Prediction of the Effect of Impeller Trimming on the Hydraulic Performance of Low Specific-Speed Centrifugal Pumps

2018 ◽  
Vol 140 (8) ◽  
Author(s):  
D. G. J. Detert Oude Weme ◽  
M. S. van der Schoot ◽  
N. P. Kruyt ◽  
E. J. J. van der Zijden
Keyword(s):  
Flow Field ◽  
Prediction Method ◽  
Hydraulic Performance ◽  
New Method ◽  
Prediction Methods ◽  
Centrifugal Pumps ◽  
Flow Rates ◽  
Pump Head ◽  
Low Specific Speed ◽  
Specific Speed

The effect of trimming of radial impellers on the hydraulic performance of low specific-speed centrifugal pumps is studied. Prediction methods from literature, together with a new prediction method that is based on the simplified description of the flow field in the impeller, are used to quantify the effect of trimming on the hydraulic performance. The predictions by these methods are compared to measured effects of trimming on the hydraulic performance for an extensive set of pumps for flow rates in the range of 80% to 110% of the best efficiency point. Of the considered methods, the new prediction method is more accurate (even for a large impeller trim of 12%) than the considered methods from literature. The new method generally overestimates the reduction in the pump head after trimming, and hence results less often in impeller trims that are too large when the method is used to determine the amount of trimming that is necessary in order to attain a specified head.

The effect of wear ring clearance on flow field in the impeller sidewall gap and efficiency of a low specific speed centrifugal pump

2017 ◽  
Vol 232 (17) ◽  
pp. 3062-3073 ◽  
Author(s):  
M DaqiqShirazi ◽  
R Torabi ◽  
A Riasi ◽  
SA Nourbakhsh
Keyword(s):  
Flow Field ◽  
Centrifugal Pump ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Volumetric Efficiency ◽  
Centrifugal Pumps ◽  
Disk Friction ◽  
Low Specific Speed ◽  
Overall Efficiency ◽  
Specific Speed

In this paper, the flow in the impeller sidewall gap of a low specific speed centrifugal pump is analyzed to study the effect of wear ring clearance and the resultant through-flow on flow field in this cavity and investigate the overall efficiency of the pump. Centrifugal pumps are commonly subject to a reduction in the flow rate and volumetric efficiency due to abrasive liquids or working conditions, since the wear rings are progressively worn, the internal leakage flow is increased. In the new operating point, the overall efficiency of the pump cannot be predicted simply by using the pump characteristic curves. The flow field is simulated with the use of computational fluid dynamics and the three-dimensional full Navier–Stokes equations are solved using CFX software. In order to verify the numerical simulations, static pressure field in volute casing and pump performance curves are compared with the experimental measurements. The results show that, for the pump with minimum wear ring clearance, the disk friction efficiency is the strongest factor that impairs the overall efficiency. Therefore, when the ring clearance is enlarged more than three times, although volumetric efficiency decreases effectively but the reduction in overall efficiency is remarkably smaller due to improvement in the disk friction losses.

scholarly journals Experimental and Numerical Investigation of Pressure Fluctuation in a Low-Specific-Speed Centrifugal Pump with a Gap Drainage Impeller

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Li Zhang ◽  
Hui Li ◽  
Hong Xu ◽  
Weidong Shi ◽  
Yang Yang ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Flow Field ◽  
Pressure Pulsation ◽  
Internal Flow ◽  
Stable Operation ◽  
Simulation Methods ◽  
Centrifugal Pumps ◽  
Numerical Simulation Methods ◽  
Low Specific Speed ◽  
Specific Speed

In order to analyze the effect of impeller with different slot widths on the performance of the low-specific-speed centrifugal pumps, based on the impeller of a single-stage pump with the specific speed of 21, two gap drainage schemes with slot widths of 1.5 mm and 6.0 mm, slot diameter of 180 mm, and lap length of 5 mm were designed. Both experimental and numerical simulation methods were applied to compare the steady performance, which includes the head, efficiency, and the internal flow field distribution, and the unsteady pressure pulsation performance between new designed pumps and the original pump. The results show that gap drainage would cause a certain degree of head reduction, but a smaller slot width could achieve higher efficiency. Meanwhile, a reasonable open seam scheme can reduce the development of pressure pulsation, which provides experience and reference for the stable operation of low-specific-speed centrifugal pumps.

