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Journal of Drainage and Irrigation Machinery Engin
 
2015 Vol.33 Issue.1
Published 2015-01-25
article
article
1 State-of-the-art and prospects in study on viscous oil cavitating flows
Li Wenguang,
Viscous oils can degrade the cavitation performance of a centrifugal pump, how to improve the impaired performance is a problem which we must deal with, naturally it is quite necessary to have a full understanding of characteristics of viscous oil cavitating flows. In the paper, outcomes in the study on viscous oil cavitating flows are reviewed briefly; effects of liquid surface tension, viscosity and non-condensable gas(air)content on the characteristics are explained. The cavitation nucleation mechanism, cavitation CFD modeling and cavitation criteria are argued, a few prospects in the study on viscous oil cavitating flows are proposed as well. In conclusion, there are many experiments on viscous oil cavitating flows over a hydrofoil or through a cascade or inside a centrifugal pump that need to be done; updates in the cavitation CFD models are on demand too. Additionally the applicability of the maximum tension cavitation criterion into viscous oil cavitating flows needs to be clarified.
2015 Vol. 33 (1): 1-9 [Abstract] ( 2203 ) [HTML 1KB] [ PDF 1667KB] ( 2651 )
10 Numerical simulation of low specific speed constant-head pump
Wang Yang, Yin Gang, Wang Weijun, Li Guidong, Cui Yurui
The steady flow in a low specific speed constant-head pump is simulated numerically by using ANSYS CFX software with the RNG k-ε turbulence model at five flow rates:0.6Qd, 0.8Qd, 1.0Qd, 1.2Qd and 1.4Qd. The static pressure and velocity fields on the mid-span surface of the impeller at flow rates:0.6Qd, 1.0Qd and 1.4Qd are investigated and the blade loading on the mid-span surface are analyzed as well. The normalized helicity Hn is used to analyze the flow conditions on the mid-span surface of the impeller and in the eight sections of the volute. The results show that an obvious backflow can be seen at the impeller outlet, and the angle of backflow tends to get small with the increasing flow rate. The blade shape has a certain influence on the blade loading distribution. The forward direction vortexes exist in the impeller passages, while a pair of symmetrical vortexes always occurs in the volute sections. This pair of vortexes experiences a stable, unstable and stable again development process when the fluid particles flow to the eighth section from the cut-water of the volute.
2015 Vol. 33 (1): 10-15 [Abstract] ( 2303 ) [HTML 1KB] [ PDF 2925KB] ( 2505 )
16 Inlet design and it′s influence on vibration and noise centrifugal pump
Zhou Pan, Zhang Quan, Shuai Zhijun, Li Wanyou
In order to research influence of inlet shape on centrifugal pump vibration and noise, ensuring the pump and impeller′s other geometric parameters constant, only changing the form of the centrifugal pump inlet, the vibration induced by inlet was studied from two aspects, test and numerical simulatione velocity and the unsteady state pressure characteristics of the two forms of centrifugal pump before and after improvement were obtained, analyzed comparatively and verified experimentally, measuring the vibration signals of model pump feet under different forms of inlet, and processing the vibration signal data to verify the simulation conclusion and the vibration generated by modifying centrifugal pump inlet. The results showed that: the changed centrifugal pump inlet has a certain improvement effect on pressure and velocity distribution within the inlet and impeller, straight centrifugal pump had smaller influence than the pre-impact spin one on flow field, all the observation points′ pressure fluctuations of impeller and volute were reduced and the seat vibration response was reduced by 5 dB under experimental verification.
2015 Vol. 33 (1): 16-19 [Abstract] ( 1742 ) [HTML 1KB] [ PDF 2088KB] ( 3893 )
20 Effects of impeller outlet width on pressure pulsation in two side chambers of centrifugal pump
Dai Hanwei, Liu Houlin, Ding Jian, Tan Minggao, Wang Yong
The effects of impeller outlet width on pressure pulsation in two side chambers of a centrifugal pump are studied based on the mutual authentication between experiment and numerical simulation. The pump performance curves are measured and predicted with CFD simulation at different impeller outlet widths, the fluid static pressure and pressure pulsation as well as pulsation amplitude distributions in both side chambers are obtained and analyzed comparatively across the different width cases. The predicted performance curves are in good agreement with the experimental data. It is turned out that the static pressure and pressure pulsation in the front side chamber ascend with the enlarging outlet width and reducing radius. However, there is no significant change in them with variable outlet width and radius in the rear side chamber. Based on a compromise between pump performance and pressure pulsation in the chambers and volute, the ratio of the impeller outlet width to the impeller diameter should be less than 0.06 at the specific speed ns=97. In order to make the pressure pulsations effectively decayed in the side chambers, the best ratio of the impeller outlet width to the gap of the front side chamber should be in the vicinity of 1.81. The results can be used to guide the optimal design of the impeller of centrifugal pumps. 
