Shock-Tube Performance at Low Initial Pressure

1959 ◽  
Vol 2 (2) ◽  
pp. 207 ◽  
Author(s):  
Russell E. Duff
Keyword(s):  
Shock Tube ◽  
Initial Pressure

Numerical Calculations on Reflection Processes of Ionizing Shocks on the End Wall of a Shock Tube

1977 ◽  
Vol 32 (9) ◽  
pp. 986-993 ◽  
Author(s):  
Yasunari Takano ◽  
Teruaki Akamatsu
Keyword(s):  
Shock Tube ◽  
Initial Pressure ◽  
Inviscid Flow ◽  
Incident Shock ◽  
Numerical Calculations ◽  
Relaxation Processes ◽  
Flow Problems ◽  
Shock Mach Number ◽  
Ionizing Gases ◽  
End Wall

Abstract Numerical calculations have been made about shock reflection processes in ionizing argon on the end wall of a shock: tube. The two-step Lax-Wendroff scheme was employed to solve time-dependent one-dimensional inviscid flow problems for ionizing gases. Complicated flowfields were found to occur due to interactions between ionization relaxation processes and reflected shocks. Calculations were performed for three cases: incident-shock Mach number M s = 16 and initial pressure p1 = 1 torr; Ms = 14 and p1 = 3 torr; M s = 12 and p1 = 5 torr.

Measurements of Decompression Wave Speed in Natural Gas Containing 2-8% (Mole) Hydrogen by a Specialized Shock Tube

2016 ◽  
Author(s):  
K. K. Botros ◽  
S. Igi ◽  
J. Kondo
Keyword(s):  
Natural Gas ◽  
Shock Tube ◽  
Hydrogen Concentration ◽  
Wave Speed ◽  
Accurate Determination ◽  
Initial Pressure ◽  
Propagation Speed ◽  
Wave Speeds ◽  
Decompression Wave ◽  
Curve Method

The Battelle two-curve method is widely used throughout the industry to determine the required material toughness to arrest ductile (or tearing) pipe fracture. The method relies on accurate determination of the propagation speed of the decompression wave into the pipeline once the pipe ruptures. GASDECOM is typically used for calculating this speed, and idealizes the decompression process as isentropic and one-dimensional. While GASDECOM was initially validated against quite a range of gas compositions and initial pressure and temperature, it was not developed for mixtures containing hydrogen. Two shock tube tests were conducted to experimentally determine the decompression wave speed in lean natural gas mixtures containing hydrogen. The first test had hydrogen concentration of 2.88% (mole) while the second had hydrogen concentration of 8.28% (mole). The experimentally determined decompression wave speeds from the two tests were found to be very close to each other despite the relatively vast difference in the hydrogen concentrations for the two tests. It was also shown that the predictions of the decompression wave speed using the GERG-2008 equation of state agreed very well with that obtained from the shock tube measurements. It was concluded that there is no effects of the hydrogen concentration (between 0–10% mole) on the decompression wave speed, particularly at the lower part (towards the choked pressure) of the decompression wave speed curve.

Shock tube flows past partially opened diaphragms

2008 ◽  
Vol 602 ◽  
pp. 267-286 ◽  
Author(s):  
PAOLO GAETANI ◽  
ALBERTO GUARDONE ◽  
GIACOMO PERSICO
Keyword(s):  
Shock Wave ◽  
Shock Tube ◽  
Shock Front ◽  
Compressible Flows ◽  
Wave Speed ◽  
Initial Pressure ◽  
Normal Shock ◽  
Relative Area ◽  
Simple Analytical Model ◽  
Pressure Oscillations

Unsteady compressible flows resulting from the incomplete burst of the shock tube diaphragm are investigated both experimentally and numerically for different initial pressure ratios and opening diameters. The intensity of the shock wave is found to be lower than that corresponding to a complete opening. A heuristic relation is proposed to compute the shock strength as a function of the relative area of the open portion of the diaphragm. Strong pressure oscillations past the shock front are also observed. These multi-dimensional disturbances are generated when the initially normal shock wave diffracts from the diaphragm edges and reflects on the shock tube walls, resulting in a complex unsteady flow field behind the leading shock wave. The limiting local frequency of the pressure oscillations is found to be very close to the ratio of acoustic wave speed in the perturbed region to the shock tube diameter. The power associated with these pressure oscillations decreases with increasing distance from the diaphragm since the diffracted and reflected shocks partially coalesce into a single normal shock front. A simple analytical model is devised to explain the reduction of the local frequency of the disturbances as the distance from the leading shock increases.

