Energy loss mechanism due to tip leakage flow of axial flow pump as turbine under various operating conditions

Kan, Kan; Zhang, Qingying; Xu, Zhenshan; Zheng, Yuan; Gao, Qiang; Shen, Lian

doi:10.1016/j.energy.2022.124532

Cited by 98 publications

(36 citation statements)

References 33 publications

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“…Compared with the original design, both the low-velocity area in the descending segment and the velocity gradient are significantly reduced, which can effectively avoid the generation of vortices. 31 These comparisons indicate that the optimized design greatly improves the flow pattern of the flow field when stable siphon flow is formed.…”

Section: Flow Analysismentioning

confidence: 95%

Multi-objective shape optimization of siphon outlet in pumping station considering two-phase flow

Chen

et al. 2022

Proceedings of the Institution of Mechanical Engineers, Part A:

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The siphon outlet is widely used in pumping stations due to its reliable and convenient cut-off performance. Long siphoning time or high hydraulic loss caused by the inappropriate design of the siphon outlet can significantly affect the safety of stations. The air compressibility volume-of-fluid (VOF) method is conducted to simulate the two-phase flow in the siphoning formation process at the design points selected by the optimal Latin hypercube design (OLHD), the results of which show good agreement with the experimental data. In this work, the siphoning time and hydraulic loss coefficient are selected as the objective functions, and a multi-objective shape optimization strategy is proposed for the siphon outlet in conjunction with the response surface method (RSM). This optimization strategy can not only reconcile conflicting objective functions but also obtain the effect and interaction of design variables. Sensitivity analysis on the constructed response surface models indicates that among three design variables, the aspect ratio has the greatest effect on the objective functions, the descending angle has the second greatest effect, and the ascending angle has almost no effect. Compared with the original design, the hydraulic loss coefficient and siphoning time of the optimized design are reduced by 2.95% and 26.76%, respectively. A higher vorticity magnitude and more uniform outflow are created in the optimized design, which results in the improvement of hydraulic performance.

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Section: Flow Analysismentioning

confidence: 95%

Multi-objective shape optimization of siphon outlet in pumping station considering two-phase flow

Chen

et al. 2022

Proceedings of the Institution of Mechanical Engineers, Part A:

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“…Considering parameters in Equation ( 4), the equation of wall roughness profile can be formulated as to Equation ( 5) and the mean line as to Equation (6).…”

Section: Equivalent Sand-grain Roughnessmentioning

confidence: 99%

“…Due to the landform and climate reasons, wet seasons are dominated by a lot of floods and stagnant waters. To achieve considerable economic benefits, pumping stations can make full use of such water energy resources by means of pump as turbine (PAT) technology [5,6]. Thanks to the control valve utilization, the flow direction can be reversed for power generation.…”

Section: Introductionmentioning

confidence: 99%

Investigation into Influence of Wall Roughness on the Hydraulic Characteristics of an Axial Flow Pump as Turbine

et al. 2022

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Pump as turbine (PAT) is a factual alternative for electricity generation in rural and remote areas where insufficient or inconsistent water flows pose a threat to local energy demand satisfaction. Recent studies on PAT hydrodynamics have shown that its continuous operations lead to a progressive deterioration of inner surface smoothness, serving the source of near-wall turbulence build-up, which itself depends on the level of roughness. The associated boundary layer flow incites significant friction losses that eventually deteriorate the performance. In order to study the influence of wall roughness on PAT hydraulic performance under different working conditions, CFD simulation of the water flow through an axial-flow PAT has been performed with a RNG k-ε turbulence model. Study results have shown that wall roughness gradually decreases PAT’s head, efficiency, and shaft power. Nevertheless, the least wall roughness effect on PAT hydraulic performance was experienced under best efficiency point conditions. Wall roughness increase resulted in the decrease of axial velocity distribution uniformity and the increase of velocity-weighted average swirl angle. This led to a disorderly distribution of streamlines and backflow zones formation at the conduit outlet. Furthermore, the wall roughness impact on energy losses is due to the static pressure drop on the blade pressure surface and the increase of turbulent kinetic energy near the blade. Further studies on the roughness influence over wider range of PAT operating conditions are recommended, as they will lead to quicker equipment refurbishment.

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“…At the same time, it makes it possible to carry out quantitative research on the mechanism of flow loss in pumps. (Kan, et al, 2022) investigated the influences of the tip leakage vortex on the axial flow pump as turbine through numerical simulations, where the energy loss mechanism due to tip leakage flow was revealed K. (Pu, et al, 2022) studied the influence of vortex on steady flow and pressure fluctuation of circulating axial pump through numerical simulations, where energy loss caused by the low-speed vortex was analyzed quantitatively and the structure position of the low-speed vortex can be predicted Li et al (Li, et al, 2021) studied the energy loss mechanism of a mixed-flow pump under stall condition with the numerical method. Especially, the combination of entropy generation theory and numerical simulation can well conduct…”

Section: Introductionmentioning

confidence: 99%

Numerical study on the mechanism of fluid energy transfer in an axial flow pump impeller under the rotating coordinate system

Guo

Yang

et al. 2023

Front. Energy Res.

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It is a necessary condition to obtain the fluid movement law and energy transfer and loss mechanism in the impeller of the axial pump for achieving an efficient and accurate design of the axial flow pump. Based on the shear stress transport k-ω turbulence model, a three-dimensional unsteady numerical simulation of the whole flow field of an axial flow pump was presented at different flow rates. Combined with the Bernoulli equation of relative motion, the flow field structure in the impeller under design condition was studied quantitatively in the rotating coordinate system. The fluid movement law and energy transfer and loss mechanism in the impeller of the axial flow pump was described in detail. In the relative coordinate system, the mechanical energy of the fluid on the same flow surface conserves. The dynamic energy is continuously transformed into pressure energy from the leading edge to the trailing edge and the dynamic energy is continuously transformed into pressure energy from the leading edge to the trailing edge. The energy conversion is mainly completed in the front half of the blade. The friction loss and the mixing loss are the basic sources of losses in the impeller flow passage. Most hydraulic losses of impeller flow passage are caused by friction and the hydraulic losses near the trailing edge are dominated by mixing loss. This research has certain reference significance for further understanding the flow field structure in the impeller of the axial flow pump, improving its design theory and method, and then realizing its efficient and accurate design of the axial flow pump.

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Energy loss mechanism due to tip leakage flow of axial flow pump as turbine under various operating conditions

Cited by 98 publications

References 33 publications

Multi-objective shape optimization of siphon outlet in pumping station considering two-phase flow

Multi-objective shape optimization of siphon outlet in pumping station considering two-phase flow

Investigation into Influence of Wall Roughness on the Hydraulic Characteristics of an Axial Flow Pump as Turbine

Numerical study on the mechanism of fluid energy transfer in an axial flow pump impeller under the rotating coordinate system

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