In the printing industry,vacuum pumps play a critical role in sheet feeding and gripping processes.In order to improve the efficiency of vacuum pumps,By analyzing the internal flow field of the vane type vacuum pump,t...In the printing industry,vacuum pumps play a critical role in sheet feeding and gripping processes.In order to improve the efficiency of vacuum pumps,By analyzing the internal flow field of the vane type vacuum pump,the CFD method was used to simulate the internal flow field of the air pump,and it was found that a main vortex was formed near the rotor of the trailing blade.Based on this observation,a new rotor shape design was proposed in this study,which design places arc-shaped depressed on the circumference of the rotor where the main vortex forms.The existence of the depression facilitated forward motion of the main airflow and thus effectively restricting reverse flow.Simulation results demonstrated that the proposed design is able to decrease pressure-induced torque load on the pump,and the reduction increases for an increasing operating speed.For all three operating speeds tested,the reduction in pressure-induced torque ranges from 5%to up to 10%comparing to the original pump.展开更多
The rotating speed fluctuation for turbomachinery is a common problem, which will cause severe destruction for equipments and basis when the fluctuation is very strong. In this paper,in order to study the transient re...The rotating speed fluctuation for turbomachinery is a common problem, which will cause severe destruction for equipments and basis when the fluctuation is very strong. In this paper,in order to study the transient response characteristics of a radial vane pump subjected to slight( 5%) and strong( 20%)fluctuating rotational speeds, the variation characteristics of the external hydraulic performances are numerically predicted by means of computational fluid dynamics( CFD) technology. The results manifest that the responses of head and flow rate are different relative to the fluctuating characteristics of rotational speed. The response of the former is very satisfied in synchronism,while that of the latter is hysteretic. Meanwhile,it is found that the variation tendencies of the static pressures at the inlet and outlet of the pump are completely opposite, while the response characteristics of the dynamic pressures at the inlet and outlet are nearly identical.Subsequently,in order to further reveal the transient behavior during the instantaneous operating periods,two non-dimensional parameters are employed to deeply analyze it. The result shows that the variation tendencies of these two parameters are also approximately opposite.Moreover,the quasi-steady assumption is not able to be used to accurately assess the transient flow during transient operating periods. The comparison results show that the transient behavior does not show obvious distinctions between slight and strong fluctuating rotating speeds.展开更多
As core components of eroengine lubricating oil systems,the reliability of lubricating oil pumps is crucial for maintaining oil circulation and ensuring engine operational integrity.Rotary vane pumps(RVPs)are highly e...As core components of eroengine lubricating oil systems,the reliability of lubricating oil pumps is crucial for maintaining oil circulation and ensuring engine operational integrity.Rotary vane pumps(RVPs)are highly efficient,stable,and compact,making them suitable for eroengine lubricating oil systems.However,they suffer from performance degradation under prolonged high-speed operation,owing to vane tip wear and clearance expansion.This study numerically investigates the effects of vane tip clearance on cavitation and gas-liquid twophase flow in a high-speed RVP.The RNG k-εturbulence model,Singhal full cavitation model,and volume-of-fluid(VOF)multiphase flow model are employed.The results indicate that under single-phase oil inlet conditions,increased vane tip clearance has a minimal influence on cavitation in the pump chamber,but reduces outlet flow pulsation amplitude and volumetric efficiency.Pressure fluctuations at the pump outlet remain relatively stable,with the dominant pulsation frequency being equal to the rotational frequency.Under two-phase oil-gas conditions,increased vane tip clearance leads to decreased instantaneous flow fluctuation,induces uneven oil-gas phase distribution in the pump chamber,lowers the maximum outlet pressure,and increases leakage.Spectral analysis reveals that the dominant frequency of pressure pulsations corresponds to the shaft rotation and that the secondary frequency is the vane frequency.To optimize performance and reduce leakage,it is recommended to maintain a vane tip clearance of 0.035 mm and avoid operating the pump under high-gas-content conditions.These results provide theoretical guidance for designing and selecting RVPs,with significant implications for the further development of eroengine lubricating oil systems.展开更多
Experimental studies of a model pump-turbine S-curve characteristics and its improvement by misaligned guide vanes （MGV） were extended to prototype pump turbine through 3-D transient flow simulations. The unsteady R...Experimental studies of a model pump-turbine S-curve characteristics and its improvement by misaligned guide vanes （MGV） were extended to prototype pump turbine through 3-D transient flow simulations. The unsteady Reynolds-averaged Navier-Stokes equations with the SST turbulence model were used to model the transient flow within the entire flow passage of a reversible pump-turbine with and without misaligned guide vanes during turbine model start-up. The unstable S-curve and its improvement by using misaligned guide vane were verified by model test and simulation. The transient flow calculations were used to clarify the variations of pressure pulse and internal flow behavior in the entire flow passage. The use of misaligned guide vanes can eliminate the S-curve characteristics of a pump-turbine, and can significantly increase the pressure pulse amplitude in the entire flow passage and the runner radial forces during start-up. The MGV only decreased the pulse amplitude on the guide vane suction side when the rotating speed was less than 50% rated speed. The hydraulic reason is that the MGV dramatically changed the flow patterns inside the entire flow passage, and destroyed the symmetry of the flow distribution inside the guide vane and runner.展开更多
