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Abstract

The cavitation structures formed inside enlarged transparent replicas of tapered Diesel valve covered orifice nozzles have been characterized using high speed imaging visualization. Cavitation images obtained at fixed needle lift and flow rate conditions have revealed that although the conical shape of the converging tapered holes suppresses the formation of geometric cavitation, forming at the entry to the cylindrical injection hole, string cavitation has been found to prevail, particularly at low needle lifts. Computational fluid dynamics simulations have shown that cavitation strings appear in areas where large-scale vortices develop. The vortical structures are mainly formed upstream of the injection holes due to the nonuniform flow distribution and persist also inside them. Cavitation strings have been frequently observed to link adjacent holes while inspection of identical real-size injectors has revealed cavitation erosion sites in the area of string cavitation development. Image postprocessing has allowed estimation of their frequency of appearance, lifetime, and size along the injection hole length, as function of cavitation and Reynolds numbers and needle lift

Publication Type:	Article
Additional Information:	This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. Along with the following message: The following article appeared in Characterization of string cavitation in large-scale Diesel nozzles with tapered holes. Gavaises, M. and Andriotis, A. and Papoulias, D. and Mitroglou, N. and Theodorakakos, A., Physics of Fluids, 21, 052107 (2009), DOI:http://dx.doi.org/10.1063/1.3140940 and may be found at http://scitation.aip.org/content/aip/journal/pof2/21/5/10.1063/1.3140940
Subjects:	T Technology > TA Engineering (General). Civil engineering (General)
Departments:	School of Science & Technology > Engineering
SWORD Depositor:	Symplectic Administrator

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