Experimental and Numerical Investigation On the Transient Cavitating Flows in a Mixed Flow Pump with Different Number of Blades At Startup

2021 ◽  
Author(s):  
ZHANG Desheng ◽  
Zhou Qiang ◽  
Gu Qi ◽  
Zhang Guangjian ◽  
Bin Xu ◽  
...  
Keyword(s):  
Growth Stage ◽  
Transient Flow ◽  
Inhibitory Effect ◽  
Cavitation Flow ◽  
Mixed Flow ◽  
Coverage Area ◽  
Reduction Stage ◽  
Sheet Cavitation ◽  
Blade Number ◽  
Flow Pump

Abstract The objective of this paper is to experimentally and numerically investigate the transient cavitation flow during the startup process of mixed flow pump with emphasis on studying the influence of blade numbers. The transient cavitation simulation was studied based on the improved SST k-ω turbulence model and the Zwart cavitation model. Firstly, in order to obtain the relationship between transient flow rate and the variation of rotational speed at startup, a theoretical analysis based on the fast transients of centrifugal pump was first applied to mixed flow pump and was verified by the current experiment study. Subsequently, the influence of blade number on the cavitation flow in the startup was studied. It is found that the transient cavitation could be classified into four stages regardless of the number of blades: no cavitation stage, the cavitation growth stage, the cavitation reduction stage and the cavitation stabilization stage. However, the blade number does have an impact on the spatial-temporal evolution of cavitation. More specifically, when the blade number increases, the initial cavitation appeared lately, the coverage area of the triangular cavitation cloud and sheet cavitation both decreased, and the increase in blade number has a better inhibitory effect on the sheet cavitation at the cavitation growth stage, and can make sheet cavitation disappear more quickly at the cavitation reduction stage.

Particle image velocimetry experiment of the inlet flow field in a mixed-flow pump during the startup period

2019 ◽  
Vol 234 (3) ◽  
pp. 300-314 ◽  
Author(s):  
Wei Li ◽  
Leilei Ji ◽  
Weidong Shi ◽  
Enda Li ◽  
Lingling Ma ◽  
...  
Keyword(s):  
Particle Image ◽  
Transient Flow ◽  
Rotation Speed ◽  
Mixed Flow ◽  
Inlet Flow ◽  
Start Up ◽  
Image Velocimetry ◽  
Startup Period ◽  
External Characteristics ◽  
Flow Pump

The transient characteristics of the inlet flow field of mixed-flow pump during start-up process are hard to be measured experimentally. The elbow structure with viewport is designed before the mixed-flow pump for capturing the transient inlet flow fields of the mixed-flow pump. Meanwhile, the synchronous data acceptance system is also designed to collect the data from different sensors synchronously. Besides, uncertainty analysis is carried out after the experiment to ensure the accuracy and reliability of this test system. The transient external characteristics are obtained and the velocity distribution of a mixed-flow pump during the startup period is measured using particle image velocimetry technique. The results show that the overall uncertainty for the external characteristics was 0.2345%, which indicates the high accuracy of this test bench for capturing the transient flow condition in the mixed-flow pump during the startup period. At the beginning of the start-up process, the head of the mixed-flow pump increases and reaches the maximum once the rotation speed meets the maximum value and an instantaneous impulsive head appears at the end of the accelerating process. However, with the increase of the rotating speed, wall boundary layer gradually develops from laminar to turbulent flow, and the flow moves continuously from the hub center to the inlet. At the end stage of the accelerating process, more intensive entrainment effect of the impeller is found. When the rotation speed is steady, the influence of the elbow on the internal flow fields gradually decreases, compared with the startup process. The results can serve as a fundamental reference for the investigation of transient flow characteristics of the mixed-flow pump during the startup period.

