Assessment of a turbulence model for numerical predictions of sheet-cavitating flows in centrifugal pumps

Houlin Liu,Yong Wang,Dongxi Liu,Shouqi Yuan,Jian Wang 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.9

Various approaches have been developed for numerical predictions of unsteady cavitating turbulent flows. To verify the influence of a turbulence model on the simulation of unsteady attached sheet-cavitating flows in centrifugal pumps, two modified RNG k-ε models (DCM and FBM) are implemented in ANSYS-CFX 13.0 by second development technology, so as to compare three widespread turbulence models in the same platform. The simulation has been executed and compared to experimental results for three different flow coefficients. For four operating conditions, qualitative comparisons are carried out between experimental and numerical cavitation patterns,which are visualized by a high-speed camera and depicted as isosurfaces of vapor volume fraction αv = 0.1, respectively. The comparison results indicate that, for the development of the sheet attached cavities on the suction side of the impeller blades, the numerical results with different turbulence models are very close to each other and overestimate the experiment ones slightly. However, compared to the cavitation performance experimental curves, the numerical results have obvious difference: the prediction precision with the FBM is higher than the other two turbulence models. In addition, the loading distributions around the blade section at midspan are analyzed in detail. The research results suggest that, for numerical prediction of cavitating flows in centrifugal pumps, the turbulence model has little influence on the development of cavitation bubbles, but the advanced turbulence model can significantly improve the prediction precision of head coefficients and critical cavitation numbers.

Influence of the empirical coefficients of cavitation model on predicting cavitating flow in the centrifugal pump

Houlin Liu,Jian Wang,Yong Wang,Hua Zhang,Haoqin Huang 대한조선학회 2014 International Journal of Naval Architecture and Oc Vol.6 No.1

The phenomenon of cavitation is an unsteady flow, which is nearly inevitable in pump. It would degrade the pump performance, produce vibration and noise and even damage the pump. Hence, to improve accuracy of the nu¬merical prediction of the pump cavitation performance is much desirable. In the present work, a homogenous model, the Zwart-Gerber-Belamri cavitation model, is considered to investigate the influence of the empirical coefficients on predicting the pump cavitation performance, concerning a centrifugal pump. Three coefficients are analyzed, namely the nucleation site radius, evaporation and condensation coefficients. Also, the experiments are carried out to validate the numerical simulations. The results indicate that, to get a precise prediction, the approaches of declining the initial bubble radius, the condensation coefficient or increasing the evaporation coefficient are all feasible, especially for de¬clining the condensation coefficient, which is the most effective way.

Fluid-Structure Interaction Study on Diffuser Pump With a Two-Way Coupling Method

Xu, Huan,Liu, Houlin,Tan, Minggao,Cui, Jianbao Korean Society for Fluid machinery 2013 International journal of fluid machinery and syste Vol.6 No.2

In order to study the effect of the fluid-structure interaction (FSI) on the simulation results, the external characteristics and internal flow features of a diffuser pump were analyzed with a two-way flow solid coupling method. And the static and dynamic structure analysis of the blade was also caculated with the FEA method. The steady flow field is based on Reynolds Averaged N-S equations with standard $k-{\varepsilon}$ turbulent model, the unsteady flow field is based on the large eddy simulation, and the structure response is based on elastic transient structural dynamic equation. The results showed that the effect of FSI on the head prediction based on CFD really exists. At the same radius, the van mises stress on the nodes closed shroud and hub was larger than other nodes. A large deformation region existed near inlet side at the middle of blades. The strength of impeller satisfied the strength requirement with static stress analysis based on the fourth strength theory. The dynamic stress varied periodically with the impeller rotating. It was also found that the fundamental frequency of the dynamic stress is the rotating frequency and its harmonic frequency. The frequency of maximum stress amplitude at node 1626 was 7 times of the rotating frequency. The frequency of maximum stress amplitude at node 2328 was 14 times of the rotating frequency. No matter strength failure or fatigue failure, the root of blades near shroud is the key region to analyse.

