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Journal of Drainage and Irrigation Machinery Engin
 
2018 Vol.36 Issue.12
Published 2018-12-25
article
article
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2018 Vol. 36 (12): 1- [Abstract] ( 178 ) [HTML 1KB] [ PDF 20887KB] ( 500 )
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2018 Vol. 36 (12): 2- [Abstract] ( 195 ) [HTML 1KB] [ PDF 1291KB] ( 447 )
1205 Speed-throttling combined optimization for high reliability in parallel centrifugal pump system
LAI Zhounian, YANG Shuai, WU Peng, WU Dazhuan,*
Centrifugal pumps are widely used in industries. Although many pumps are well designed with high efficiency, a large percent of them are operating in off-design points as a result of inapprop-riate pump selection and inefficient operations. Off-design operation makes the operation point of a pump deviate from the high efficiency zone around the design point and wastes a large amount of energy. Moreover, it decreases the pump reliability, makes the pump vulnerable to failures and may cause economic losses and accidents. To solve the pump off-design problems, a method was proposed to improve the reliability of pumps in a parallel pump system. The method introduced a pump number optimization scheme and a control valve to solve the off-design problems of centrifugal pumps based on the conventional PID speed regulation method. A three-pump water supply system was built to verify the proposed method. The results show that the proposed method improves the off-design point of centrifugal pumps. However, when the off-design deviation is too large, the proposed method will greatly increase the pipeline resistance and waste a huge amount of energy, which makes it uneconomic. If the control valve regulation is abandoned and only the pump number optimization scheme is kept, the proposed method can reduce energy consumption and partly solve the off-design problem, but the overall off-design problem remains serious.
2018 Vol. 36 (12): 1205-1210 [Abstract] ( 318 ) [HTML 1KB] [ PDF 3896KB] ( 494 )
1211 Unsteady flow simulation and performance prediction of a metal single screw pump based on CFD
HUANG Si, KANG Wenming, QIU Guangqi, WANG Xueqian
A metal screw pump is a kind of machines by clearance fitting of stator and rotor, with many advantages such as the resistance against wear, high temperature and corrosion. Flow domain inside a screw pump is a complex three-dimensional space varying with time, thus the dynamic mesh technique in CFD was performed in this study to numerically simulate 3D transient flow field of a metal single screw pump used in oil-fields. The unsteady flow characteristics of the pump and leakage data through the gap of the screw pump were acquired accordingly. Furthermore, the flow rate, power and global efficiency of the pump were predicted based on the CFD results under the conditions of different rotational speed, pump head and fluid viscosity. The results show that the screw pump has significant unsteady characteristics during operation. In one rotation period, flow pulsation frequency is consistent with the lead ratio of stator and rotor of the screw pump. Leakage and the pulse amplitude of flow value in higher pressure condition are considerably greater than those in lower head condition. For the calculation of screw pump input power in high pressure head, mechanical and the volumetric loss can not be ignored. The trend of the performance prediction based on CFD in this study is consistent with that of the measured data from the literature, and the error is within the allowable range for engineering, indicating that the proposed simulation method is feasible.
2018 Vol. 36 (12): 1211-1215 [Abstract] ( 355 ) [HTML 1KB] [ PDF 4115KB] ( 626 )
1216 Checking method on 1000 MW RCP impeller profile
JIA Yun,,*, LIU Xiangsong,, GAO Yushuang,
To check the deviation of profiles of the blade profiles after the numerical processing of parts of RCP hydraulic parts is finished, one set of checking and evaluation methods was proposed. Through adopting a reversal engineering analysis software PolyWorks, together with a three-dimensianal measu-ring machine, three coordinates for pressure and suction at the ingress and egress side of impeller model blades and product blades were measured. At the same time, the root mean square of the deviation of profiles of the blade profiles was calculated. Through statistic and theoretical analysis on the measured data of profiles at the ingress side and egress side of blades, a calculation formula for deviating angle Δβ of profiles at the ingress and egress side of blades, the deviation formula for the angle between blades Δφ, and the modifier formula K for the part of deviation of profiles of blade profiles were proposed. This method can accurately and effectively check the scattering of profiles of hydraulic blade profiles and ensure the same wrap angle for each profile. Based on the checking and evaluation on the airfoil profiles of the impeller of the RCP impeller for Tianwan 5,6 and Fangjiashan Nuclear Plant, full load test has shown that compared with the result of numerical analysis, RCP flow meets the design deviation flow ±2.5% and pump lift deviation±1.5% required by the specification.
