Numerical investigation of the aerodynamic breakup of Diesel and heavy fuel oil droplets

Stefanitsis, Dionisis; Malgarinos, Ilias; Strotos, George; Νikolopoulos, Nikos; Kakaras, E.; Gavaises, Manolis

doi:10.1016/j.ijheatfluidflow.2017.10.012

Cited by 25 publications

(22 citation statements)

References 48 publications

(115 reference statements)

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“…Two-dimensional (2-D) axisymmetric and three-dimensional (3-D) simulations are performed with the commercial CFD tool ANSYS FLUENT v16 [22] along with the use of various User Defined Functions (UDFs); these account for the following: i) adaptive local grid refinement technique around the liquid-gas interface [23], ii) adaptive time-step scheme for the implicit VOF solver based on the velocity at the droplet interface [24], and iii) moving mesh technique based on the average velocity of the droplets. The CFD model has been developed and validated in previous works of the authors for a number of applications; among them are the free fall of a droplet [23], the droplet impingement on a flat wall [25] or a spherical particle [26][27][28], the aerodynamic droplet breakup [4,24,[29][30][31][32][33][34][35] and the droplet evaporation [24,31,36]. It should be noted that he extension of the model validation for the case of droplet clusters is not possible since, to the author's best of knowledge, there are no experimental studies in the literature with droplet clusters, only a few featuring two droplets [5,15,16].…”

Section: Computational Setup and Examined Conditionsmentioning

confidence: 99%

Numerical investigation of the aerodynamic breakup of a parallel moving droplet cluster

Stefanitsis

Strotos

Νikolopoulos

et al. 2019

International Journal of Multiphase Flow

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The present work examines numerically the aerodynamic breakup of a cluster of Diesel droplets moving in parallel with respect to the gas flow. Two-and three-dimensional simulations of the incompressible Navier-Stokes equations together with the VOF method are performed for Weber (We) numbers in the range of 5 up to 60 and non-dimensional distance between the droplets (H/D0) ranging from 1.25 to 20. The numerical results indicate that the proximity of droplets affects their breakup for distances H/D0≤5. For low droplet proximity distances (H/D0≤2.5), the droplets experience the socalled shuttlecock breakup mode, which has been also identified for droplets in tandem formations in a previous authors' work and is characterized by an oblique peripheral stretching of the droplet. With decreasing H/D0 the breakup initiation time decreases, while the drag coefficient increases relative to that of isolated droplets. When the distance between the droplets is low enough (H/D0<1.5), this can result in critical We number, i.e. minimum We number leading to breakup, lower than that of an isolated droplet at the same conditions.

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Section: Computational Setup and Examined Conditionsmentioning

confidence: 99%

Numerical investigation of the aerodynamic breakup of a parallel moving droplet cluster

Stefanitsis

Strotos

Νikolopoulos

et al. 2019

International Journal of Multiphase Flow

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“…When the viscosity of liquid cannot be neglected, Oh will be another key parameter [79][80][81][82][83][84]. Many researches show that the We range of drop breakup mode will increase with the increase of Oh nonlinearly.…”

Section: Secondary Atomizationmentioning

confidence: 99%

Breakup Morphology and Mechanisms of Liquid Atomization

Zhao¹,

Liu²

2020

Environmental Impact of Aviation and Sustainable Solutions

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Fuel atomization, the transformation of bulk liquid into sprays, is of importance in jet engines. In this chapter, we will introduce the latest research advances on breakup morphology and mechanism of liquid atomization. On primary atomization, based on the morphological difference, the twin-fluid atomization could be classified into different regimes. The influence of Kelvin-Helmholtz and Rayleigh-Taylor instability on breakup morphology and fragment size is great and nonmonotonic. On secondary atomization, Rayleigh-Taylor instability is considered as the main driving mechanism in different bag-breakup modes; for higher Weber number, it will be in concurrence with the shear instability. Based on ligamentmediated spray formation model, ligament breakup is found to be well represented by the gamma distributions. Atomization of complex fluids has special characteristics and mechanisms. There are also a lot of research advances recently in this field.

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“…The simulations are performed in a two-dimensional axisymmetric domain with the commercial CFD tool ANSYS FLUENT v16 [46]. At low Reynolds numbers, such as those examined in this work (Table 4), the axisymmetric approximation has proven to be relatively accurate during the deformation stages of breakup [16,47,48]. Various User Defined Functions (UDFs) are employed for i) the adaptive local grid refinement technique around the liquid-gas interface [49], ii) the adaptive time-step scheme for the implicit VOF solver based on the velocity at the droplet interface [13], and iii) the moving mesh technique based on the average velocity of the droplet.…”

Section: Computational Setup and Examined Conditionsmentioning

confidence: 99%

“…Various User Defined Functions (UDFs) are employed for i) the adaptive local grid refinement technique around the liquid-gas interface [49], ii) the adaptive time-step scheme for the implicit VOF solver based on the velocity at the droplet interface [13], and iii) the moving mesh technique based on the average velocity of the droplet. The CFD model has been developed and validated in previous works for the case of aerodynamic droplet breakup [13,16,17,[50][51][52][53], as well as for other applications such as the free fall of droplet [49], the droplet impingement on a flat wall [54] or a spherical particle [55][56][57], and the droplet evaporation [13,52,58]. The 2-dimensional axisymmetric computational domain and boundary conditions are presented in Figure 1.…”

Section: Computational Setup and Examined Conditionsmentioning

confidence: 99%

“…The former can be calculated using the drag coefficient of each droplet and the droplet motion equation. The drag coefficient of deforming droplets has been thoroughly studied in [3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. The droplet deformation, which is the focus of this study, is usually quantitatively described by the cross-stream droplet diameter ( Figure 2) and several models have been developed for its estimation as a function of time.…”

Section: Introductionmentioning

confidence: 99%

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Improved droplet breakup models for spray applications

Stefanitsis

Strotos

Νikolopoulos

et al. 2019

International Journal of Heat and Fluid Flow

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The current study examines the performance of two zero-dimensional (0D) aerodynamically-induced breakup models, utilized for the prediction of droplet deformation during the breakup process in the bag, multi-mode and sheet-thinning regimes. The first model investigated is an improved version of the widely used Taylor analogy breakup (TAB) model, which compared to other models has the advantage of having an analytic solution. Following, a model based on the modified Navier-Stokes (M-NS) is examined. The parameters of both models are estimated based upon published experimental data for the bag breakup regime and CFD simulations with Diesel droplets performed as part of this work for the multi-mode and sheet-thinning regimes, for which there is a scarcity of experimental data. Both models show good accuracy in the prediction of the temporal evolution of droplet deformation in the three breakup regimes, compared to the experimental data and the CFD simulations. It is found that the best performance of the two is achieved with the M-NS model. Finally, a unified secondary breakup model is presented, which incorporates various models found in the literature, i.e. TAB, nonlinear TAB (NLTAB), droplet deformation and breakup (DDB) and M-NS, into one equation using adjustable coefficients, allowing to switch among the different models.

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Numerical investigation of the aerodynamic breakup of Diesel and heavy fuel oil droplets

Cited by 25 publications

References 48 publications

Numerical investigation of the aerodynamic breakup of a parallel moving droplet cluster

Numerical investigation of the aerodynamic breakup of a parallel moving droplet cluster

Breakup Morphology and Mechanisms of Liquid Atomization

Improved droplet breakup models for spray applications

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