2015 Vol. 33 (1): 20-25 [Abstract] ( 1925 ) [HTML 1KB] [ PDF 10958KB] ( 2025 )
26 Structure optimization and flow numerical simulation in rotor cavity of roto-jet pump
Liu Yi, Chen Wenpeng, Liang Rundong, Han Zhengjie
The flows in different structures of the rotor cavity in XP300-3 roto-jet pump are simulated by using the CFD software Fluent. The Reynolds-averaged Navier-Stokes equations, the standard k-ε turbulence model and SIMPLE algorithm are adopted in the simulations. According to the existing studies on rotor cavity structures, the cavity structure is optimized by using three configurations, namely adding a rib on the cavity outer surface, reducing the cavity axial width, integrating them together. The flows in the rotor-jet pumps with these configurations are simulated and their performances are extracted and compared with that for the original cavity structure. It is turned out that under the same working condition both added rib and reduced axial width are helpful to effectively reduce the residence time of fluid in the cavity and to shrink the cavity cross-section area as well as to relieve wear of pump casing. The configuration either with the rib or reduced width can improve pump head and efficiency significantly, especially for the head. For the configuration with both rib and reduced width, the pump is subject to remarked improvement in head and efficiency at the same operational condition. These results show that the rotor cavity structure can be optimized with a superposition approach.
2015 Vol. 33 (1): 26-30 [Abstract] ( 2142 ) [HTML 1KB] [ PDF 1757KB] ( 2638 )
31 Comparison of influence factors on natural frequency of rotor in multistage centrifugal pump
Wang Qilei
In order to improve the critical speed of multistage centrifugal pump rotor system effectively, the effects of several impact factors on the speed or natural frequency of the rotor are analyzed and compared by means of rotor dynamics and finite element method. Additionally, the vibration modal analysis is conducted based on a whole rotor system, and the corresponding bending and torsional vibration modal shapes are provided as well. A quantitative comparison of the fluid-structure interaction and spin softening effect on natural frequency or critical speed is made, the factors affecting the critical speed of rotor and the optimization methods for the speed are given, and the numerical analysis and experimental results are compared. It is shown that accurately simplifying support, reasonably determining support stiffness and damping matrix are necessary prerequisites for precise predictions of critical speed. The fluid-structure coupling effect is equivalent to add a virtual mass on the rotor. The spin softening effect works by the Coriolis effect. The "dry" and "wet" critical speeds of multistage centrifugal pump rotor are quite different. The calculated and measured critical speeds are in good agreement. The numerical simulation of ANSYS is in a good accuracy and can provide a certain reference for the rotor design of multistage centrifugal pump.
2015 Vol. 33 (1): 31-36 [Abstract] ( 2117 ) [HTML 1KB] [ PDF 1876KB] ( 3350 )
37 Pressure fluctuation features of sand particle-laden water flow in volute of double-suction centrifugal pump
Cheng Xiaorui,, Zhang Nan,, Zhao Weiguo,
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 remarked 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 Vol. 33 (1): 37-42 [Abstract] ( 2010 ) [HTML 1KB] [ PDF 2157KB] ( 2374 )
43 Masonry structure reforming and strengthening by means of frame structure with double-beam wide column
Jiao Jianhua, Cao Dafu, Qin Xiaochuan, Ge Wenjie
Under the condition that a facade remains unchanged, more inner space can be got by removing its internal walls. In doing so, an underpinning framework is constructed firstly and then the bearing wallboards are demolished once the framework can bear a load; finally the masonry structure is strengthened and reformed by using a frame structure with double beam wide column. In this method, the force transmission system, the change in load applied to foundation, and the connection between external wall and internal frame as well as the building functional requirements are considered. By using this method, a hotel building has been reformed into a supermarket with large space and many business offices. In this reformation project, the existing problems are pointed out, a design process is proposed, and the internal forces in the building are calculated by using PKPM software. The internal force envelope diagram is analyzed and summarized, the structures that are subject to the maximum internal force are targeted and strengthened. In addition, a series of means such as setting shear bolts and concreting rebar network laminated layers to make the renovation project safer and more reliable so as to improve the overall building earthquake resistant capacity.