2018 Vol. 36 (12): 1216-1221 [Abstract] ( 512 ) [HTML 1KB] [ PDF 4807KB] ( 522 )
1222 Optimization of the liquid-ring pump case based on DFFD method
ZHANG Renhui,*, LIANG Meng, YANG Junhu,, LI Rennian,, MEGN Fanrui
To optimize the liquid-ring pump case, the response surface method based on the direct free-form deformation(DFFD)was proposed. The case profile of liquid-ring pump was parameterized precisely using the direct free-form deformation method. The design of experiment was carried out in the control variables space. The gas-liquid flow in the liquid-ring pump was simulated by using VOF multiphase model. The optimization analysis of the pump case profile was based on the response surface method, and the response relationship between the case profile of liquid-ring pump and the corresponding inlet vacuum pressure and efficiency was established. The inlet vacuum pressure and the pump efficiency of the liquid-ring pump were optimized respectively. The calculation case shows that the pump case profile has a great effect on the hydraulic performance of the liquid-ring pump. The pump efficiency and inlet vacuum pressure can be improved within a certain range. The pump case profile with a higher area expansion ratio for the suction zone would result in the higher inlet vacuum pressure, and the pump efficiency is on the contrary. With the increase of pump inlet vacuum, the pump efficiency shows an approximately linear decreasing in the design variable space.
2018 Vol. 36 (12): 1222-1226 [Abstract] ( 318 ) [HTML 1KB] [ PDF 3239KB] ( 509 )
1227 Influence of oblique trimmed impeller on recirculation at impeller outlet and stability of performance curves
CAO Rui, YUAN Shouqi*, SI Qiaorui, CUI Qianglei, SHENG Guochen
In order to study the influence of the oblique trimmed impeller on the stability of the performance curves of pumps, the centrifugal pump(IS 65-50-174)was chosen as the research object. The performance curves of the pump with original impeller and the oblique trimmed impeller were obtained by the experiment, while the corresponding internal flow field and the pressure fluctuations were acquired from the unsteady numerical simulation with SST turbulence model. The experimental results show that the centrifugal pump with the oblique trimmed impeller could eliminate the instability of the performance curve and consume more shaft power at the reduced flow rate. By analyzing the internal flow field at 0.2, 0.3 and 0.4 times of the designed flow rate, some conclusions could be got: With the decrease of the flow rate, the low energy zone in the original impeller transferred from the front shroud to the rear shroud.While the recirculation zone of the oblique trimmed impeller occurs near the rear shroud and its intensity of the recirculation increases with the decrease of the flow rate. The analysis of the pressure pulsation at the impeller outlet showed that the pulsation at the low frequency became lower in the oblique trimmed impeller compared with the original impeller, which indicates that the instability of the flow at the impeller outlet becomes lower.
2018 Vol. 36 (12): 1227-1232 [Abstract] ( 426 ) [HTML 1KB] [ PDF 3468KB] ( 489 )
1233 Hydraulic performance of guide vane mixed-flow pump based on loading distribution
SU Shaohua,, LIU Zhuqing,*
Based on the three dimensional inverse design method, a new option to achieve a higher hydraulic efficiency was made by optimizing the blade loading and the guide vane loading combined with the CFD method. In the traditional design method, only after the completion of a design can we get the blade surface pressure distribution, post-processing to get through the CFD method, while the pressure distribution has a very important effect on the efficiency. However, through the control of blade loading distribution with the inverse design method, we can achieve the goal of controlling blade shape directly.The CFD results showed that the hydraulic efficiency was higher when the top loading was in the middle and a bit closer to the inlet of the impeller.By comparing the optimized model with the conventional model, the hydraulic efficiency was increased by 3.56%,which improved the flow uniformity and the jet-wake phenomenon at the same time. Unsteady calculation results showed that the pressure fluctuation had a high value at the inlet of the impeller of both the conventional model and the optimize model,which had a great influence on the steady of the stability of operation. However, the pressure pulsation amplitude at the impeller inlet and the outlet of the guide vane get better by the 3-D inverse design method for reasons of better blade loading distribution. The vortex in the aft part of the guide vane disappears in the inverse-method design model because of the improvement of the jet-wake in the impeller, which leads to a better flow character in the guide vane flow zon, thus helping to get good hydraulic efficiency.
