Study of Boilover Suppression by Air Bubble Blowing

Research Project

Project/Area Number	05650189
Research Category	Grant-in-Aid for General Scientific Research (C)
Allocation Type	Single-year Grants
Research Field	Thermal engineering
Research Institution	Tohoku University
Principal Investigator	KITANO Michio Tohoku University Faculty of Engineering Associate Professor, 工学部, 助教授 (30005467)
Project Period (FY)	1993 – 1994
Project Status	Completed (Fiscal Year 1994)
Budget Amount *help	¥1,600,000 (Direct Cost: ¥1,600,000) Fiscal Year 1994: ¥500,000 (Direct Cost: ¥500,000) Fiscal Year 1993: ¥1,100,000 (Direct Cost: ¥1,100,000)
Keywords	Fire Safety / Boilover / Air Bubble Blowing / Boiling / 防災 / 微細空気泡吹込み
Research Abstract	Burning up the oil spilled over the sea is considered to be one of the possible ways to remove the oil quickly. But a boilover phenomenon is an obstacle to putting this way to practical use. As a method to suppress boilover we proposed blowing air bubbles into the oil layr through the water layr under it, which might stir the layrs and decrease the heat transfer rate between the two layrs, and made experiments to confirm the effectiveness of this method. First, with the cup-type burner made of Pyrex glass, effects of some factors, such as fuel kind (n-heptane, ethylbenzene and n-dodecylbenzene), initial layr thickness of fuel or water, cup diameter, on the boilover characteristics were investigated. Next, based on the results the burner able to blow fine air bubbles into the two layrs from its bottom was made. With this apparatus the time history of temperature distribution inside the layrs during burning and the boilover occurrence time, t_<bo>, were measured. This time was used to ev … More aluate the effectiveness of the proposed method. The main results are as follows : 1. Among the three kinds of fuels used here, boilover occurred only for dodecylbenzene whose boiling temperature (331ﾟC) is relatively higher than that of water. 2. Concerning the boliover of dodecylbenzene : (1) The time t_<bo> becomes longer with an increase in the layr thickness of fuel or water, but it tends to be saturated for the latter. (2) With the burner cup diameter, t_<bo> becomes shorter because of the decrease in heat loss at the burner wall. It gets to be constant when the diameter is larger than 60 mm. (3) A proper amount of air bubble supply can suppress boilover effectively. In this case the fuel burned moderately and almost completely, unlike the case of the occurrence of strong boilover where much fuel was left unburned. However the reduction of smoke amount, which was expected from the fuel-air premixing effect, was not definitely confirmed. And when the amount of air supply becomes large the flame was extinguished before the fuel was completely consumed. Less