scholarly journals Effect of Short Blade Circumferential Position Arrangement on Gas-Liquid Two-Phase Flow Performance of Centrifugal Pump

Processes ◽  
2020 ◽  
Vol 8 (10) ◽  
pp. 1317
Author(s):  
Biaobiao Wang ◽  
Haoyang Zhang ◽  
Fanjie Deng ◽  
Chenguang Wang ◽  
Qiaorui Si
Keyword(s):  
Flow Field ◽  
Centrifugal Pump ◽  
Two Phase Flow ◽  
Low Flow ◽  
Phase Flow ◽  
Centrifugal Pumps ◽  
Suction Surface ◽  
Two Phase ◽  
Low Specific Speed ◽  
Specific Speed

In order to study the internal flow characteristics of centrifugal pumps with a split impeller under gas-liquid mixed transportation conditions, this paper conducted a steady calculation of the flow field in the centrifugal pump under the conditions of different inlet gas volume fractions based on the Eulerian-Eulerian heterogeneous flow model, using air and water as the working media and the Schiller Nauman model for the interphase resistance. This paper takes a low specific speed centrifugal pump as the research object, through the controlling variables, using the same pump body structure and pump body geometric parameters and setting three different arrangements of long and short blades (each plan uses the same long and short blades) to explore the influence of the short blade arrangement on the low specific speed centrifugal pump performance under a gas-liquid two-phase flow. The research results show that, under pure water conditions, the reasonable arrangement of the short blade circumferential position can eliminate the hump of the centrifugal pump under low-flow conditions, can make the flow velocity in the impeller more uniform, and can optimize the performance of the pump. Under the design conditions and the gas-liquid two-phase inflow conditions, when the circumferential position of the short blades is close to the suction surface of the long blades, some of the bubbles on the suction surface of the long blade can be broken under the work of the pressure surface of the short blade and flow out of the impeller with the liquid, which improves the flow state of the flow field in the impeller.

scholarly journals Optimal Design of Slit Impeller for Low Specific Speed Centrifugal Pump Based on Orthogonal Test

2021 ◽  
Vol 9 (2) ◽  
pp. 121
Author(s):  
Yang Yang ◽  
Ling Zhou ◽  
Hongtao Zhou ◽  
Wanning Lv ◽  
Jian Wang ◽  
...  
Keyword(s):  
Numerical Simulation ◽  
Centrifugal Pump ◽  
Large Scale ◽  
Internal Flow ◽  
Orthogonal Test ◽  
Centrifugal Pumps ◽  
Initial Model ◽  
Low Specific Speed ◽  
Specific Speed ◽  
Four Levels

Marine centrifugal pumps are mostly used on board ship, for transferring liquid from one point to another. Based on the combination of orthogonal testing and numerical simulation, this paper optimizes the structure of a drainage trough for a typical low-specific speed centrifugal pump, determines the priority of the various geometric factors of the drainage trough on the pump performance, and obtains the optimal impeller drainage trough scheme. The influence of drainage tank structure on the internal flow of a low-specific speed centrifugal pump is also analyzed. First, based on the experimental validation of the initial model, it is determined that the numerical simulation method used in this paper is highly accurate in predicting the performance of low-specific speed centrifugal pumps. Secondly, based on the three factors and four levels of the impeller drainage trough in the orthogonal test, the orthogonal test plan is determined and the orthogonal test results are analyzed. This work found that slit diameter and slit width have a large impact on the performance of low-specific speed centrifugal pumps, while long and short vane lap lengths have less impact. Finally, we compared the internal flow distribution between the initial model and the optimized model, and found that the slit structure could effectively reduce the pressure difference between the suction side and the pressure side of the blade. By weakening the large-scale vortex in the flow path and reducing the hydraulic losses, the drainage trough impellers obtained based on orthogonal tests can significantly improve the hydraulic efficiency of low-specific speed centrifugal pumps.

scholarly journals Optimization of Centrifugal Slurry Pump Through the Splitter Blades Position

