Flow regime effects on non-cavitating injection nozzles over spray behavior R. Payri ⇑ , F.J. Salvador, J. Gimeno, R. Novella CMT-Motores Térmicos, Universidad Politécnica de Valencia, Camino de Vera s/n, Valencia E-46022, Spain article info Article history: Received 2 March 2010 Received in revised form 8 October 2010 Accepted 13 October 2010 Available online 16 November 2010 Keywords: Diesel injection Flow regime Turbulence Spray Visualization abstract This paper deals with the influence of flow regime (laminar, transition or turbulent) on the internal flow behavior, and how it affects the spray development in diesel nozzles. In particular, the research described here aims at studying and quantifying the internal flow regime effects on the spray behavior. With this purpose, internal flow results, based on mass flow rate and momentum flux measurements performed on three different tapered nozzles and which helped to determine the flow regime, has been taken into account as a point of departure for the spray behavior analysis. Thus, in this work, spray macroscopic visualization tests have been performed and analyzed which clearly revealed a change in the behavior of the angle and penetration of the spray related to the change of the flow nature. Moreover, with all the experimental data available, it has been possible to relate macroscopic parameters of the spray with those describing the internal flow (momentum and effective velocity) or the geometry of the nozzle (length or diameter) through correlations. Ó 2010 Elsevier Inc. All rights reserved. 1. Introduction One of the diesel engine components that most interest has arisen in recent years has been the injection system. This interest is not accidental, since the quality of the air–fuel mixture, and in turn, the engine performance and pollutant emissions depend fun- damentally on the proper operation of this system, more so given the increasing engine pollutant control requirements. Undoubtedly, if one intends to improve the performance of the injection system and the subsequent combustion, one must first deeply understand all the phenomena involved in the own process of injection and atomization of the spray (Som and Aggarwal, 2009; Payri et al., 2009; Park et al., 2009a,b,c; Ramírez et al., 2009). As a result of the operating conditions, including high injec- tion pressures which result in a extremely high spray exit veloc- ity, the characteristics of the spray correspond to the latest spray regimes defined by Reitz and Bracco (1979), and mainly in the known as the atomization regime, which is characterized by the atomization of the spray beginning just outside the hole. Espe- cially for this regime, the mechanisms that cause the breakdown of the liquid vein are not fully understood or even known. De- spite numerous experimental studies, there is currently no one theory that can explain all observed behaviors. Thus, due to the high spray velocities, mechanisms other than the aerody- namic interaction such as turbulence, and cavitation. begin to appear. The exact role of these mechanisms is not well known and they can vary depending on operating conditions. Thus, the atomization will be caused by the superposition of these independent mechanisms and, depending on injection condi- tions, they can charge more or less relative importance. Within these mechanisms, some authors like Ruiz (1998) have described the turbulence as one of the major causes of atomization. Such turbulence is generated in the injection system, particularly in the injector orifice. The radial turbulent velocities in this section are contained by the walls of the injector. At the exit of the noz- zle, the radial component of turbulent fluctuations eject part of the fuel outside the fluid vein, causing atomization. This mecha- nism can explain the fragmentation of sprays injected into the vacuum, for which there is no aerodynamic interaction with the environment. On the other hand, this is clearly not the un- ique mechanism of atomization of a diesel spray because it is unrelated to the increased atomization of the spray when increasing gas density. The objective of this work is to study the influence of flow re- gime, laminar, transition or turbulent on the internal flow behav- ior, and how it affects the development of the spray. In order to do this, an experimental study has been performed using three convergent nozzles with different diameter, where tests of spray macroscopic visualization have been obtained and analyzed, clearly observing a change in the behavior of the angle and the penetration of the spray related to the change of the flow regime. Furthermore, from all information available, it has been possible to relate the parameters of the spray with those of the internal flow (which take into account the flow regime) through correlations. 0142-727X/$ - see front matter Ó 2010 Elsevier Inc. All rights reserved. doi:10.1016/j.ijheatfluidflow.2010.10.001 ⇑ Corresponding author. Tel.: +34 963879658; fax: +34 963877659. E-mail address: rpayri@mot.upv.es (R. Payri). International Journal of Heat and Fluid Flow 32 (2011) 273–284 Contents lists available at ScienceDirect International Journal of Heat and Fluid Flow journal homepage: www.elsevier.com/locate/ijhff