On the relation between the external structure and the internal characteristics in the near-nozzle field of diesel sprays

[EN] In this paper, a high-resolution visualization technique has been used in combination with an extensively validated 0D model in order to relate the external structure of a diesel spray to the internal properties in the vicinity of the nozzle. For this purpose, three single-hole convergent nozzles with different diameters have been tested for several pressure conditions. The analysis of the obtained images shows that the spray width significantly changes along the very first millimeters of the spray. From the high resolution images captured, two parameters have been evaluated. The first one is the external non-perturbed length, where droplet detachment has not been observed. The second one is a transitional length, defined as the axial position where the spray width increases linearly after a transient behavior, making it possible to establish a spray cone angle definition. Furthermore, the internal liquid core length has been estimated for these nozzles using an extensively validated zero-dimensional model. The intact liquid core length has proved to be correlated with both the transitional length and the non-perturbed length with a very high degree of reliability. In the case of the transitional length, a quadratic correlation has been observed, whereas a linear relationship has been confirmed between the intact core length and the non-perturbed length. The results presented here may help to shed light on better understanding of such a complex process as atomization.The author(s) disclosed receipt of the following financial support for the research, authorship, and/or publication of this article: This work was supported by the Ministerio de Economia y Competitividad, Spanish Government, under the project 'Comprension de la influencia de combustibles no convencionales en el proceso de injeccion y combustion tipo diesel' (project number TRA2012-36932) The PhD studies of D. Jaramillo have been funded by "Conselleria d'Educacio'Cultura i Esports'' of "Generalitat Valenciana'', Spain, by means of ''Programa Vali+ d per a personal investigador en formacio''. Reference ACIF/2015/040.Benajes, J.; Salvador, FJ.; Carreres, M.; Jaramillo-Císcar, D. (2017). On the relation between the external structure and the internal characteristics in the near-nozzle field of diesel sprays. Proceedings of the Institution of Mechanical Engineers Part D Journal of Automobile Engineering. 231(3):360-371. doi:10.1177/0954407016639464S360371231