مطالعهي تجربي فركانس حبابهاي تيلور در جريان دوفازي گاز ـ مايع در داخل يك زانويي بزرگ

Experimental Study of Frequency of Taylor Bubbles in Gas-Liquid Two-Phase Flow in a Large Bend

در تحقيق حاضر، الگوي جريان حبابهاي تيلور و فركانس تشكيل آن‌ها در يك زانويي بزرگ متشكل از سه شيب متوالي بررسي شده است. بدين‌منظور، ابتدا نمودارهاي جريان براي مقاطع مختلف مسير ترسيم، و ضمن بيان روند تشكيل حباب‎ها، تاثير دبي جريان فازها بر فركانس آن‎ها مطالعه شده است. نتايج حاصله نشان مي‎دهد كه با توجه به عدم وقوع پديده‎‌ي ادغام حباب‎ها، تغييرات شيب كانال در امتداد زانويي، تاثيري بر فركانس حبابها ندارد. در جريانهايي با 22000 > Resl مقدار فركانس حبابها در طول زانويي و فركانس اسلاگ در بالادست زانويي نزديك بوده و افزايش دبي جريان مايع سبب كاهش فركانس حبابها ميشود. اين در حالي است كه در جريانهايي با 22000 < Resl، عكس اين موارد رخ ميدهد. همچنين با توجه به نتايج، در هر دو ناحيه‌ي مذكور افزايش دبي جريان گاز، سبب كاهش فركانس حبابها ميشود. در انتها نيز روابطي براي تعيين فركانس حبابها براساس اعداد رينولدز ظاهري فازها پيشنهاد شده است.

Gas–liquid two-phase flow occurs frequently in many cases of industry, depending on the geometry of the duct, and the topography of the interface which creates different flow regimes. The Taylor bubble regime is one of the most possible patterns that exist over a wide range of gas-liquid flow rates. It is characterized by the motion of an elongated bubble among a continuous zone of liquid. The transient and intermittent nature of this regime causes sequence changes of pressure inside the channel and increases the fatigue and corrosion of the channel wall. In the present research, for its high importance, the frequency of Taylor bubbles was investigated in a large bend with three consecutive inclinations. At first, the flow regimes and flow diagrams of the inclined sections, as well as the horizontal section, in the upstream of the bend, were considered. It was noted that the Taylor bubble area stayed unchanged without the channel slope effect, and three areas were also coincident. As the bubbles merge and the bubble collapse phenomenon does not occur, the slope change of the channel does not affect the Taylor bubble frequency. A detailed explanation is given on Taylor bubble formation in the bend due to slug flow, which was generated on the upstream of the bend. The effect of gas and liquid flow rates on Taylor bubble frequency in the bend, as well as slug frequency at upstream of the bend, was also conducted in the present study. The results showed that an increase in gas flow rate decreases the Taylor bubble frequency in the whole range of liquid flow rates. In the flows with Resl < 22000, close correspondence exists between Taylor bubble frequency at the bending location and slug frequency at the upstream of the bend, and the increase in liquid flow rate decreases bubble frequency. However, the opposite result was found during flows with Resl > 22000. Finally, correlations were proposed to evaluate Taylor bubble frequency, based on phase superficial Reynolds number. These correlations are important for flow regime evaluation, in addition to the lack of similar subject matter in the literature.