The transient behavior of centrifugal pumps during transient operating periods, such as startup and stopping, has drawn more and more attention recently because of urgent needs in engineering. Up to now, almost all th...The transient behavior of centrifugal pumps during transient operating periods, such as startup and stopping, has drawn more and more attention recently because of urgent needs in engineering. Up to now, almost all the existing studies on this behavior are limited to using water as working fluid. The study on the transient behavior related to solid-liquid two-phase flow has not been seen yet. In order to explore the transient characteristics of a high specific-speed centrifugal pump during startup period delivering the pure water and solid-liquid two-phase flow, the transient flows inside the pump are numerically simulated using the dynamic mesh method. The variable rotational speed and flow rate with time obtained from experiment are best fitted as the function of time, and are written into computational fluid dynamics （CFD） code-FLUENT by using a user defined function. The predicted heads are compared with experimental results when pumping pure water. The results show that the difference in the transient performance during startup period is very obvious between water and solid-liquid two-phase flow during the later stage of startup process. Moreover, the time for the solid-liquid two-phase flow to achieve a stable condition is longer than that for water. The solid-liquid two-phase flow results in a higher impeller shaft power, a larger dynamic reaction force, a more violent fluctuation in pressure and a reduced stable pressure rise comparing with water. The research may be useful to tmderstanding on the transient behavior of a centrifugal pump under a solid-liquid two-phase flow during startup period.展开更多
The flow with solid-liquid two-phase media inside centrifugal pumps is very complicated and the relevant method for the hydraulic design is still immature so far. There exist two main problems in the operation of the ...The flow with solid-liquid two-phase media inside centrifugal pumps is very complicated and the relevant method for the hydraulic design is still immature so far. There exist two main problems in the operation of the two-phase flow pumps, i.e., low overall efficiency and severe abrasion. In this study, the three-dimensional, steady, incompressible, and turbulent solid-liquid two-phase flows in a low-specific-speed centrifugal pump are numerically simulated and analyzed by using a computational fluid dynamics （CFD） code based on the mixture model of the two-phase flow and the RNG k-~ two-equation turbulence model, in which the influences of rotation and curvature are fully taken into account. The coupling between impeller and volute is implemented by means of the frozen rotor method. The simulation results predicted indicate that the solid phase properties in two-phase flow, especially the concentration, the particle diameter and the density, have strong effects on the hydraulic performance of the pump. Both the pump head and the efficiency are reduced with increasing particle diameter or concentration. However, the effect of particle density on the performance is relatively minor. An obvious jet-wake flow structure is presented near the volute tongue and becomes more remarkable with increasing solid phase concentration. The suction side of the blade is subject to much more severe abrasion than the pressure side. The obtained results preliminarily reveal the characteristics of solid-liquid two-phase flow in the centrifugal pump, and are helpful for improvement and empirical correction in the hydraulic design of centrifugal pumps.展开更多
The law governing the movement of particles in the centrifugal pump channel is complicated; thus, it is difficult to examine the solid-liquid two-phase turbulent flow in the pump. Consequently, the solid-liquid two-ph...The law governing the movement of particles in the centrifugal pump channel is complicated; thus, it is difficult to examine the solid-liquid two-phase turbulent flow in the pump. Consequently, the solid-liquid two-phase pump is designed based only on the unary theory. However, the obvious variety of centrifugal-pump internal flow appears because of the existence of solid phase, thus changing pump performance. Therefore, it is necessary to establish the flow characteristics of the solid-liquid two-phase pump. In the current paper, two-phase numerical simulation and centrifugal pump performance tests are carried out using different solid-particle diameters and two-phase mixture concentration conditions. Inner flow features are revealed by comparing the simulated and experimental results. The comparing results indicate that the influence of the solid-phase