The Decompression Behaviour of Carbon Dioxide in the Dense Phase

2012 ◽  
Author(s):  
Andrew Cosham ◽  
David G. Jones ◽  
Keith Armstrong ◽  
Daniel Allason ◽  
Julian Barnett
Keyword(s):  
Carbon Dioxide ◽  
Natural Gas ◽  
Shock Tube ◽  
Gaseous Phase ◽  
Initial Pressure ◽  
Successful Implementation ◽  
Dense Phase ◽  
Test Programme ◽  
Rich Mixtures ◽  
Arrest Toughness

Pipelines can be expected to play a significant role in the transportation infrastructure required for the successful implementation of carbon capture and storage (CCS). National Grid is undertaking a research and development programme to support the development of a safety justification for the transportation of carbon dioxide (CO2) by pipeline in the United Kingdom. The ‘typical’ CO2 pipeline is designed to operate at high pressure in the ‘dense’ phase. Shock tube tests were conducted in the early 1980s to investigate the decompression behaviour of pure CO2, but, until recently, there have been no tests with CO2-rich mixtures. National Grid have undertaken a programme of shock tube tests on CO2 and CO2-rich mixtures in order to understand the decompression behaviour in the gaseous phase and the liquid (or dense) phase. An understanding of the decompression behaviour is required in order to predict the toughness required to arrest a running ductile fracture. The test programme consisted of three (3) commissioning tests, three (3) test with natural gas, fourteen (14) tests with CO2 and CO2-rich mixtures in the gaseous phase, and fourteen (14) tests with CO2 and CO2-rich mixtures in the liquid (or dense) phase. The shock tube tests in the liquid (dense) phase are the subject under consideration here. Firstly, the design of the shock tube test rig is summarised. Then the test programme is described. Finally, the results of the dense phase tests are presented, and the observed decompression behaviour is compared with that predicted using a simple (isentropic) decompression model. Reference is also made to the more complicated (non-isentropic) decompression models. The differences between decompression through the gaseous and liquid phases are highlighted. It is shown that there is reasonable agreement between the observed and predicted decompression curves. The decompression behaviour of CO2 and CO2-rich mixtures in the liquid (dense) phase is very different to that of lean or rich natural gas, or CO2 in the gaseous phase. The plateau in the decompression curve is long. The following trends (which are the opposite of those observed in the gaseous phase) can be identified in experiment and theory: • Increasing the initial temperature will increase the arrest toughness. • Decreasing the initial pressure will increase the arrest toughness. • The addition of other components such as hydrogen, oxygen, nitrogen or methane will increase the arrest toughness.

Effects of hydrogen impurities on shock structure and stability in ionizing monatomic gases: 2. Krypton

1977 ◽  
Vol 55 (14) ◽  
pp. 1269-1279 ◽  
Author(s):  
I. I. Glass ◽  
W. S. Liu ◽  
F. C. Tang
Keyword(s):  
Shock Tube ◽  
Shock Front ◽  
Initial Pressure ◽  
Adsorbed Water ◽  
Radiation Energy ◽  
Shock Structure ◽  
Wall Material ◽  
Quasi Equilibrium ◽  
Relaxation Length ◽  
Electron Cascade