2015 Vol. 33 (1): 43-48 [Abstract] ( 2037 ) [HTML 1KB] [ PDF 1964KB] ( 2951 )
49 Analysis of flow field in draft tube of pump-turbine during load increasing period
Li Rennian, Jiang Lei, Li Qifei, Han Wei, Liu Baofu
To study the internal transient flow characteristics of the draft tube in a pump-turbine during its load increasing period, the unsteady fluid flow in the pump-turbine is simulated based on the dynamic mesh method in Fluent. According to the simulated results, the transient evolution of flow structure in the draft tube is analyzed extensively. The results show that the relationships of pressure with time are basically similar in the cone and elbow during the period. A sudden increase and remarked fluctuation in static pressure just occurs at the first period of time(0-0.9 s)during the wicket gate opening starting to change. After 0.9 s, the averaged fluctuation in the static pressure is not beyond 9.76 kPa, showing the static pressure remains constant roughly. Besides, a notable vortex rope and a reverse flow structure exist in the draft tube in smaller wicket gate openings, which can easily lead to the instability in operation of the pump-turbine. With the increasing wicket gate opening, the flow in the draft tube becomes steady gradually, suggesting the increase of flow rate can make the flow in the draft tube smoother.
2015 Vol. 33 (1): 49-54 [Abstract] ( 2069 ) [HTML 1KB] [ PDF 1876KB] ( 2579 )
55 Effects of boundary slip on performance of upstream pumping mechanical seal
Chen Huilong, Xu Cheng, Hu Ji, Liu Zhibin , Zhao Binjuan, Li Shulin
To study effects of boundary slip on performance of upstream pumping mechanical seal, the geometric and computational models of fluid film are built. The Navier-Stokes equations of the fluid film flow are solved in Fluent by employing SIMPLEC algorithm and finite volume method. The boun-dary conditions are modified with the Navier linear slip model and the effects of boundary slip on the film pressure distribution, opening force, friction torque and fluid leakage are analyzed. The results show that the slip velocity has a greater influence than the location of slip occurrence. When the slip velocity is tinier, the results of simulation are almost the same as the data without slip, indicating the non-slip assumption for macro flow of a fluid is reasonable. However, when the slip is larger, the dynamic effect of fluid film is weakened and the opening force, friction torque and fluid leakage are decreased with the increasing slip velocity. Additionally, the reduction in both friction torque and leakage is more significant than that in opening force. If the opening force is smaller, the boundary slip should be avoided. If the opening force is large enough, the boundaries should be made super hydrophobic to introduce boundary slip effect so as to reduce the friction torque, eventually to save energy consumption. The results are useful to the design of an upstream pumping mechanical seal.
2015 Vol. 33 (1): 55-60 [Abstract] ( 1844 ) [HTML 1KB] [ PDF 1790KB] ( 2629 )
61 Study on throttle performance of throttling orifice based on entropy analysis
Yuan Shihao, Lou Panlong, Lü Jianhao
The structural characteristics of a V-shaped throttling orifice are analyzed to evaluate its throttle performance. In doing so, four performance indices are proposed, namely the slope of equivalent hydraulic diameter, dV2, ratio of equivalent throttling section areas, k, cavitation numbers, σ2A1in and σ2A1out at the smallest throttling section A2. Homogeneous design is introduced into the structural design of V-shaped throttling orifice, and then the values of four evaluation indices of 16 design cases are calculated. Entropy analysis is applied into the study on throttle performance of these orifices, and then the orifice structure is optimized to achieve the best throttle performance. Compared with the initial structure of the orifice, the optimized one has an improved throttle performance.
