The characteristics investigation under the unsteady cavitation condition in a centrifugal pump

Jiaxing Lu,Shouqi Yuan,Parameswaran Siva,Jian-Ping Yuan,Xudong Ren,Banglun Zhou 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.3

Numerical simulation and experimental method are combined to investigate the pump inlet and outlet pressure fluctuations, the vibration characteristics and the internal flow instabilities under the unsteady cavitation condition in a centrifugal pump. It is found that the unsteady cavitation starts to generate as the NPSHa is lower than 5.93 m. Apparent asymmetric and uneven cavity volume distribution on each blade and in the impeller can be observed as the NPSHa decreases from 4.39 m to 1.44 m, which includes the cavitation develops from cavitation surge, rotating cavitation to asymmetric cavitation. The flow vortexes in each blade channel are produced in the cavity trailing edges by the shedding and collapse of cavitation, which interfere with each other and aggravate the flow instabilities. The dominant frequencies of the pump inlet and outlet pressure fluctuations are the shaft frequency and blade passing frequency under the unsteady cavitation conditions, respectively. Broadband pulses are obtained from both the pump inlet and outlet pressure pulsations, which results from the random shedding and collapse of unsteady cavitation bubbles. Obvious corresponding relationship between the root mean squares of the vibration measured in different positions and the suction performance curve is found under both the non-cavitation and unsteady cavitation conditions.

Fluid-structure coupling effects on periodically transient flow of a single-blade sewage centrifugal pump

Ji Pei,Shouqi Yuan,Jian-Ping Yuan 대한기계학회 2013 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.27 No.7

A partitioned fluid-structure interaction (FSI) solving strategy that depends on problem characteristics is applied to quantitatively obtain the coupling effects of a fluid-structure system in a single-blade centrifugal pump on the unsteady flow. A two-way coupling method is employed to realize strong FSI effects in the calculation procedure. The successful impeller oscillation measurement using two proximity sensors validated the FSI simulation accuracy in a complicated and practical fluid-structure system having a rotating component. The results show that the hydrodynamic force deviation can be observed in the results for the coupled versus uncoupled cases. Additionally,the coupled unsteady pressure is larger than the uncoupled value for every monitoring point at every impeller rotation position. Comparison results for different monitoring points under an overload condition and partial-load condition display the same regularities. To some extent, this interaction mechanism would affect the accuracy and reliability of the unsteady flow and rotor deflection analysis.

Optimization of impulse water turbine based on GA-BP neural network arithmetic

Lingdi Tang,Shouqi Yuan,Yue Tang,Zhipeng Qiu 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.1

To develop an optimum design method for impulse water turbines with low specific speed, a representative impulse water turbine with low specific speed used in agricultural irrigation machinery was optimized with a combination of an orthogonal experimental design, a genetic algorithm, and a BP neural network in this study. Numerical calculation was applied to analyze interflow characteristics for optimized and original water turbines. Results showed that the internal flow characteristics of the optimized water turbine presented remarkable improvement compared with the original water turbine. Pressure distribution increased, the vortex strip in the draft tube was reduced remarkably, and impeller torque increased by 26 %. In addition, the optimized impeller was manufactured by 3D printing, and performance comparison was conducted between experiments of the optimized and original water turbines. The efficiency of the optimized water turbine reached 42.5 %, which exceeded the original water turbine’s of 8.5 %. With increasing rotating speed, maximum efficiency running point moved to a high flow rate, and highly efficient areas expanded. Internal characteristic analysis and a full-scale experiment for both water turbines showed that the performance of the optimized water turbine exhibited substantial improvement. The analysis and experiment also verified the theoretical correctness and feasibility of the proposed optimum design method.