At shock Mach numbers [Formula: see text] in pure krypton, at initial pressures p0 ~ 5 Torr, and final electron number densities ne ~ 1017 cm−3, the translational shock front in a 10 cm × 18 cm hypervelocity shock tube develops sinusoidal instabilities which affect the entire shock structure including the ionization relaxation region, the electron-cascade front and the final quasi-equilibrium state. By adding a small amount of hydrogen (~0.5% of the initial pressure), the entire flow is stabilized. However, the relaxation length for ionization is drastically reduced to about one half of its pure-gas value. Unlike argon the stability appears to diminish with the addition of hydrogen beyond about 0.5%. Using the familiar two-step collisional model coupled with radiation-energy loss and the appropriate chemical reactions, it was possible from dual-wavelength interferometric measurements to deduce a more precise value for the krypton–krypton collision excitation cross-section, S*Kr–Kr = 1.2 × 10−19 cm2/eV, with or without the presence of hydrogen impurities. The reason for the success of hydrogen, and not other gases, in bringing about stabilized Shock waves in argon and krypton is not clear. It was also found that the electron-cascade front approached closely to the translational-shock front with increasing proximity to the shock-tube wall. This effect appears independent of the wall material and is not affected by the evolution of adsorbed water vapour from the walls or by water added deliberately to the test gas. The sinusoidal instabilities investigated here may offer some important clues to the abatement of instabilities that lead to detonations and explosions.

ACCELERATION AND DECELERATION OF PLASMAS IN ELECTROMAGNETIC SHOCK-TUBES

1963 ◽  
Vol 41 (10) ◽  
pp. 1591-1603 ◽  
Author(s):  
G. D. Cormack
Keyword(s):  
Shock Tube ◽  
Initial Pressure ◽  
Large Mass ◽  
Experimental Results ◽  
Shock Tubes ◽  
Electromagnetic Shock ◽  
Proposed Model ◽  
Theoretical Predictions ◽  
Wave Forms ◽  
Acceleration And Deceleration

The applicability of snowplough theory for the description of the motion of plasmas in electromagnetic shock-tubes is studied. The effects of various means of mass pickup and of various wave forms of driving current are included in the analysis. A comparison of the theoretical predictions with experimental results reveals the importance of materials eroded from the components of the driver. Snowplough theory is also found to predict the observed motion of the decelerating plasma fairly accurately when the initial pressure in the shock tube is low and the mass of the driver gases large. The proposed model for the decelerating plasma is suggestive of one reason, a large mass of driver gases present, why various workers have obtained different values for β in the often-quoted relation [Formula: see text].

Measurement of microwave reflexion from a longitudinally magnetized plasma-filed co-axial wave-guide

1971 ◽  
Vol 5 (1) ◽  
pp. 89-105 ◽  
Author(s):  
M. L. G. Oldfield ◽  
R. N. Franklin
Keyword(s):  
Magnetic Field ◽  
Shock Tube ◽  
Microwave Plasma ◽  
Axial Magnetic Field ◽  
Initial Pressure ◽  
Coaxial Line ◽  
Plasma Boundary ◽  
Magnetized Plasma ◽  
Electron Collision ◽  
Ion Density

The voltage refiexion coefficient from a vacuum-plasma boundary in a co-axial transmission line with an axial magnetic field B0 applied has been measured. The results agree well with a previously published theory for conditions where the microwave-, plasma-, electron collision-, and electron cyclotron-frequencies are of the same order. A 9 GHz co-axial microwave probe is mounted along the axis of a 44mm diameter, hydrogen driven, dry air filled, shock tube in an axial d.c. magnetic field. Shock ionized air (Ms = 9–14, T 4000 °K, electron density nc = 1017 to 3 x 1019 m−3, initial pressure p0 = 1–10 Torr, electron collision frequency v = 1010 to 1011/S) fills the coaxial line and partially reflects a microwave signal. Initially this probe, and a similar rectangular waveguide probe, were used with B0 = 0 to calibrate the plasma (ne, v) in terms of the shock tube parameters (p0, Ms). Measurement of the saturated-ion current to electrostatic probes inset into a fiat plate in the shock tube flow showed that the sheath-edge ion density is close to the predicted free-stream equilibrium ion density. The apparent ionization potential derived from electrostatic probe results decreased as p0 was reduced from 10 to 1 Torr.

