Shadowgraph, Schlieren and interferometry in a 2D cavitating channel flow

Cavitation plays an important role in fuel atomization mechanisms, but the physics of cavitation and its impact on spray formation and injector efficiency are not well documented yet. Experimental investigations are required to support the development and the validation of numerical models and the d...

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Bibliographic Details
Published in:	Experiments in fluids Vol. 53; no. 6; pp. 1895 - 1913
Main Authors:	Mauger, Cyril, Méès, Loïc, Michard, Marc, Azouzi, Alexandre, Valette, Stéphane
Format:	Journal Article
Language:	English
Published:	Berlin/Heidelberg Springer-Verlag 01-12-2012 Springer Springer Verlag (Germany)
Subjects:	Applied sciences Cavitation Channel flow Computational fluid dynamics Density Energy Energy. Thermal use of fuels Engineering Engineering Fluid Dynamics Engineering Sciences Engineering Thermodynamics Engines and turbines Equipments for energy generation and conversion: thermal, electrical, mechanical energy, etc Exact sciences and technology Fluid dynamics Fluid- and Aerodynamics Fluids mechanics Fundamental areas of phenomenology (including applications) Heat and Mass Transfer Holes Injectors Instrumentation for fluid dynamics Mathematical models Mechanics Nonhomogeneous flows Physics Research Article Shear layers Recirculation Zone Pressure Drop Cavitation Channel Inlet Shear Layer Optical interferometry Motor fuel injection Pipe flow Test facility Schlieren method Internal combustion engine Cavitating flow Experimental study Pulverized fuel Shadowscopy
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Summary:	Cavitation plays an important role in fuel atomization mechanisms, but the physics of cavitation and its impact on spray formation and injector efficiency are not well documented yet. Experimental investigations are required to support the development and the validation of numerical models and the design of tomorrow’s injectors, in the context of pollutant and fuel consumption reduction. The complexity of modern injectors and the extreme conditions of injection do not facilitate experimental investigations. In this paper, experiments are conducted in a simplified geometry. The model nozzle consists of a transparent 2D micro-channel supplied with a test oil (ISO 4113). Three different optical techniques are proposed to investigate the channel flow, with the pressure drop between upstream and downstream chambers as a parameter. A shadowgraph-like imaging technique allows the observation of cavitation inception and vapor cavities development throughout the channel. The technique also reveals the presence of density gradients (pressure or temperature) in the channel flow. However, this additional information is balanced by difficulties in image interpretation, which are discussed in the paper. In addition, a combination of Schlieren technique and interferometric imaging is used to measure the density fields inside the channel. The three techniques results are carefully analyzed and confronted. These results reveal a wealth of information on the flow, with pressure waves generated by bubble collapses, turbulence in the wake of vapor cavities and bubble survival in flow regions of high pressure. Our results also show that cavitation inception is located in the shear layers between the recirculation zones and the main flow, relatively far from the inlet corner, where the pressure is minimum in average. To explain this behavior, we propose a scenario of cavitation inception based on the occurrence and the growing of instabilities in the shear layers.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	0723-4864 1432-1114
DOI:	10.1007/s00348-012-1404-3