2021 ◽  
Author(s):  
Ehsan Abdolahnejad ◽  
Mahdi Moghimi ◽  
Shahram Derakhshan
Keyword(s):  
Optimal Number ◽  
Centrifugal Pumps ◽  
Slurry Flow ◽  
Suction Surface ◽  
Two Phase ◽  
Flow Rates ◽  
Simulation Tools ◽  
Slip Factor ◽  
Pump Head ◽  
Solid Liquid

Abstract Optimal transfer of two-phase solid-liquid flow (slurry flow) has long been a major industrial challenge. Slurry pumps are among the most common types of centrifugal pumps used to deal with this transfer issue. The approach of improving slurry pumps and consequently increasing the efficiency of a flow transmission system requires overcoming the effects of slurry flow such as the reduction in head, efficiency, and wear. This study attempts to investigate the changes in the pump head by modifying the slip factor distribution in the impeller channel. For this purpose, the effect of splitter blades on slip factor distribution to improve the pump head was investigated using numerical simulation tools and validated based on experimental test data. Next, an optimization process was used to determine the characteristics of the splitter (i.e., length, number, and environmental position of the splitter) based on a combination of experimental design methods, surface response, and genetic algorithm. The optimization results indicate that the splitters were in a relative circumferential position of 67.2% to the suction surface of the main blade. Also, the optimal number and length of splitter blades were 6 and 62.8% of the length of the main blades, respectively. Because of adding splitter blades and the reduction in the flow passage, the best efficiency point (BEP) of the slurry pump moved toward lower flow rates. The result of splitter optimization was the increase in pump head from 29.7 m to 31.7 m and the upkeep of efficiency in the initial values.

Effects of short blades on performance and inner flow characteristics of a low-specific-speed centrifugal pump

2017 ◽  
Vol 231 (4) ◽  
pp. 290-302 ◽  
Author(s):  
Can Kang ◽  
Ning Mao ◽  
Chen Pan ◽  
Yang Zhu ◽  
Bing Li
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
Pressure Fluctuations ◽  
Flow Characteristics ◽  
Low Flow ◽  
Back Surface ◽  
Flow Rates ◽  
Pump Operation ◽  
Low Specific Speed ◽  
Specific Speed

A low-specific-speed centrifugal pump equipped with long and short blades is studied. Emphasis is placed on the pump performance and inner flow characteristics at low flow rates. Each short blade is intentionally shifted towards the back surface of the neighboring long blade, and the outlet parts of the short blades are uniformly shortened. Unsteady numerical simulation is conducted to disclose inner flow patterns associated with the modified design. Thereby, a comparison is enabled between the two schemes featured by different short blades. Both practical operation data and numerical results support that the deviation and cutting of the short blades can eliminate the positive slope of pump head curve at low flow rates. Therefore, the modification of short blades improves the pump operation stability. Due to the shortening of the outlet parts of the short blades, velocity distributions between impeller outlet and radial diffuser inlet exhibit explicitly altered circumferential flow periodicity. Pressure fluctuations in the radial diffuser are complex in terms of diversified periodicity and amplitudes. Flow rate influences pressure fluctuations in the radial diffuser considerably. As flow rate decreases, the regularity of the orbit of hydraulic loads exerted upon the impeller collapses while hydraulic loads exerted upon the short blades remain circumferentially periodic.

Effects of Blade Outlet Width on Flow Field and Characteristic of Centrifugal Pumps

2009 ◽  
Author(s):  
Ming-gao Tan ◽  
Hou-lin Liu ◽  
Shou-qi Yuan ◽  
Yong Wang ◽  
Kai Wang
Keyword(s):  
Flow Field ◽  
Flow Curve ◽  
High Efficiency ◽  
Field Analysis ◽  
Centrifugal Pumps ◽  
Research Results ◽  
Rotor Stator Interaction ◽  
Nominal Condition ◽  
Specific Speed ◽  
Width Change

