On Improvement of Characteristic Instability and Internal Flow in Mixed Flow Pumps

Miyabe, Masahiro; Furukawa, Akinori; Maeda, Hideaki; Umeki, Isamu; Jittani, Yoshinori

doi:10.1299/jfst.3.732

Cited by 28 publications

(16 citation statements)

References 4 publications

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“…After mesh sensitivity checks, it is noted that the pump head under nominal flow rate decrease 0.2 % with the mesh number increasing and, finally, the value of the pump head is constant. Finally, Case 3 of a total mesh number nearly 7×10 6 is selected for numerical simulation considering the…”

Section: Mesh Generationmentioning

confidence: 99%

“…An investigation on the internal flow in the mixed-flow nuclear reactor coolant pump is one of the key problems for the development of reactor coolant pumps in large pressurized water reactors. Some investigations have been conducted to study the design of the mixed-flow pump [4] and [5] and flows instabilities [6] and [7]. However, most of them only focus on the unsteady pressure pulsation in impeller [8] and [9] or the performance of the nuclear reactor coolant pump [10] and [11].…”

Section: Introductionmentioning

confidence: 99%

“…With the development of non-contact measuring techniques, unsteady particle image velocimetry (PIV) [18] and laser Doppler velocimetry (LDV), measuring techniques are often applied to investigate complex unsteady internal flow in pumps, in such a way that no external disturbance is imposed on the flow field. Miyabe et al [6] and [7] used PIV and pressure fluctuation measurements to investigate the propagation mechanism of a rotating stall in a mixed-flow pump. It was found that unstable performance was caused by periodic large-scale abrupt backflow generated from the diffuser to the impeller outlet.…”

Section: Introductionmentioning

confidence: 99%

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Flow Unsteadiness and Pressure Pulsations in a Nuclear Reactor Coolant Pump

Ni¹,

Yang²,

Gao³

et al. 2016

SV-JME

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A nuclear reactor coolant pump (RCP) [1], the device in the reactor core and the steam generator that transfers the heat energy [2], is the "heart" of a nuclear reactor driving the circulation flow of the coolant in the main loop [3]. The nuclear reactor coolant pump is the only rotating part of the nuclear island, so it belongs in a nuclear safety grade one facility. Moreover, it is also the main energy-consuming equipment in the nuclear power plants, which must be guaranteed to operate continuously over a long term and without trouble. An investigation on the internal flow in the mixed-flow nuclear reactor coolant pump is one of the key problems for the development of reactor coolant pumps in large pressurized water reactors. Some investigations have been conducted to study the design of the mixed-flow pump [4] and [5] and flows instabilities [6] and [7]. However, most of them only focus on the unsteady pressure pulsation in impeller [8] and [9] or the performance of the nuclear reactor coolant pump [10] and [11]. The unsteady flow structure of a mixed-flow nuclear reactor coolant pump, especially in certain specific regions, is very important to the safety analysis of a nuclear reactor, as it could generate serious flow-induced vibration, threatening the pump integrity [8]. Therefore, a comprehensive analysis and prediction of pressure pulsation caused by intense rotor-stator interaction are essential for the design of the mixed-flow nuclear reactor coolant pump [12] and [13]. At present, in order to improve the efficiency and stable operation of the nuclear reactor coolant pump, the complicated internal unsteady flow structures should be thoroughly illustrated.The nuclear reactor coolant pump has a special structure equipped with a spherical casing, which determines a typical and complex flow pattern within the pump. Knierim et al.[14] designed a new type of reactor coolant pump for a 1400 MW nuclear power plant. The impeller and diffuser were gradually optimized based on the computational fluid dynamics (CFD). The volute casing is a spherical shape with a discharge nozzle facing the impeller, and the flow structures in the region around the discharge nozzle are uniform. The region of the discharge nozzle itself is characterized by the fact that the flow below the outlet port is divided into two parts. One portion flows out of the casing discharge nozzle, whereas the other portion circulates around the casing once more prior to exiting. Kato et al.[15] and [16] described internal flows of a high-specific-speed mixed-flow pump at low flow rates using large-eddy simulation (LES), and it showed that the head-flow curve exhibited weak • Flow separations and backflows easily occur at the diffuser channels near the discharge nozzle region.• At the left region of the casing, the discharge nozzle is affected significantly by an intense rotor-stator interaction effect.• In the right and middle of the casing nozzle, unsteady flow structures are more complicated.• An unsteady vortex-shedding effect would motivate evid...

