Showing papers on "Shock tube published in 1980"
TL;DR: In this article, the ignition delay characteristics of methane-oxygen mixtures highly diluted with argon were studied behind reflected shock waves, and the equivalence ratio was varied from 0.2 to 5.0.
Abstract: A brief summary of the previous experimental studies on the ignition of methane in shock tubes is given by way of introduction. The ignition delay characteristics of methane-oxygen mixtures highly diluted with argon were studied behind reflected shock waves. Ignition was identified by pressure rise and visible light emissions using piezoelectric transducers and photomultiplier detection respectively. The measurements covered a temperature range of 1600-2100 K and a pressure range of 1 to 6 atm. The equivalence ratio was varied from 0.2 to 5.0. The following expression $ was found to correlate the results very well.
25 citations
TL;DR: In this article, a new method of generating a tension pulse in a liquid column is described, where the test liquid (deionised water) is contained in the lower part of a sealed vertical tube, the upper part of which contains a combustible gaseous mixture.
Abstract: A new method of generating a tension pulse in a liquid column is described. The test liquid (deionised water) is contained in the lower part of a sealed vertical tube, the upper part of which contains a combustible gaseous mixture. When a detonation wave is initiated in the gas it is propagated down the liquid column as a compressional wave. At the base of the column, which is supported by a thin Mylar diaphragm, this pulse is reflected as an upward-going tension pulse. The pressure changes in the liquid are monitored by pressure transducers mounted in the wall of the tube and the cavitation bubbles are studied using schlieren photography techniques. The measured value of the breaking tension agrees well with those of other dynamic methods.
19 citations
18 citations
TL;DR: In this paper, an annular shock tube is fitted with axisymmetric area contraction, which redirects an incident shock into a cylindrical implosion chamber, and the contraction profile is designed in accordance with Whitham's ray-shock theory, and a three-element profile is found to provide the best overall performance on the basis of twodimensional tests.
Abstract: AN improved experimental technique for the production of cylindrical converging shock waves is presented. This is accomplished with an annular shock tube fitted with an axisymmetric area contraction which redirects an annular incident shock into a cylindrical implosion chamber. The contraction profile is designed in accordance with Whitham's ray-shock theory, and a three-element profile is found to provide the best overall performance on the basis of twodimensional tests. Experiments with a three-element conical contraction demonstrate that highly symmetrical cylindrical implosions may be achieved by this method, and that the cylindrical shock amplification is well predicted by the Chester-Chisnell-Whitham (CCW) area Mach No. rule.
17 citations
TL;DR: In this paper, an extension of shock tube techniques to the study of ignition and burnout of pulverized coal is examined, and nonintrusive optical techniques for characterizing the particle size distribution and the particle temperature as a function of time during burnout are described.
Abstract: The extension of shock tube techniques to the study of ignition and burnout of pulverized coal is examined. Nonintrusive optical techniques for characterizing the particle size distribution and the particle temperature as a function of time during burnout are described. Comparison of surface oxidation rates of soot particles and several bituminous coals obtained in the shock tube are in excellent agreement with the higher temperature results found in other apparatus. Because of the wide but controllable ranges of total pressures, oxygen parital pressures, particle temperatures, and coal loadings obtainable, the shock tube offers an additional instrument for the study of solid particle ignition and reactivity under conditions comparable to those found in mine explosions and anticipated in high intensity combustors.
14 citations
TL;DR: In this paper, the double-Mach reflection (DMR) of oblique shock waves in pseudo-stationary flows has been investigated, and the equations of motion of the first and second triple points were formulated, as well as the relative motion between these two triple points.
Abstract: The double-Mach reflection (DMR) of oblique shock waves in pseudo-stationary flows has been investigated. The equations of motion of the first and second triple point were formulated, as well as the relative motion between these two triple points. The equation of motion for each triple point consists of 14 nonlinear algebraic equations. An analytical method of solution is presented. Consequently, for the first time a complete analytical solution of a DMR is given. Utilizing this analytical solution a method for predicting the second triple-point trajectory angle is developed. The analytical results are compared with experiments that were performed on the 10 x 18 cm Hypervelocity Shock Tube at the University of Toronto Institute for Aeronautical Studies. Good agreement was obtained.
