To enhance the gas-liquid mixed transport performance of the first-stage centrifugal impeller of the multistage side-channel pump,a diagonal perforation oriented towards the exit is fabricated in the front shroud of t...To enhance the gas-liquid mixed transport performance of the first-stage centrifugal impeller of the multistage side-channel pump,a diagonal perforation oriented towards the exit is fabricated in the front shroud of the impeller.Based on the Euler-Euler non-homogeneous model and the SST k-ωturbulence model,the gas-liquid two-phase unsteady numerical simulation of the internal flow under various inlet gas volume fraction(IGVF)is conducted,the reliability of the simulation is verified through comparison with experiments.The results indicate that under the circumstances of high flowrate and high IGVF,the perforation design of the front shroud can increase the head of the centrifugal impeller by 4%–7%while the efficiency is slightly decreased under gas-liquid two phase flow.According to the internal flow analysis and Liutex vortex identification,the high-pressure and high-speed fluid in the front pump chamber is introduced into the impeller through the front shroud perforation,smashing and dispersing the originally aggregated bubble groups in the flow channel,causing the average pressure in the impeller to rise after the perforation,increasing the number and intensity of vortexes,significantly reducing the number and the accumulation area of bubbles,greatly reducing the air volume fraction of the impeller.The bubble blockage phenomenon in the flow channel is observably improved,and the gas-liquid mixed transport capacity of the centrifugal impeller is significantly enhanced,providing a theoretical basis for the optimization design of the gas-liquid two-phase flow of vane pumps.展开更多
Centrifugal pumps are being widely used in many industrial and commercial applications.Many of these pumps are being operated at constant speed but could provide energy savings through adjustable speed operations.The ...Centrifugal pumps are being widely used in many industrial and commercial applications.Many of these pumps are being operated at constant speed but could provide energy savings through adjustable speed operations.The purpose of this study was to get the energy saving rates of the multistage centrifugal pump with variable speed conditions.For this investigation an experimental set up of variable flow and pressure system was made to get energy saving rates and numerical analyses are applied to validate the pump performance.The energy saving and therefore the cost saving depends on the specific duty cycle of which the machine operates.Duty cycle is the proportion of time during which a component,device and system is operated.The duty cycle segmented into different flow rates and weighting the average value for each segment by the interval time.The system was operated at 50%or less of the pump capacity.The input power of the system was carried out by pump characteristics curve of each operating point.The energy consumption was done by the product of specific duty cycle and the input power of the system for constant speed and variable speed drive operation.The total energy consumed for constant speed drive pump was 75,770 k W.hr and for variable speed drive pump was 31,700 k W.hr.The total energy saving of the system was 44,070 k W.hr or 58.16%annually.So,this paper suggests a method of implementing an energy saving on variable-flow and pressure system of the multistage centrifugal pump.展开更多
Tip leakage flow(TLF)trajectory in a pump with gas entrainment is investigated via visualization experiments and numerical simulations.Starting position of tip leakage vortex(TLV)is determined accurately by numerical ...Tip leakage flow(TLF)trajectory in a pump with gas entrainment is investigated via visualization experiments and numerical simulations.Starting position of tip leakage vortex(TLV)is determined accurately by numerical simulation.Under high liquid flow rate(Q_(l))and high inlet gas volume fraction(IGVF)conditions,TLF flows from suction surface to pressure surface near the leading edge of blade,and the direction of TLF gradually changes along the chord which flows from pressure surface to suction surface near the tailing edge.The angle between TLF and blade mean camberline increases progressively as either Q_(l)or IGVF decreases,and starting position of TLV moves towards leading edge direction.As Q_(l)or IGVF decreases,value of vorticity increases and high vorticity region moves towards leading edge.The entropy production rate at blade tip clearance is high,and entropy diffuses from pressure surface to suction surface due to jet flow in blade tip clearance.The greater the amount of accumulated gas there is,the greater the amount of entropy in the area.In addition,when gas is entrained in pump,there are many low frequency fluctuations generated in blade tip clearance.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.52279086).
