| Project/Area Number |
62550398
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| Research Category |
Grant-in-Aid for General Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Research Field |
都市工学・衛生工学
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| Research Institution | University of Tokyo |
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Principal Investigator |
TOMONORI MATSUO Professor, Faculty of Engineering, University of Tokyo, 工学部, 教授 (80010784)
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| Co-Investigator(Kenkyū-buntansha) |
KEISUKE HANAKI Associate Professor, Faculty of Engineering, Univ. of Tokyo, 工学部, 助教授 (00134015)
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| Project Period (FY) |
1987 – 1988
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| Project Status |
Completed (Fiscal Year 1988)
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| Budget Amount *help |
¥2,100,000 (Direct Cost: ¥2,100,000)
Fiscal Year 1988: ¥800,000 (Direct Cost: ¥800,000)
Fiscal Year 1987: ¥1,300,000 (Direct Cost: ¥1,300,000)
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| Keywords | Pressurized sewer / gas-liquid flow / oxygen transfer / turbulence / スペクトル解析 |
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| Research Abstract |
Disadvantage of conventional sewer system is the difficulty in ensuring satisfactory flow velocity in flat land area. Low flow velocity would result in accumulation of solid rich with organic material in sewer pipe. Pressurized sewer system was developed to overcome this disadvantage. The idea of air injection into the pressurized sewer may make this system more attractive, because prevention of solid accumulation and keeping sewage in aerobic condition are expected by the air injection. Laboratory-scale experiments using pipe were carried out to examine the effects of air injection.
1. Effects on oxygen transfer:
Pipe with 65 mm of inner diameter and 27 m of length was used and air was injected midway of the pipe. Two DO sensors were installed at two different points downstream of air injection. DO at each point was measure with DO Analyzer and overall oxygen transfer coefficient (K_La) was determined. The value of K_La greatly depended on type of flow. Two layer flow was observed at li
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quid flow velocity less than 0.5 m/s. Greater velocity resulted in smaller K_La value due to the decrease of interface area, a. Plug flow, in which large air part was contained in liquid flow, was observed at flow velocity higher than 1.0 m/s. The K_La value increased exponentially with the increase of velocity. This was due to the significance increase of K_L value at high flow velocity.
2. Effects on turbulent characteristics:
Liquid flow velocity was measured with hot film anemometer, and the data analysis such as spectrum analysis was conducted after output was converted to digital data. Injection of air remarkably increased the fluctuating fraction and turbulent intensity in liquid flow velocity. More injection of air caused stronger effects. Production of turbulence was greatly contributed by passing the air bubbles. Resuspension of settled material by flow with air injection was examined by applying the flow after having laid inorganic floc on the bottom of the pipe. Liquid flow velocity of 0.52 cm/s was required for resuspension when no air was injected. Injection of air alone brought about the resuspension. The results suggest that the air injection is effective to prevent sedimentation in sewer pipe. The use of two type of hot film sensor (conical type and wedge type) revealed that vertical component of turbulence contribute to oxygen transfer than the component along the flow. Less
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