To control the position of differential cylinder closed loop without usingany throttle elements, a flew idea that two speed variable pumps are used to compensate thenon-symmetric flow of differential cylinder is carri...To control the position of differential cylinder closed loop without usingany throttle elements, a flew idea that two speed variable pumps are used to compensate thenon-symmetric flow of differential cylinder is carried out. According to the leaking property of thesystem, a speed offset principle is also proposed to eliminate the cavitation and tension caused bythe leakage and condensation of oil, which makes the system be in the same state as a valvecontrolled circuit. This principle is explained theoretically and experimentally. Further therelationship that the pressures in cylinder chambers change with load and leakage, and therelationship between biasing speed and pre-load pressures in cylinder chambers are established. Theresearch has proved that the new system has similar technique features as those of controlled withservo valves, but due to the elimination of all the throttle lose the efficiency of system can beimproved greatly.展开更多
The experimental study is carried out on high-speed centrifugal pumps withthree different impellers. The experimental results and analysis show that high-speed centrifugalpumps with a closed complex impeller can achie...The experimental study is carried out on high-speed centrifugal pumps withthree different impellers. The experimental results and analysis show that high-speed centrifugalpumps with a closed complex impeller can achieve the highest efficiency and the lowest headcoefficient followed by those with half-open impeller and open-impeller, and can obtain much easilystable head-capacity characrastic curve, while those with a half-open complex impeller can't. Thecharacteristic curve with a open impeller is almost constant horizontal line before droppingsharply. The results also show that the axial clearance between pump casing and impeller caninfluence greatly on the performance of centrifugal pumps.展开更多
Variable speed pumped storage machines are used extensively in wind power plant and pumped storage power plant. This paper presents direct torque and flux control(DTFC) of a variable speed pumped storage power plant(V...Variable speed pumped storage machines are used extensively in wind power plant and pumped storage power plant. This paper presents direct torque and flux control(DTFC) of a variable speed pumped storage power plant(VSPSP). By this method both torque and flux have been applied to control the VSPSP. The comparison between VSPSP's control strategies is studied. At the first, a wind turbine with the capacity 2.2 k W and DTFC control strategies simulated then a 250 MW VSPSP is simulated with all of its parts(including electrical, mechanical, hydraulic and its control system) by MATLAB software. In all of simulations, both converters including two-level voltage source converter(2LVSC) and three-level voltage source converter(3LVSC) are applied. The results of applying 2LVSC and 3LVSC are the rapid dynamic responses with better efficiency, reducing the total harmonic distortion(THD) and ripple of rotor torque and flux.展开更多
Cryogenic ground supporting equipment (CGSE) developed for international cooperation scientific experimental item AMS-02 is the ground supporting and cooling system, which will complete the cooling process of the supe...Cryogenic ground supporting equipment (CGSE) developed for international cooperation scientific experimental item AMS-02 is the ground supporting and cooling system, which will complete the cooling process of the superconductor of AMS-02 from ambient temperature to 1.8 K. Obtaining 1.8 K He Ⅱ by vacuum-pumping is discussed in detail and compared with the other three schemes. The results show that the scheme of vacuum-pumping not only could meet the requirement of the project much better but also has higher reliability compared with other schemes. To select the vacuum pump, the energy conservation model is presented according to the experimental system of CGSE. Therefore, the pumping speed is also determined.展开更多
