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X-ray computed microtomography applications for complex geometries and multiphase flow

Lorenzi, M. (2017). X-ray computed microtomography applications for complex geometries and multiphase flow. (Unpublished Doctoral thesis, City, University of London)

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Abstract

In all fields, fundamental and applied research seek to produce experimental measurements without causing interferences to the process being observed. This capability is of paramount importance, since small perturbations of the phenomenon can alter it to the point of producing biased or even incorrect results. Xray techniques, based on synchrotron or laboratory X-ray sources, have attracted the attention of the research and industrial R&D community thanks to their characteristic of having little to no detectable influence on the subject under study. Moreover, if declined as tomography, this technique can provide localized full volume information at the micrometre scale, from which arbitrary shaped geometries and material densities can be deduced.

During this thesis an X-ray microtomography instrument, based on a laboratory X-ray source, has been exploited to gain three main objectives.

The first one is the analysis of how a liquid drop, of water or glycol, adapts its shape to reach an equilibrium state when gently deposed on a flat or patterned surface. So far this has been done using 2D techniques but introducing the knowledge of the third dimension and being able to see the drop shape even in not optically accessible locations, opens new possibilities to better understand the physics that regulate it.

The second one is the reconstruction of the internal geometries of automotive diesel injectors with high resolution to detect and highlight differences between nominal and real geometries, key information to produce more realistic CFD simulations of the flow inside production grade injectors geometries. A scaled -up model made of PEEK was also studied, producing successive tomographies, to detect small geometrical changes induced by part usage, giving an in-depth view of the locations more prone to be damaged by cavitation flow.

The third one is the study of a multiphase flow inside the same scaled-up model injection channel with flowing conditions exhibiting cavitation. The geometry of the non-axisymmetric model mimics the flow pattern of a real diesel injection channel and automotive grade diesel was consequently selected as fluid. Understanding the dependence of cavitation development on flow characteristics in a three-dimensional way, through the determination of the localized void fraction of the multiphase flow, can lead to improvements in the knowledge of such a phenomenon that can guide the design of future fuel injection equipment.

Item Type: Thesis (Doctoral)
Subjects: T Technology > TA Engineering (General). Civil engineering (General)
Divisions: City, University of London theses
School of Engineering & Mathematical Sciences > Engineering
City, University of London theses > School of Mathematics, Computer Science and Engineering theses
URI: http://openaccess.city.ac.uk/id/eprint/19794

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