characteristics on centrifugal-pump performance is small when the flow rate is low, specifically when it is less than 2 m3/h. The maximum efficiency declines, and the best efficiency point tends toward the low flow-rate direction along with increasing solid-particle diameter and volume fraction, leading to reduced pump steady efficient range. The variation tendency of the pump head is basically consistent with that of the efficiency. The efficiency and head values of the two-phase mixture transportation are even larger than those of pure-water transportation under smaller particle diameter and volume fraction conditions at the low-flow-rate region. The change of the particle volume fraction has a greater effect on the pump performance than the change in the particle diameter. The experimental values are totally smaller than the simulated values. This research provides the theoretical foundation for the optimal design of centrifugal pump.展开更多
Molten salt pump is applied to pump high-temperature molten salt as the primary coolant of a molten salt reactor.The pump,generally a vertical rotor system,suffers from radial force generated by the liquid seal compon...Molten salt pump is applied to pump high-temperature molten salt as the primary coolant of a molten salt reactor.The pump,generally a vertical rotor system,suffers from radial force generated by the liquid seal component,and the rotordynamic characteristics of the pump are affected considerably.In this paper,the rotordynamic coefficients of the tooth-on-stator liquid seal in molten salt pump are studied.The flow in the seal region is simulated using computational fluid dynamics technique.Parameters of the inlet loss and the pre-swirl at the inlet region of the seal are calculated.The coefficients of resistance and the wall parameters are obtained from the simulation results by data fitting method.The rotordynamic coefficients are analyzed based on the bulk-flow model of liquid seal.The rotordynamic characteristics,with and without the liquid seal,of the objective molten salt pump are inspected.The first critical speed of the rotor is found to increase.Harmonic analysis shows that the pump,being sensitive to unbalance force though,can operate safely under its design specifications.展开更多
In view of the present situation of low cavitation performance of deep-sea mining slurry pump, the effect of solid phase on the cavitation performance of deep-sea mining pump is analyzed theoretically. The relationshi...In view of the present situation of low cavitation performance of deep-sea mining slurry pump, the effect of solid phase on the cavitation performance of deep-sea mining pump is analyzed theoretically. The relationship between gas and liquid phases are established by cavitation nucleon theory and mass energy equation as well as solid phase and liquid phase, and then we explored the relationship between gas phase and solid phase. The results show that the critical bubble radius and solid-phase concentration flow rate during the cavitation can be related to the liquid pressure. Eq.(19) show that the larger the solid particle concentration and the solid phase flow, the earlier the cavitation will occur, and pump anti-cavitation performance will decline.展开更多
A modified one-dimensional model is developed for prediction of multiphase pump performance. Taken into account in the model are the gas compressibility, the slip speed gap between two phases and the flow cross-sectio...A modified one-dimensional model is developed for prediction of multiphase pump performance. Taken into account in the model are the gas compressibility, the slip speed gap between two phases and the flow cross-sectional depth gradient in the flow line. By using this model, we can select appropriate geometrical parameters of the impellers and guide vanes, and thus higher-pressure boost is obtained but phase separation does not occur. Accordingly, the design method can be optimized. The drag coefficients are analyzed for different flows. Results predicted by the modified model are compared with a series of experimental data and found in good agreement. This model provides a convenient and economical tool for engineering design over a traditional one.展开更多