In order to widen the high-efficiency operating range of a low-specific-speed centrifugal pump, an optimization process for considering efficiencies under 1.0Qd and 1.4Qd is proposed. Three parameters, namely, the bla...In order to widen the high-efficiency operating range of a low-specific-speed centrifugal pump, an optimization process for considering efficiencies under 1.0Qd and 1.4Qd is proposed. Three parameters, namely, the blade outlet width b2, blade outlet angle β2, and blade wrap angle φ, are selected as design variables. Impellers are generated using the optimal Latin hypercube sampling method. The pump efficiencies are calculated using the software CFX 14.5 at two operating points selected as objectives. Surrogate models are also constructed to analyze the relationship between the objectives and the design variables. Finally, the particle swarm optimization algorithm is applied to calculate the surrogate model to determine the best combination of the impeller parameters. The results show that the performance curve predicted by numerical simulation has a good agreement with the experimental results. Compared with the efficiencies of the original impeller, the hydraulic efficiencies of the optimized impeller are increased by 4.18% and 0.62% under 1.0Qd and 1.4Qd, respectively. The comparison of inner flow between the original pump and optimized one illustrates the improvement of performance. The optimization process can provide a useful reference on performance improvement of other pumps, even on reduction of pressure fluctuations.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
Cavitation in pumps must be detected and prevented. The present work is an attempt to use the simultaneous measurements of vibration and sound for variable speed pump to detect cavitation. It is an attempt to declare ...Cavitation in pumps must be detected and prevented. The present work is an attempt to use the simultaneous measurements of vibration and sound for variable speed pump to detect cavitation. It is an attempt to declare the relationship between the vibration and sound for the same discharge of 780 L/h and NPSHA of 0.754 at variable speeds of 1476 rpm, 1644 rpm, 1932 rpm, 2190 rpm, 2466 rpm, and 2682 rpm. Results showed that: the occurrence of cavitation depends on the rotational speed, and the sound signals in both no cavitation and cavitation conditions appear in random manner. While, surveying the vibration and sound spectrums at the second, third, and fourth blade passing frequencies reveals no indications or phenomenon associated with the cavitation at variable speeds. It is recommended to survey the vibration spectra at the rotational and blade passing frequencies simultaneously as a detection unique method of cavitation.展开更多
The stability of the grid is jeopardized with the large percentage of non-dispatchable renewables like wind power and also with increasing solar power. This creates various problems because these forms of energy are v...The stability of the grid is jeopardized with the large percentage of non-dispatchable renewables like wind power and also with increasing solar power. This creates various problems because these forms of energy are very volatile and difficult to predict. In most countries the in-feed of these sources must not be curtailed. In addition most of the renewables do not provide short circuit capacity and inertia in the same way as classical units and so further worsen the stability of the grid. The growing exploitation of wind and solar might be limited due to grid stability problems. In order to compensate those problems a large amount of reserve capacity is needed and therefore new technologies for electricity storage are required. Hydraulic pumped storage—the classical storage technology—has some disadvantages. These plants are in mountain regions often far away from wind farms. The distance to the wind farms mean additional loading for the already stressed grid and additional transmission losses. To compensate the very volatile wind energy, the pump input power should be varied continuously. This is so far only possible with variable speed units. Up to now double-fed asynchronous motor-generators are used which are rather expensive. In order to provide a solution for the described situation, ANDRITZ HYDRO has developed a new innovative concept of decentralized pump storage plants. Small standardized pump turbines are combined with a synchronous motor-generator and a full size converter which allows speed variation in pump and turbine mode over a wide range. These plants can be built locally close to wind farms and other sources to be balanced, allowing the increase of renewable energy without increasing the transmission line capacity. For the future smart grids this will be a key storage technology. This concept is reliable, innovative and more economic than other storage technologies.展开更多
为提高泵前过滤器自清洗性能,解决过滤系统频繁中断问题,该研究将阿基米德螺旋转轮应用于泵前过滤器自清洗过程,通过数值仿真与物理试验,结合相关性分析和线性回归分析,探究叶片螺距、叶片角度、叶片数量对阿基米德螺旋转轮转速的影响...为提高泵前过滤器自清洗性能,解决过滤系统频繁中断问题,该研究将阿基米德螺旋转轮应用于泵前过滤器自清洗过程,通过数值仿真与物理试验,结合相关性分析和线性回归分析,探究叶片螺距、叶片角度、叶片数量对阿基米德螺旋转轮转速的影响规律。结果表明:转轮转速随螺距的增加逐渐下降,且降低幅度逐渐上升,随叶片角度和叶片数量的增加转轮转速的提升较小且提升幅度不断减小,对转轮转速影响程度由大到小为螺距、叶片角度和叶片数量。通过TOPSIS法(technique for order preference by similarity to an ideal solution)综合评价得到最佳结构参数组合为:螺距133 mm,叶片角度90°,叶片数量1。优化后水驱式自清洗泵前过滤器开展自清洗试验,结果显示流量经过最初下降阶段后稳定在294.9~296.6 m^(3)/h区间,流量降幅仅为1.13%~1.70%,利用水力驱动阿基米德螺旋转轮带动自清洗装置的滤网清洗效果良好。研究结果可为水驱式自清洗泵前过滤器的结构设计和优化提供参考。展开更多
基金This project is supported by National Natural Science Foundation of China(No.50275102) National Foundation for Abroad Return People, China (No.2001345).