Fluid-structure interaction analysis of an impeller for a high-pressure booster pump for seawater desalination

Tingyun Yin,Ji Pei,Shouqi Yuan,Majeed Koranteng Osman,Jiabin Wang,Wenjie Wang 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.11

A High-pressure booster pump (HPBP) is an essential piece of equipment in a Seawater reverse osmosis (SWRO) system. As the corerotating component in the HPBP, the impeller operates extensively in a high-pressure and corrosive environment and its work status directly affects the reliability of the pump device. The vibration characteristics of the rotor were analyzed using fluid-structure interaction theory to determine the characteristics that would ensure the long-term safe operation of the HPBP. The stress and deformation analysis was performed on a partitioned solution for an impeller in a moving fluid, and the modal analysis of the impeller was conducted in still fluid based on a monolithic solution. The influence of the impeller shroud thickness on the resulting vibration characteristics was investigated by using three modifications of the impeller. A comparison of the results with the initial impeller geometry was then carried out under partial load operations. Three commonly used materials for an impeller were also evaluated. The three-dimensional turbulent flow was modeled utilizing the SST k-ω turbulence model, and the numerical results were verified by the experimental data. The results show that natural frequency of the 20CrMnTi is the highest among the three materials for each order mode, followed by 00Cr17Ni14Mo2Ti (316L) and HT250Ni2Cr. Increasing the rear shroud thickness would result in a notable reduction in its deformation. Evidently, the thicker the front and rear shrouds, the lower the shroud deformations. Among the three operating points, the displacement fields of the impeller were quite akin. An outward displacement growth was observed within the impeller hub to the outer diameter, thereby leaving both shrouds with a local maximum on the blade passage. Additionally, higher equivalent stress values were observed at the junction between the blade and the shroud. These results reveal the deformation and stress affecting the impeller, which then enables identification of and provides specific theoretical guidance for the optimization of the structural design of the pump.

Multi-point optimization on meridional shape of a centrifugal pump impeller for performance improvement

Ji Pei,Wenjie Wang,Shouqi Yuan 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.11

A wide operating band is important for a pump to safely perform at maximum efficiency while saving energy. To widen the operating range, a multi-point optimization process based on numerical simulations in order to improve impeller performance of a centrifugal pump used in nuclear plant applications is proposed by this research. The Reynolds average Navier Stokes equations are utilized to perform the calculations. The meridional shape of the impeller was optimized based on the following four parameters; shroud arc radius, hub arc radius, shroud angle, and hub angle as the design variables. Efficiencies calculated under 0.6Q d , 1.0Q d and 1.62Q d were selected as the three optimized objectives. The Design of experiment method was applied to generate various impellers while 35 impellers were generated by the Latin hypercube sampling method. A Response surface function based on a second order function was applied to construct a mathematical relationship between the objectives and design variables. A multi-objective genetic algorithm was utilized to solve the response surface function to obtain the best optimized objectives as well as the best combination of design parameters. The results indicated that the pump performance predicted by numerical simulation was in agreement with the experimental performance. The optimized efficiencies based on the three operating conditions were increased by 3.9 %, 6.1 % and 2.6 %, respectively. In addition, the velocity distribution, pressure distribution,streamline and turbulence kinetic energy distribution of the optimized and reference impeller were compared and analyzed to illustrate the performance improvement.

Application of different surrogate models on the optimization of centrifugal pump

Wenjie Wang,Ji Pei,Shouqi Yuan,Jinfeng Zhang,Jian-Ping Yuan,Changzheng Xu 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.2

An optimization process for impellers was carried out based on numerical simulation, Latin hypercube sampling (LHS), surrogate model and Genetic algorithm (GA) to improve the efficiency of residual heat removal pump. The commercial software ANSYS CFX 14.5 was utilized to solve the Reynolds-averaged Navier-Stokes equations by using the Shear stress transport turbulence model. The impeller blade parameters, which contain the blade inlet incidence angle ∆β, blade wrap angle φ, and blade outlet angle β 2 , were designed by random sample points according to the LHS method. The efficiency predicted under the design flow rate was selected as the objective function. The best combination of parameters was obtained by calculating the surrogate model with the GA. Meanwhile, the prediction accuracies of three surrogate models, namely, Response surface model (RSM), Kriging model, and Radial basis neural network (RBNN), were compared. Results showed that the calculated findings agree with the experimental performance results of the original pump. The RSF model predicted the highest efficiency, while the RBNN had the highest prediction accuracy. Compared with the simulated efficiency of the original pump, the optimization increased efficiency by 8.34% under the design point. Finally, the internal flow fields were analyzed to understand the mechanism of efficiency improvement. The optimization process, including the comparison of the surrogate models, can provide reference for the optimization design of other pumps.

