Development of X-ray absorption diagnostics for gas-phase reacting flows

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Accurate experimental measurements are critical to the design and understanding of efficient combustion systems. While new heterogeneous combustion technologies such as Porous Media Burners (PMBs) have demonstrated favorable combustion properties including an extended lean flammability limit, low emissions, and wide dynamic power range, they also pose challenges for traditional experimental techniques. Because combustion occurs within a porous ceramic matrix, physical probes can disturb the combustion environment while engineering optical access becomes difficult. Further, data provided by existing methods is generally of insufficient spatial dimensionality to fully describe complex internal PMB physics. In this context, the development of new diagnostics that can provide measurements of relevant physical quantities non-intrusively, without optical access, and with high spatial resolution becomes a challenge in creating experimental datasets that improve fundamental physical understanding of PMB systems. In this work, a diagnostic for gas-phase reacting flows is developed based on the principles of X-ray computed Tomography (XCT) at clinical energies, and applied to three different systems of interest. Clinical fan-beam XCT is first applied to a turbulent gas-phase krypton jet, and it is shown that X-ray attenuation measurements can resolve krypton mole fraction within the jet in three dimensions with high quantitative accuracy. A cone-beam X-ray system is then used to image a krypton-diluted, premixed Bunsen flame via XCT. Simultaneous data series describing visual emission and X-ray attenuation are performed, and scanner noise trends are evaluated via both experiment and simulation. Comparison of experimental data to an axisymmetric simulation with detailed chemistry is demonstrative of both the utility and phenomenology of the X-ray attenuation signal as a density surrogate in reacting flow measurements. Effects of the krypton contrast agent on important combustion quantities such as flame speed and temperature are also evaluated. Finally, measurements of a porous media burner are performed with cone-beam XCT, and theory is developed to relate X-ray attenuation to gas-phase temperature. Using this method, experiments are performed to demonstrate temperature measurement of a krypton-diluted flame within the optically opaque porous ceramic matrix of the PMB. Temperature measurements in the gas phase are contrasted with direct thermocouple measurements, and the effect of imaging artifacts and experimental uncertainties is analyzed in detail.


Type of resource text
Form electronic; electronic resource; remote
Extent 1 online resource.
Publication date 2017
Issuance monographic
Language English


Associated with Dunnmon, Jared Alexander
Associated with Stanford University, Department of Mechanical Engineering.
Primary advisor Ihme, Matthias
Thesis advisor Ihme, Matthias
Thesis advisor Bowman, Craig T. (Craig Thomas), 1939-
Thesis advisor Eaton, John K
Thesis advisor Pelc, Norbert J
Advisor Bowman, Craig T. (Craig Thomas), 1939-
Advisor Eaton, John K
Advisor Pelc, Norbert J


Genre Theses

Bibliographic information

Statement of responsibility Jared Alexander Dunnmon.
Note Submitted to the Department of Mechanical Engineering.
Thesis Thesis (Ph.D.)--Stanford University, 2017.
Location electronic resource

Access conditions

© 2017 by Jared Alexander Dunnmon
This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).

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