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Shock tube
About: Shock tube is a research topic. Over the lifetime, 6963 publications have been published within this topic receiving 99372 citations.
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TL;DR: In this article, a nonlocal collisional radiative model was proposed to solve a simplified master equation and include radiative transport and nonlocal absorption in the shock tube. But the model still underpredicts the intensity decay rate in the low-pressure case.
Abstract: Assessment of nonequilibrium thermochemical models for shock-layer radiation in N 2 /CH 4 mixtures is presented via comparisons with spectrally and temporally resolved intensity measurements from a set of shock tube experiments. The experiments were carried out at the Electric Arc Shock Tube facility at NASA Ames Research Center in a rarified environment [13.3-133.3 Pa (0.1 and 1 torr)] representative of the peak heating conditions of a Titan aerocapture trajectory (5-9 km/s). The baseline model that assumes a Boltzmann population of the CN excited states consistently overpredicts the shock-layer radiation intensity at lower pressure [13.3 Pa (0.1 torr)]. A nonlocal collisional radiative model that solves a simplified master equation and includes radiative transport and nonlocal absorption in the shock tube is presented. The proposed model improves the prediction of the nonequilibrium radiation overshoot peak, but still underpredicts the intensity decay rate in the low-pressure case. Further analysis suggests possible reasons for the remaining disagreement, the most likely being a slow CN consumption in the current chemical kinetics model in the intensity fall-off region.
58 citations
TL;DR: In this article, some oxygenated hydrocarbons were tested as pure fuels in two different DI diesel engines, and their emission potential was compared to n-tetradecane combustion.
Abstract: Some oxygenated hydrocarbons were tested as pure fuels in two different DI diesel engines, and their emission potential was compared to n-tetradecane combustion. Two colours pyrometry method was used to infer in-cylinder sooting tendency of tested fuels. Pure pyrolysis of the same fuels was also investigated in a conventional shock lube at high temperature (1700–2500 K) and pressure (9–13 bar), using light scattering/extinction methods. All oxygenated compounds tested in the engines exhibited a strong decrease of soot loading compared with tetradecane combustion. The long soot induction times, as measured in shock tube experiments, and the oxygen content of the fuel molecules seem to provide a plausible explanation of soot lacking in oxygenated fuels combustion. Emission measurements at the exhaust of a four cylinder engine fully confirm the trends obtained by two colours pyrometry and shock tube experiments. As a matter of fact, the oxygenated synthetic fuels strongly reduce both gaseous and total partic...
58 citations
TL;DR: In this paper, the authors evaluated the performance of a new shock tube facility used to produce blast loading in controlled laboratory environments and found that the properties of the shock wave proved to be a function of driver length and driver pressure, and the positive phase of the measured pressure time histories was similar to those generated from actual far-field explosive detonations.
Abstract: This study evaluates the performance of a new shock tube facility used to produce blast loading in controlled laboratory environments. The facility was found to generate a planar shock wave over the tube cross section by measuring the pressure distribution on a massive steel plate located at the end of the tube. The properties of the shock wave proved to be a function of driver length and driver pressure, and the positive phase of the measured pressure–time histories was similar to those generated from actual far-field explosive detonations. However, the shock tube is also suited to investigate fluid–structure interaction effects and the behaviour of materials in blast events. This was demonstrated using a three-dimensional digital image correlation technique to measure the deformation field of thin steel plates. Synchronization of the three-dimensional digital image correlation and pressure measurements enabled a thorough investigation of the entire experiment and identification of fluid–structure intera...
58 citations
01 Jan 2009
TL;DR: In this paper, a new experimental flow facility, an aerosol shock tube, was used to measure diesel fuel ignition delay times at pressures from 2.3 to 8.0m and temperatures from 900 to 1300 K. The aerosol tube combines conventional shock tube methodology with aerosol loading of fuel-oxidizer mixtures.
Abstract: Shock tube ignition delay times were measured for DF-2 diesel/21% O 2 /argon mixtures at pressures from 2.3 to 8.0 atm, equivalence ratios from 0.3 to 1.35, and temperatures from 900 to 1300 K using a new experimental flow facility, an aerosol shock tube. The aerosol shock tube combines conventional shock tube methodology with aerosol loading of fuel-oxidizer mixtures. Significant efforts have been made to ensure that the aerosol mixtures were spatially uniform, that the incident shock wave was well-behaved, and that the post-shock conditions and mixture fractions were accurately determined. The nebulizer-generated, narrow, micron-sized aerosol size distribution permitted rapid evaporation of the fuel mixture and enabled separation of the diesel fuel evaporation and diffusion processes that occurred behind the incident shock wave from the chemical ignition processes that occurred behind the higher temperature and pressure reflected shock wave. This rapid evaporation technique enables the study of a wide range of low-vapor-pressure practical fuels and fuel surrogates without the complication of fuel cracking that can occur with heated experimental facilities. These diesel ignition delay measurements extend the temperature and pressure range of earlier flow reactor studies, provide evidence for NTC behavior in diesel fuel ignition delay times at lower temperatures, and provide an accurate data base for the development and comparison of kinetic mechanisms for diesel fuel and surrogate mixtures. Representative comparisons with several single-component diesel surrogate models are also given.
58 citations
TL;DR: In this article, the authors measured the relaxation times of CO2 in an atmosphere of N2, Ne, He, D2 and H2 and showed that during the approach to equilibrium the relaxation time changes in the way to be expected from the change in the translational temperature.
Abstract: times and that during the approach to equilibrium the relaxation time changes in the way to be expected from the change in the translational temperature. These observations have been confirmed by infrared measurements on shock heated CO2 (Hodgson & line i969) and are consistent with recent laser fluorescence measurements on the rate of deactivation of the asymmetric stretching mode (Hocker, Kovacs, Rhodes, Flynn & Javan i966; Moore, Wood, Ho & Yardley i967). In the present paper results are given for the relaxation times of C02 in an atmosphere of N2, Ne, He, D2 and H2. The object of these experiments was to measure relaxation times over a wide range of temperatures for these collision partners. The results give some insight into the relative importance of the effeets of the reduced masses and force fields at different temperatures. They provide the grounds for testing current calculations of relaxation times and help in the understanding of the collision processes important in the CO2 laser.
58 citations