13 citations
TL;DR: In this paper, the authors evaluate the effect of gas cooling on reaction kinetics and show that the simple flow hemisphere-Tbl overlay greatly overestimates cooling, that Tbl growth is retarded in the vicinity of the orifice, and that center core sampling with a skimmer is strongly favored.
Abstract: In shock tube studies of reaction kinetics the gas to be analyzed is often leaked through a pin hole at the tube end wall into a mass spectrometer. Such samples may be influenced by the growing thermal boundary layer (Tbl) at the cold end wall. In order to assess the effect of this cooling on kinetic measurements, the temperature history of the gas sample reaching the analyzer must be known. This paper allows, based on independent orifice flow and Tbl solutions and their limited interaction, an evaluation of the extent of gas cooling. It shows that the simple flow hemisphere–Tbl overlay greatly overestimates cooling, that Tbl growth is retarded in the vicinity of the orifice, and that center‐core sampling with a skimmer is strongly favored. It provides the kineticist with the basic tools required to assess these effects and gives some illustrative kinetic examples.
10 citations
9 citations
8 citations
01 Jan 1980
TL;DR: In this article, it was shown that magnetic shear has a stabilizing effect on the current-carrying layer of the shocked gas and a clean, chemically inert metal wall is even more effective.
Abstract: Magnetic fields in the range 0.2 – 2.0 MG produce shocks in 0.1 – 1.0 atmosphere xenon gas which have shock mach numbers as high as 100. Using pulsed x-ray and other diagnostics, our studies of velocity, compression, and luminosity are in good agreement with a simple snowplow theory. In some of the experiments, ultraviolet radiation from the shocked xenon produces luminous precursors and interactions with the metal walls of the shock tube. The addition of an ultraviolet absorbing organic impurity vapor diminishes the amplitude of these effects. A clean, chemically inert metal wall is even more effective. Further experiments show that magnetic shear has a stabilizing effect on the current-carrying layer of the shocked gas. We conclude that a megagauss magnetic field is a useful shock tube driver for producing high velocity shock waves.
8 citations
TL;DR: In this paper, the authors compare the heat transfer rate of flat plate nickel and silicon dioxide surfaces from dissociated hydrogen/argon mixtures at temperatures from 2000 to 6000 K, and show that the results may be interpreted to yield an experimental value tor the catalytic efficiency (γ') of silicon dioxide surface to hydrogen atom recombination of 25 × 10−4.
TL;DR: In this paper, it was shown that at high velocities of shock waves (V ≳ 9.5 km/sec) an important factor influencing the rate of ionization is the depletion of the number of excited states of the atoms through de-excitation.
Abstract: It is shown that at high velocities of shock waves (V ≳ 9.5 km/sec) an important factor influencing the rate of ionization is the depletion of the number of excited states of the atoms through de-excitation. In the case of low pressures (p∞ ≲ 1 torr) and for a bounded and optically transparent region of gas heated by the shock wave (for example, for the motion of gas in a shock tube or in a shock layer near a blunt body), the effective ionization rate kf depends on the pressure [1], which leads to violation of the law of binary similarity which holds under these conditions without allowance for de-excitation. On leaving the relaxation zone, the gas arrives at a stationary state with constant parameters differing from those in thermodynamic equilibrium. The electron concentration and also the radiation intensity in the continuum and the lines are lower than the values for thermodynamic equilibrium. These considerations explain the results of known experiments and some new experiments on ionization and radiation of air behind a travelling shock wave.
TL;DR: A lower limit of 4 on the ratio of maximum to minimum turbulent intensities in contact surface instabilities has been estimated in this paper, where the fluctuations are interpreted using a boundary layer model of contact surface flow and results form a kinetic theory of turbulence.
Abstract: A shock tube's driver gas can apparently provide flow with turbulent bursts. The fluctuations are interpreted using a boundary layer model of contact surface flow and results form a kinetic theory of turbulence. With this, a lower limit of 4 on the ratio of maximum to minimum turbulent intensities in contact surface instabilities has been estimated.