scholarly journals RFNC–VNIITF multifunctional shock tube for investigating the evolution of instabilities in nonstationary gas dynamic flows

2003 ◽  
Vol 21 (3) ◽  
pp. 381-384 ◽  
Author(s):  
Yu.A. KUCHERENKO ◽  
O.E. SHESTACHENKO ◽  
S.I. BALABIN ◽  
A.P. PYLAEV
Keyword(s):  
Shock Wave ◽  
Shock Tube ◽  
Turbulent Mixing ◽  
Wire Array ◽  
Density Ratio ◽  
Initial Pressure ◽  
Taylor Instability ◽  
Interfacial Instability ◽  
Rayleigh Taylor Instability ◽  
Dynamic Flows

The design, operation, and functionality of the multifunctional shock tube (MST) facility at the Russian Federal Nuclear Center–VNIITF are described. When complete, the versatile MST consists of three different driver sections that permit the execution of three different classes of experiments on the compressible turbulent mixing of gases induced by the (1) Richtmyer–Meshkov instability (generated by a stationary shock wave with shock Mach numbers <5), (2) Rayleigh–Taylor instability (generated by compression wave such that acceleration of the interface is <105g0, whereg0= 9.8 m/s2), and (3) combined Richtmyer–Meshkov and Rayleigh–Taylor instability (generated by a nonstationary shock wave with initial pressure at the front 5 × 106Pa and acceleration of ≤106g0of the interface). For each of these types of experiments, the density ratio of the gases is ρ2/ρ1≤ 34. Perturbations are imposed on a thin membrane, embedded in a thin wire array of microconductors that is destroyed by an electric current. In addition, various limitations of experimental techniques used in the study of interfacial instability generated turbulent mixing are also briefly discussed.

Influence of Pipe Friction and Heat Transfer on Pressure Waves in Gases: Effects in a Shock Tube

1964 ◽  
Vol 6 (3) ◽  
pp. 278-292 ◽  
Author(s):  
F. K. Bannister
Keyword(s):  
Heat Transfer ◽  
Shock Tube ◽  
Wave Motion ◽  
Combustion Engine ◽  
Pressure Ratio ◽  
Initial Pressure ◽  
Finite Amplitude ◽  
Theoretical Treatment ◽  
Pressure Waves ◽  
Engine Exhaust

Finite-amplitude pressure waves travelling in gases in pipes are subject to the influence of pipe friction and heat transfer to or from the pipe wall. Where the pipe section is moderate or small these factors cause serious departures from the classical laws governing wave motion under frictionless adiabatic conditions. The paper presents a theoretical analysis of the effects of friction and heat transfer, assuming that at any instant and location the frictional force and heat-transfer rate in a pipe element are those for steady flow at the same Reynolds number. Based on the three-directional method of characteristics, a step-by-step procedure is developed for the solution of practical problems involving wave motion in pipes of moderate diameter, for example, in internal-combustion engine exhaust pipes. The procedure is illustrated by application to the wave motion in a simple shock tube of moderate initial pressure ratio. Experiments using such a shock tube confirm the validity of the theoretical treatment.

The boundary layer in a shock tube

1972 ◽  
Vol 56 (1) ◽  
pp. 19-47 ◽  
Author(s):  
J. D. A. Walker And ◽  
S. C. R. Dennis
Keyword(s):  
Boundary Layer ◽  
Thermal Properties ◽  
Shock Tube ◽  
Constant Temperature ◽  
Tube Wall ◽  
Initial Pressure ◽  
Compressible Boundary Layer ◽  
Boundary Layer Equations ◽  
Expansion Waves ◽  
Medium Strength

The boundary layer that forms on the walls of a shock tube, after the diaphragm which initially separates two gases at different pressures is burst, is investigated. Both the driver and driven gases are assumed to have the same thermal properties and the shock tube wall is maintained at constant temperature. Crocco variables are used and a method is presented for solving the compressible boundary-layer equations within the tube in similarity variables. Three cases, corresponding to different initial pressure ratios of the driver and driven gases, are calculated which are representative of weak and medium-strength shock and expansion waves.

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