Numerical investigations of tip clearance flow characteristics of a pumpjet propulsor

Lü, Lin; Yue-fei, Gao; Li, Qiang; Du, Lin

doi:10.1016/j.ijnaoe.2017.09.001

Cited by 33 publications

(11 citation statements)

References 19 publications

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“…Also, the pressure difference drives the wall jet flow and finally leads to a shear layer with a high level of turbulent kinetic energy. Besides, from the study of Lu et al., 17 they concluded that there would be enough space for tip leakage flow to transport and develop with the tip clearance width increasing. Then with bigger tip clearance width, both the area and intensity of tip leakage vortex are bigger and has more effect on the main flow field.…”

Section: Resultsmentioning

confidence: 99%

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Numerical investigation of tip flow dynamics and main flow characteristics with varying tip clearance widths for an axial-flow pump

Shen

Zhou

et al. 2018

Proceedings of the Institution of Mechanical Engineers, Part A:

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The effects of varying tip clearance widths on tip flows dynamics and main flows characteristics for an axial-flow pump are studied employing computational fluid dynamics method. An analysis is presented for the distributions of turbulent kinetic energy, mean axial velocity, and mean vorticity magnitude at the specific flow rate of 0.7 Q BEP , focusing on flow patterns in the tip region with different tip clearance widths and associated flows. From the simulation results we find that the flow structure of tip vortex and its transportation strongly depend on the tip clearance width, especially for the extension of tip leakage vortex, appearance of induced vortex and the area of tip separation vortex. For a small clearance of 0.15 mm at 0.7 Q BEP, there is no tip separation vortex at the tip. When tip clearance width becomes larger, a tip separation vortex attaches more on the surface of blade tip as well as vortex intensity of tip flows increases. For tip clearances of 0.9 and 1.2 mm, there is a small part of induced vortex near the blade leading edge. Meanwhile, no induced vortex can be captured for tip clearances of 0.15 and 0.45 mm. The relative angle between the blade chord and tip leakage vortex trajectory reduces gradually when tip clearance width increases from 0.45 to 1.2 mm. Additionally, the radial position of tip leakage vortex core moves inwards as tip clearance width increases. Furthermore, a larger tip clearance width has greater effects on the main-stream characteristics especially near the shroud, which is due to more energy being exchanged between tip flows and main flows. At the flow rate 0.7 Q BEP, both the efficiency and head of the pump reduce with an increasing tip clearance because of greater energy loss.

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Section: Resultsmentioning

confidence: 99%

“…Additionally, relative angle between blade chord and TLV trajectory gradually decreased with an increasing flow rate. Additionally, other fields on the energy performance, 14–16 tip flow characteristics, 17 and its associated cavitating flow 18,19 with different tip clearances in the turbines or hydrofoil have already been investigated.…”

Section: Introductionmentioning

confidence: 99%

Numerical investigation of tip flow dynamics and main flow characteristics with varying tip clearance widths for an axial-flow pump

Shen

Zhou

et al. 2018

Proceedings of the Institution of Mechanical Engineers, Part A:

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“…Meanwhile, the SST has a better behavior in adverse pressure gradients and separating flow. Qin [19] carried out numerical simulations of PJP with three different turbulence models, namely standard k-ε, realizable k-ε, and SST k-ω turbulence models. The results showed that the SST configuration is much more accurate.…”

Section: Numerical Simulation Methodsmentioning

confidence: 99%

“…The tip clearance is a key factor for the shrouded rotor and has been a research hotspot for PJP. The authors of [18][19][20][21] numerically investigated the influence of tip clearance on post-stator PJP. Results showed that efficiency is closely related to the size of clearance due to the energy loss generated by tip leakage vortex (TLV).…”

Section: Introductionmentioning

confidence: 99%

Influence of Various Stator Parameters on the Open-Water Performance of Pump-Jet Propulsion

