Interaction between Impeller and Axial Diffuser of Mixed Flow Pump

2014 ◽  
Vol 630 ◽  
pp. 35-42 ◽  
Author(s):  
Michal Varchola ◽  
Peter Hlbočan
Keyword(s):  
Internal Flow ◽  
Performance Curve ◽  
Performance Parameters ◽  
Energy Transformation ◽  
Mixed Flow ◽  
And Performance ◽  
Design Factors ◽  
Stated Problem ◽  
Important Design ◽  
Flow Pump

Topic related to an impeller - diffuser hydraulic interaction is important especially in term of energy transformation and performance parameters. A connection of particular functional parts is one of the most important design factors which determine a shape of performance parameters and efficiency. The stated problem is possible to discuss in two possible ways. In term of internal flow pattern and in term of external pump parameters which are represented by performance curve courses. The contribution deals with the influence of the change of the impeller - axial diffuser interaction on quantitative courses of specific energy and efficiency curves.

1507 Performance Curve Instability and Internal Flow of Mixed-Flow Pump

2005 ◽  
Vol 2005 (0) ◽  
pp. 209
Author(s):  
Sunao Miyauchi ◽  
Kengo Okamoto ◽  
Yuiki Kiyoto ◽  
Junichiro Fukutomi
Keyword(s):  
Internal Flow ◽  
Performance Curve ◽  
Mixed Flow ◽  
Flow Pump

scholarly journals Cause specification of performance curve instability in mixed-flow pump by LES

2016 ◽  
Vol 82 (834) ◽  
pp. 15-00533-15-00533
Author(s):  
Isao HAGIYA ◽  
Chisachi KATO ◽  
Yoshinobu YAMADE ◽  
Takahide NAGAHARA ◽  
Masashi FUKAYA
Keyword(s):  
Performance Curve ◽  
Mixed Flow ◽  
Flow Pump

Transient characteristics of internal flow fields of mixed-flow pump with different tip clearances under stall condition

2020 ◽  
pp. 095765092096225
Author(s):  
Leilei Ji ◽  
Wei Li ◽  
Weidong Shi ◽  
Ramesh Agarwal
Keyword(s):  
Swirling Flow ◽  
Internal Flow ◽  
Flow Fields ◽  
Design Flow ◽  
Tip Clearance ◽  
Tip Leakage Flow ◽  
Mixed Flow ◽  
Transient Characteristics ◽  
Initial Starting ◽  
Flow Pump

This paper investigates the influence of different tip clearances on the transient characteristics of mixed-flow pump under stall condition. The instantaneous internal flow fields of mixed-flow pump with four tip clearances (0.2 mm, 0.5 mm, 0.8 mm and 1.1 mm) are explored by conducting unsteady time accurate simulations. Reynolds-averaged Navier-Stokes (RANS) equations are employed in the simulations and the results of computations are compared with experimental data. The results show that the pump head decreases by 22.1% and the pump efficiency drops by 13.9% at design flow condition when the impeller tip clearance increases from 0.2 mm to 1.1 mm. The swirling flow occurs in the inlet pipe of the mixed-flow pump with different tip clearances under stall condition, and the initial starting point of the swirling flow gets further away from the impeller inlet with increase in tip clearance because of increase in circumferential velocity and change in momentum of the tip leakage flow (TLF). The high turbulent eddy dissipation (TED) regions in the flow are attributed to the TLF, swirling flow, back flow and stall vortex, and their intensity are affected by the change in tip clearance. The oscillating trend of time domain distribution of TED enhances first and then decreases with increase in tip clearance and it exhibits a propagation feature under the effect of stall vortex, while most of the energy in the frequency domain remains concentrated in the low frequency part under stall condition.

Influence of tip leakage flow and inlet distortion flow on a mixed-flow pump with different tip clearances within the stall condition

2019 ◽  
Vol 234 (4) ◽  
pp. 433-453 ◽  
Author(s):  
Leilei Ji ◽  
Wei Li ◽  
Weidong Shi
Keyword(s):  
Internal Flow ◽  
Energy Performance ◽  
Rotating Stall ◽  
Design Flow ◽  
Tip Clearance ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Mixed Flow ◽  
Tip Leakage ◽  
Flow Pump

In order to investigate the effect of impeller tip clearance on internal flow fields and the rotating stall inception impacted by tip leakage vortex and inlet unsteady flow in a mixed-flow pump, mixed-flow pump models with tip clearances of 0.5 mm, 0.8 mm, and 1.1 mm were numerically calculated, and then the energy performance curves and internal flow structures were obtained and compared. The results show that the pump efficiency and the internal flow fields of numerical calculation are in good agreement with experimental results at design flow rate and near-stall condition. A portion of the positive slope segment appears in the energy performance curves under different tip clearances. The lowest head of the mixed-flow pump in the positive slope region decreases with the increase of the tip clearance while the highest head shows an opposite situation indicating that mixed-flow pumps are easier to stall under small tip clearance. At the design flow rate condition, the tip leakage vortex is relatively stable under different tip clearances and appears as a “snail shell” shape, whereas in rotating stall conditions, the “snail shell” shape disappear and the tip leakage flow on blade front forms a “flat” vortex structure. The inlet swirl flow not only affects the tip leakage flow in rotating stall conditions under different tip clearances, but also blocks the fluid from the inlet pipe. Under the circumstance of the same tip clearance, the main frequency amplitude of pressure pulsation coefficient gradually shifts away from blade passing frequency (96.67 Hz) to the axial frequency (24.17 Hz) when the pump operates in the stall condition.