2015 Vol. 33 (1): 61-66 [Abstract] ( 2644 ) [HTML 1KB] [ PDF 1437KB] ( 2696 )
67 Quality evaluation of soil in land along Bohai Sea Coast by principal component analysis and GIS
Liu guangming, Lü Zhenzhen, Yang Jingsong, Li Keye, Yu Shipeng
Considering the land along Bohai Sea Coast as the study field, based on a detailed survey on the field, soil samples are collected at representative points across 0-30 cm depth layer, then the physical and chemical properties, such as soil nutrient, salt and texture and so on are measured. The evaluation indexes include soil salt content, pH, nitrogen, phosphorus, potassium, organic matter, total nitrogen, sand content, clay content. Finally, principal component analysis and GIS technique are used to evaluate soil quality comprehensively. The results show that the soil organic matter, total nitrogen and clay content have a positive effect on soil quality, but the soil salt content, pH, and soil sand content have a negative impact. The composite score of soil quality is obtained and a soil quality grade is established. The study field can be divided into six fertility levels according to soil quality composite scores. It is turned out the soil quality in the study field is so poor that its more than 50% areas belong to the 5th and 6th grades. The results of the study can provide an important reference for comprehensive improvement in soil quality in the land along Bohai Sea Coast.
2015 Vol. 33 (1): 67-72 [Abstract] ( 1942 ) [HTML 1KB] [ PDF 2000KB] ( 2855 )
73 Impacts of irrigation water amount on flue-cured tobacco yield and water use efficiency
Hu Xiujun, Ji Xuhui
Improper irrigation period or excessive irrigation can reduce tobacco yield and cause water waste, so it is very important to explore a suitable irrigation water amount for flue-cured tobacco. In this paper, a series of experiment are carried out in a field by means of Lysimeter to study the effects of irrigation water amount on yield and water use efficiency of flue-cured tobacco. The experimental results show that the soil moisture is more greatly influenced by climatic factors, such as temperature, sunshine and so on. The soil moisture changes dramatically in(10, 20］ cm thick soil layer, while in(20, 60］ cm thick soil layer, it keeps a little variation during the whole growth period. Note that in the late maturity period the soil moisture is slightly increased in(20, 60］ cm layer because of reduced water demand by the weakened physiological activity of tobacco plants, suggesting a less irrigation water should be applied in that period. Dry mass yield of tobacco rises with increasing irrigation water amount in a certain range at the maturity stage. However, if the irrigation water amount is beyond a certain high level, the yield can be lowed, i.e. the 'diminishing returns' phenomenon occurs. Considering dry leaf yield, plant growing, water consumption and water use efficiency as a whole, the suitable irrigation water amount for flue-cured tobacco K326 should be 2 700-3 000 m3/hm2. The relationships among yield, water consumption and water use efficiency should be well balanced and coordinated in flue-cured tobacco cultivation. Under the premise of high yield, irrigation water amount should be reduced properly to achieve a compromise between high yield and water saving. 
2015 Vol. 33 (1): 73-77 [Abstract] ( 1665 ) [HTML 1KB] [ PDF 1479KB] ( 2372 )
78 Status, problems, trends and suggestions for water-saving irrigation equipment in China
Yuan Souqi, Li Hong, Wang Xinkun
Water-saving irrigation equipment plays an important role in improving agricultural water use efficiency, increase farmer income and construction of ecological environment, also it has an important strategic position to ease the shortage in water resources, ensure the national food security, and promote the sustainable development of rural economy. The development of water-saving irrigation equipment has taken nearly for 60 years, a considerable progress has been made in its theoretical study and technical level and so on; further the scale of production can basically meet the development of water-saving irrigation in China, but the ability in technological innovation, research and development is weaker, the improvements in product quality, technical performance and reliability are on demand. The developing trends in water-saving irrigation equipment should include strengthening basic theoretical study, enhancing the capability of independent innovation, designing and manufacturing intelligent, precise, cheap and green water-saving irrigation equipment with multi-function, low energy consumption and cost. It is suggested that the comprehensive technology and equipment for water-saving irrigation in hilly land should be investigated. The multi-function, intelligent and precise sprinkler irrigation systems should be developed. Also, the irrigation technology and equipment with low cost, high efficiency and collaborative precision in water and pesticide spraying as well as fertilizing should be innovated. The water-saving irrigation technology and equipment by using clean energy should be exploited. These suggestions may promote the water-saving irrigation equipment industry to develop in a comprehensive and healthy manner in China.
2015 Vol. 33 (1): 78-92 [Abstract] ( 2863 ) [HTML 1KB] [ PDF 1511KB] ( 4512 )
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