Key Laboratory of Fluid Machinery and Systems

Lanzhou, China

Key Laboratory of Fluid Machinery and Systems

Lanzhou, China
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Li Y.,Lanzhou University of Technology | Li Y.,Key Laboratory of Fluid machinery and Systems | Hu P.,Lanzhou University of Technology | Li R.,Lanzhou University of Technology | And 3 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2014

The mixed-flow pump has some good characteristics, such as high efficiency, good start performance, and wide working condition. The traditional design methods of mixed-flow pumps cannot evaluate the sensitivity of the tip clearance's impact on pump performance quantificationally. In order to reveal the tip clearance effect on the internal flow field and the performance of mixed-flow pump, and given the selection range of blade tip clearance, four mixed-flow pumps with different tip clearance values, 0, 0.5, 1.0, and 1.5 mm, respectively, were studied. The distorted triangle method was adopted to design the impeller and guide vane, and based on the software ICEM CFD to generate block hexahedron structured grids of the computational domain, and then the topological structure of the grids of the blade tip region was optimized. The internal flow field of the pumps was simulated based on the SST k-ω turbulence model and SIMPLEC algorithm, using the structured grid technology mentioned above, and the numerical simulation results were compared with the test experimental data, which agreed well with each other. The results show that the value of tip clearance have a significant effect on mixed-flow pump hydraulic performance, when tip clearance was 0.5 mm. The head-flow positive slope characteristic of the pump can be suppressed effectively, and the efficiency value of mixed-flow pump is highest at this time; when tip clearance was 0, the pump head-flow positive slope characteristic is relatively obvious; when tip clearance was 1mm, simulation values and experimental values matched well, so the SST k-ω model can simulate the flow characteristics of tip clearance of mixed-flow pumps well, so that the results of the performance prediction have some credibility. Under small flow conditions, small tip clearance values can restrain unstable positive slope features of mixed-flow pump. When tip clearance was 0.5mm, the performance of the pump with small tip clearance is the best. With the increasing of tip clearance value, tip leakage flow became outstanding gradually, the axis plane flow velocity of the near wall region of the impeller outlet and the vorticity change significantly, which indicates that tip clearance affects the axis plane velocity distributions of the impeller and the load distributions of the blades directly. As influenced by the frictional resistance and the viscous resistance of the wall, the impeller axis plane flow velocity of the impeller hub region and tip clearances areas is relatively small. When tip clearance increase, blades load of the impeller hub region and tip clearances areas decay rapidly, and it affects the performance ability of impeller blades. At the same time, serious mix permeability and entrainment effects come into being between the leakage flow near the blade tip and the main stream flow, and cause the significant decline in the axis plane flow velocity in the region near the blade tip of impeller outlet. At the moment, the jet effect of the tip leakage flow decays gradually, and the sphere of influence gradually extends to the entire blade tip region. ©, 2014, Chinese Society of Agricultural Engineering. All right reserved.


Zhao W.,Lanzhou University of Technology | Zhao W.,Key Laboratory of Fluid Machinery and Systems | Sheng J.,Lanzhou University of Technology | Yang J.,Lanzhou University of Technology | And 2 more authors.
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2015

