On the occurrence of air entrainment in a suction sump
| Autor: | Katsuya, Hirata, Jiro, Funaki, Yoshihiro, Kubota, Katsuhisa, Inagaki, Miki, Taoka |
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| Jazyk: | japonština |
| Rok vydání: | 2011 |
| Předmět: | |
| Zdroj: | 同志社大学理工学研究報告 = The Science and Engineering Review of Doshisha University. 52(1):1-17 |
| ISSN: | 0036-8172 |
| Popis: | ポンプ吸込水槽の設計が不適当であると吸込管内部への空気吸込が発生し,それらは振動,騒音,さらには揚水不能という事態をもたらす.本研究では,空気吸込に関係した臨界没水深さScに着目して系統的な実験を行う.すなわち,力学パラメーターとして,ReとWe ,Frを考える.形状パラメーターとして,背面管隙Xと吸込水槽幅B,底面間隙Zを考える.ここで,代表長さと代表速度には,それぞれ,吸込管外径Dと吸込管入口速度Viを採用する.結果として,Scに及ぼす以上六パラメーターの影響を明らかにしている.We>12の範囲で,We効果は無視できる.Re>3×10[4]の範囲で,Re効果は無視できる.よって,これらの条件下では,Fr効果だけを考えれば充分である.X/D効果とB/D効果を考えると,どちらも,ある値でSc/Dが極大値をとる.一方,Z/D効果は単調であり,かつ,Z/D>2.5の範囲で小さくなる.これらの形状効果のいくつかは,Sc/DとFrとの関係に基づき,局所フルード数を考えることで説明できる.一方,他のいくつかは,吸込水槽内の流れを考慮する必要がある. In the present study, we consider the air entrainment into a suction pipe which is vertically inserted down into a suction sump across a mean free-water surface. This configuration is often referred to as the “vertical wet-pit pump", and has many practical advantages in construction, maintenance and operation. In particular, we focus our concern upon the critical submergence depth Sc, which is one of the prime and conventional indicators for the air-entrainment occurrence. By a systematic approach, we experimentally investigate the influences of kinetic and geometric parameters upon Sc. As the kinetic parameters, we consider the Reynolds number Re and the Weber number We, in addition to the Froude number Fr, on such a basis as Fr is not much larger than unity in many actual cases. As the geometric parameters, we consider back clearance X, sump breadth B and bottom clearance Z. Here, all parameters are non-dimensionalized by the outside diameter D and the intake velocity Vi of the suction pipe. As a result, we reveal the effects of such six parameters upon Sc. The We effect, namely, the surface-tension effect can be ignored at We > 12. And, the Re effect, namely, the viscous effect becomes negligibly small at Re > 3×10[4]. Under such conditions for We and Re, we could consider only the Fr effect, namely, the gravitational effect. Concerning the X/D and B/D effects, Sc/D attains the maximum at a certain X/D or B/D. On the other hand, the Z/D effect is monotonous, and becomes small at Z/D > 2.5. Some aspects of these geometric effects can be evaluated by a local-Froude-number effect on the basis of the global relation between Sc/D and Fr. And, the other aspects is necessarily considered to be related with the flow structure in the suction sump. 抄録の「3X10[4]」の[4]は上付き |
| Databáze: | OpenAIRE |
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