文摘To control the position of differential cylinder closed loop without usingany throttle elements, a flew idea that two speed variable pumps are used to compensate thenon-symmetric flow of differential cylinder is carried out. According to the leaking property of thesystem, a speed offset principle is also proposed to eliminate the cavitation and tension caused bythe leakage and condensation of oil, which makes the system be in the same state as a valvecontrolled circuit. This principle is explained theoretically and experimentally. Further therelationship that the pressures in cylinder chambers change with load and leakage, and therelationship between biasing speed and pre-load pressures in cylinder chambers are established. Theresearch has proved that the new system has similar technique features as those of controlled withservo valves, but due to the elimination of all the throttle lose the efficiency of system can beimproved greatly.
基金This project is supported by National Natural Science Foundation of China (No.50105018) and Provincial Natural Science Foundation of Zhejiang of China (No.501119).
文摘The experimental study is carried out on high-speed centrifugal pumps withthree different impellers. The experimental results and analysis show that high-speed centrifugalpumps with a closed complex impeller can achieve the highest efficiency and the lowest headcoefficient followed by those with half-open impeller and open-impeller, and can obtain much easilystable head-capacity characrastic curve, while those with a half-open complex impeller can't. Thecharacteristic curve with a open impeller is almost constant horizontal line before droppingsharply. The results also show that the axial clearance between pump casing and impeller caninfluence greatly on the performance of centrifugal pumps.
基金the output of a research project (Title: Application of Doubly Fed Asynchronous machine in Pumped Storage Hydropower Plant in Generate Mode, supported by Islamic Azad University South Tehran Branch)
文摘Variable speed pumped storage machines are used extensively in wind power plant and pumped storage power plant. This paper presents direct torque and flux control(DTFC) of a variable speed pumped storage power plant(VSPSP). By this method both torque and flux have been applied to control the VSPSP. The comparison between VSPSP's control strategies is studied. At the first, a wind turbine with the capacity 2.2 k W and DTFC control strategies simulated then a 250 MW VSPSP is simulated with all of its parts(including electrical, mechanical, hydraulic and its control system) by MATLAB software. In all of simulations, both converters including two-level voltage source converter(2LVSC) and three-level voltage source converter(3LVSC) are applied. The results of applying 2LVSC and 3LVSC are the rapid dynamic responses with better efficiency, reducing the total harmonic distortion(THD) and ripple of rotor torque and flux.
基金The National Natural Science Foundation of China ( No. 50476022 )Ministries and Commissions of Science and Technology of Shanghai Government (No. 03DZ 14014)
文摘Cryogenic ground supporting equipment (CGSE) developed for international cooperation scientific experimental item AMS-02 is the ground supporting and cooling system, which will complete the cooling process of the superconductor of AMS-02 from ambient temperature to 1.8 K. Obtaining 1.8 K He Ⅱ by vacuum-pumping is discussed in detail and compared with the other three schemes. The results show that the scheme of vacuum-pumping not only could meet the requirement of the project much better but also has higher reliability compared with other schemes. To select the vacuum pump, the energy conservation model is presented according to the experimental system of CGSE. Therefore, the pumping speed is also determined.