The centrifugal pump is one of the most widely used fluid machinery. However, 3 problems i.e. lower efficiency, unsteady flow and bad cavitations performance are perplexing the development of centrifugal pump. For a single centrifugal pump, the impeller is one of the most important flow components, so it is selected as the optimum objective. Parametric fitting is a prerequisite in impeller optimization design. This process provides optimization variables and controls impeller automatically for the optimization design. Bezier curve and B-spline curve are used to reconstruct the impeller to obtain the profile of the blade and the meridional surface. The stacking point is reference point which defines the position of the two-dimensional (2D) blade section on a stream surface. This point is first defined on the 2D blade section, and then positioned on the corresponding stream surface in the meridional and tangential directions. Trailing edge is selected as stacking curve. Bezier-line-Bezier curve can be used to fit tangential location. The optimization variables are the angle between linear segment and vertical direction and the angle between the second Bezier curve and vertical direction with the span of 1, which 2 variables control the tangential position of stacking line on the 2D blade section. The range of -3°-3° is chosen as the constraint condition of optimization variables. Recently, CFD (computational fluid dynamics) technology has been widely applied to numerical computation of the three-dimensional viscous flow inside turbomachinery, which has made much progress. Meanwhile, many excellent optimization algorithms have been proposed. Fortunately, the CFD technology isn't confined to the research of centrifugal pump inner flow. Combining the CFD technology and optimization algorithm will play a very important role in the increase of pump efficiency, the decrease of flow loss and the extension of high-performance areas. An automatic optimization design platform for the centrifugal impellers is constructed by the genetic algorithm combined with the parameterization method and the commercial computational fluid dynamics software NUMECA. Based on the genetic algorithm and the artificial neural network, a new optimization method for the optimization of a centrifugal impeller is presented. Different from the traditional optimization method, the performance of centrifugal impeller is predicted with the CFD technology in the new developed method. The relationship between objective function and optimization variables is established by the learning function of artificial neural network. The results show that the efficiency of impeller achieves the maximum, when the angle between linear segment and vertical direction is -2.886° and the angle between the second Bezier curve and vertical direction with the span of 1 is 1.31°. Compared with the original, the efficiency is improved by 4.02% for optimum impeller in the design point. The centrifugal pump efficiency is increased by 4.41%, and the head is increased by 2.63 m. Volute is one of important flow components and has a great effect on the single centrifugal pump. The loss in volute is very great with optimized impeller, or with original one, especially in the large flow area. The volute is redesigned and the numerical simulation of modified volute with optimum impeller is performed for the flow field analysis of the flow passage components. The efficiency is improved by 1.59% compared with the pump with optimum impeller and original volute in design point, and by 6% compared with the pump with original impeller and original volute in design point. The performance of centrifugal pump is optimized, and the purpose of energy saving is achieved. These findings confirm that the optimization design method is effective for the centrifugal impellers. ©, 2015, Chinese Society of Agricultural Engineering. All right reserved.


Yang C.,Lanzhou University of Technology | Yang C.,Key Laboratory of Fluid Machinery and Systems | Gao Z.,Lanzhou University of Technology | Zhang X.,Lanzhou University of Technology
Nongye Gongcheng Xuebao/Transactions of the Chinese Society of Agricultural Engineering | Year: 2016

Currently, as an effective technique to face the energy crisis, large-scale wind turbines in MW level is more and more widely used in the field of environment protection and green energy industry. In boundary layer wind field, random wind load can bring more obvious aerodynamic load fluctuation to long blades and high tower, which affects the structural stability of wind turbines. An accurate random wind speed model plays a significant role in the aerodynamic load calculations of wind turbines in the atmospheric boundary layer. Random wind speed can be decomposed into averaging wind speed and fluctuating wind speed. The averaging wind speed can be described by wind shear effect, and the fluctuating wind speed can be described by turbulence spectra. In the runtime environment of wind turbines, it's proper to use specific turbulence spectra to describe the fluctuating wind speed of inflow on the inlet because the entrance region of wind farm is the equal of a flat field. Compared with static buildings, the dynamic turbine rotor causes great disturbances to the wind speed. So the hybrid numerical simulation to combine the random wind speed generated by specific turbulence spectra on the inlet with turbulence models is more appropriate to the aerodynamic load calculations. In this paper, we verified the accuracy of random wind speed generation methods on the inlet of wind turbines. IEC61400-1 and many research papers recommend to use exponential law to describe the wind shear effect. The improved Von Karman spectrum corrected the flaws of Von Karman spectrum below about 150 m, which is more appropriate to wind farms. Based on the exponential law, 3D improved Von Karman spectrum and cross-spectrum model. We used the harmony superposition method and auto-regressive moving-average method to generate fluctuating wind speed of a 33 kW horizontal axis wind turbine. The hub height of this wind turbine was 15.4 m, and the rated wind speed was 11 m/s. The terrain roughness length was 0.03 m and the wind shear index was 0.2. The time step was 0.1 s and the upper rate limit was 2π rad/s. The length of the simulation was 100 s. The inlet was a rectangular area with 30 m × 30 m, and the grid step was 2 m. As a contrast, in this paper, we used the PSCAD to generate fluctuating wind speed with the same parameter. We compared these three methods, power spectrum, self-correlation and cross-correlation. The results showed that the power spectrum which was produced by HSM fit well with target power spectrum. The self-correlation of these three methods decreased as time increased, and the self-correlation of ARMA and PSCAD was better than HSM. The cross-correlation from the HSM method decreased as distance increased, which fit well with the measured results. Last, in this paper, we compared the turbulence intensity and got the three-dimensional distributions of velocity on the inlet. The turbulence intensity decreased as height increased, the difference value of turbulence intensity in the along-wind, crosswind, vertical wind was 8.96%, 6.98%, and 4.91%, respectively. This difference value would be more obvious on the large-scale wind turbines. © 2016, Editorial Department of the Transactions of the Chinese Society of Agricultural Engineering. All right reserved.