2018 Vol. 36 (12): 1233-1239 [Abstract] ( 368 ) [HTML 1KB] [ PDF 5231KB] ( 507 )
1240 Blade number match of impeller and guide vane of submersible centrifugal pump
GE Mingya*, CUI Baoling, FANG Chen
To investigate the influence of blade number match of impeller and guide vane on the performance of submersible pump, 9 submersible pump models with different blades were designed based on the prototype pump(the numbers of impeller blade and guide vane are 7 and 8). And the flow field in the first two levels of submersible pump was numerically calculated based on time-ave-raged N-S equation and the Spalart-Allmaras turbulence model. The numerical curves of head and efficiency with capacity were obtained. It is found that when the numbers of impeller blades are 6 and the guide vanes are 8, the submersible pump can get the best overall performance. The performance of the optimal submersible pump increases by 2.61%. The centrifugal pump head improves 0.574 m. Compared with prototype, the high-pressure area in the optimal model is larger. And it has little influence on the distribution of velocity when changing the blade number. The characteristic curves of prototype achieved by numerical simulation basically agree with those by the experiment.
2018 Vol. 36 (12): 1240-1245 [Abstract] ( 463 ) [HTML 1KB] [ PDF 3913KB] ( 497 )
1246 Internal flow characteristic analysis on outlet conduit based on whole flow field
ZHANG Fan, ZHANG Jinfeng*, ZHANG Xia, YUAN Shouqi, LI Yalin, XIE Liheng
In order to investigate the flow characteristics of the outlet conduit flow characteristics of the vertical axial-flow pump device, a certain pumping station was taken as the research object, and the numerical simulation was conducted on the model pump device based on the whole flow field. Combining with the turbulent kinetic energy, streamline distribution and pressure distribution, the dynamic characteristics of unsteady flow inside the outlet conduit was researched. Then, the Q criterion was used to analyze the vortex structure in the outlet conduit. Based on the eigenvalue method and the vorticity method, the vortex core was extracted from the outlet conduit under different working conditions in an unsteady rotation cycle. The results show that under part-load conditions, more vortex structure and vortex core could be captured at the inlet of outlet conduit, and these vortex gradually disappear along the exit direction. Besides, the strength of vortex core reduces gradually as the fluid flows from the entrance of the outlet conduit; the number of vortex under the designed condition is the least for the two methods; under the designed condition, there is no vortex core at the middle part.
2018 Vol. 36 (12): 1246-1251 [Abstract] ( 327 ) [HTML 1KB] [ PDF 5382KB] ( 574 )
1252 Effects of axial gap of impeller side cavity on pressure and leakage in balance chamber in centrifugal pump
LIU Zailun,, ZHOU Jinxin*, CHEN Xiaochang
In order to study influences of axial gap of impeller side cavity on pressure and leakage in the balance chamber of a centrifugal pump, the turbulent flows in the IS80-50-315 centrifugal pump were numerically simulated by using the RNG k-ε turbulence model when the axial gaps of impeller side cavity in the pump were 1, 4, 8, 12, 16 and 20 mm, respectively. The pressure distribution rules and variations of leakage with the gap size in the balance chamber were analyzed. An empirical formula of leakage was established based on the discharge coefficient, which was related to the dimensionless axial gap and the flow resistance coefficients across the side cavity, wear-ring gap and balance holes, respectively. The empirical relationship was applicable for the leakage prediction when the dimensionless axial gap was in a range of 0.006-0.127. It was found that the pressure in the balance chamber increased with increasing axial gap, especially for the gap in the range of 4 -16 mm. A little variation in the pressure was shown at the inlet of balance holes. The pressure on the wall of lid decreased with increasing cavity gap, but this phenomenon was not more obvious when the axial gap was 1 mm and 12 mm. Under the same working condition, the leakage increased with increasing axial gap. At a fixed axial gap, however, the leakage decreased with increasing pump flow rate.
