A breakup model for transient Diesel fuel sprays

Abstract

In this paper a breakup model for analysing the evolution of transient fuel sprays characterised by a coherent liquid core emerging from the injection nozzle, throughout the injection process, is proposed. The coherent liquid core is modelled as a liquid jet and a breakup model is formulated. The spray breakup is described using a composite model that separately addresses the disintegration of the liquid core into droplets and their further aerodynamic breakup. The jet breakup model uses the results of hydrodynamic stability theory to de ne the breakup length of the jet, and downstream of this point, the spray breakup process is modelled for droplets only. The composite breakup model is incorporated into the KIVA II Computational Fluid Dynamics (CFD) code and its results are compared with existing breakup models, including the classic WAVE model and a previously developed composite WAVE model (modi ed WAVE model) and in{house experimental observations of transient Diesel fuel sprays. The hydrodynamic stability results used in both the jet breakup model and the WAVE droplet breakup model are also investigated. A new velocity pro le is considered for these models which consists of a jet with a linear shear layer in the gas phase surrounding the liquid core to model the e ect of a viscous gas on the breakup process. This velocity pro le changes the driving instability mechanism of the jet from a surface tension driven instability for the currently used plug ow jet with no shear layers, to an instability driven by the thickness of the shear layer. In particular, it is shown that appreciation of the shear layer instability mechanism in the composite model allows larger droplets to be predicted at jet breakup, and gives droplet sizes which are more consistent with the experimental observations. The inclusion of the shear layer into the jet velocity pro le is supported by previous experimental studies, and further extends the inviscid ow theory used in the formulation of the classic WAVE breakup model

Non-modal stability of round viscous jets

“…The investigation of the latter problem is important for various environmental and engineering applications, including diesel 98 S. A. Boronin, J. J. Healey and S. S. Sazhin engines (Sazhin et al 2003;Crua et al 2004;Sazhin et al 2008;Turner et al 2012b). The understanding of the jet break-up would help us to control it, although the latter problem is beyond the scope of this paper.…”

“…Since then, the practical importance of the problem has given rise to a large number of theoretical and experimental investigations (Lin & Reitz 1998;Söderberg & Alfredsson 1998;Sazhin et al 2008;Turner et al 2012b).…”

Modeling the atomization of high-pressure fuel spray by using a new breakup model

“…A review of literature clearly reveals that the primary atomization is the result of complex phenomena like surface wave growth, internal jet turbulence fluctuations and cavitation inside the injection nozzle [19]. Since, none of the previous theories alone is able to describe the whole spray dynamics, a more accurate breakup model taken into account much of factors should be presented.…”

“…The spray breakup is described using a composite model to separately address the disintegration of the liquid core into droplets and their further aerodynamic breakup. The jet breakup model uses the results of hydrodynamic stability theory to define the breakup length of the jet, and downstream of this point, the spray breakup process is modeled for droplets only [19]. But none of these theories alone can explain the complexity of the atomization phenomenon.…”

Probing into the Effects of Fuel Injection Pressure and Nozzle Hole Diameter on Spray Characteristics under Ultra-high Injection Pressures Using Advanced Breakup Model

“…Desantes et al [8] developed a model which is able to predict spray tip penetration and spray axis velocity. Recently, Turner et al [9] proposed a breakup model for analyzing the evolution of transient fuel. Also, Yadollahi and Boroomand [10] used AVL FIRE software to perform an investigation into direct injection of natural gas into the cylinder of spark ignition internal combustion engines.…”