The calculation method for vane numbers is obtained on the intention that itshould have no back flow area in the flow passage of centrifugal passage. Then a criterion that thedesign of splitting vanes of centrifugal c...The calculation method for vane numbers is obtained on the intention that itshould have no back flow area in the flow passage of centrifugal passage. Then a criterion that thedesign of splitting vanes of centrifugal compound impeller should ensure that the back flow arearatio be the minimum is proposed. On the basis of the criterion, the slippery theory is used as oneof CFD methods to analyze the inner flow field of the impeller of various kinds of splitting vanesdesign, therefore, the optimized design of splitting vanes is obtained and which agrees with that ofsome testing results.展开更多
Different guide vane structures will affect the flow inside the pump,and then affect the transformation of the pressure energy and kinetic energy,and change the velocity distribution of the pump outlet.In order to stu...Different guide vane structures will affect the flow inside the pump,and then affect the transformation of the pressure energy and kinetic energy,and change the velocity distribution of the pump outlet.In order to study the influence of long and short guide vanes on the water-jet pump,on the basis of conventional design,eight schemes of guide vane with different vertical heights were designed in the method of computational fluid dynamics for numerical calculation,the performance curve of water-jet pumps with different long and short guide vanes was obtained,and finally the influence of different guide vanes on hydraulic performance and internal flow was analyzed.The results show that all of schemes reducing the height of blade can improve the head and efficiency.In the schemes reducing the height on the shroud,the guide vanes that the height of the blade is equal to the height difference between hub and shroud in impeller have the highest head and efficiency.In all schemes decreasing the blade height,with the increase of the height difference,the velocity increases gradually and the distribution of turbulence kinetic energy becomes more reasonable in the guide vane outlet.The schemes reducing the height on the hub have more reasonable distribution of velocity and turbulence kinetic energy according to schemes reducing the height on the shroud.The guide vanes of long and short blades can be used to stagger the position of the diffusion flow generated by adjacent blades,which can reduce the effect of the velocity circulation and make the flow of the outlet position more stable.展开更多
文摘In the printing industry,vacuum pumps play a critical role in sheet feeding and gripping processes.In order to improve the efficiency of vacuum pumps,By analyzing the internal flow field of the vane type vacuum pump,the CFD method was used to simulate the internal flow field of the air pump,and it was found that a main vortex was formed near the rotor of the trailing blade.Based on this observation,a new rotor shape design was proposed in this study,which design places arc-shaped depressed on the circumference of the rotor where the main vortex forms.The existence of the depression facilitated forward motion of the main airflow and thus effectively restricting reverse flow.Simulation results demonstrated that the proposed design is able to decrease pressure-induced torque load on the pump,and the reduction increases for an increasing operating speed.For all three operating speeds tested,the reduction in pressure-induced torque ranges from 5%to up to 10%comparing to the original pump.
基金Zhejiang Provincial Natural Science Foundation of China(No.LY14E090011)Quzhou Science and Technology Development Fund,China(No.20121057)Zhejiang Provincial Science and Technology Project,China(No.2015C31129)
文摘The rotating speed fluctuation for turbomachinery is a common problem, which will cause severe destruction for equipments and basis when the fluctuation is very strong. In this paper,in order to study the transient response characteristics of a radial vane pump subjected to slight( 5%) and strong( 20%)fluctuating rotational speeds, the variation characteristics of the external hydraulic performances are numerically predicted by means of computational fluid dynamics( CFD) technology. The results manifest that the responses of head and flow rate are different relative to the fluctuating characteristics of rotational speed. The response of the former is very satisfied in synchronism,while that of the latter is hysteretic. Meanwhile,it is found that the variation tendencies of the static pressures at the inlet and outlet of the pump are completely opposite, while the response characteristics of the dynamic pressures at the inlet and outlet are nearly identical.Subsequently,in order to further reveal the transient behavior during the instantaneous operating periods,two non-dimensional parameters are employed to deeply analyze it. The result shows that the variation tendencies of these two parameters are also approximately opposite.Moreover,the quasi-steady assumption is not able to be used to accurately assess the transient flow during transient operating periods. The comparison results show that the transient behavior does not show obvious distinctions between slight and strong fluctuating rotating speeds.
