Numerical investigation of flow features in the vaneless region of a centrifugal pump by large eddy simulation

2018 ◽  
Vol 35 (1) ◽  
pp. 395-410 ◽  
Author(s):  
Xianbei Huang ◽  
Yaojun Li ◽  
Zhuqing Liu ◽  
Wei Yang
Keyword(s):  
Experimental Data ◽  
Transport Equation ◽  
Centrifugal Pump ◽  
Reynolds Stress ◽  
Pressure Pulsation ◽  
Third Order ◽  
Production Term ◽  
Content Type ◽  
Blade Passing Frequency ◽  
Rotor Stator Interaction

Purpose The purpose of this paper is to obtain a better understanding of the rotor–stator interaction in the vaneless region of a centrifugal pump. Design/methodology/approach A third-order sub-grid scale (SGS) model containing the rotation rate tensor named the dynamic cubic non-linear model (DCNM) is used for simulating the flow field in a centrifugal pump with a vaned diffuser. The pressure coefficient and velocity distributions are compared with the experimental data. Focusing on the vaneless region, the pressure pulsation, Reynolds stress pulsation and Reynolds stress transport equation are analyzed. Findings The comparison of the calculation results with the experimental data indicates that the DCNM can accurately capture the distributions of pressure and velocity in the vaneless region. Based on the instantaneous pressure signals, the pressure pulsation is analyzed to show that in the vaneless region, the dominant frequency near the impeller is twice the blade passing frequency, whereas it is equal to the blade passing frequency near the diffuser. Further exploration of the Reynolds stress pulsation shows the correlation between the two variables. Additionally, the extreme low frequency of Reynolds stress near the diffuser is found to be related to the rotation instability. To explore the turbulence characteristics in the vaneless region, the Reynolds stress transportation equation is studied. In the vaneless region, the rotation term of the Reynolds stress transport equation is negligible compared to the production term, although the rotation instability is obvious near the diffuser. The production of the Reynolds stress plays the role of redistributing the energy from the uu component to the vv component, except for the region near the impeller outlet. Originality/value The third-order SGS model DCNM has proved to be promising in simulating the rotor–stator interaction. The analysis of the rotation instability and the Reynolds stress transport equation shed light on the further understanding of the rotor–stator interaction.

Measurement and modelling of homogeneous axisymmetric turbulence

1998 ◽  
Vol 374 ◽  
pp. 59-90 ◽  
Author(s):  
TORBJÖRN SJÖGREN ◽  
ARNE V. JOHANSSON
Keyword(s):  
Transport Equation ◽  
Reynolds Stress ◽  
Turbulence Models ◽  
Theoretical Description ◽  
Wind Tunnel Experiments ◽  
Third Order ◽  
Point Velocity ◽  
First Time ◽  
Rapid Pressure

A new method for determining the slow and rapid pressure-strain rate terms directly from wind-tunnel experiments has been developed with the aid of a newly developed theoretical description of the kinematics of homogeneous axisymmetric turbulence. Both the straining and the return-to-isotropy process of homogeneous axisymmetric turbulence are studied with the aim of improving Reynolds stress closures. Direct experimental determination of the different terms in the transport equation for the Reynolds stress tensor plays a major role in the validation and development of turbulence models. For the first time it is shown that the pressure{strain correlation can be determined with good accuracy without balancing it out from the Reynolds stress transport equation (and without measuring the pressure). Instead it is determined through evaluation of integrals containing second- and third-order two-point velocity correlations. All the terms in the Reynolds stress equations are measured directly and balance is achieved.

Numerical study on instantaneous radial force of a centrifugal pump for different working conditions

2019 ◽  
Vol 37 (2) ◽  
pp. 458-480
Author(s):  
Xiaoqi Jia ◽  
Sheng Yuan ◽  
Zuchao Zhu ◽  
Baoling Cui
Keyword(s):  
Numerical Simulation ◽  
Unsteady Flow ◽  
Centrifugal Pump ◽  
Working Conditions ◽  
Flow Rate ◽  
Pressure Pulsation ◽  
Radial Force ◽  
Leakage Rate ◽  
Content Type ◽  
Three Components