Numerical simulation of transient flow field in a mixed-flow pump during starting period

2018 ◽  
Vol 28 (4) ◽  
pp. 927-942 ◽  
Author(s):  
Wei Li ◽  
Yang Zhang ◽  
Weidong Shi ◽  
Leilei Ji ◽  
Yongfei Yang ◽  
...  
Keyword(s):  
Flow Field ◽  
Transient Flow ◽  
Rotation Speed ◽  
Flow Characteristics ◽  
Mixed Flow ◽  
Content Type ◽  
Start Up ◽  
Study Results ◽  
Flow Pump ◽  
Stable Stage

Purpose This paper aims to study the transient flow characteristics in a mixed-flow pump during the start-up period. Design/methodology/approach In this study, numerical calculation of the internal flow field in a mixed-flow pump using the sliding mesh method was carried out. The regulation of the pressure, streamline and the relative speed during the start-up period was analyzed. Findings The trend of the simulated head is consistent with the experimental results, and the calculated head is around 0.3 m higher than the experimental head when the rotation speed reached the stable stage, indicating that the numerical method for the start-up process simulation of the mixed-flow pump has a high accuracy. At the beginning, the velocity inside the impeller changes little along the radius direction and the flow rate increases slowly during the start-up process. As the rotation speed reached the stable stage, the flow inside the impeller became steady, the vortex reduced and transient effects disappeared gradually. Originality/value The study results have significant value for revealing the internal unsteady flow characteristics of the mixed-flow pump and providing the reference for the design optimization of the mixed-flow pump.

scholarly journals Unsteady Hydraulic Force in Mixed-Flow Pump with Volute Casing.

1997 ◽  
Vol 63 (614) ◽  
pp. 3330-3337 ◽  
Author(s):  
Hayato SHIMIZU ◽  
Chisachi KATO ◽  
Tomoyoshi OKAMURA ◽  
Takehiko KOMATSU
Keyword(s):  
Mixed Flow ◽  
Hydraulic Force ◽  
Flow Pump

Effect of Blade Thickness on Rotating Stall of Mixed-Flow Pump Using Entropy Generation Analysis

Energy ◽  
2021 ◽  
pp. 121381
Author(s):  
Leilei Ji ◽  
Wei Li ◽  
Weidong Shi ◽  
Fei Tian ◽  
Ramesh Agarwal
Keyword(s):  
Entropy Generation ◽  
Rotating Stall ◽  
Mixed Flow ◽  
Blade Thickness ◽  
Flow Pump

DEVELOPMENT OF A MINIATURE MIXED-FLOW PUMP TO REPLACE TOTAL HEART FUNCTION

ASAIO Journal ◽  
1996 ◽  
Vol 42 (2) ◽  
pp. 8
Author(s):  
H. Anai ◽  
K. Araki ◽  
M. Oshikawa ◽  
T. Hadama ◽  
Y. Uchida
Keyword(s):  
Heart Function ◽  
Mixed Flow ◽  
Flow Pump

Effect of Tip Clearance on Suction Performance at Different Flow Rates in a Mixed Flow Pump

2014 ◽  
Author(s):  
Yo Han Jung ◽  
Young Uk Min ◽  
Jin Young Kim
Keyword(s):  
Performance Test ◽  
Stokes Equations ◽  
Flow Characteristics ◽  
Tip Clearance ◽  
Low Flow ◽  
Tip Leakage Flow ◽  
Mixed Flow ◽  
Flow Rates ◽  
Suction Performance ◽  
Flow Pump

This paper presents a numerical investigation of the effect of tip clearance on the suction performance and flow characteristics at different flow rates in a vertical mixed-flow pump. Numerical analyses were carried out by solving three-dimensional Reynolds-averaged Navier-Stokes equations. Steady computations were performed for three different tip clearances under noncavitating and cavitating conditions at design and off-design conditions. The pump performance test was performed for the mixed-flow pump and numerical results were validated by comparing the experimental data for a system characterized by the original tip clearance. It was shown that for large tip clearance, the head breakdown occurred earlier at the design and high flow rates. However, the head breakdown was quite delayed at low flow rate. This resulted from the cavitation structure caused by the tip leakage flow at different flow rates.