Xiao L.,Lanzhou University of Technology | Li Y.,Lanzhou University of Technology | Li Y.,Key Laboratory of Fluid Machinery and Systems | Liu Y.,Lanzhou University of Technology | And 4 more authors.
Paiguan Jixie Gongcheng Xuebao/Journal of Drainage and Irrigation Machinery Engineering | Year: 2016

In order to investigate the effect of wear-ring clearance on the cavitation performance of the centrifugal pump with the pre-positioned inducer, the cavitation flow and performance in the centrifugal pump with the pre-positioned inducer were numerical simulated with four different projects which were 0.15, 0.25, 0.40 and 0.60 mm based on the RNG k-ε turbulent model combined with Rayleigh-Plesset Homogeneous cavitation model, and compared with experimental results. The results show that the size of the wear-ring clearance has a greater influence on the external performance and cavitation performance; with the increasing of the wear-ring clearance, compared with 0.15 mm, the total head efficiency and the head efficiency of the impeller decrease, the changes of the head are up to 0.60% and 4.21%, and the changes of the efficiency are up to 6.50% and 9.32%. Moreover, the head and efficiency of the inducer increase, and they are up to 29.86% and 28.40%.The cavitation curves wave with the increasing of the wear-ring clearance and the decreasing of the cavitation number, and the wider the clearance is, the more obvious the flactuation is. The cloudy cavitation bubbles are distributed on the pressure surface that is close to the front shroud, which causes cavitation instability, and the wider the clearance is, the more the cavitaion is, the greater the critical cavitation number is. It is found that the factors that influence the cavitation instability of the pump are possibly related to the impact of leakage high-pressure fluid of the wear-ring outlet on the main flow, the occurrence of cavitation at the intersection of impeller inlet and wear-ring clearance outlet and the change of the outlet flow angel caused by cavitating in the pre-positioned inducer. © 2016, Editorial Department of Journal of Drainage and Irrigation Machinery Engineering. All right reserved.


Cheng X.,Lanzhou University of Technology | Cheng X.,Key Laboratory of Fluid Machinery and Systems | Bao W.,Lanzhou University of Technology
Paiguan Jixie Gongcheng Xuebao/Journal of Drainage and Irrigation Machinery Engineering | Year: 2016

The numerical simulations of flow of water in AP1000 reactor coolant pump model are performed based on the Reynolds averaged N-S equations and RNG k-ε turbulence model by using SIMPLE algorithm. Firstly, the size of the gap between the impeller shroud and the diffuser side wall is designed with four values. Secondly, the flow field in the pumps with these sizes are simulated. Finally, the axial thrust and flow structures in the gap and collector are obtained and discussed under va-rious gap sizes. The results show that the gap size has a certain impact on the pump head and efficiency in a range of 0.8Qd-1.2Qd flow rate. The change in gap size cause a shift of best efficiency point from the design point, but the shift scale and direction do not correlate with the gap size evidently. Under the design condition, the pump efficiency at 0.6 mm gap is better than at the others, and increased by 1.66% compared with 1.8mm gap. Under 1.2Qd flow condition, the pump is more efficient at 1.8 mm gap than at other gaps, and the pump efficiency is improved by 2.17% compared with 2.4 mm gap. Under all working conditions, the gap size has less influence on the axial thrust which shows a monotonic decreasing trend as the flow rate increases. The analytical axial thrust is much lower than the tested va-lue obviously. With increasing flow rate, the analytical axial thrust approaches the measurement. © 2016, Editorial Department of Journal of Drainage and Irrigation Machinery Engineering. All right reserved.