Experimental research on pressure fluctuation and vibration in a mixed flow pump

Kai Wang,Houlin Liu,Xiaohua Zhou,Wenbo Wang 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.1

To study the pressure fluctuation and vibration in mixed flow pumps, we chose a mixed flow pump with specific speed of 436.1 tomeasure. The time domains and frequency domain at each monitoring point on diffuser and outlet elbow were analyzed, as well as thevibration frequency domain characteristics at the impeller outlet and near the motor. The results show that the peak value of pressurefluctuation peak decreased gradually with the increase of flow rate. The pressure fluctuation of each monitoring point had periodicity,and the frequency domain dominated by blade passing frequency and multiple shaft frequency. The vibration frequency of each monitoringpoint occurred at shaft frequency and its multiple shaft frequency. The dominant frequency and the second frequency were distributedin shaft frequency and double shaft frequency.

Visualizing test on the pass-through and collision characteristics of coarse particles in a double blade pump

Minggao Tan,Yichao Lian,Houlin Liu,Xianfang Wu,Rong Ding 대한조선학회 2018 International Journal of Naval Architecture and Oc Vol.10 No.1

As the key equipment in deep ocean mining, the slurry pump suffers from wear and blocking problems. In this paper, high-speed photography technique is applied to track the movement rule of single particle of the coarse particle solideliquid two-phase flow in a double blade slurry pump. The influences of particle diameter and particle density on the pass-through and collision characteristics of particles are analyzed as well. The results show that the average of the passing pump time first decreases and then increases when the particle diameter increases. The average of the passing pump time decreases by 22.7%, when the particle density increases from 1.09 g/cm3 to 1.75 g/cm3. Besides, the particle density has great influence on the location where the particle hits the tongue. Most particles of 1.09 g/cm3 hit the tongue on the left side, while collision location of particles of 1.75 g/cm3 is mainly on the top and at the right side of the tongue. The research can provide a basis for the optimization design of slurry pump in deep ocean mining system.

Visualizing test on the pass-through and collision characteristics of coarse particles in a double blade pump

Tan, Minggao,Lian, Yichao,Liu, Houlin,Wu, Xianfang,Ding, Rong The Society of Naval Architects of Korea 2018 International Journal of Naval Architecture and Oc Vol.10 No.1

As the key equipment in deep ocean mining, the slurry pump suffers from wear and blocking problems. In this paper, high-speed photography technique is applied to track the movement rule of single particle of the coarse particle solid-liquid two-phase flow in a double blade slurry pump. The influences of particle diameter and particle density on the pass-through and collision characteristics of particles are analyzed as well. The results show that the average of the passing pump time first decreases and then increases when the particle diameter increases. The average of the passing pump time decreases by 22.7%, when the particle density increases from $1.09g/cm^3$ to $1.75g/cm^3$. Besides, the particle density has great influence on the location where the particle hits the tongue. Most particles of $1.09g/cm^3$ hit the tongue on the left side, while collision location of particles of $1.75g/cm^3$ is mainly on the top and at the right side of the tongue. The research can provide a basis for the optimization design of slurry pump in deep ocean mining system.

Image post-processed approaches for cavitating flow in orifice plate

Yong Wang,Suguo Zhuang,Houlin Liu,Zhenjiang Zhao,Matevž Dular,Jian Wang 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.7

A comprehensive investigation on cavitating flow and cavitation-induced erosion was performed experimentally in an orifice plate system. Three image post-processed approaches were applied to analyze the test data, in order to obtain the cavitation characteristics. The cavitating flow pattern was studied by high speed images. In one cavitation developing period, there could be three distinct cavitation clouds, whereas the second one is not fully developed. The first image post-processing approach was applied to obtain the mean value and standard deviation distribution, which indicate the erosion area may cover almost all the cavitation developing route and the most vulnerable erosion area locates near the cavitation collapse site. It is coincides with the erosion tests analyzed through the pit-count algorithm approach. The cavitation circulation frequency was invested via PSD analysis approach. It shows that the frequency linearly decreasing with decreasing cavitation number. Additionally, the cavitation intensity effect on cavitation erosion was quantitatively studied based. It is found that the damages are strongly enhanced when increasing the flow velocity. Moreover, the growth rate of eroded pits number is actually stepwise instead of linear (similar to our previous work in a venturi tube), which supports the idea that the cloud cavitation collapse is the primary reason for erosion. The present approaches applied here shows good potential ability of investigating cavitating flows and can be utilized for other apparatus.