Purpose Instantaneous radial force induced from unsteady flow will intensify vibration noise of the centrifugal pump, especially under off-design working conditions, which will affect safety reliability of pump operation in severe cases. This paper aims to conduct unsteady numerical computation on one centrifugal pump; thus, unsteady fluid radial force upon the impeller and volute is obtained, so as to study the evolution law of instantaneous radial force, the internal relationship between radial force and pressure pulsation, the relationship among each composition of radial force that the impeller received and the influence of leakage rate of front and back chamber on radial force. Design/methodology/approach The unsteady numerical simulation with SST k-ω turbulence model was carried out for a low specific-speed centrifugal pump using computational fluid dynamics codes FLUENT. The performance tests and pressure tests were conducted by a closed loop system. The performance curves and the pressure distribution from numerical simulation agree with that of the experiment conducted. The unsteady pressure distributions and the instantaneous radial forces induced from unsteady flow were analyzed under different flow rates. Contribution degrees of three components of the radial force on the impeller and the relation between the radial force and leakage rate were analyzed. Findings Radial force on the volute and pressure pulsation on the volute wall have the same distribution tendency, but in contrast to the distribution trend of the radial force on the impeller. In the component of radial force that the impeller received, radial force on the blade accounts for the main position. With the decrease of flow rate, ratio of the radial force on front and back casings will be increased; under large flow rate, vortex and flow blockage at volute section will enhance the pressure and radial force fluctuation greatly, and the pulsation degree may be much more intense than that of a smaller flow rate. Originality/value This paper revealed the relation of the radial force and the pressure pulsation. Meanwhile, contribution degrees of three components of the radial force on the impeller under different working conditions as well as the relation between the radial force and leakage rate of front and rear chambers were analyzed.

Influence of Impeller Sinusoidal Tubercle Trailing Edge On Pressure Pulsation in a Centrifugal Pump At Nominal Flow Rate

2021 ◽  
Author(s):  
Yanpi Lin ◽  
Xiaojun Li ◽  
Bowen Li ◽  
Xiao-Qi Jia ◽  
Zuchao Zhu
Keyword(s):  
Centrifugal Pump ◽  
High Speed ◽  
Pressure Pulsation ◽  
Humpback Whales ◽  
Centrifugal Pumps ◽  
Trailing Edge ◽  
Rotor Stator Interaction ◽  
High Speed Rotation ◽  
Operation Stability ◽  
Speed Rotation

Abstract The high-speed rotation of impellers leads to strong rotor-stator interaction, which mainly causes the pressure pulsation of centrifugal pumps. An impeller with a bionic sinusoidal tubercle trailing edge (STTE) can reduce the intensity of the rotor-stator interaction and thus reduce the pressure pulsation of the centrifugal pump. In this study three profiles of STTE were designed based on the pectoral fin structure of humpback whales of which the influence on the pressure pulsation of centrifugal pumps was studied via experiment and numerical simulation. Results show that a reasonable design of STTE can effectively eliminate the high-frequency pressure pulsation in the rotor-stator interaction region of the centrifugal pump. The use of STTE2 and STTE3 profiles affects the amplitude reduction of pressure pulsation at the blade passing frequency (fBPF). Compared with the impeller without the STTE profile, the amplitudes of pressure pulsation with STTE2 and STTE3 profiles are decreased by 47.10% and 44.20% at the pump discharge, while the decrease, at the volute throat are 30.36% and 25.97%, respectively. Detailed flow structures inside the pump show that the STTE profile can inhibit the vortex generation at the blade trailing edge, and the local high-intensity pressure pulsation can be reasonably avoided. This study helps improve the pressure pulsation characteristic of centrifugal pumps and their operation stability.

Centrifugal Pump Pressure Pulsation Prediction Accuracy Dependence Upon CFD Models and Boundary Conditions

2009 ◽  
Author(s):  
Sang Hyun Park ◽  
Gerald L. Morrison
Keyword(s):  
Experimental Data ◽  
Boundary Conditions ◽  
Mass Flow Rate ◽  
Centrifugal Pump ◽  
Mass Flow ◽  
Flow Rate ◽  
Pressure Pulsation ◽  
Cfd Simulations ◽  
Pump Performance ◽  
Inlet Condition

Unsteady CFD simulations for a low specific speed open faced impeller centrifugal pump operating with and without balancing holes and having cut-away sections of the impeller are performed and compared to experimental data obtained using the actual pump simulated. For this simulation, the entire pump from suction inlet to exit flange is modeled. General pump performance characteristics are compared between the actual pump and the simulation. Pressure pulsation data are recorded at various locations in the pump using flush mounted pressure transducers and directly compared to the simulation results. Pressure spectrum data are used to evaluate the effects of three different boundary conditions upon the accuracy of the pressure pulsation simulations as well as the overall pump performance. These boundary conditions are a) fixed inlet and exit pressure, b) mass flow rate inlet condition with outflow exit, and c) target mass flow rate inlet with outflow exit which lets the inlet pressure fluctuate. All of these are available in the commercial CFD package utilized. Based upon comparisons between CFD simulations and experimental data for both the steady and unsteady conditions, the mass inlet condition is found to produce the best overall results for the installed pump.