Analysis of internal flow and cavitation characteristics for a mixed-flow pump with various blade thickness effects

2019 ◽  
Vol 33 (7) ◽  
pp. 3333-3344 ◽  
Author(s):  
Yong-In Kim ◽  
Sung Kim ◽  
Hyeon-Mo Yang ◽  
Kyoung-Yong Lee ◽  
Young-Seok Choi
Keyword(s):  
Internal Flow ◽  
Mixed Flow ◽  
Blade Thickness ◽  
Flow Pump

Investigation of Internal Flow and Characteristic Instability of a Mixed Flow Pump

2009 ◽  
Author(s):  
Masahiro Miyabe ◽  
Akinori Furukawa ◽  
Hideaki Maeda ◽  
Isamu Umeki
Keyword(s):  
Flow Rate ◽  
Internal Flow ◽  
Rotating Stall ◽  
Leakage Flow ◽  
Suction Surface ◽  
Mixed Flow ◽  
Vaned Diffuser ◽  
Flow Angle ◽  
Pressure Surface ◽  
Flow Pump

The relationship between pump characteristic instabilities and internal flow was investigated in a mixed flow pump with specific speed of 700 (min−1 m3/min, m) or 1.72 (non-dimensional) by using a commercial CFD code and a dynamic PIV (DPIV) measurement. This pump has two positive slopes of a head-flow characteristic at the flow rates of about 60%Qopt and 82%Qopt. In the authors’ previous study, it was clarified that the characteristic instability at 82%Qopt is caused by the diffuser rotating stall (DRS) and the backflow near the hub of the vaned diffuser plays an important role on the onset of the diffuser rotating stall. In the present paper, the investigation is focused on the instability at about 60% Qopt. Based on both of experimental and numerical results, it was clarified that the characteristic instability at 60%Qopt is caused by the backflow at the inlet of the impeller tip and the leakage flow from the impeller pressure surface to the suction surface plays an important role on the onset of the backflow. The behaviors of backflow at the impeller inlet were visualized by the DPIV measurements and CFD simulation. Moreover, internal flow was investigated in detail and the occurrence of characteristic instability is assumed as follows: At the partial flow rate, the flow angle at the inlet of the impeller tip decreases and the flow hits the impeller pressure surface. Then, the blade loading at the inlet of impeller tip is increased and the recirculation at the leading edge and the leakage flow rate from pressure surface to suction surface increases. The leakage flow causes to generate vortices at the inlet of the suction surface of the impeller. As the flow rate is further decreased, the vortices develop to backflow with swirl. The leakage flow has peripheral component of absolute velocity and the swirling energy is continuously supplied by the backflow. Therefore, even the passage flow at the inlet of the impeller has been getting pre-swirling. The theoretical head, the Euler head is decreased due to the pre-swirling. Moreover, based on the CFD results, the pre-swirling and unsteady vortices near the suction surface of the impeller causes pump characteristic instability. When the flow rate is decreased further more, total head rises because the flow pattern in the impeller changes to centrifugal type due to the backflow from the vaned diffuser at the hub region.

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

Water ◽  
2021 ◽  
Vol 13 (24) ◽  
pp. 3575
Author(s):  
Shuo Li ◽  
Wei Li ◽  
Leilei Ji ◽  
Weidong Shi ◽  
Ramesh K. Agarwal
Keyword(s):  
Flow Field ◽  
Vortex Core ◽  
Guide Vane ◽  
Internal Flow ◽  
Tip Leakage Flow ◽  
Mixed Flow ◽  
Tip Leakage ◽  
L1 And L2 ◽  
The Impact ◽  
Flow Pump

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.

scholarly journals Effect of Rotational Speed on Performance of Mixed Flow Pump as Turbine

2021 ◽  
Vol 2021 ◽  
pp. 1-8
Author(s):  
Jun Chen ◽  
Tao Dai ◽  
Qing Yang
Keyword(s):  
Energy Recovery ◽  
Theoretical Calculations ◽  
Flow Characteristics ◽  
Internal Flow ◽  
High Water ◽  
Mixed Flow ◽  
High Water Period ◽  
Shaft Power ◽  
Pumped Storage ◽  
Flow Pump

In order to research the flow characteristics of mixed flow pump as turbine (MF-PAT) with different rotation speeds, a hydraulic model of mixed flow pump was established based on a pumped storage power station. The k-ε turbulent model was used to simulate internal flow fields with three rotation speeds by SMPLEC algorithms. Subsequently, theoretical calculations and experiments were carried out to verify the precision of numerical simulation. The results showed that the rotation speed of MF-PAT has a significant impact on its performance. Both numerical calculations and experimental test presented that all efficiency curves consist of ascending and descending stages, while the shaft power and head increase nonlinearly from 1000 to 2000 r/min. When the MF-PAT  deviates from the rated environment, increase in speed is positive to the energy recovery efficiency in the high water period and negative in the dry season. This work could provide a reference for further study of MF-PAT.

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