Research on Common Fault Diagnosis and Classification Method of Centrifugal Pump Based on ReliefF and SVM

Xingxin Xiao,Hui Chen,Liang Dong,Houlin Liu,Chuanhan Fan 한국유체기계학회 2022 International journal of fluid machinery and syste Vol.15 No.2

The centrifugal pump is an important rotating machine and it is very critical to identify and differentiate among its common faults as quickly and accurately as possible. Based on the ReliefF algorithm and the sparrow search algorithm (SSA) in conjunction with support vector machine (SVM), an approach for faults classification and diagnosis of centrifugal pumps is proposed, its advantages over traditional fault diagnosis methods include a reduction in the number of characteristic parameters, shorter diagnosis times, as well as improved classification accuracy and robustness. We collected the fault data by designing a centrifugal pump fault test bench that recorded vibration signals for the rotor misalignment fault, the rotor unbalance fault, the seal ring wear fault, and normal operating conditions, and preprocessed the collected signals with Kalman filtering to remove noise interference, the time domain characteristic indexes and the frequency domain characteristic indexes of the filtered signal were extracted, each feature index is given a distinct weight using the ReliefF method, and the eigenvalues with weights less than the threshold are deleted, and the feature indexes that remain create a defect feature matrix. Particle swarm optimization (PSO), genetic algorithm (GA), and simulated annealing algorithm (SA) were used to optimize the SVM for comparison in order to verify the SSA-SVM model's performance for fault diagnosis. The comparison results show that the model has high recognition accuracy, short Classification time, and strong robustness.

Performance of water-jet pump under acceleration

Wu Xian-Fang,Li Ming-Hui,Liu Houlin,Tan Minggao,Lu You-Dong 대한조선학회 2021 International Journal of Naval Architecture and Oc Vol.13 No.1

The instantaneous acceleration affects the performance of the water-jet pump obviously. Here, based on the user-defined function, the method to simulate the inner flow in water-jet pumps under acceleration conditions was established. The effects of two different acceleration modes (linear acceleration and exponential acceleration) and three kinds of different acceleration time (0.5s, 1s and 2s) on the performance of the water-jet pump were analyzed. The results show that the thrust and the pressure pulsation under exponential acceleration are lower than that under linear acceleration at the same time; the vapor volume fraction in the impeller under linear acceleration is 27.3% higher than that under exponential acceleration. As the acceleration time increases, the thrust gradually increases and the pressure pulsation amplitude at the impeller inlet and outlet gradually decreases, while the law of pressure pulsation is the opposite at the diffuser outlet. The main frequency of pressure pulsation at the impeller outlet is different under different acceleration time. The research results can provide some reference for the optimal design of water-jet pumps.

Rotor Profile Design and Motion Simulation Analysis of Hydrogen Circulating Pump

Jiawei Lin,Lixin Zhang,Liang Dong,Houlin Liu,Cui Dai 한국유체기계학회 2021 International journal of fluid machinery and syste Vol.14 No.4

With the development of automotive fuel cells towards high power and high efficiency, higher requirements are put forward for the speed and boost ratio of hydrogen circulation pump, while high speed and boost ratio increase the pulsation characteristics and accelerate the aging of hydrogen fuel cells. Cam type hydrogen cycle pump has the advantages of compact structure, high efficiency under low boost ratio, and good adaptability to low temperature, so it has become an important research direction. The efficient and reasonable rotor profile design can improve the volumetric efficiency of the cam rotor pump. It can reduce the pressure pulsation and flow pulsation in the pump. The equation of multi-stage circular arc rotor profile is established according to the meshing principle of the rotor. Motion Simulation module in UG NX is employed to conduct dynamic interference detection of rotor mechanism and simulation analysis of rotor mechanism meshing motion on the rotating parts of the hydrogen circulating pump. So the angular velocity curve and meshing force change curve of the driven gear is obtained. In order to verify the rationality of rotor profile design, the meshing force is compared with the standard spur gear.