TL;DR: In this paper, a characteristic method has been used to study the propagation of a strong diverging cylindrical shock wave through a rotating gas, and an analytical expression for shock velocity has been obtained.
Abstract: A characteristic method has been used to study the propagation of a strong diverging cylindrical shock wave through a rotating gas. An analytical expression for shock velocity has been obtained. It is shown that, for smaller values of the propagation distancer, the shock velocity must decrease with shock propagation; for larger values ofr, however, it must increase with further advancement of the shock. The shock propagation distance corresponding to the minimum value of the shock velocity has also been obtained.
TL;DR: In this article, the authors measured the vibrational relaxation times in SO 2, SO 3 Ar (11, 20% and 54% SO 2 ) and SO 2 ǫHe (9.5%) using the laser schlieren technique in the temperature ranges 550-1200 K, 700-2100 K and 700-1600 K respectively.
TL;DR: In this paper, a scanning i.r. spectrometer was used for the quantitative spectral measurement of the signatures and band strengths of molecular boron species using the shock tube technique.
Abstract: Shock-tube measurements are described for the quantitative spectral measurement of the i.r. signatures and band strengths of molecular boron species. The boron species were effectively isolated under conditions of optimum concentration and calculated thermodynamic conditions using the shock tube technique. Spectral measurements were performed using a scanning i.r. spectrometer which was specially designed for these experiments. System calibration experiments were performed using shock heated CO and CO 2 mixtures in diluent argon, and the measured band strengths were in excellent agreement with the accepted values for these molecules. Quantitative spectral measurements were performed on the HBO 2 fundamentals at 2.7 and 5.0 μm and OBF at 5.0 μm. The corresponding band strength values measured for these band systems were 650, 1375, and 1760 cm -2 amagat -1 , respectively.
TL;DR: In this paper, a laser schlieren method is applied to measure the density-gradient profile of the shock-tube end-wall boundary layer in argon, and the experimental boundary-layer structure is found to agree within an error bound of 2% with the theoretical calculation based on accurate thermal-conductivity data, if the variation of the pressure is taken into account.
TL;DR: In this article, a dual-wavelength Mach-Zehnder interferometer with the hypervelocity shock tube at shock Mach numbers M∼13 and 16 at an initial pressure of 5 Torr and temperature of 300 °K was used to measure the plasma density and electron number density profiles of ionizing-argon flows behind moving shock waves.
Abstract: Plasma‐density and electron‐number‐density profiles of ionizing‐argon flows behind moving shock waves were measured using a dual‐wavelength Mach–Zehnder interferometer with the hypervelocity shock tube at shock Mach numbers M∼13 and 16 at an initial pressure of 5 Torr and temperature of 300 °K.
TL;DR: Flow of a liquid through distensible tubes is of interest primarily in biological systems, and some properties of shock waves in such tubes are discussed.
Abstract: Flow of a liquid through distensible tubes is of interest primarily in biological systems, and some properties of shock waves in such tubes are discussed. In shock-fixed coordinates, these flows are steady, and the shock is associated with an increase of pressure and cross-sectional area. Shock transition is analyzed for two flow models, namely, immediate flow separation, when the flow enters the shock zone, and no separation. Shock properties are expressed in terms of the speed index (ratio of the velocity of the shock to that of a small-amplitude wave) and dissipation (loss of total pressure). Examples are worked out for the thoracic aorta of an anesthetized dog, a perfectly elastic tube, and a partially collapsed tube. Appreciable differences in shock velocity and dissipation result if either flow separation or no separation is assumed.
Abstract: New systematatic trends in one of the performance parameters of pressure loaded arc driven shock tubes have been determined. For a given configuration, the Mach number increases with the cube root of capacitor energy; however, the initial driver gas pressure is relatively unimportant. A qualitative model based on the assumption of Joule‐preheating by the arc discharge is discussed.
