Numerical simulation of cavitating flow in a centrifugal pump as turbine

2016 ◽  
Vol 232 (2) ◽  
pp. 135-154 ◽  
Author(s):  
Wenguang Li ◽  
Yuliang Zhang
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
Pressure Coefficient ◽  
Cavitating Flow ◽  
Pump Mode ◽  
Flow Models ◽  
Rate Dependent ◽  
Cavitation Performance ◽  
Critical Cavitation ◽  
Turbine Mode

In this study, the cavitating flow and cavitation performance are studied by employing the computational fluid dynamics method in the turbine mode of a centrifugal pump at part-load, best efficiency, and over-load points. The flow models are validated in the pump mode under noncavitation condition. The relationships between the performance variables and net positive suction head available are obtained, and the corresponding net positive suction heads required are extracted. The flow patterns, location, and shape of the cavity are illustrated; the pressure coefficient profiles on the blade surfaces are clarified and compared with those in the pump mode under both noncavitation and critical cavitation conditions. The cavitation performance and flow pattern as well as cavity shape in the turbine mode are distinguishably different from the pump mode. It is found out that the cavitation behavior in the turbine mode exhibits three notable features: a lower and less flow rate-dependent net positive suction head required, a flow rate-dependent suppressed rotational flow in the draft tube, as well as a rotational and extendable cavitating rope originated from the impeller cone. The results and methods can be important and useful for the design and selection of a centrifugal pump as turbine.

scholarly journals Influence of wall roughness on cavitation performance of centrifugal pump

2021 ◽  
Vol 43 (6) ◽  
Author(s):  
Weihui Xu ◽  
Xiaoke He ◽  
Xiao Hou ◽  
Zhihao Huang ◽  
Weishu Wang
Keyword(s):  
Flow Field ◽  
Centrifugal Pump ◽  
Internal Flow ◽  
Wall Roughness ◽  
Blade Surface ◽  
Centrifugal Pumps ◽  
Three Dimensional Model ◽  
Cavitation Inception ◽  
Cavitation Performance ◽  
Critical Cavitation

AbstractCavitation is a phenomenon that occurs easily during rotation of fluid machinery and can decrease the performance of a pump, thereby resulting in damage to flow passage components. To study the influence of wall roughness on the cavitation performance of a centrifugal pump, a three-dimensional model of internal flow field of a centrifugal pump was constructed and a numerical simulation of cavitation in the flow field was conducted with ANSYS CFX software based on the Reynolds normalization group k-epsilon turbulence model and Zwart cavitation model. The cavitation can be further divided into four stages: cavitation inception, cavitation development, critical cavitation, and fracture cavitation. Influencing laws of wall roughness of the blade surface on the cavitation performance of a centrifugal pump were analyzed. Research results demonstrate that in the design process of centrifugal pumps, decreasing the wall roughness appropriately during the cavitation development and critical cavitation is important to effectively improve the cavitation performance of pumps. Moreover, a number of nucleation sites on the blade surface increase with the increase in wall roughness, thereby expanding the low-pressure area of the blade. Research conclusions can provide theoretical references to improve cavitation performance and optimize the structural design of the pump.

Effect of Bionic Groove Surface Blade on Cavitation Characteristics of Centrifugal Pump

2019 ◽  
Author(s):  
Zicheng Zhang ◽  
Yun Dai ◽  
Yunqing Gu ◽  
Zhengzan Shi ◽  
Jiegang Mou
Keyword(s):  
Centrifugal Pump ◽  
Simulation Method ◽  
Cavitation Resistance ◽  
Suction Surface ◽  
Groove Surface ◽  
Circular Groove ◽  
Cavitation Performance ◽  
Pressure Area ◽  
Grooved Surface ◽  
Critical Cavitation

Abstract In order to improve the cavitation resistance of centrifugal pump, bionic groove surface structure was arranged on the suction surface of centrifugal pump blade which is the most prone to cavitation. Numerical simulation method was used to study the influence of different-shape groove blade on cavitation performance of centrifugal pump. The results showed that the head and efficiency of the centrifugal pump with circular grooved surface blades were close to the smooth surface blade centrifugal pump and higher than those with triangular grooved surface blades and rectangular grooved surface blades. The low pressure area of the circular groove blade was the smallest and the cavitation resistance was the best. At the critical cavitation margin point, circular groove blade can effectively reduce the probability of negative incidence, and the cavitation inhibition effect was the most obvious.