Huang

Pan

et al. 2021

JMSE

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In order to improve the hydrodynamic performance of pump-jet propulsion (PJP) when matching stator with the rotor, the RANS method with SST k-ω turbulence model is employed to study the influence of six kinds of stator parameters, which are classified into three groups, i.e., stator solidity, stator angles and rotor–stator spacing (S). Results show that the stator solidity involves the blade number (Ns) and chord length (L), has an obvious acceleration effect at and after stator, and produces a higher thrust and torque with a slight efficiency change. Further comparing Ns and L results, we find greater distinctions between the two cases when stator solidity is greatly adjusted. Three stator angles, i.e., stagger angle (α), lean angle (γ), and sweep angle (β), are studied. The α has the biggest effect on the thrust, torque, and efficiency; meanwhile, it shifts the advance number that corresponds to maximum efficiency. The effect of γ is similar to α, but its influence is far less than α. However, there is little difference between various β cases except for off-design conditions, where the efficiency drops dramatically as β increases. The S has a slight effect on PJP performance. Even though S decreases 34% relative to the original PJP, the rotor thrust and torque increase by less than 1%. In addition, we compare torque balance locations under various parameters, and each component force is analyzed in detail to explain the reason for performance variation. The present work is conducive to future optimization in PJP design.

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“…Compared with the propulsor without a tip clearance, the proportion of the primary tip vortex to the tip shed circulation decreases in the propulsor with ducted rotor, but the flow pattern near the tip seems to be more unstable. In a pump-jet propulsor [61,62], several important characteristics of the flow under the influence of the tip clearance are revealed: (1) Under the noncavitation condition, the variation trend of propulsor efficiency with the increase in the advance ratio is nearly unaffected by the tip clearance; (2) the rotational speed and the tip-clearance size have great impact on the cavitation performance curve, (3) tip-clearance flow intensifies the cavitation under a low rotational velocity; and (4) the stator blade contributes to stabilizing the flow field and decreasing the negative impact caused by tip-clearance leakage.…”

Section: Other Hydraulic Machinery Typesmentioning

confidence: 99%

A Review of Tip Clearance in Propeller, Pump and Turbine

2018

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Propellers, pumps, and turbines are widely applied in marine equipment, water systems, and hydropower stations. With the increasing demand for energy conservation and environmental protection, the high efficiency and the stable operation of pumps and turbine have been drawing great attention in recent decades. However, the tip clearance between the rotating impeller and the stationary shroud can induce leakage flow and interact with the main stream, introducing complex vortex structures. Consequently, the energy performance and the operation stability of pumps and turbines deteriorate considerably. Constant efforts are exerted to investigate the flow mechanism of tip-clearance flow and its induced influence on performance. However, due to various pump and turbine types and the complexity of tip-clearance flow, previous works are usually focused on a specific issue. Therefore, a systematic review that synthesizes the related research is necessary and meaningful. This review investigates related research in the recent two decades in the perspectives from fundamental physics to engineering applications. Results reveal the vortex types, trajectory, evolution, and cavitation behaviors induced by tip-clearance flow. It is concluded that the influence characteristics of tip clearance on energy performance are closely related to the machinery type. Tip-clearance size and tip shape are found to be crucial parameters for tip-leakage vortex (TLV). The proposed optimization schemes are also demonstrated to provide inspiration for future research. Overall, this review article provides a coherent insight into the characteristics of tip-clearance flow and the associated engineering-design applications. On the basis of these understandings, comments on conducted research and ideas on future research are proposed.

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Numerical investigations of tip clearance flow characteristics of a pumpjet propulsor

Cited by 33 publications

References 19 publications

Numerical investigation of tip flow dynamics and main flow characteristics with varying tip clearance widths for an axial-flow pump

Numerical investigation of tip flow dynamics and main flow characteristics with varying tip clearance widths for an axial-flow pump

Influence of Various Stator Parameters on the Open-Water Performance of Pump-Jet Propulsion

A Review of Tip Clearance in Propeller, Pump and Turbine

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