

2015

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“…As discussed in the design of HIEST, because pressure and heat losses occur, numerical analysis cannot reproduce experiments without considering these effects. [15][16][17] However, this analysis assumes isentropic process to predict the maximum attainable pressure and find the optimum operational conditions. As shown in Fig.…”

Section: Compression By Free Piston and Attainable Pres-mentioning

confidence: 99%

Development of Shock Tube for Ground Testing Reentry Aerothermodynamics

Yamada

Suzuki

Takayanagi

et al. 2011

Trans. Japan Soc. Aero. S Sci.

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A free-piston double-diaphragm shock tube with 70 Â 70 mm cross-section at test section is newly developed to investigate thermochemical nonequilibrium phenomena behind a shock wave. This paper presents the performance of the shock tube and the measurement system newly developed. Experimental investigations to clarify its characteristics are conducted for various operational parameters, such as rupture pressure of the first diaphragm and initial pressures in the low-pressure tube, the high-pressure tube, and the compression tube. Based on the characteristics experiment, a performance map of the shock tube is obtained by changing the operation parameters. The result shows that the shock tube can generate the post-shock condition corresponding to super-orbital reentry flight conditions. The newly developed measurement system enables us to obtain a spatial distribution of spectra behind a shock wave with high spatial and time resolution. A description of the measurement system and typical examples of the measured spectra are presented.

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“…This involved allowing the piston to travel with a sufficient velocity upon the rupturing of the primary diaphragm such that the venting driver gas mass flow could be matched by the piston volumetric rate of displacement (Itoh et al, 1998). Consequently, the non-dimensional piston speed at diaphram rupture, β, would be equal to 1 (Itoh et al, 1998).…”

Section: Operational Challengesmentioning

confidence: 99%

“…This involved allowing the piston to momentarily continue to increase the driver gas pressure before the pressure would begin to fall again after the primary diaphragm is ruptured (Itoh et al, 1998). This significantly extended the useful supply time of driver gas pressure where the acceptable limits of varying driver gas pressure would be within 10% (Itoh et al, 1998).…”

Section: Operational Challengesmentioning

confidence: 99%

“…This significantly extended the useful supply time of driver gas pressure where the acceptable limits of varying driver gas pressure would be within 10% (Itoh et al, 1998). Refer to Figure 17 for the illustration of this concept where β > 1 represents the over-tailored operation (Itoh et al, 1998). Making sure the piston dynamics are correct as to satisfy over-driven piston operation but also avoid structural damage to the facility is challenging.…”

Section: Operational Challengesmentioning

confidence: 99%

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Explicit finite element analysis of high speed piston impacts

Yusuf¹

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The University of Queensland operates three large scale free-piston drivers which consists of the T4, X2 and X3 facilities. These facilities are designed for the worst case scenarios based on conservative analytical impact mechanics, in terms of avoiding catastrophic piston impacts. However, these do not accurately predict the mechanical response for complex real geometry in the event of a piston impact.In 2009, there was a high speed impact of a heavy piston that rendered the facility inoperable for two months. Repeated attempts were made to relieve enough stress in the plastically deformed piston to dislodge it from the compression tube. This impact reiterated the potential damage that can be caused by incorrect operation of the free-piston drivers and revealed that there was no structured methodology to estimate the condition of the facility to inform the repair procedure.In this study, the AUTODYN solver was used to investigate three main explicit structural analysis problems including recreating the 2009 T4 high speed piston impact, perfoming a transient stress analysis of the peak pressure loadings acting on X2's lightweight piston using high strain rate material data and analysing the buffer for the X3 facility.The approach to this study involved testing the solver's ability to capture the physical mechanisms involved during a high speed piston impact. An axisymmetric analysis of T4 shot 10509 was later developed where the numerical results were compared to observational comments of the facility made by the technician following the repair job. This approach to using an axisymmetric model was also used to analyse the peak pressure loadings acting on the X2 piston and the results from this were validated against a static structural analysis. An axisymmetric model of the X3 buffer was developed and this was validated against a 3D model. This study has shown that the AUTODYN solver can be used to model high speed piston impacts with relative confidence. Furthermore, there was enough evidence to show that the numerical recreation of T4 shot 10509 did agree with the technician's observations following T4 shot 10509. This allowed for the response of the facility at higher impact speeds and with varying material properties to be investigated. The transient analysis conducted for the X2 lightweight piston agreed closely with the static structural analysis conducted prior. Since the X3 lightweight piston was made out of similar materials to the X2 piston, this validated the material data used for the X3 piston. It was also discovered that the nylon studs in the X3 facility would not likely fracture from an impact speed of 30 m/s by the X3 lightweight piston. This quantification of safe impact speeds for the X3 buffer was deemed important following the development of new driver operating conditons for the X3 facility.ii Acknowledgements Foremost, I would like to thank my supervisor Dr Gildfind for his continued support throughout the year, and faith in my ability to overcome all obstacles that got in my way....

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Improvement of a free piston driver for a high-enthalpy shock tunnel

Cited by 71 publications

References 5 publications

Free-piston driver performance characterisation using experimental shock speeds through helium

Free-piston driver performance characterisation using experimental shock speeds through helium

Development of Shock Tube for Ground Testing Reentry Aerothermodynamics

Explicit finite element analysis of high speed piston impacts

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