Shock tube

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

Combustion of CO/H2 mixtures at elevated pressures ☆

Abstract: The high pressure oxidation of dilute CO mixtures doped with 150–200 ppm of H 2 has been studied behind reflected shock waves in the UIC high pressure single pulse shock tube. The experiments were performed over the temperature range from 1000 to 1500 K and pressures spanning 21–500 bars for stoichiometric ( Φ = 1) and fuel lean ( Φ = 0.5) oxidation. Stable species sampled from the shock tube were analyzed by standard GC, GC/MS techniques. The experimental data obtained in this work were simulated using a detailed model for H 2 /CO combustion that was validated against a variety of experimental observables/targets that span a wide range of conditions. These simulations have shown that within experimental error the model is able to capture the experimental trends for the lower pressure data sets (average nominal pressures of 24 and 43 bars). However the model under predicts the CO and O 2 decay and subsequent CO 2 formation for the higher pressure data sets (average nominal pressures of 256 and 450 bars). The current elevated pressure data sets span a previously unmapped regime and have served to probe HO 2 radical reactions which appear to be among the most sensitive reactions in the model under these conditions. With updated rate parameters for a key HO 2 radical reaction OH + HO 2 = H 2 O + O 2 , the model is able to reconcile the elevated pressure data sets thereby extending its capability to an extreme range of conditions.

A suggestion for the numerical solution of the steady Navier-Stokes equations.

Abstract: The great difficulties connected with the numerical solution of the steady compressible Navier-Stokes equations can be avoided if the steady flow is considered as the asymptotic form of a time-dependent flow, thus profiting from the techniques available for the numerical solution of initial value problems. In practice, the numerical procedure can imitate the natural development of the final steady flow in a shock tube. It is observed, however, that the accuracy and the consistency of the transient flow computations is here of no concern; this part of the calculations is merely fulfilling the function of an iteration procedure. This gives a great freedom in the choice of the numerical schemes, which therefore can be adjusted to fit, in the best way, the stability requirements. As a simple example of this technique, calculations have been performed of the one-dimensional formation of a standing shock in a divergent duct with initially supersonic flow when a back pressure is applied. Stability of the calculations is assured through the use of a suitable, conditionally stable, difference scheme. The results of the calculations show indeed that stability can be obtained in practice, provided certain precautions are taken in the application of the back pressure, and that the resulting flow converges to the expected mixed supersonic-subsonic flow with a standing shock. However, for sufficiently low viscosity the steady solution exhibits a wavy character with no counterpart in nature. These waves are analytically shown to appear whenever the space interval becomes larger than half the shock thickness.

Calibration of reaction temperatures in a very high pressure shock tube using chemical thermometers

Abstract: Two chemical thermometers, 1,1,1-trifluoroethane and cyclohexene, have been used to calibrate the temperatures behind reflected shock waves, T5real, in a unique high-pressure, single-pulse shock tube. Experiments with 1,1,1-trifluoroethane were performed at nominal postshock pressures of 5000 psi and 9000 psi, and T5real was calculated from the extent of the reaction and literature values for k∞. Both parent molecule decomposition and product formation were used to calculate the extent of reaction. At each pressure the two methods of calculating T5real are in excellent agreement. The values for T5real obtained from the cyclohexene experiments are in good agreement with those from 1,1,1-trifluoroethane. The range of the temprature calibration is 1050–1350 K. No discernable pressure dependence between the two sets of experiments was observed for the calculated values of T5real. The effect of a 10% rise in pressure during the residence time on the calculated temperatures was also examined and is found to give rise to only small errors in T5real. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 722–731, 2001