A new type of contactless stirrer and/or pump has been developed for Aluminium industry.Large scale synchronously rotating permanent magnet cylinders,which are magnetized orthogonal to the axes,are used to create trav...A new type of contactless stirrer and/or pump has been developed for Aluminium industry.Large scale synchronously rotating permanent magnet cylinders,which are magnetized orthogonal to the axes,are used to create travelling magnetic field in Aluminium furnace through a thick bottom or wall,which induces stirring in a liquid metal pool similarly to traditional AC three-phase inductors.Flowrate of up to 600 tons per hour can be achieved with negligible energy dissipation even if the total wall thickness of the furnace is 30 cm.The advantage of the permanent magnet inductor is much lower energy consumption-maximum energy consumption of the stirrer to produce sufficiently high mechanical torque does not exceed 20 kW even for 600 ton per hour stirrer.Produced metal flow is quite similar to that,which is achieved by the AC three-phase induction stirrers offered by ABB and other companies.AC three-phase inductors exhibit very high Joule losses in the coils of the machine,but the permanent magnet system working at frequency in the range from 0.5 Hz to 2 Hz produces negligible Joule losses both in liquid Aluminium as well as in stainless steel plate of the furnace bottom enclosure and in the permanent magnet material itself,so relatively weak air cooling is sufficient.The linear permanent magnet stirrer has been experimentally tested on a small scale lab model in a shallow pool of InGaSn eutectic. The tests confirm the predicted flow intensities and flow pattern,and give sufficient results for validation of the large scale flow simulations.Principal schematics of investigated system and the free surface deformation of the liquid metal due to action of the stirrer are shown below.The linear permanent magnet system may be used also as a contactless pump for liquid Aluminium in two-chamber furnaces,for tapping the liquid metal or for transportation and precision dozing.If high flow rate is required simultaneously with considerable elevation of the liquid metal level,the wall thickness of the channel should be lower and frequency of the travelling magnetic field higher comparing to the case of stirring application.Two sided pump has also been considered for a fiat channel,promising two times higher magnetic field induction and four times higher delivered pressure head.Seeing in perspective wide range applications of the proposed system a patent has been obtained.展开更多
The high temperature liquid is injected into the micro-size capillary and its light propagation behavior is investigated. We focus on two different liquid pumping methods. The first method can pump the high temperatur...The high temperature liquid is injected into the micro-size capillary and its light propagation behavior is investigated. We focus on two different liquid pumping methods. The first method can pump the high temperature liquid tin into the micro-size capillary by using a high pressure difference system. After pumping, a single mode fiber(SMF) connected with the optical carrier based microwave interferometry(OCMI) system is used to measure different liquid tin levels in the micro-size capillary. The second method can pump the room temperature engine oil into the capillary by using a syringe pump. This method can avoid the air bubbles when the liquids are pumped into the capillary.展开更多
基金supported by National Natural Science Foundation of China(Grant Nos.51076144,51276172)Zhejiang Provincial Natural Science Foundation of China(Grant Nos.R1100530,LY12E06002)National Basic Research Program of China(973 Program,Grant No.2009CB724303)
文摘The transient behavior of centrifugal pumps during transient operating periods, such as startup and stopping, has drawn more and more attention recently because of urgent needs in engineering. Up to now, almost all the existing studies on this behavior are limited to using water as working fluid. The study on the transient behavior related to solid-liquid two-phase flow has not been seen yet. In order to explore the transient characteristics of a high specific-speed centrifugal pump during startup period delivering the pure water and solid-liquid two-phase flow, the transient flows inside the pump are numerically simulated using the dynamic mesh method. The variable rotational speed and flow rate with time obtained from experiment are best fitted as the function of time, and are written into computational fluid dynamics （CFD） code-FLUENT by using a user defined function. The predicted heads are compared with experimental results when pumping pure water. The results show that the difference in the transient performance during startup period is very obvious between water and solid-liquid two-phase flow during the later stage of startup process. Moreover, the time for the solid-liquid two-phase flow to achieve a stable condition is longer than that for water. The solid-liquid two-phase flow results in a higher impeller shaft power, a larger dynamic reaction force, a more violent fluctuation in pressure and a reduced stable pressure rise comparing with water. The research may be useful to tmderstanding on the transient behavior of a centrifugal pump under a solid-liquid two-phase flow during startup period.