基金Supported by Jiangsu Provincical Natural Science Foundation of China(Grant No.BK20140554)National Natural Science Foundation of China(Grant No.51409123)+2 种基金China Postdoctoral Science Foundation(Grant No.2015T80507)Innovation Project for Postgraduates of Jiangsu Province,China(Grant No.KYLX15_1066)the Priority Academic Program Development of Jiangsu Higher Education Institutions,China(PAPD)
文摘In order to widen the high-efficiency operating range of a low-specific-speed centrifugal pump, an optimization process for considering efficiencies under 1.0Qd and 1.4Qd is proposed. Three parameters, namely, the blade outlet width b2, blade outlet angle β2, and blade wrap angle φ, are selected as design variables. Impellers are generated using the optimal Latin hypercube sampling method. The pump efficiencies are calculated using the software CFX 14.5 at two operating points selected as objectives. Surrogate models are also constructed to analyze the relationship between the objectives and the design variables. Finally, the particle swarm optimization algorithm is applied to calculate the surrogate model to determine the best combination of the impeller parameters. The results show that the performance curve predicted by numerical simulation has a good agreement with the experimental results. Compared with the efficiencies of the original impeller, the hydraulic efficiencies of the optimized impeller are increased by 4.18% and 0.62% under 1.0Qd and 1.4Qd, respectively. The comparison of inner flow between the original pump and optimized one illustrates the improvement of performance. The optimization process can provide a useful reference on performance improvement of other pumps, even on reduction of pressure fluctuations.
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.
文摘Cavitation in pumps must be detected and prevented. The present work is an attempt to use the simultaneous measurements of vibration and sound for variable speed pump to detect cavitation. It is an attempt to declare the relationship between the vibration and sound for the same discharge of 780 L/h and NPSHA of 0.754 at variable speeds of 1476 rpm, 1644 rpm, 1932 rpm, 2190 rpm, 2466 rpm, and 2682 rpm. Results showed that: the occurrence of cavitation depends on the rotational speed, and the sound signals in both no cavitation and cavitation conditions appear in random manner. While, surveying the vibration and sound spectrums at the second, third, and fourth blade passing frequencies reveals no indications or phenomenon associated with the cavitation at variable speeds. It is recommended to survey the vibration spectra at the rotational and blade passing frequencies simultaneously as a detection unique method of cavitation.
文摘The stability of the grid is jeopardized with the large percentage of non-dispatchable renewables like wind power and also with increasing solar power. This creates various problems because these forms of energy are very volatile and difficult to predict. In most countries the in-feed of these sources must not be curtailed. In addition most of the renewables do not provide short circuit capacity and inertia in the same way as classical units and so further worsen the stability of the grid. The growing exploitation of wind and solar might be limited due to grid stability problems. In order to compensate those problems a large amount of reserve capacity is needed and therefore new technologies for electricity storage are required. Hydraulic pumped storage—the classical storage technology—has some disadvantages. These plants are in mountain regions often far away from wind farms. The distance to the wind farms mean additional loading for the already stressed grid and additional transmission losses. To compensate the very volatile wind energy, the pump input power should be varied continuously. This is so far only possible with variable speed units. Up to now double-fed asynchronous motor-generators are used which are rather expensive. In order to provide a solution for the described situation, ANDRITZ HYDRO has developed a new innovative concept of decentralized pump storage plants. Small standardized pump turbines are combined with a synchronous motor-generator and a full size converter which allows speed variation in pump and turbine mode over a wide range. These plants can be built locally close to wind farms and other sources to be balanced, allowing the increase of renewable energy without increasing the transmission line capacity. For the future smart grids this will be a key storage technology. This concept is reliable, innovative and more economic than other storage technologies.
文摘为提高泵前过滤器自清洗性能,解决过滤系统频繁中断问题,该研究将阿基米德螺旋转轮应用于泵前过滤器自清洗过程,通过数值仿真与物理试验,结合相关性分析和线性回归分析,探究叶片螺距、叶片角度、叶片数量对阿基米德螺旋转轮转速的影响规律。结果表明:转轮转速随螺距的增加逐渐下降,且降低幅度逐渐上升,随叶片角度和叶片数量的增加转轮转速的提升较小且提升幅度不断减小,对转轮转速影响程度由大到小为螺距、叶片角度和叶片数量。通过TOPSIS法(technique for order preference by similarity to an ideal solution)综合评价得到最佳结构参数组合为:螺距133 mm,叶片角度90°,叶片数量1。优化后水驱式自清洗泵前过滤器开展自清洗试验,结果显示流量经过最初下降阶段后稳定在294.9~296.6 m^(3)/h区间,流量降幅仅为1.13%~1.70%,利用水力驱动阿基米德螺旋转轮带动自清洗装置的滤网清洗效果良好。研究结果可为水驱式自清洗泵前过滤器的结构设计和优化提供参考。