2018 Vol. 36 (12): 1252-1257 [Abstract] ( 322 ) [HTML 1KB] [ PDF 4011KB] ( 443 )
1258 Effect of jet centrifugal pump with different throat length on the performance of self-priming
WU Wen, WANG Yang, HAN Yawen
In order to study effect of jet centrifugal pump with different throat length on the perfor-mance of self-priming, the steady numerical simulation of gas-liquid two-phase flow in a jet centrifugal pump with different throat length was carried out with the Eulerian-Eulerian multiphase flow model of the CFX software. The internal pressure, gas velocity and gas phase volume fraction of the jet centrifugal pump were obtained by numerical simulation and the self-priming performance of the jet centrifugal pump was analyzed and verified by experiments. The results of simulation show that when throat length is 10 mm, the static pressure in throat cylinde decrease, the entrainment action is strengthened, and the gas phase velocity on the axis increases,the gas phase separation capacity will be enhanced, and the self-priming performance of the pump is improved. When throat length is 15 mm, it has a little effect on the static pressure and gas velocity of the jet centrifugal pump. The hydraulic performance of the pump becomes poor because of the increase of the flow loss. The experiments state that when throat length is 10 mm, self-priming performance has been significantly improved, and met design requirements, with self-priming height increasing from 7.45 m to 9.15 m and self-priming time decreasing from 148.5 s to 90.0 s.
2018 Vol. 36 (12): 1258-1263 [Abstract] ( 388 ) [HTML 1KB] [ PDF 4452KB] ( 521 )
1264 Numerical simulation of internal flow-induced noise in submersible sewage pump based on the direct boundary element method
CAI Xiaotong, SHI Weidong*, ZHANG Desheng, ZHANG Junjie, SHI Lei
In order to reveal the influence of the different turbulence models on the flow characteristics and noise in the submersible sewage pump, a low specific speed pump with ultra-thick blades was adopted as a model. The computational fluid dynamics(CFD)based on the Lighthill equation theory was adopted to calculate the flow field and sound field respectively. The pressure distribution at different flow rates of 0.6QN, 0.8QN, 1.0QN, 1.2QN, 1.4QN was analyzed, and the causes of noise generation and distribution characteristics in the inner and outer fields were discussed. The results show that the performance curve obtained by SST model is the closest to the test results. When the impeller rotaties from moment a to moment d, the high-pressure area near the tongue increases. The pressure fluctuation at tongue is the most dramatic, indicating that the tongue is the main noise source. The noise is lower near the optimal condition and the larger noise deviates from the optimal condition; The maximum noise appears at 30°-75°, the minimum value oppears at 225°-250°.
2018 Vol. 36 (12): 1264-1269 [Abstract] ( 323 ) [HTML 1KB] [ PDF 5003KB] ( 526 )
1270 Pressure fluctuation in vaneless space of pump turbine with Misaligned Guide Vanes
LI Qifei,, ZHANG Zhen*, LI Rennian,, Song Qice, Zhang Jianxun
In order to study the characteristics of pressure fluctuation at low load of pump turbine with the Misaligned Guide Vanes(MGV)in the vaneless space, the model pump turbine of a pumped storage power station served as the research object. Based on the detached eddy simulation method, we studied the flow in the vaneless space and analyed the influence of pre-opened guide vanes on the flow, besides a pump turbine with pre-opened guide vanes with angle 24° and 33° was modeled, and four MGVs were designed, in the hope of finding the most optimal solution to the vibration of the pump turbine at low load through fully three-dimensional numerical simulation of flow. The analysis results of the four pre-opening programs show that a region at the wake of pre-opened guide vanes and close to the pressure side of blade has a larger pressure amplitude. And equally-distributed guide vanes are better than centrally-distributed ones in improving pressure amplitude. It is concluded that the program of 7#,8# and 17#,18# two-pair guide vanes can most effectively mitigate the pump turbine vibration.