Influence of different blade numbers on the performance of “saddle zone” in a mixed flow pump

2021 ◽  
pp. 095765092110460
Author(s):  
Leilei Ji ◽  
Wei Li ◽  
Weidong Shi ◽  
Fei Tian ◽  
Shuo Li ◽  
...  
Keyword(s):  
Flow Field ◽  
Leading Edge ◽  
Leakage Flow ◽  
Tip Leakage Flow ◽  
Mixed Flow ◽  
Impeller Blade ◽  
Flow Angle ◽  
Tip Leakage ◽  
Vorticity Transport ◽  
Flow Pump

In order to study the effect of different numbers of impeller blades on the performance of mixed-flow pump “saddle zone”, the external characteristic test and numerical simulation of mixed-flow pumps with three different impeller blade numbers were carried out. Based on high-precision numerical prediction, the internal flow field and tip leakage flow field of mixed flow pump under design conditions and stall conditions are investigated. By studying the vorticity transport in the stall flow field, the specific location of the high loss area inside the mixed flow pump impeller with different numbers of blades is located. The research results show that the increase in the number of impeller blades improve the pump head and efficiency under design conditions. Compared to the 4-blade impeller, the head and efficiency of the 5-blade impeller are increased by 5.4% and 21.9% respectively. However, the increase in the number of blades also leads to the widening of the “saddle area” of the mixed-flow pump, which leads to the early occurrence of stall and increases the instability of the mixed-flow pump. As the mixed-flow pump enters the stall condition, the inlet of the mixed-flow pump has a spiral swirl structure near the end wall for different blade numbers, but the depth and range of the swirling flow are different due to the change in the number of blades. At the same time, the change in the number of blades also makes the flow angle at 75% span change significantly, but the flow angle at 95% span is not much different because the tip leakage flow recirculates at the leading edge. Through the analysis of the vorticity transport results in the impeller with different numbers of blades, it is found that the reasons for the increase in the values of the vorticity transport in the stall condition are mainly impacted by the swirl flow at the impeller inlet, the tip leakage flow at the leading edge and the increased unsteady flow structures.

Multi-Objective Design Optimization of a Mixed-Flow Pump

2009 ◽  
Author(s):  
Yumiko Takayama ◽  
Hiroyoshi Watanabe
Keyword(s):  
Performance Characteristic ◽  
Performance Characteristics ◽  
Inverse Design ◽  
Surface Model ◽  
Objective Functions ◽  
Mixed Flow ◽  
Multi Objective ◽  
Design Variables ◽  
Flow Head ◽  
Flow Pump

In most cases of high specific speed mixed-flow pump applications, it is necessary to satisfy more than one performance characteristic such as deign point efficiency, shut-off power/head and non-stall characteristic (no positive slope in flow-head curve). However, it is known that these performance characteristics are in relation of trade-offs. As a result, it is difficult to optimize these performance characteristics by conventional way such as trial and error approach by modifying geometrical parameters. This paper presents the results of the multi-objective optimization strategy of mixed-flow pump design by means of three dimensional inverse design approach, Computational Fluid Dynamics (CFD), Design of Experiments (DoE), response surface model (RSM) and Multi Objective Genetic Algorism (MOGA). The parameters to control blade loading distributions and meridional geometries for impeller and diffuser blades in inverse design were chosen as design variables of the optimization process. Pump efficiency, maximum slope in flow-head curve and shut-off power/head were selected as objective functions. Objective functions of pumps, designed by design variables specified in DoE, were evaluated by using CFD. Then, trade-off relations between objective functions were analyzed by using Pareto fronts obtained by MOGA. Some pumps which have specific performance characteristic (non-stall, low shut-off power, high efficiency etc.) designed along the Pareto front were numerically evaluated.

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