01 Aug 1980
TL;DR: In this paper, the authors investigated the stability of converging cylindrical shock waves in an annular shock tube and found that initially symmetric shocks are found to retain their symmetry during implosion except at small radius where a breakdown in shock front curvature eventually occurs.
Abstract: S of converging cylindrical shock waves is investigated experimentally in an annular shock tube. Initially symmetric shocks are found to retain their symmetry during implosion except at small radius where a breakdown in shock front curvature eventually occurs. Artificially generated shock front perturbations are observed to promote this type of instability. In all cases, instability is manifest by the appearance of vortex pairs during the expansive shock motion which follows the implosion.
01 Jan 1980
TL;DR: In this article, a 6.4 cm-diameter scale model of the Jovian entry vehicle is tested in an electric-arc-driven shock tube and a 5 cmdiameter sphere model is tested with sensors imbedded in the models in a stream consisting of 10% hydrogen in a bath of either neon or argon.
Abstract: A 6.4-cm-diameter scale model of the Jovian entry vehicle is tested in an electric-arc-driven shock tube and a 5-cm-diameter sphere model is tested in a combustion-driven shock tube and in an electric-arc-driven shock tunnel. The radiative heat-transfer rate and pressure on the front and the base regions are measured in the absence of ablation with sensors imbedded in the models in a stream consisting of 10% hydrogen in a bath of either neon or argon. The measured radiative heat-transfer rates and pressures range to about 22 kW/sq cm and 12 atm, respectively, at the front stagnation point. The ratio of the radiative heat-transfer rate at the base stagnation point to that at the front stagnation point is found to be about 1/4 for the sphere at Mach 1.8, about 1/30 for the sphere at Mach 4.8, and about 1/6 for the scale model at Mach 1.7. The present experimental results agree well with the theoretical predictions of Park, thus indicating that Park's theory is valid.
01 Apr 1980
TL;DR: In this paper, a 0.914m (36in.)-dia. shock tube was constructed on the New Mexico State University caompus to simulate low-grade explosions.
Abstract: This report documents the construction of a 0.914-m (36-in.)-dia. shock tube on the New Mexico State University caompus. Highly variable low-grade explosions can be simulated with the shock tube. We plan to investigate the response of nuclear facility ventilation system components to low-grade explosions. Components of particular interest are high-capacity, high efficiency paticulate air (HEPA) filters. Shock tube construction details, operating principles, firing sequence, and preliminary results are reported.
01 Jan 1980
TL;DR: In this article, an explosive driven, water filled, conical shock tube was designed and evaluated regarding its ability to amplify a charge weight and to produce hydrodynamic spherical shock waves.
Abstract: An explosive driven, water filled, conical shock tube was designed and evaluated regarding its ability to amplify a charge weight and to produce hydrodynamic spherical shock waves. The results show that the shock waves in the tube are essentially spherical in nature--with an initial exponential shape, peak pressure attenuation as (l/R) 1 · 13 and the time constant spreading roughly as
TL;DR: The vibrational relaxation time of O2(1Δg) in oxygen has been measured by observing the variation of dimol emission at 579 nm on shock heating the products from a flowing discharge in oxygen, in the temperature range 1000-1850 K as mentioned in this paper.
Abstract: The vibrational relaxation time of O2(1Δg) in oxygen has been measured by observing the variation of dimol emission at 579 nm on shock heating the products from a flowing discharge in oxygen, in the temperature range 1000–1850 K. The results are similar to those obtained for ground-state oxygen, O2(3∑–g), in previous studies.While the change in emission in the pre-shock glow supports the earlier conclusions of Parker and Ritke concerning electronic deactivation of the v= 1 state, the results at high temperatures appear to support the conclusion of Collins and Husain on the predominance of V–V exchange.
TL;DR: A TEA CO2 laser was simultaneously Q-switched and mode-locked when an underdense plasma was injected into the cavity as discussed by the authors, which was produced in an electromagnetic shock tube.
Abstract: A TEA CO2 laser was simultaneously Q-switched and mode-locked when an underdense plasma was injected into the cavity. The plasma was produced in an electromagnetic shock tube. Plasma density and te...