The present deficiency about numerical simulation research on blade outlet width of centrifugal pumps is pointed out. In the case of different outlet widths, the flow field in six centrifugal pumps whose specific speed vary from 45 to 260 are simulated by using commercial code FLUENT and the characteristics are predicted. The standard k-ε turbulence model and SIMPLEC algorithm are chosen in FLUENT. The simulation is steady and moving reference frame is used to consider rotor-stator interaction. The research results show that the change of impeller outlet width has obvious impacts on characteristics at design point, flow field and the shape of performance curves. At nominal condition, the change of outlet width has more important effects on moderate specific speed centrifugal pumps. The flow field analysis indicates that blade outlet width change has an important effect on the location and area of low pressure region behind the blade inlet, jet-wake structure in impellers, the secondary flow in volute cross section and the back flow in impellers. The head-flow curve becomes more flat with the increase of outlet width. For moderate and low specific speed centrifugal pumps, the high efficiency area of efficiency-flow curve get bigger with the increase of outlet width and the area will be constant within certain outlet width change scope for high specific speed centrifugal pump. The research results agree well with experiment results.

Experimental Tests With Centrifugal Pumps: Degradation of Performance, Instability and Dynamic Phenomena With Non-Newtonian Suspensions of Kaolin in Water

2019 ◽  
Author(s):  
Matteo Occari ◽  
Enrico Munari ◽  
Valentina Mazzanti ◽  
Michele Pinelli ◽  
Francesco Mollica ◽  
...  
Keyword(s):  
Experimental Tests ◽  
Newtonian Fluids ◽  
Low Flow ◽  
Time Varying ◽  
Centrifugal Pumps ◽  
Strong Reduction ◽  
Flow Rates ◽  
Specific Speed ◽  
Dynamic Phenomena ◽  
Newtonian Behavior

Abstract The performance of pumps when working with non-Newtonian fluids significantly change with respect to water. In several experimental tests with non-Newtonian fluids, significant deration of head and the presence of head instability were observed. The present work aims to better understand this phenomenon since the reasons that originate it are not clear. Two small size centrifugal pumps were experimentally tested with different mixtures of kaolin-in-water, which showed a verified non-Newtonian behavior. The rheology of the mixtures and the particle size distribution of kaolin powder were measured to characterize the fluids. Similar to previous tests, a strong reduction of head and the appearance of instability were observed at low flow rates and, in some cases, also at higher flow rates. This behavior was related to the presence of air trapped into the fluid that, within the pump, generated a phenomenon known as gas-locking, which in literature it has been studied in detail with water but not with non-Newtonian fluids. Moreover, in some working conditions, non-stable time-varying phenomena are observed and their consequence on performance commented. Comparing the two pumps, characterized by a similar specific speed but by a different geometry, the head drop manifested itself with different intensity.

scholarly journals Numerical Simulation of 3D Solid-Liquid Turbulent Flow in a Low Specific Speed Centrifugal Pump: Flow Field Analysis

2014 ◽  
Vol 6 ◽  
pp. 814108 ◽  
Author(s):  
Baocheng Shi ◽  
Jinjia Wei
Keyword(s):  
Turbulent Flow ◽  
Centrifugal Pump ◽  
Centrifugal Pumps ◽  
Numerical Convergence ◽  
Phase Calculation ◽  
Low Specific Speed ◽  
Specific Speed ◽  
3D Solid ◽  
Solid Liquid ◽  
Numeral Simulation

For numerically simulating 3D solid-liquid turbulent flow in low specific speed centrifugal pumps, the iteration convergence problem caused by complex internal structure and high rotational speed of pump is always a problem for numeral simulation researchers. To solve this problem, the combination of three measures of dynamic underrelaxation factor adjustment, step method, and rotational velocity control means according to residual curves trends of operating parameters was used to improve the numerical convergence. Numeral simulation of 3D turbulent flow in a low specific speed solid-liquid centrifugal pump was performed, and the results showed that the improved solution strategy is greatly helpful to the numerical convergence. Moreover, the 3D turbulent flow fields in pumps have been simulated for the bottom ash-particles with the volume fraction of 10%, 20%, and 30% at the same particle diameter of 0.1 mm. The two-phase calculation results are compared with those of single-phase clean water flow. The calculated results gave the main region of the abrasion of the impeller and volute casing and improve the hydraulic design of the impeller in order to decrease the abrasion and increase the service life of the pump.

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