文摘To enhance the gas-liquid mixed transport performance of the first-stage centrifugal impeller of the multistage side-channel pump,a diagonal perforation oriented towards the exit is fabricated in the front shroud of the impeller.Based on the Euler-Euler non-homogeneous model and the SST k-ωturbulence model,the gas-liquid two-phase unsteady numerical simulation of the internal flow under various inlet gas volume fraction(IGVF)is conducted,the reliability of the simulation is verified through comparison with experiments.The results indicate that under the circumstances of high flowrate and high IGVF,the perforation design of the front shroud can increase the head of the centrifugal impeller by 4%–7%while the efficiency is slightly decreased under gas-liquid two phase flow.According to the internal flow analysis and Liutex vortex identification,the high-pressure and high-speed fluid in the front pump chamber is introduced into the impeller through the front shroud perforation,smashing and dispersing the originally aggregated bubble groups in the flow channel,causing the average pressure in the impeller to rise after the perforation,increasing the number and intensity of vortexes,significantly reducing the number and the accumulation area of bubbles,greatly reducing the air volume fraction of the impeller.The bubble blockage phenomenon in the flow channel is observably improved,and the gas-liquid mixed transport capacity of the centrifugal impeller is significantly enhanced,providing a theoretical basis for the optimization design of the gas-liquid two-phase flow of vane pumps.
基金supported by the Korea government through the Korea institute of Energy Technology Evaluation and Planning(KETEP)The grant number is 20132010101870 for the Promotion of Science
文摘Centrifugal pumps are being widely used in many industrial and commercial applications.Many of these pumps are being operated at constant speed but could provide energy savings through adjustable speed operations.The purpose of this study was to get the energy saving rates of the multistage centrifugal pump with variable speed conditions.For this investigation an experimental set up of variable flow and pressure system was made to get energy saving rates and numerical analyses are applied to validate the pump performance.The energy saving and therefore the cost saving depends on the specific duty cycle of which the machine operates.Duty cycle is the proportion of time during which a component,device and system is operated.The duty cycle segmented into different flow rates and weighting the average value for each segment by the interval time.The system was operated at 50%or less of the pump capacity.The input power of the system was carried out by pump characteristics curve of each operating point.The energy consumption was done by the product of specific duty cycle and the input power of the system for constant speed and variable speed drive operation.The total energy consumed for constant speed drive pump was 75,770 k W.hr and for variable speed drive pump was 31,700 k W.hr.The total energy saving of the system was 44,070 k W.hr or 58.16%annually.So,this paper suggests a method of implementing an energy saving on variable-flow and pressure system of the multistage centrifugal pump.
基金supported by the National Natural Science Foundation of China(Grant Nos.52409119,52439006,52079108 and 52309118).
文摘Tip leakage flow(TLF)trajectory in a pump with gas entrainment is investigated via visualization experiments and numerical simulations.Starting position of tip leakage vortex(TLV)is determined accurately by numerical simulation.Under high liquid flow rate(Q_(l))and high inlet gas volume fraction(IGVF)conditions,TLF flows from suction surface to pressure surface near the leading edge of blade,and the direction of TLF gradually changes along the chord which flows from pressure surface to suction surface near the tailing edge.The angle between TLF and blade mean camberline increases progressively as either Q_(l)or IGVF decreases,and starting position of TLV moves towards leading edge direction.As Q_(l)or IGVF decreases,value of vorticity increases and high vorticity region moves towards leading edge.The entropy production rate at blade tip clearance is high,and entropy diffuses from pressure surface to suction surface due to jet flow in blade tip clearance.The greater the amount of accumulated gas there is,the greater the amount of entropy in the area.In addition,when gas is entrained in pump,there are many low frequency fluctuations generated in blade tip clearance.