Quan H.,Lanzhou University of Technology | Quan H.,Key Laboratory of Fluid Machinery and Systems | Li R.,Lanzhou University of Technology | Li R.,Key Laboratory of Fluid Machinery and Systems | And 7 more authors.
Nongye Jixie Xuebao/Transactions of the Chinese Society for Agricultural Machinery | Year: 2015

In order to research the internal flow mechanism of screw centrifugal pump, the PIV testing technology was used after the pump was improved with the transparent handling. The velocities of shaft section and radial section at different stages were obtained. The flow of each section was received and then the internal flow in screw centrifugal pump was revealed. The results showed that the perturbation of physical parameters at the whole shaft section was bigger than the one at radial section. The vortex was appeared obviously at shaft section of impeller passage and the vortex volume increased significantly in the impeller passage which was deep into volute. With the depth of the fluid flow, it caused fluid force reallocation by the spiral vane segment. At radial section, velocity was rotated along with the direction of the flow line. Simultaneously, there was a trend that fluid moved from the center to the outside due to the centrifugal force from the centrifugal section, which played an important role after the spiral section. The spiral propulsion of spiral section and the energy conversion of centrifugal section were cooperated with each other to make up the working process of screw centrifugal pump. ©, 2015, Chinese Society of Agricultural Machinery. All right reserved.


Li R.,Lanzhou University of Technology | Li R.,Key Laboratory of Fluid Machinery and Systems | Bi Z.,Lanzhou University of Technology | Li Y.,Lanzhou University of Technology | And 2 more authors.
Paiguan Jixie Gongcheng Xuebao/Journal of Drainage and Irrigation Machinery Engineering | Year: 2016

In order to clarify the effect of inducer deflection on cavitation performance of centrifugal pump impeller, improve centrifugal pump cavitation performance, and get the best circumferential position, based on the homogeneous flow assumption, the IDM cavitation model and the RNG k-ε turbulence model were adopted and six projects which deflections are 0°, 10°, 20°, 30°, 40° and 50° were selected, to compare numerical simulation values and experimental values of pump's external characteristics and cavitation performances of inducer and impeller. The centrifugal pump characteristic performance data of different projects were obtained. Calculated NPSHR curves match well with experimental ones, which can verify the accuracy of the calculation methods. Based on numerical simulation results, vapor volume fraction distributions within inducer and impeller blades under various conditions were analyzed. It was found that cavitation bubbles' development processes at different positions are basically the same, but the cavitation rate and vapor volume fraction distribution areas are smaller when the deflection is 10°, therefore two deflections of 5° and 15° were further selected to do simulation analysis to get more accurate results, i.e. the pump's overall hydraulic characteristic is the best when the deflection is 5°. © 2016, Editorial Department of Journal of Drainage and Irrigation Machinery Engineering. All right reserved.


Wang X.,Lanzhou University of Technology | Wang X.,Key Laboratory of Fluid Machinery and Systems | Li Y.,Lanzhou University of Technology | Li Y.,Key Laboratory of Fluid Machinery and Systems | And 2 more authors.
Paiguan Jixie Gongcheng Xuebao/Journal of Drainage and Irrigation Machinery Engineering | Year: 2016