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.

Multi-component optimization of a vertical inline pump based on multiobjective pso and artificial neural network

Xingcheng Gan,Ji Pei,Wenjie Wang,Shouqi Yuan,Yajing Tang 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.12

The vertical inline pump is a single-stage single-suction centrifugal pump with a curved inlet pipe before the impeller, which is widely used in where the constraint is installation space. In this paper, with the objective functions of efficiencies at 0.5 , d Q 1.0 , d Q and 1.5 , d Q a multi-objective optimization on inlet pipe and impeller was proposed to broaden the efficient operating period of a vertical inline pump. Two 5th order Bézier curves were adopted to fit the shape of the mid curve of the inlet pipe and the trend of the blade angle of the impeller. Fourteen design variables were selected after the data-mining process. 300 sample cases were generated using Latin hypercube sampling (LHS), and they were solved by 3D RANS code to obtain the objective functions. The feed-forward artificial neural network with a hidden layer and an output layer was adopted to fit the two objective functions and the 14 design variables. The Pareto frontiers were generated for the three objectives using multi-objective particle swarm optimization (MOPSO), and three different configurations on the Pareto front are selected for detailed study by computational fluid dynamics (CFD). The results showed that the profile of the inlet pipe and the blade have a dramatic impact on the performance of the vertical inline pump. The Pareto frontiers reported that the performance under the overload condition usually keeps stable when the nominal efficiency is lower than 82 %, or the part-load efficiency is lower than 62 %, and it will decrease rapidly after that. After optimization, the improvement of efficiencies at the part-load condition and nominal condition of the picked case were 9.65 % and 7.95 %, respectively.

Carbon quantum dots modified CdSe loaded reduced graphene oxide for enhancing photocatalytic activity

Pengwei Huo,Jingru Guan,Mingjun Zhou,CHANGCHANG MA,XINLIN LIU,Yongsheng Yan,Shouqi Yuan 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.50 No.-

Carbon quantum dots (CQDs)/CdSe/reduced graphene oxide (rGO) was fabricated by hydrothermalmethod. The structures, optical and electronic properties of as-obtained photocatalysts were analyzed bytransmission electron microscopy (TEM), X-ray diffraction (XRD) and photoelectrochemical testing. Thephotocatalytic performances were investigated by degradation of tetracycline hydrochloride (TC HCl). The results showed CQDs modified CdSe loaded rGO could effectively remove TC HCl, the CdSe modifiedwith 7 mL CQDs showed higher photocatalytic degradation rate; the 5 wt% loaded rGO for CQDs/CdSeshowed highest photocatalytic activity. The photocatalytic mechanism exhibited OH, O2and 1O2radicals play key roles

Energy efficiency optimization of water pump based on heuristic algorithm and computational fluid dynamics

Wang Wenjie,Han Zhenhua,Pei Jin,Pavesi Giorgio,Gong Xiaobo,Yuan Shouqi 한국CDE학회 2023 Journal of computational design and engineering Vol.10 No.1

To reduce the energy consumption of large centrifugal pumps, modified heuristic intelligent algorithms are used to directly optimize the diffuser of centrifugal pumps. Considering the hydraulic efficiency under the design condition as the optimization target, in this study, 14 geometric parameters such as the inlet diameter, outlet diameter, and leading and trailing vane angles of the diffuser are selected as design variables, and the modified particle swam optimization and gravitational search algorithm are used to directly search for optimization in the design space. The performance and loss of internal entropy production of the different models before and after optimization are compared and analyzed in detail. The results show that the global optimization ability of the modified algorithm is improved. The diffuser model changes from cylindrical to twisted, the vane wrap angle increases, and the thickness of the leading edge decreases. Under the design condition, the efficiency of modified particle swarm optimization algorithm solution is increased by 2.75% and modified gravitational search algorithm solution by 2.21%, while the power remains unchanged. Furthermore, the optimization solution has the largest lift efficiency improvement under part-load conditions. After optimization, the unstable flow in the model is improved and internal entropy production loss is reduced significantly. The interior of the diffuser is dominated by turbulent entropy production and direct entropy production under different operating conditions, and the wall entropy production accounts for the smallest proportion.