Basic Study on Spiral Grooved Vacuum Pumps Which Work in Low Vacuum Ranges
Project/Area Number |
62550120
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Research Category |
Grant-in-Aid for General Scientific Research (C)
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Allocation Type | Single-year Grants |
Research Field |
Fluid engineering
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Research Institution | Akita University |
Principal Investigator |
SAWADA Tadashi Akita University, Mining College, Professor, 鉱山学部, 教授 (40087466)
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Project Period (FY) |
1987 – 1988
|
Project Status |
Completed (Fiscal Year 1988)
|
Budget Amount *help |
¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 1988: ¥400,000 (Direct Cost: ¥400,000)
Fiscal Year 1987: ¥1,200,000 (Direct Cost: ¥1,200,000)
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Keywords | Clean Vacuum / Vacuum Pump / Turbomolecular Pump / Compound Molecular Pump / Spiral Grooved Rotor / Low Vacuum / 乱流 / 広帯域分子ポンプ / ねじみぞ真空ポンプ |
Research Abstract |
Considering increasing demend for oil free vacuum in high pressure ranges, the performance of spiral grooved pumps in the pressure range above 1000 Pa was studied experimentally and theoretically. For the case of zero flow, measured pressure difference between upstream and downstream sides were plotted against downstream pressure. The pressure difference was constant in a low pressure range and rose above a certain value of pressure when peripheral speed was high. Since this rise was considered to be caused by the transition from laminar flow to turbulent flow, The Reynolds number based on four times the hydraulic radius was taken as the abscissa and the dimensionless pressure difference P= P ^2/( UL) (U:peripheral speed, :radial clearance, L:length of rotor) was plotted. All the data points lay along a single curve regardless of peripheral speed. For any rotor ivestigated here, the dimensionless pressure difference was constant in a low pressure range, but it began to rise around the R
… More
eynolds number of 2000. It seemed that the rising rate of pressure difference with Reynolds number was high for the rotors with small aspect ratio and large helix angle. Next, experiments were performed on the case where a net-axial flow existed. The results showed that there existed linear relations between dimensionless pressure difference and dimensionless flow rate, and that the flow rate for zero-pressure difference (maximum dimensionless pressure ratio) took a constant value regardless of Reynolds number. The turbulent flow in the spiral grooves was treated theoratically by a simplified Reynolds stress model (O-equation model). Theoretical results showed reasonable agreement with the experimental ones in a low Reynolds number range (below 5000), but deviation between theoretical and experimental results became larger with the increase in Reynolds number. Comparing the theoretical results of a couple of rotors with the same groove shape, agreement with the experiments was better for rotors with smaller helix angle than ones with larger helix angle. Less
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Report
(3 results)
Research Products
(4 results)