基金supported by the National Natural Science Foundation of China(Grant No.52376031)the School-Enterprise Collaborative Innovation Fund for graduate students of Xi’an University of Technology(Grant No.252062402).
文摘As core components of eroengine lubricating oil systems,the reliability of lubricating oil pumps is crucial for maintaining oil circulation and ensuring engine operational integrity.Rotary vane pumps(RVPs)are highly efficient,stable,and compact,making them suitable for eroengine lubricating oil systems.However,they suffer from performance degradation under prolonged high-speed operation,owing to vane tip wear and clearance expansion.This study numerically investigates the effects of vane tip clearance on cavitation and gas-liquid twophase flow in a high-speed RVP.The RNG k-εturbulence model,Singhal full cavitation model,and volume-of-fluid(VOF)multiphase flow model are employed.The results indicate that under single-phase oil inlet conditions,increased vane tip clearance has a minimal influence on cavitation in the pump chamber,but reduces outlet flow pulsation amplitude and volumetric efficiency.Pressure fluctuations at the pump outlet remain relatively stable,with the dominant pulsation frequency being equal to the rotational frequency.Under two-phase oil-gas conditions,increased vane tip clearance leads to decreased instantaneous flow fluctuation,induces uneven oil-gas phase distribution in the pump chamber,lowers the maximum outlet pressure,and increases leakage.Spectral analysis reveals that the dominant frequency of pressure pulsations corresponds to the shaft rotation and that the secondary frequency is the vane frequency.To optimize performance and reduce leakage,it is recommended to maintain a vane tip clearance of 0.035 mm and avoid operating the pump under high-gas-content conditions.These results provide theoretical guidance for designing and selecting RVPs,with significant implications for the further development of eroengine lubricating oil systems.
基金supported by the National Natural Science Foundation of China(51009077)State Key Laboratory of Hydroscience and Engineering(2014-KY-05)
文摘Experimental studies of a model pump-turbine S-curve characteristics and its improvement by misaligned guide vanes （MGV） were extended to prototype pump turbine through 3-D transient flow simulations. The unsteady Reynolds-averaged Navier-Stokes equations with the SST turbulence model were used to model the transient flow within the entire flow passage of a reversible pump-turbine with and without misaligned guide vanes during turbine model start-up. The unstable S-curve and its improvement by using misaligned guide vane were verified by model test and simulation. The transient flow calculations were used to clarify the variations of pressure pulse and internal flow behavior in the entire flow passage. The use of misaligned guide vanes can eliminate the S-curve characteristics of a pump-turbine, and can significantly increase the pressure pulse amplitude in the entire flow passage and the runner radial forces during start-up. The MGV only decreased the pulse amplitude on the guide vane suction side when the rotating speed was less than 50% rated speed. The hydraulic reason is that the MGV dramatically changed the flow patterns inside the entire flow passage, and destroyed the symmetry of the flow distribution inside the guide vane and runner.
基金This project is supported by National Natural Science Foundation of China(No.50279011).
文摘The calculation method for vane numbers is obtained on the intention that itshould have no back flow area in the flow passage of centrifugal passage. Then a criterion that thedesign of splitting vanes of centrifugal compound impeller should ensure that the back flow arearatio be the minimum is proposed. On the basis of the criterion, the slippery theory is used as oneof CFD methods to analyze the inner flow field of the impeller of various kinds of splitting vanesdesign, therefore, the optimized design of splitting vanes is obtained and which agrees with that ofsome testing results.
基金The Fundamental Research Funds for the Central Universities(JD2016XGKP1062)
文摘Different guide vane structures will affect the flow inside the pump,and then affect the transformation of the pressure energy and kinetic energy,and change the velocity distribution of the pump outlet.In order to study the influence of long and short guide vanes on the water-jet pump,on the basis of conventional design,eight schemes of guide vane with different vertical heights were designed in the method of computational fluid dynamics for numerical calculation,the performance curve of water-jet pumps with different long and short guide vanes was obtained,and finally the influence of different guide vanes on hydraulic performance and internal flow was analyzed.The results show that all of schemes reducing the height of blade can improve the head and efficiency.In the schemes reducing the height on the shroud,the guide vanes that the height of the blade is equal to the height difference between hub and shroud in impeller have the highest head and efficiency.In all schemes decreasing the blade height,with the increase of the height difference,the velocity increases gradually and the distribution of turbulence kinetic energy becomes more reasonable in the guide vane outlet.The schemes reducing the height on the hub have more reasonable distribution of velocity and turbulence kinetic energy according to schemes reducing the height on the shroud.The guide vanes of long and short blades can be used to stagger the position of the diffusion flow generated by adjacent blades,which can reduce the effect of the velocity circulation and make the flow of the outlet position more stable.
