Title: Temporally and spatially resolved X-ray densitometry in a shock tube

Abstract

Gas densities were measured by x-ray absorption spectroscopy to examine spatial inhomogeneity in density behind incident and reflected shock waves in a miniature (12.7 mm bore) high repetition rate shock tube. Shock waves were generated in argon. The pressure and temperature behind the incident shock were P₂ ~ 1.72 bar and T₂ ~ 800 K, while those behind the reflected shock were P₅ ~ 6.5 bar and T₅ ~ 1480 K. Time-resolved line-of-sight transmission measurements using x-rays at 9 keV photon energy were made along various axial and transverse locations covering the entire shock tube cross section. The x-ray transmission at each location was converted to pathlength-integrated densities, which in some conditions could be further converted to pathlength-averaged densities. The measured gas densities were compared with those calculated by the normal shock wave relations, and good agreement was found in the preshock and immediately behind the incident shock regions. Similar agreement was found for reflected shock conditions very near the endwall. However, increasingly large differences between the measured and calculated gas densities were found as distance from the endwall increased. Furthermore, reconstruction by Abel inversion allowed time and radially resolved densities to be obtained from the transverse measurements. While themore » profiles measured in this experiment are of insufficient signal-to noise level and resolution to definitively assign boundary layer thicknesses, future improvements may be able to do this. The radially resolved densities reveal growing sidewall thermal boundary layers in gases behind the reflected shock. These reconstructions were compared with a model of the thermal boundary layer and are consistent with values of the thermal boundary layer thickness being between 0.25 mm and 1 mm at 0.7 ms after shock reflection.« less

Authors:

Shaik, R. A.  ^[1];

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Kastengren, A. L. ^[2]; Tranter, R. S. ^[3]; Lynch, P. T. ^[1]

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+ Show Author Affiliations

1. Univ. of Illinois, Chicago, IL (United States)
2. Argonne National Lab. (ANL), Lemont, IL (United States). Advanced Photon Source (APS)
3. Argonne National Lab. (ANL), Lemont, IL (United States)

Publication Date:

Sat Oct 30 00:00:00 EDT 2021

Research Org.:

Argonne National Lab. (ANL), Argonne, IL (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES). Chemical Sciences, Geosciences & Biosciences Division; USDOE

OSTI Identifier:

1776718

Alternate Identifier(s):

OSTI ID: 1775669

Grant/Contract Number:  

AC02-06CH11357; 1747774

Resource Type:

Accepted Manuscript

Journal Name:

Combustion and Flame

Additional Journal Information:

Journal Volume: 224; Journal ID: ISSN 0010-2180

Publisher:

Elsevier

Country of Publication:

United States

Language:

English

Subject:

42 ENGINEERING; Abel inversion; Boundary layer; Shock tube; Shock waves; Tomographic reconstruction; X-ray absorption