Influences of wear-ring clearance leakage on performance of a small-scale pump-turbine

2019 ◽  
Vol 234 (4) ◽  
pp. 454-469 ◽  
Author(s):  
Jianru Yan ◽  
Zhitao Zuo ◽  
Wenbin Guo ◽  
Hucan Hou ◽  
Xin Zhou ◽  
...  
Keyword(s):  
Flow Rate ◽  
Total Pressure ◽  
Labyrinth Seal ◽  
Work Capacity ◽  
Small Scale ◽  
Leakage Flow ◽  
Pump Mode ◽  
Pump Turbine ◽  
Flow Angle ◽  
Turbine Mode

Wear-ring clearance leakage would affect performance of pump-turbine significantly. In this paper, the variation of the leakage and efficiency of flat ring seal and labyrinth seal are numerically studied on one pump-turbine when the width of clearance is 0.2 mm and 0.5 mm. The result shows that the effect of leakage flow cannot be neglected. The pump-turbine performance affected by leakage in turbine mode is more than that in pump mode at the same sealing structure and width of clearance. Each component’s proportion of total pressure loss hardly varies with flow rate at pump mode, which is opposite to that at turbine mode. Leakage does not change proportionally with system flow rate. When the width of clearance decreases to 0.2 mm, the leakage is reduced obviously because the maximum entropy occurs in the front pump chamber. The mixing of leakage flow and mainstream at impeller inlet at pump mode will increase the total pressure and decrease the flow angle and relative flow angle. Finally, it reduces the impeller’s work capacity.

Performance Analysis of Centrifugal Pump at Different Operating Mode

2018 ◽  
Vol 4 (11) ◽  
pp. 8
Author(s):  
Bhanwar Lal ◽  
Dr. T. S. Deshmukh
Keyword(s):  
Numerical Simulation ◽  
Performance Analysis ◽  
Centrifugal Pump ◽  
Operating Mode ◽  
Operating Conditions ◽  
Maximum Efficiency ◽  
Pump Mode ◽  
Design Discharge ◽  
Rate Of Increase ◽  
Turbine Mode

The   aim of this research is to perform numerical simulation of centrifugal pump and PATs mode to analyse its cavitation characteristics and NPSHr at different operating conditions. It was found that maximum efficiency at design discharge for the PAT is about 2 % less than the efficiency in pump mode. It is observed that the efficiencies increase steadily on increasing the discharge from 8.88 kg/s to 14.8 kg/s. in both pump and turbine mode. Thereafter the rate of increase in efficiency becomes very less when increase in discharge to 17.76 kg/s.  Maximum efficiency of 59.49 % being achieved at 14.8 kg/s.

Modeling Viscous Oil Cavitating Flow in a Centrifugal Pump

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Wen-Guang Li
Keyword(s):  
Centrifugal Pump ◽  
Volume Ratio ◽  
Cavitating Flow ◽  
Liquid Volume ◽  
Cavitation Model ◽  
Gas Concentration ◽  
Noncondensable Gas ◽  
Cavitation Performance ◽  
Pump Head ◽  
Cfd Method

Properly modeling cavitating flow in a centrifugal pump is a very important issue for prediction of cavitation performance in pump hydraulic design optimization and application. As a first trial, the issue is explored by using computational fluid dynamics (CFD) method plus the full cavitation model herein. To secure a smoothed head-net positive suction head available (NPSHa) curve, several critical techniques are adopted. The cavitation model is validated against the experimental data in literature. The predicted net positive suction head required (NPSHr) correction factor for viscosity oils is compared with the existing measured data and empirical correlation curve, and the factor is correlated to impeller Reynolds number quantitatively. A useful relation between the pump head coefficient and vapor plus noncondensable gas-to-liquid volume ratio in the impeller is obtained. Vapor and noncondensable gas concentration profiles are illustrated in the impeller, and a “pseudocavitation” effect is confirmed as NPSHa is reduced. The effects of exit blade angle on NPSHr are presented, and the contributions of liquid viscosity and noncondensable gas concentration to the increase of NPSHr at a higher viscosity are identified.

Three-Objective Optimization of a Centrifugal Pump to Reduce Flow Recirculation and Cavitation

2018 ◽  
Vol 140 (9) ◽  
Author(s):  
Hyeon-Seok Shim ◽  
Kwang-Yong Kim ◽  
Young-Seok Choi
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
Stokes Equations ◽  
Cavitation Number ◽  
Design Flow ◽  
Pareto Optimal ◽  
Objective Functions ◽  
Flow Recirculation ◽  
Critical Cavitation ◽  
Design Flow Rate

This work presents a three-objective design optimization of a centrifugal pump impeller to reduce flow recirculation and cavitation using three-dimensional (3D) Reynolds-averaged Navier–Stokes equations. A cavitation model was used to simulate the multiphase cavitating flow inside the centrifugal pump. The numerical results were validated by comparing them with experimental data for the total head coefficient and critical cavitation number. To achieve the optimization goals, blockage at 50% of the design flow rate, hydraulic efficiency at the design flow rate, and critical cavitation number for a head-drop of 3% at 125% of the design flow rate were selected as the objective functions. Based on the results of the elementary effect (EE) method, the design variables selected were the axial length of the blade, the control point for the meridional profile of the shroud, the inlet radius of the blade hub, and the incidence angle of tip of the blade. Kriging models were constructed to approximate the objective functions in the design space using the objective function values calculated at the design points selected by Latin hypercube sampling (LHS). Pareto-optimal solutions were obtained using a multi-objective genetic algorithm (MOGA). Six representative Pareto-optimal designs (POD) were analyzed to evaluate the optimization results. The PODs showed large improvements in the objective functions compared to the baseline design. Thus, both the hydraulic performance and the reliability of the centrifugal pump were improved by the optimization.

