Numerical investigation of energy loss mechanism of mixed-flow pump under stall condition

Li, Wei; Ji, Leilei; Li, Enda; Shi, Weidong; Agarwal, Ramesh K.; Zhou, Lian

doi:10.1016/j.renene.2020.11.146

Cited by 67 publications

(13 citation statements)

References 29 publications

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“…It can be seen that when the roughness is less than 60 µm, the roughness has little influence on the pressure near the leading edge. From Figure 12c Turbulent kinetic energy (TKE) is a measure of the turbulence intensity, associated with momentum transport through turbulence eddies in the boundary layer region [32].…”

Section: Effect Of Wall Roughness On Streamline Of Outlet Conduitmentioning

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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Section: Effect Of Wall Roughness On Streamline Of Outlet Conduitmentioning

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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“…The y+ on the blade wall is lower than 50, which meets the requirements of the turbulence model for y+ near the wall. The grid is shown in Figure 3 [38,39].…”

Section: Meshingmentioning

confidence: 99%

A Study on the Cavitation and Pressure Pulsation Characteristics in the Impeller of an LNG Submerged Pump

Wei

et al. 2021

Machines

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Based on CFD analysis technology, this paper studies the cavitation performance of an LNG submerged pump and the pressure pulsation characteristics under cavitation excitation. The variation laws of the waveform, amplitude and frequency of the pressure pulsation in the impeller of the LNG submerged pump under different flow rates and NPSHa are also analysed. By calculating the root mean square of the pressure coefficient of the low-frequency pulsation, the influence of the aggravation process of cavitation on the low-frequency pulsation in the LNG submerged pump is quantitatively analysed, and the characteristics of the pressure pulsation in the LNG submerged pump under the cavitation condition are revealed. The results show that with the increase in flow rate, the pressure pulsation in the impeller becomes stronger, periodically, and the amplitude decreases. The influence of cavitation on the pressure pulsation in the primary impeller is greater than that in the secondary impeller. When critical cavitation occurs, the low-frequency signal amplitude of pressure pulsation in the primary impeller increases and exceeds the blade frequency, becoming the main frequency.

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“…Taking the mixed-flow pump as the research object, based on the previous study of its internal flow and shafting vibration [26][27][28][29], the numerical calculation method of a mixed-flow pump under the Alford effect is established, and the vortex structure of non-uniform blade tip clearance is identified by using the Q-criterion method. Based on the vorticity moment theorem, the stress of non-uniform blade tip clearance is analyzed, and the internal flow of the mixed-flow pump under the Alford effect is explored.…”

Section: Introductionmentioning

confidence: 99%

Vortex Dynamics Analysis of Internal Flow Field of Mixed-Flow Pump under Alford Effect

Wei

et al. 2021

Water

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A multi-region dynamic slip method was established to study the internal flow characteristics of the mixed-flow pump under the Alford effect. The ANSYS Fluent software and the standard k-ε two-equation model were used to numerically predict the mixed-flow pump’s external characteristics and analyze the forces on the impeller and guide vane internal vortex structure and non-uniform tip gap of the mixed-flow pump at different eccentric distances. The research results show that the external characteristic results of the numerical calculation are consistent with the experimental measurement. The head error of the design flow operating point is about 5%, and the efficiency error is no more than 3%, indicating the high accuracy of numerical calculation. Eccentricity has a significant influence on the flow field in the tip area of the mixed-flow pump impeller, the distribution of vortex core in the impeller presents obvious asymmetry, the strength and distribution area of the vortex core in the small gap area of the tip increase obviously, which aggravates the flow instability and increases the energy loss. With the increase of eccentricity, the strength and number of vortex core structures in the guide vane also increase significantly, and obvious flow separation occurs near the inlet of the guide vane suction surface on the eccentric side of the impeller. The circumferential distribution of L1 and L2 values represents the friction pressure gap in the eccentric state, and the eccentricity has a more noticeable effect on L1 and L2 values at the small gap; With the increase of eccentricity, the values of vorticity moment components L1 and L2 increase, and the Alford moment on the impeller increases. The leading-edge region of the blade is the main part affected by the unstable torque of the flow field. With the increase of eccentricity, the impact degree of tip leakage flow deepens, and the change of the tip surface pressure is the most obvious. The impact area of tip leakage flow is mainly concentrated in the first half of the impeller channel, which has an impact on the blade inlet flow field but has little impact on the blade outlet flow field.

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Numerical investigation of energy loss mechanism of mixed-flow pump under stall condition

Cited by 67 publications

References 29 publications

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

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

A Study on the Cavitation and Pressure Pulsation Characteristics in the Impeller of an LNG Submerged Pump

Vortex Dynamics Analysis of Internal Flow Field of Mixed-Flow Pump under Alford Effect

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