2018 Vol. 36 (12): 1270-1275 [Abstract] ( 316 ) [HTML 1KB] [ PDF 5245KB] ( 514 )
1276 Improvement of ultrasonic flowmeter and its application in large Yellow River Irrigated District
SHI Zhongxing, ZHANG Shiwei, ZHANG Yanrui, YU Jinwen
To improve the measurement accuracy of the ultrasonic flowmeter in the application of largediameter, and high sediment concentration irrigated area, based on the principle of ultrasonic flowmeter, the ultrasonic flowmeter is improved by increasing the signal intensity of the sound source, reducing the propagation attenuation loss, and modifying temperature curves. The results show that the sensor with a frequency of 1 MHz has lower sound intensity and receiving quality than those of 05 MHz and 02 MHz, and the signal is severely interrupted; polyether-ether-ketone acoustic material has less acoustic attenuation than polysulfone; the larger the pipe diameter, the greater the sound attenuation, therefore, the largediameter ultrasonic flowmeter can be installed in singlemode mode; temperature and sediment have a certain influence on the measurement accuracy, and the summer detection failure rate is higher than other seasons; the digital signal processing (DSP) can increase the amount of source signal processing, shorten the effective calculation period, and eliminate the loss of scattered sound source caused by the change of sediment content; the modified temperature curve can reduce the effect of the temperature on measurement accuracy. The research results can provide a certain technical support for the accurate measurement of the Yellow River water by the large diameter ultrasonic flowmeter.
2018 Vol. 36 (12): 1276-1281 [Abstract] ( 362 ) [HTML 1KB] [ PDF 4005KB] ( 455 )
1282 Characteristics of micromixer with periodic blocks and baffles
HE Xiuhua, WANG Yan*, GAO Lingfeng
Based on the principle of chaotic convection, a passive micromixer with periodic blocks and baffles was designed to enhance the mixing performance of the micro-electro mechanical system. First of all, the static Taguchi analysis was taken to evaluate the relative effectiveness of the geometrical parameters of microchannel structure; then, compared with the available experiments and numerical simulation results, it was verified that the numerical simulation method used in this article was reliable; finally, the fluid flow and mixing characteristics of the micromixer were studied by using commercial software ANSYS CFX. The analysis results indicate that the arrangement of periodic blocks and baffles makes lateral velocity uy periodically change at the center of the micromixer, which leads to the improvement of chaotic convection. When the Reynolds number is over 20, a series of complex expanded vortexes and separated vortexes are generated in the microchannel of micromixer, which leads to the complete mixing of two different fluids.
2018 Vol. 36 (12): 1282-1287 [Abstract] ( 277 ) [HTML 1KB] [ PDF 3912KB] ( 467 )
1288 Numerical simulation of internal flow field in stirred tank with combined impeller
DONG Min, XIA Chenliang, LI Xiang
In order to solve the problem of extensive application in the mixing field, the position of the double-belt agitator and the hexagonal oblique disc turbo agitator was changed by the computational fluid dynamics(CFD)analysis method. Based on the Navier-Stokes equation and standard k-ε turbulence model, the flow field generated by the internal fluid of the stirred tank is numerically calculated to obtain the flow field data of the stirring blade at the stirring speed of 240 r/min. We analyzed the axial, circumferential, radial velocity vector of the agitator at the specific interface and its integrated velocity contour, and compared the flow field of the position change. The suitable industrial production paddle type for the upper double-helical paddle impeller blades was selected as the best combination of paddles. The combination of these paddles is helpful to improving the mixer in the application and development.