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Section: Mesh Generationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Flow Unsteadiness and Pressure Pulsations in a Nuclear Reactor Coolant Pump

Ni¹,

Yang²,

Gao³

et al. 2016

SV-JME

View full text Add to dashboard Cite

show abstract

“…He concluded that a rotating stall is flow instability caused by a positive slope of the head-flow rate performance curve, whereby the rotational frequency of rotating stall depends on the performance and the geometry of the rotor. Miyabe et al visualized the unsteady internal flow in diffuser with Dynamic PIV [15,16]. The authors clarified that the diffuser rotating stall causes the positive slope of a head-flow characteristic, and the backflow (i.e., a stall cell or a vortex) at the hub side of the diffuser plays an important role in the onset of a diffuser rotating stall.…”

Section: Review Of Rotating Stall In Pumpsmentioning

confidence: 99%

Dynamic Characteristics of Rotating Stall in Mixed Flow Pump

Yuan

Pan

et al. 2013

Journal of Applied Mathematics

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Rotating stall, a phenomenon that causes flow instabilities and pressure hysteresis by propagating at some fraction of the impeller rotational speed, can occur in centrifugal impellers, mixed impellers, radial diffusers, or axial diffusers. Despite considerable efforts devoted to the study of rotating stall in pumps, the mechanics of this phenomenon are not sufficiently understood. The propagation mechanism and onset of rotating stall are not only affected by inlet flow but also by outlet flow as well as the pressure gradient in the flow passage. As such, the complexity of these concepts is not covered by the classical explanation. To bridge this research gap, the current study investigated prerotation generated at the upstream of the impeller, leakage flow at the tip clearance between the casing and the impeller, and strong reserve flow at the inlet of the diffuser. Understanding these areas will clarify the origin of the positive slope of the head-flow performance curve for a mixed flow pump. Nonuniform pressure distribution and adverse pressure gradient were also introduced to evaluate the onset and development of rotating stall within the diffuser.

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“…Based on the time lag of the two pressure signals mounted on the casing wall of the adjacent diffuser passage and the results obtained by DPIV, it is confirmed that the diffuser rotating stall occurs and the number of the stall cell is one, and the propagating direction of the stall cell is the same as that of impeller rotation. The cause of the onset of a diffuser rotating stall is closely related to the backflow at the vaned diffuser hub-side and it is investigated by using CFD in the reference [12]. Figure 8 shows the relationship between measured static pressure and internal flow patterns at the inlet of the vaned diffuser atφ=0.069.…”

Section: Pump Characteristics and Static Pressure Fluctuationsmentioning

confidence: 99%

A Behavior of the Diffuser Rotating Stall in a Low Specific Speed Mixed-Flow Pump

Miyabe¹,

Furukawa

Maeda³

et al. 2009

International Journal of Fluid Machinery and Systems

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The flow instability in a low specific speed mixed-flow pump, having a positive slope of head-flow characteristics was investigated. Based on the static pressure measurements, it was found that a rotating stall in the vaned diffuser occurs at about 65% flow rate of best efficiency point (BEP). A dynamic Particle Image Velocimetry (DPIV) measurement and the numerical simulations were conducted in order to investigate the flow fields. As a result, the diffuser rotating stall was simulated even by Computational Fluid Dynamics (CFD) and the calculated periodic flow patterns agree well with the measured ones by DPIV. It is clarified that a periodical large scaled backflow, generated at the leading edge of the suction surface of the diffuser vane, causes the instability. Furthermore, the growth of the strong vortex at the leading edge of the diffuser vane induces the strong backflow from the diffuser outlet to the inlet. The scale of one stall cell is covered over four-passages in total thirteen vane-passages.

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On Improvement of Characteristic Instability and Internal Flow in Mixed Flow Pumps

Cited by 28 publications

References 4 publications

Flow Unsteadiness and Pressure Pulsations in a Nuclear Reactor Coolant Pump

Flow Unsteadiness and Pressure Pulsations in a Nuclear Reactor Coolant Pump

Dynamic Characteristics of Rotating Stall in Mixed Flow Pump

A Behavior of the Diffuser Rotating Stall in a Low Specific Speed Mixed-Flow Pump

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