Shock tube

About: Shock tube is a research topic. Over the lifetime, 6963 publications have been published within this topic receiving 99372 citations.

The Refraction of Shock Waves at a Gaseous Interface.

Abstract: A programme of shock tube experiments has been conducted to study the refraction of plane shock waves at interfaces between two gases. Shocks of strength ζ = 0·85 (weak) and ζ = 0·30 (fairly strong) were allowed to impinge, at various angles of incidence, on interfaces between air/CO2 and air/CH4, and the resulting configurations were photographed through a Mach-Zehnder interferometer. From the interferograms, measurements were made of the strengths of the reflected waves, and of the angles of refraction, and the values were compared with the theoretical calculations of Polachek & Seeger (1951). Within the range of parameters for which the refraction model assumed by the theory is applicable–the so-called ‘regular refraction’ region–the observations were in excellent agreement with the theoretical predictions.When the study was extended to ranges of the parameters for which the theory is clearly inadequate, a succession of rather complex ‘irregular refraction’ patterns was observed. Although these configurations were highly interesting qualitatively, each of them involved curved shocks, non-uniform regions of flow, and other less simple processes which discouraged any formal theoretical analysis. On a less rigorous basis, however, it could be shown that these patterns were internally consistent, and that each represented a distortion of a regular refraction process which was reasonable under the prevailing aerodynamic conditions.Certain observations in these refraction experiments appear to be of some significance outside the specific problem. (i) The sensitivity of strong shock refractions to the values of the specific heat ratio λ for the two gases suggests a possible technique for the measurement of λ and its temperature dependence. (ii) Two of the irregular refraction patterns display a transition process which would be equally appropriate to the onset of the Mach configuration in the shock reflection problem. (iii) Some irregular refractions can be considered as special cases in the problem of the interaction of a shock and a boundary layer.

Conservative Models and Numerical Methods for Compressible Two-Phase Flow

Abstract: The paper presents the computational framework for solving hyperbolic models for compressible two-phase flow by finite volume methods. A hierarchy of two-phase flow systems of conservation-form equations is formulated, including a general model with different phase velocities, pressures and temperatures; a simplified single temperature model with equal phase temperatures; and an isentropic model. The solution of the governing equations is obtained by the MUSCL-Hancock method in conjunction with the GFORCE and GMUSTA fluxes. Numerical results are presented for the water faucet test case, the Riemann problem with a sonic point and the water-air shock tube test case. The effect of the pressure relaxation rate on the numerical results is also investigated.

BURNING VELOCITIES AND A HIGH-TEMPERATURE SKELETAL KINETIC MODEL FOR n-DECANE

Abstract: Laminar flame speeds of n-decane/air mixtures were determined experimentally over an extensive range of equivalence ratios at 500 K and at atmospheric pressure. The effect of N2 dilution on the laminar flame speed was also studied at these same conditions. The experiments employed the stagnation jet–wall flame configuration with the flow velocity field determined by particle image velocimetry. Reference laminar flame speeds were obtained using linear extrapolation from low to zero stretch rate. The determined flame speeds are significantly different from those predicted using existing published kinetic models, including a model validated previously against high-temperature data from flow reactor, jet-stirred reactor, shock tube ignition delay, and burner-stabilized flame experiments. A significant update of this model is described that continues to predict the earlier validation experiments as well as the newly acquired laminar flame speed data and other recently published shock-tube ignition del...

Shock-tube investigations on the self-ignition of hydrocarbon-air mixtures at high pressures

Abstract: The self-ignition behaviour of various fuel-air mixtures has been investigated without inert gas dilutionusing a high-pressure shock tube. In order to obtain data directly applicable to the modeling of engine combustion, the shock-tube facility was designed to handle fuel-air mixtures up to initial pressures of more than 40 bar and to achieve measuring times up to 10 ms. As typical representatives of engine fuel components, n-heptane, benzene, iso-octane, methanol, and methyl-tert-butylether (MTBE) were investigated. Two pressure levels for the investigation, 13 bar and nearly 40 bar, have been chosen. The ignition of n-heptane begins with a rapid pressure increase, especially at higher temperatures. Benzene, iso-octane, methanol, and MTBE show a slow initiation of the ignition without distinct pressure peak (mild ignition) at low temperatures, which at higher temperatures changes to a rapid pressure increase after a variable time lag (strong ignition). The strong ignition limit depending on temperature, pressure, and fuel was determined. An investigation was made of the dependence of the ignition delay times of iso-octane and benzene on equivalence ratio and temperature at nearly 40 bar. A comparison of the ignition delay times of all the fuels investigated is presented for stoichiometric mixtures and at two pressure levels.