In order to reveal pressure fluctuation characteristics of internal fluid field's structures in vortex pump, a multistage side pump with unshrouded impellers and closed runners was developed. Based on RNG k-ω turbulence model, SIMPLEC algorithm and structural grid, numerical simulations and experimental tests of the vortex pump were conducted. The external characteristic predictions indicated that the pump performance meet design requirements. Based on numerical simulation techniques, the internal flow field in the vortex pump was simulated. The results show that the vortex pump's head has the tendency of plunge and at the same time blade power capacity becomes worse, blade pressurizing ability to liquid decreases gradually. Inside the blade runner of impeller inlet and outlet, degrees of velocity and turbulence energy distribution change sharply, velocity and turbulence energy distributions in other blade runners are very much alike. Inside the middle of impeller blade tip flow channel exists a low velocity region and the region becomes smaller and smaller with the flow rate increasing gradually. Inside the middle of impeller blade root flow channel exists a concentration zone of velocity gradient, in which the turbulence kinetic energy is larger, namely there exists a larger dissipation loss area in impeller blade root flow channel, and it is becoming smaller with the increasing of flow rate. Analysis of pressure fluctuation characteristics in vortex pump's characteristic locations found that at different monitoring locations of impeller blades and closed runners, pressure fluctuation frequency characteristics are more obvious, where obvious hydraulic vibration and noise can be induced. The results reveal the impact mechanism of internal fields and performance of vortex pump, which provides a theoretical basis for vortex pump's design. © 2016, Editorial Department of Journal of Drainage and Irrigation Machinery Engineering. All right reserved.


Zhao W.,Lanzhou University of Technology | Zhao W.,Key Laboratory of Fluid Machinery and Systems | Liu M.,Lanzhou University of Technology | Liu Y.,Lanzhou University of Technology | And 2 more authors.
Paiguan Jixie Gongcheng Xuebao/Journal of Drainage and Irrigation Machinery Engineering | Year: 2015

In order to research the effects of blade thickness on the performance of a low-specific-speed centrifugal pump, a centrifugal pump with a specific speed of 48 was selected as the study object. With other geometric parameters fixed, five kinds of impellers with different blade thickness of a centrifugal pump were constructed. Based on the standard k-ε turbulence model and SIMPLE algorithm, numerical simulation was performed by commercial software Fluent under six different operation conditions. The relationship between the blade thickness and the hydraulic performance was analyzed from the external characteristics and internal flow. The results show that when the blade thickness increases in a certain range, the best efficiency point of the pump moves to the small flow direction and the top efficiency increases slightly. Additionally, the internal turbulence energy loss increases gradually under the design condition. Under the prerequisite of having met the blade structural strength, selecting appropriate blade thickness could ensure the better hydraulic performance of a centrifugal pump. © 2015, Editorial Department of Journal of Drainage and Irrigation Machinery Engineering. All right reserved.


Cheng X.,Lanzhou University of Technology | Cheng X.,Key Laboratory of Fluid Machinery and Systems | Zhang N.,Lanzhou University of Technology | Zhang N.,Key Laboratory of Fluid Machinery and Systems | And 2 more authors.
Paiguan Jixie Gongcheng Xuebao/Journal of Drainage and Irrigation Machinery Engineering | Year: 2015

In order to study fluid pressure fluctuation features in the volute of a centrifugal pump under solid-liquid two-phase flow conditions, a series of unsteady, three-dimensional, turbulent, sand particle-laden water flows in a single-stage double-suction centrifugal pump are simulated based on the ASMM solid-liquid two-phase flow model and SIMPLEC algorithm as well as the RNG k-ε two-equation turbulence model. The pressure fluctuations are characterized at various solid volume fractions and sand particle diameters; additionally, the simulated results of two-phase flow with 12% solid phase volume fraction and 0.05 mm particle diameter are compared with those of water alone. The results show that the pressure fluctuation of solid-liquid two-phase flow is much greater than the water single phase flow, and the pulse waveform of the two-phase flow is with 0.002 s lag. The pressure fluctuation rises with the increasing solid phase volume fraction, but the change in fluctuation amplitude is not significant. Also, the fluctuation is reduced with the increasing particle diameter. Compared with particle diameter, the solid volume fraction affects the pressure fluctuation more remarkable than the particle diameter does. The blade passing frequency is dominated in the pressure fluctuations in the volute, further the maximum pressure fluctuation occurs at the double blade passing frequency. ©, 2015, Editorial Department of Journal of Drainage and Irrigation Machinery Engineering. All right reserved.

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