A Note on the Empirical Constant in the Kolmogorov-Prandtl Eddy-Viscosity Expression

1975 ◽  
Vol 97 (3) ◽  
pp. 386-389 ◽  
Author(s):  
W. Rodi
Keyword(s):  
Experimental Data ◽  
Transport Equation ◽  
Reynolds Stress ◽  
Eddy Viscosity ◽  
Shear Layers ◽  
Empirical Constant ◽  
Empirical Factor

The transport equation for the Reynolds stress is simplified to yield the Kolmogorov-Prandtl eddy viscosity expression, and the conditions are studied under which the empirical factor cμ in this expression can be a constant. By reference to experimental data, it is shown that these conditions are not generally satisfied. The measured variation of cμ is given for various thin shear layers. Those flows are identified, which can be calculated with a constant value of cμ.

Prediction of the Flow Around an Airfoil Using a Reynolds Stress Transport Model

1995 ◽  
Vol 117 (1) ◽  
pp. 50-57 ◽  
Author(s):  
Lars Davidson
Keyword(s):  
Experimental Data ◽  
Reynolds Stress ◽  
Transport Model ◽  
Suction Side ◽  
Equation Model ◽  
Staggered Grid ◽  
Poor Agreement ◽  
Third Order ◽  
Reynolds Stress Transport Model ◽  
Quick Scheme

A second-moment Reynolds Stress Transport Model (RSTM) is used in the present work for computing the flow around a two-dimensional airfoil. An incompressible SIMPLEC code is used, employing a non-staggered grid arrangement. A third-order QUICK scheme is used for the momentum equations, and a second-order, bounded MUSCL scheme is used for the turbulent quantities. As the RSTM is valid only for fully turbulent flow, an eddy viscosity, one-equation model is used near the wall. The two models are matched along a preselected grid line in the fully turbulent region. Detailed comparisons between calculations and experiments are presented for an angle of attack of α = 13.3 deg. The RSTM predictions agree well with the experiments, and approaching stall is predicted for α = 17 deg, which agrees well with experimental data. The results obtained with a two-layer κ – ∈ model show poor agreement with experimental data; the velocity profiles on the suction side of the airfoil show no tendency of separation, and no tendency of stall is predicted.

Numerical analysis for wake flow field of Ahmed model based on a nonlinear-LRN/DES turbulence model

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Le Dian Zheng ◽  
Yi Yang ◽  
Guang Lin Qiang ◽  
Zhengqi Gu
Keyword(s):  
Experimental Data ◽  
Flow Field ◽  
Reynolds Stress ◽  
Turbulence Model ◽  
Turbulence Models ◽  
Aerodynamic Characteristics ◽  
Wake Flow ◽  
Field Analysis ◽  
Content Type ◽  
Des Model

Purpose This paper aims to propose a precise turbulence model for automobile aerodynamics simulation, which can predict flow separation and reattachment phenomena more accurately. Design/methodology/approach As the results of wake flow simulation with commonly used turbulence models are unsatisfactory, by introducing a nonlinear Reynolds stress term and combining the detached Eddy simulation (DES) model, this paper proposes a nonlinear-low-Reynolds number (LRN)/DES turbulence model. The turbulence model is verified in a backward-facing step case and applied in the flow field analysis of the Ahmed model. Several widely applied turbulence models are compared with the nonlinear-LRN/DES model and the experimental data of the above cases. Findings Compared with the experimental data and several turbulence models, the nonlinear-LRN/DES model gives better agreement with the experiment and can predict the automobile wake flow structures and aerodynamic characteristics more accurately. Research limitations/implications The nonlinear-LRN/DES model proposed in this paper suffers from separation delays when simulating the separation flows above the rear slant of the Ahmed body. Therefore, more factors need to be considered to further improve the accuracy of the model. Practical implications This paper proposes a turbulence model that can more accurately simulate the wake flow field structure of automobiles, which is valuable for improving the calculation accuracy of the aerodynamic characteristics of automobiles. Originality/value Based on the nonlinear eddy viscosity method and the scale resolved simulation, a nonlinear-LRN/DES turbulence model including the nonlinear Reynolds stress terms for separation and reattachment prediction, as well as the wake vortex structure prediction is first proposed.

