1988 Fiscal Year Final Research Report Summary
Improvement of Nozzle Performance for Flashing Expansion of Initially Subcooled Hot Water
| Project/Area Number |
62460100
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
Thermal engineering
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| Research Institution | Kobe University |
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Principal Investigator |
FUJII Terushige Faculty of Engineering, Kobe University, Professor, 工学部, 教授 (70031143)
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| Co-Investigator(Kenkyū-buntansha) |
OHTA Junichi The Graduate School of Science and Technology, Kobe University, Research Associa, 大学院自然科学研究科, 助手 (20168941)
TAKENAKA Nobuyuki Faculty of Engineering, Kobe University, Research Associate, 工学部, 助手 (50171658)
AKAGAWA Koji Institute of Science and Technology, Ryukoku University, Professor, 理工学研究所, 教授 (30031032)
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| Project Period (FY) |
1987 – 1988
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| Keywords | Energy conservation / Geothermal resources / Nozzle Performance / Liquid-Gas Two-Phase Flow / Thermal noncquilibrium / Flashing / Nozzle design / 臨界流量 |
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| Research Abstract |
It was made clear that the degree of thermal nonequilibrium near a nozzle throat affects the performance characteristics of nozzles, such as the critial flowrate, the pressure profile along the axis of the nozzle, the thrust, and the thrust coefficient. As the degree of the thermalnonequilibrium increases, the delay time of flashing inception becomes longer, and droplets in the nozzle are not accelerated fully and the slip between gas and liquid ratio becomes larger. Thus, it is necessary to decrease the magnitude of the thermal nonequilibrium near the nozzle throat for improving the nozzle performance.
First of all, the performance characteristics and the reason why the nozzle efficiency de-creases were studied experimentally using conventional convergent-divergent nozzles. Second, the relationship that a pressure undershoot (as one of the degree of thermal nonequilibrium) decreases with decreasing a decompressive rate was applied to the nozzle design. It was found that the thrust coefficient of the nozzle is improved in this manner. Third, it is known that disturbance stimulates the flashing inception. Thus, the nozzle installed thin wires in the divergent passage was designed to make disturbance and then tested. The nozzles with the thin wires showed higher thrust coefficient. A methodof determining the cross-secectional area at the nozzle exit was also proposed. Last, it is important to measure axial void fraction profiles from the viewpoint of a critical flow modeling. Measurement of the axial void fraction profiles in the nozzle was tried by using neutron radio-graphy.
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