scholarly journals Theoretical, Numerical and Experimental Research of Single Stage, Radial Discharge Centrifugal Pump Operating in Turbine Mode

2019 ◽  
Vol 8 (12) ◽  
pp. 1265-1270
Keyword(s):  
Centrifugal Pump ◽  
Experimental Research ◽  
Performance Prediction ◽  
Experimental Analysis ◽  
Numerical Results ◽  
Pump Mode ◽  
Characteristic Curves ◽  
Reverse Mode ◽  
Specific Speed ◽  
Turbine Mode

In this study, the best efficiency point of end suction, radial discharge, centrifugal pump operated in turbine mode was arrived applying numerical and experimental analysis. The pump was simulated both in direct and turbine modes using Star CCM+ CFD software. Characteristic curves were developed for the pump in direct and turbine modes. A monoblock centrifugal pump of specific speed 35.89 (m, m3 /s) was used for this study. The pump was tested experimentally in turbine and pump mode .The theoretical and numerical results were verified by those obtained through experimentation. Some of the correlations proposed by earlier researchers for performance prediction of pump in reverse mode were also tested

Effects of Blade Inlet Width on Performance of Centrifugal Pump as Turbine With Special Impeller Using in Turbine Mode

2016 ◽  
Author(s):  
Tao Wang ◽  
Xiaobing Liu ◽  
Xide Lai ◽  
Qiuqin Gou
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
High Efficiency ◽  
Cost Effective ◽  
Pressure Head ◽  
Design Flow ◽  
Hydraulic Loss ◽  
Obvious Effect ◽  
Velocity Moment ◽  
Turbine Mode

A reverse running centrifugal pump is one of the attractive choices in micro-hydropower development and industrial pressure energy recovery. One of the main problems in utilizing pump as turbine (PAT) is that the performance of PAT is usually not ideal due to the impeller with the routine backward curved blades which do not match well with turbine running condition. A cost effective suitable way for solving this problem is to redesign impeller with forward curved blades from turbine working condition while the other components do not undergo any modifications. Blade inlet width is one of the main factors in impeller design. Therefore, research on the influence of blade inlet width on PAT performance is useful. In this paper, based on the constant velocity moment theory, the velocity moment at impeller inlet is acquired, firstly. Next, a relationship expression between blade inlet angle and the design flow rate is deduced. To perform research on blade inlet width influencing PAT’s performance with special impeller, three impellers which inlet widths are 13 mm, 16 mm and 19 mm, respectively, are designed by using ANSYS Bladegen software. Numerical simulation and analysis of the three PATs are performed using a verified computational fluid dynamics (CFD) technique. Comparison of three PATs’ performance curves obtained by CFD, we can find that the blade inlet width has obvious effect on the performance of PAT. The flow rate, required pressure head, generated shaft power, and efficiency at best efficiency point (BEP) increase with the increase of blade inlet width. The flow rates of three PATs at BEP are about 90 m3/h, 100 m3/h and 105 m3/h, respectively, when impeller inlet width varies from 13 mm to 16 mm and 19 mm. The BEP of three PATs shifts towards higher discharge and its high efficiency range becomes wider with the increase of blade inlet width. At above 100 m3/h discharge, the PAT efficiency increases in accordance with the increase of blade inlet width. And the hydraulic loss and turbulence kinetic energy loss within impeller decrease with the increase of blade inlet width. In order to improve efficiency, it is helpful to choose a relatively larger blade inlet width in the design of special impeller using in turbine mode of PAT.

Analytical Evaluation of Head and Flow Rate Off-Design Characteristics for Pump as Turbine Application

2018 ◽  
Vol 141 (5) ◽  
Author(s):  
Ombeni John Mdee ◽  
Cuthbert Z. Kimambo ◽  
Torbjorn K. Nielsen ◽  
Joseph Kihedu
Keyword(s):  
Centrifugal Pump ◽  
Analytical Model ◽  
Flow Rate ◽  
Rate Ratio ◽  
Flow Rate Ratio ◽  
Design Characteristic ◽  
Model Coefficient ◽  
Design Characteristics ◽  
Boundary Limits ◽  
Turbine Mode

Head and flow rate are the important parameters for proper selection of centrifugal pump. However, the reversed operation of centrifugal pump leads to the off-design characteristic of head and flow rate. This paper presents an analytical model developed by using the system curves and velocity relations derived from pump application. Also, the differential technique is applied to the analytical model to develop the off-design characteristics of head ratio and flow rate ratio relations. The off-design characteristic relations were compared with literature and available conversion methods. Then, the analytical model coefficient (AMC) with the range between −4 and +4 was developed from the off-design characteristics of head ratio and flow rate ratio relations. The AMC value was equal to 1 when the pump operates in turbine mode and pump mode at the pump best efficiency point (BEP) and extended to either side up to ±4 when tested with literature data. Therefore, the analytical model consists of the off-design head and flow rate characteristics, when simplified leading to the AMC that could be applied to select the possible boundary limits of head and flow rate for different pumps.

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