Ultra-High Speed Visualization of the Flashing Instability in Micron Size Nozzles under Vacuum Conditions

الموضوعات

علوم تطبيقية وتكنولوجية

الملخص

I visualized the flash-boiling atomization of liquid jets released into a low pressure environment at frame rates of up to five million frames per second. Such a high temporal resolution allowed us to observe for the first time the bubble expansion mechanism that atomizes the jet. To visualize the dynamics in detail, I focused closely to the outflow of the nozzle using a long distance microscope objective. I documented an abrupt transition from a laminar to a fully external flashing jet by systematically reducing the ambient pressure. I performed experiments with different volatile liquids and using nozzles with different inner diameters. The inner diameters of the nozzles varied from 30 to 480 µm. Perfluorohexane (PFnH) was our main working fluid, but also methanol, ethanol and 1-bromopropane were tested. Surprisingly, minimum intensity profiles revealed spray angles close to θs ~360°, meaning drops are ejected in all directions. Also, I measured speeds of bubble expansion up to 140 m/s. That is 45 times faster than the upper bound for inertial growth speed in complete vacuum from the Rayleigh-Plesset equation. I also calculated the trajectories of the ejected droplets as well as the drop speed distribution using particle tracking. I expect that our results bring new insight into the flash-boiling atomization mechanism.

روابط وملفات

التعريف والنوع

رقم الوثيقة

ef8928c0-7309-4628-bba9-4ec736fb6f2d

رقم العقد

0

نوع الوسائط

Crawler

نوع المحتوى

الرسائل العلمية

صيغة المصدر

رسائل ماجيستير

نوع الملف

pdf text

أسماء الملفات

1699342_1.pdf

بيانات النشر

ألقاب المؤلفين

[{"name_ar":"Sigurdur T. Thoroddsen","title_ar":"اشراف","title_en":"Supervision"},{"name_ar":"Tariq Ahmed Alghamdi","title_ar":"اعداد","title_en":"Preparation"}]

اللغة

English

المصدر والدورية

اسم المصدر

Ultra-High Speed Visualization of the Flashing Instability in Micron Size Nozzles under Vacuum Conditions

المحتوى والصفحات

عدد الصفحات

0

كلمات الباحثين

flashing-boiling , microset , spray formation

إشراف وإعداد

الإشراف

Sigurdur T. Thoroddsen

الإعداد

Tariq Ahmed Alghamdi

الاقتباسات الببليوغرافية