Numerical and experimental study in pressure pulsation and vibration of a two-stage centrifugal pump under cavitating condition

2021 ◽  
Author(s):  
Shuwei Zhang ◽  
Ruiqi Tian ◽  
Kejin Ding ◽  
Hongxun Chen ◽  
Zheng Ma
Keyword(s):  
Centrifugal Pump ◽  
Pressure Pulsation ◽  
Uncertainty Estimation ◽  
Experimental Results ◽  
Center Frequency ◽  
Two Stage ◽  
Impeller Blade ◽  
Vibration Signals ◽  
Frequency Bands ◽  
Blade Passing Frequency

Instantaneous cavitating turbulent flow in a two-stage centrifugal pump with diffuser was simulated using a hybrid RANS/LES model and rotating corrected-based cavitation model in this paper. The predicted results of numerical simulation were in good agreement with the experimental results. The mechanism of pressure pulsation in the two-stage centrifugal pump was discussed. Some representative main frequencies of pressure pulsation such as main blade passing frequency, sub-blade passing frequency and intersection frequency of impeller blade and diffuser blade were analyzed systematically. Uncertainty estimation was used to ensure the accuracy of experimental results and it was also used to analyze the variation of pressure pulsation and vibration signals at different positions with the intensification of cavitation degree in the centrifugal pump. According to the results of uncertainty estimation, the center frequency of 1/3 octave band and the root mean square method were used to evaluate the energy change of the pressure pulsation signals and vibration signals at different frequency bands as the cavitation number decreases. The characteristics of pressure pulsation and vibration signals at different positions were analyzed in different frequency bands.

Experimental Investigation on Unsteady Pressure Pulsation in a Centrifugal Pump With Special Slope Volute

2015 ◽  
Vol 137 (6) ◽  
Author(s):  
Ning Zhang ◽  
MinGuan Yang ◽  
Bo Gao ◽  
Zhong Li ◽  
Dan Ni
Keyword(s):  
Experimental Investigation ◽  
Centrifugal Pump ◽  
Pressure Pulsation ◽  
High Amplitude ◽  
Operating Conditions ◽  
Stable Operation ◽  
Flow Induced Vibration ◽  
Unsteady Pressure ◽  
Rotor Stator Interaction ◽  
Nonlinear Components

Rotor–stator interaction, a major source of high amplitude pressure pulsation and flow-induced vibration in the centrifugal pump, is detrimental to stable operation of pumps. In the present study, a slope volute is investigated to explore an effective method to reduce high pressure pulsation level, and its influence on flow structures is analyzed using numerical simulation. The stress is placed on experimental investigation of unsteady pressure pulsation inside the slope volute pump. For that purpose, pressure pulsations are extracted at nine locations along the slope volute casing covering sensitive pump regions. Results show that distinct pressure pulsation peaks at fBPF, together with nonlinear components are captured. These peaks are closely related to the position of pressure transducer and operating conditions of the pump. The improvement of rotational speed of the impeller results in rapid increase of pressure fluctuation amplitude at fBPF and corresponding root mean square (RMS) value within 10–500 Hz. A comparison with conventional spiral volute pump is implemented as well, and it is demonstrated that slope volute contributes significantly to the decline of pressure pulsation level.

scholarly journals Improvement of Internal Flow Performance of a Centrifugal Pump-As-Turbine (PAT) by Impeller Geometric Optimization

Mathematics ◽  
2020 ◽  
Vol 8 (10) ◽  
pp. 1714
Author(s):  
Jian Xu ◽  
Longyan Wang ◽  
Stephen Ntiri Asomani ◽  
Wei Luo ◽  
Rong Lu
Keyword(s):  
Centrifugal Pump ◽  
Pressure Pulsation ◽  
Internal Flow ◽  
Geometric Optimization ◽  
Numerical Results ◽  
Operating Conditions ◽  
Maximum Efficiency ◽  
Stable Operation ◽  
Operating Range ◽  
Rotor Stator Interaction

Rotor-stator interaction (RSI) in the centrifugal pump-as-turbine (PAT) is a significant source of high amplitude of the pressure pulsation and the flow-induced vibration, which is detrimental to the stable operation of PAT. It is therefore imperative to analyze the rotor-stator interaction, which can subsequently be used as a guideline for reducing the output of PAT noise, vibration and cavitation. In addition, it is important for a PAT to have a wide operating range preferably at maximum efficiency. In order to broaden the operating range, this work proposes a multi-condition optimization scheme based on numerical simulations to improve the performance of a centrifugal PAT. In this paper, the optimization of PAT impeller design variables (b2, β1, β2 and z) was investigated to shed light upon its influence on the output efficiency and its internal flow characteristics. Thus, the aim of the study is to examine the unsteady pressure pulsation distributions within the PAT flow zones as a result of the impeller geometric optimization. The numerical results of the baseline model are validated by the experimental test for numerical accuracy of the PAT. The optimized efficiencies based on three operating conditions (1.0Qd, 1.2Qd, and 1.4Qd) were maximally increased by 13.1%, 8.67% and 10.62%, respectively. The numerical results show that for the distribution of PAT pressure pulsations, the RSI is the main controlling factor where the dominant frequencies were the blade passing frequency (BPF) and its harmonics. In addition, among the three selected optimum cases, the optimized case C model exhibited the highest level of pressure pulsation amplitudes, while optimized case B reported the lowest level of pressure pulsation.

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