基金supported by National Natural Science Foundation of China (Grant No. 21076198)Zhejiang Provincial Natural Science Foundation of China (Granted No. R1100530)National Basic Research Program of China (973 Program,Grant No. 2009CB724303)
文摘The flow with solid-liquid two-phase media inside centrifugal pumps is very complicated and the relevant method for the hydraulic design is still immature so far. There exist two main problems in the operation of the two-phase flow pumps, i.e., low overall efficiency and severe abrasion. In this study, the three-dimensional, steady, incompressible, and turbulent solid-liquid two-phase flows in a low-specific-speed centrifugal pump are numerically simulated and analyzed by using a computational fluid dynamics （CFD） code based on the mixture model of the two-phase flow and the RNG k-~ two-equation turbulence model, in which the influences of rotation and curvature are fully taken into account. The coupling between impeller and volute is implemented by means of the frozen rotor method. The simulation results predicted indicate that the solid phase properties in two-phase flow, especially the concentration, the particle diameter and the density, have strong effects on the hydraulic performance of the pump. Both the pump head and the efficiency are reduced with increasing particle diameter or concentration. However, the effect of particle density on the performance is relatively minor. An obvious jet-wake flow structure is presented near the volute tongue and becomes more remarkable with increasing solid phase concentration. The suction side of the blade is subject to much more severe abrasion than the pressure side. The obtained results preliminarily reveal the characteristics of solid-liquid two-phase flow in the centrifugal pump, and are helpful for improvement and empirical correction in the hydraulic design of centrifugal pumps.
基金supported by National Natural Science Foundation of China(Grant No. 51076144)Zhejiang Provincial Key Science Foundation of China(Grant No. 2009C13006)
文摘The law governing the movement of particles in the centrifugal pump channel is complicated; thus, it is difficult to examine the solid-liquid two-phase turbulent flow in the pump. Consequently, the solid-liquid two-phase pump is designed based only on the unary theory. However, the obvious variety of centrifugal-pump internal flow appears because of the existence of solid phase, thus changing pump performance. Therefore, it is necessary to establish the flow characteristics of the solid-liquid two-phase pump. In the current paper, two-phase numerical simulation and centrifugal pump performance tests are carried out using different solid-particle diameters and two-phase mixture concentration conditions. Inner flow features are revealed by comparing the simulated and experimental results. The comparing results indicate that the influence of the solid-phase characteristics on centrifugal-pump performance is small when the flow rate is low, specifically when it is less than 2 m3/h. The maximum efficiency declines, and the best efficiency point tends toward the low flow-rate direction along with increasing solid-particle diameter and volume fraction, leading to reduced pump steady efficient range. The variation tendency of the pump head is basically consistent with that of the efficiency. The efficiency and head values of the two-phase mixture transportation are even larger than those of pure-water transportation under smaller particle diameter and volume fraction conditions at the low-flow-rate region. The change of the particle volume fraction has a greater effect on the pump performance than the change in the particle diameter. The experimental values are totally smaller than the simulated values. This research provides the theoretical foundation for the optimal design of centrifugal pump.
基金funded by the National Natural Science Foundation of China(Nos.51576125 and 51406114)
文摘Molten salt pump is applied to pump high-temperature molten salt as the primary coolant of a molten salt reactor.The pump,generally a vertical rotor system,suffers from radial force generated by the liquid seal component,and the rotordynamic characteristics of the pump are affected considerably.In this paper,the rotordynamic coefficients of the tooth-on-stator liquid seal in molten salt pump are studied.The flow in the seal region is simulated using computational fluid dynamics technique.Parameters of the inlet loss and the pre-swirl at the inlet region of the seal are calculated.The coefficients of resistance and the wall parameters are obtained from the simulation results by data fitting method.The rotordynamic coefficients are analyzed based on the bulk-flow model of liquid seal.The rotordynamic characteristics,with and without the liquid seal,of the objective molten salt pump are inspected.The first critical speed of the rotor is found to increase.Harmonic analysis shows that the pump,being sensitive to unbalance force though,can operate safely under its design specifications.
