Polytechnic University of Valencia Congress, ILASS2017 - 28th European Conference on Liquid Atomization and Spray Systems

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Effect of geometry of real-size transparent nozzles on cavitation and on the atomizing jet in the near field
Yujun Cao, Said Idlahcen, Jean-Bernard Blaisot, Claude Rozé, Loïc Méès, David Maligne

Last modified: 18-07-2017

Abstract


Cavitation inception is very sensitive to the nozzle geometry. Two diesel-like transparent nozzles with sharp andround inlet edge were investigated under moderate injection pressure. By means of backlight imaging technique,images were recorded in two regions near the orifice: within ten orifice diameter downstream the nozzle and insidethe nozzle, for different times after start of the injection. A cross-correlation technique was applied to imagesdownstream the orifice to estimate the average velocity of the spray. The development of the spray was studiedat the transient and full-opened stage, related to the needle lift motion. To analyse the flow inside the nozzle, therelative size of the vapour pockets was measured on the image and the relative frequency of the occurrence ofcavitation was determined over image series. This approach permits to examine the time variation of the cavitationoccurrence from the inlet to the outlet of the orifice. The results highlight the sensitivity of the cavitating flow to theshape of the inlet edge. Moreover, the trends of the variation over time of the velocity and of the cavitation frequencyare very similar to each other but different for each geometry, indicating that the characteristics of the diesel sprayin the near field is closely affected by the way cavitation is developing in the nozzle.

DOI: http://dx.doi.org/10.4995/ILASS2017.2017.4938


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