Shock tube

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

Study of the High-Temperature Autoignition of n-Alkane/O/Ar Mixtures

Abstract: Ignition time measurements of propane, n-butane, n-heptane, and n-decane have been studied behind reflected shock waves over the temperature range of 1300-1700 K and pressure range of 1-6 atm. The test mixture compositionvaried from approximately 2-20% O 2 , and the equivalence ratio ranged from 0.5 to 2.0. To determine more precisely the fuel mole fraction of the test mixture, a new technique has been employed in which a 3.39-μm HeNe laser and multiple-pass setup is utilized to measure the fuel in situ by absorption. Ignition delay times were measured at the shock tube endwall by a CH emission diagnostic (431 nm) that viewed the shock-heated mixture through a window in the endwall. This enabled the ignition time at the unperturbed endwall conditions to be determined accurately, thereby avoiding problems inherent in measuring ignition times from the shock tube sidewall. A parametric study of the experimental data reveals marked similarity of the ignition delay time characteristics among these four n-alkanes, and a unique correlation is presented in which the stoichiometric ignition time data for all four n-alkanes has been correlated into a single expression with an R 2 value of 0.992: Τ=9.4×10 - 1 2 P - 0 . 5 5 X O 2 - 0 . 6 3 C - 0 . 5 0 exp(46,550/RT) where the ignition time is in seconds, pressure in atmospheres, the activation energy in calories per mole, X O 2 is the mole fraction of oxygen in the test mixture, and C is the number of carbons atoms in the n-alkane. Comparisons to past ignition time studies and detailed kinetic mechanisms further validate the correlations presented here.

Experiments on the Richtmyer-Meshkov instability of an air/SF 6 interface

Abstract: Results of flow visualization experiments of an impulsively accelerated plane interface between air and SF6 are reported. The shock tube used for the experiments has a larger test section than in previous experiments. The larger extent of uniform test flow relative to nonuniform boundary-layer flow permits unambiguous interpretation of flow-visualization photographs, and the influence of shock-wave/boundary-layer interactions is no longer dominant. The strong wall vortex observed in previous studies is not observed in these experiments. It is found that the thin membrane, which forms the initially plane interface, has a significant influence on the initial growth rate of the interface thickness. However, the measured growth rates after the first reflected shock are independent of membrane configuration and are in good agreement with analytical predictions.