Analysis of primary atomization in sprays using Direct Numerical Simulation

Esposito, Marco Crialesi

doi:10.4995/thesis/10251/133975

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“…Finally, this thesis is a continuation of the works performed by CMT-Motores Termicos on [49,51,57,58] gathered in Crialesi's thesis [59]. As already introduced earlier in the document, on Salvador et al [49], the SBC approach was chosen to study the influence of the inflow turbulence on the atomization process.…”

Section: Computational Studies Of Liquid Atomizationmentioning

confidence: 98%

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Computational and Experimental Study of the Primary Atomisation Process under Different Injection Conditions

Montero¹

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The primary atomisation process is the mechanism by which a liquid vein breaks into droplets in a gaseous ambient. This process is present in many engineering applications accomplishing different tasks. Sometimes it is a previous step before being burned, as in the energy or propulsion industry, where the objective is to extract the specific energy of the liquid. In other sectors, such as the coating or fire extinction, the objective is to maximise the area covered by the droplet cloud. However, although atomisation is a fundamental part of several industrial processes, it is far from fully understood. The atomisation process is a mixture of gas-liquid interaction phenomena within a turbulent field that takes place in the near-field, which is the denser region of the spray.When trying to shed light on the primary atomisation process, the main issue is the lack of definitive physical theories able to link the complex breakup events and the turbulence. The principal impediment that prevents the investigation from breaking through the atomisation process is the inability of the classic optical techniques to provide information from the dense region of the spray. Only in the last years, newer techniques based on X-Ray could provide new information on spray characteristics near the nozzle outlet. This also affects the computational primary atomisation models that, as there is no available experimental information on the dense region, require an accurate calibration of their constants to provide reliable results on the far-field. This thesis focuses on improving the knowledge of the primary atomisation process, especially on how the injection conditions affect the spray development in the near field from two different standpoints. On the one hand, with a computational approach using Direct Numerical Simulations and on the other hand, experimentally using Near-Field Microscopy.The computational study is focused on varying the inflow Reynolds and Weber numbers. Results show that increasing the Reynolds number improves the liquid disintegration, exhibiting an increase of generated droplets and a finer droplet cloud. However, the lack of a fully developed inflow turbulent profile leads to characteristic behaviours on the breakup length of the spray that also increases with the Reynolds number. The number of droplets increases when the Weber number increases, but the characteristic droplet sizes remain the same. The breakup length does not vary, suggesting that the surface tension variations affect the droplet and ligament breakup but not the core disintegration itself. With the results obtained from both studies, a phenomenological model is proposed to predict the droplet size distribution depending on the injection conditions.Additionally, using elliptical nozzles, the number of detected droplets increases compared with the round spray and maintain similar spray apertures. However, when using extremely eccentric nozzles, the inflow turbulence decrease counteracts the elliptical sprays' benefits.Regarding the experimental ...

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Section: Computational Studies Of Liquid Atomizationmentioning

confidence: 98%

“…This means that sometimes is needed to know in advance the particularities of the problem and the main results required to extract from the simulations. In this case, many methodologies implemented in Marco's thesis [59] are used, with some modifications and additions to adapt them, in this study.…”

Section: Computational Studymentioning

confidence: 99%

Computational and Experimental Study of the Primary Atomisation Process under Different Injection Conditions

Montero¹

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Analysis of primary atomization in sprays using Direct Numerical Simulation

Cited by 1 publication

References 0 publications

Computational and Experimental Study of the Primary Atomisation Process under Different Injection Conditions

Computational and Experimental Study of the Primary Atomisation Process under Different Injection Conditions

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