基金Funded by the National Natural Science Foundation of China(No.51775561)
文摘In view of the present situation of low cavitation performance of deep-sea mining slurry pump, the effect of solid phase on the cavitation performance of deep-sea mining pump is analyzed theoretically. The relationship between gas and liquid phases are established by cavitation nucleon theory and mass energy equation as well as solid phase and liquid phase, and then we explored the relationship between gas phase and solid phase. The results show that the critical bubble radius and solid-phase concentration flow rate during the cavitation can be related to the liquid pressure. Eq.(19) show that the larger the solid particle concentration and the solid phase flow, the earlier the cavitation will occur, and pump anti-cavitation performance will decline.
文摘A modified one-dimensional model is developed for prediction of multiphase pump performance. Taken into account in the model are the gas compressibility, the slip speed gap between two phases and the flow cross-sectional depth gradient in the flow line. By using this model, we can select appropriate geometrical parameters of the impellers and guide vanes, and thus higher-pressure boost is obtained but phase separation does not occur. Accordingly, the design method can be optimized. The drag coefficients are analyzed for different flows. Results predicted by the modified model are compared with a series of experimental data and found in good agreement. This model provides a convenient and economical tool for engineering design over a traditional one.
文摘A new type of contactless stirrer and/or pump has been developed for Aluminium industry.Large scale synchronously rotating permanent magnet cylinders,which are magnetized orthogonal to the axes,are used to create travelling magnetic field in Aluminium furnace through a thick bottom or wall,which induces stirring in a liquid metal pool similarly to traditional AC three-phase inductors.Flowrate of up to 600 tons per hour can be achieved with negligible energy dissipation even if the total wall thickness of the furnace is 30 cm.The advantage of the permanent magnet inductor is much lower energy consumption-maximum energy consumption of the stirrer to produce sufficiently high mechanical torque does not exceed 20 kW even for 600 ton per hour stirrer.Produced metal flow is quite similar to that,which is achieved by the AC three-phase induction stirrers offered by ABB and other companies.AC three-phase inductors exhibit very high Joule losses in the coils of the machine,but the permanent magnet system working at frequency in the range from 0.5 Hz to 2 Hz produces negligible Joule losses both in liquid Aluminium as well as in stainless steel plate of the furnace bottom enclosure and in the permanent magnet material itself,so relatively weak air cooling is sufficient.The linear permanent magnet stirrer has been experimentally tested on a small scale lab model in a shallow pool of InGaSn eutectic. The tests confirm the predicted flow intensities and flow pattern,and give sufficient results for validation of the large scale flow simulations.Principal schematics of investigated system and the free surface deformation of the liquid metal due to action of the stirrer are shown below.The linear permanent magnet system may be used also as a contactless pump for liquid Aluminium in two-chamber furnaces,for tapping the liquid metal or for transportation and precision dozing.If high flow rate is required simultaneously with considerable elevation of the liquid metal level,the wall thickness of the channel should be lower and frequency of the travelling magnetic field higher comparing to the case of stirring application.Two sided pump has also been considered for a fiat channel,promising two times higher magnetic field induction and four times higher delivered pressure head.Seeing in perspective wide range applications of the proposed system a patent has been obtained.
基金supported by the U.S.Department of Energy,National Energy Technology Laboratory,Morgantown,WV,USA(No.DEFE0012272)the Joint Funds(NSFC-Henan)of the National Natural Science Foundation of China(No.U1204615)
文摘The high temperature liquid is injected into the micro-size capillary and its light propagation behavior is investigated. We focus on two different liquid pumping methods. The first method can pump the high temperature liquid tin into the micro-size capillary by using a high pressure difference system. After pumping, a single mode fiber(SMF) connected with the optical carrier based microwave interferometry(OCMI) system is used to measure different liquid tin levels in the micro-size capillary. The second method can pump the room temperature engine oil into the capillary by using a syringe pump. This method can avoid the air bubbles when the liquids are pumped into the capillary.