2018 Vol. 36 (12): 1288-1293 [Abstract] ( 311 ) [HTML 1KB] [ PDF 5148KB] ( 378 )
1294 Deterministic method for considering the influence of bottom surface roughness on dry gas seal performance
MAO Wenyuan,, SONG Pengyun,*, DENG Qiangguo, XU Hengjie
In order to study the influence of surface roughness at spiral groove bottom on the perfor-mance of dry gas seal, a groove bottom surface roughness model with a sinusoidal curve along the radial direction of the seal end surface was established, the influence of wavelength λ on the performance of dry gas seal were analyzed within the range of a sampling length Lr, and then the sine wave number n was determined, that is, n is 10 and the wavelength λ is 0.08 μm, the gas pressure distribution of the seal end surface gap was obtained by a approximate analytical method, the effect of surface roughness on the opening force and the leakage at different groove depths and gas film thicknesses were analyzed. As to the operating condition investigated, the results show that with respect to smooth groove bottom, the absolute value of maximum relative error for opening force is 0.12% and that for leakage rate is 0.31% when the groove bottom surface roughness Ra is 0.4 μm; the absolute value of maximum relative error for opening force is 0.50% and that for leakage rate is 1.26% when Ra is 0.8 μm. It indicates that the influence of bottom surface roughness on the sealing performance can be ignored when Ra≤0.8 μm at common operation, whereas the surface roughness Ra of the groove bottom should be less than 0.4 μm when the gas film thickness at non-groove region is smaller than 2 μm.
2018 Vol. 36 (12): 1294-1299 [Abstract] ( 283 ) [HTML 1KB] [ PDF 4042KB] ( 415 )
1300 Performance analysis and test on on-off response of DC hydraulic solenoid valve
DENG Zhihui,, ZHANG Xiliang*
In order to obtain the main factors affecting the on-off response performance of the DC hydraulic solenoid valve and their specific relationship. Taking the K-01-D12 type DC hydraulic solenoid valve as an example, on the basis of analyzing its structure and working principle, the theoretical analysis of its on-off characteristics were carried out. The kinematic model of armature was established from the aspects of electromagnetic force, spring force, friction force, hydraulic oil resistance and so on. Designing the hydraulic solenoid valve performance testing platform with industrial control computer as upper computer and single chip computer as lower computer, and the model was partly verified by experiments. The theoretical analysis and the experimental results show that the on-off response performance of DC hydraulic solenoid valve is closely related to the temperature of hydraulic oil, the stubbornness coefficient of reset spring, etc. The higher the oil temperature, the lower the viscous damping coefficient of hydraulic oil, the faster the on-off response time, however, the excessive temperature can easily lead to the leakage and affect the efficiency. The greater the reset spring stubbornness coefficient, the slower the opening time and the faster the closing time on single cavity operation, but the less effect on the direct switching between the two cavities of solenoid valve.
2018 Vol. 36 (12): 1300-1305 [Abstract] ( 411 ) [HTML 1KB] [ PDF 4063KB] ( 443 )
1306 Evaluating water management plan of winter wheat in waterlogging conditions based on entropy weighted TOPSIS model
MIAO Zimei, LI Jingchun*, CHEN Dong
In order to select the unified water level control scheme based on resources, environments and benefits, different irrigation and drainage schemes were developed to simulate the waterlogging stress of winter wheat at different growth stages. Entropy weight method and TOPSIS model were orga-nically combined, and four indicators were selected from three aspects, of high yield of winter wheat, efficient utilization of water resources, and reduction of non-point source pollution, to build a winter wheat water level management evaluation system. The weight of each index was determined by entropy weight method, and 13 different water level management schemes were calculated by using TOPSIS model. The theoretical fit Si of each treatment was obtained, and the effects of waterlogging stress on the water level management schemes were evaluated. According to the calculation results of the model, winter wheat was most affected by waterlogging at the milk-200 mm(3 d)(5 d-800 mm), resulting in a significant decrease in yield. At the tillering stage of-50 mm(1 d)(5 d-200 mm), the winter wheat yield, water saving and emission reduction can be achieved. The results accord with experimental law and are of certain practical value.
2018 Vol. 36 (12): 1306-1311 [Abstract] ( 378 ) [HTML 1KB] [ PDF 1499KB] ( 488 )
1312 Experimental study on irrigation quota of two crops harvesting feeding sweet sorghum
WANG Zengli, DONG Pingguo, HAN Wanhai
In order to explore the optimal irrigation quota and water-saving effect suitable for feeding sweet sorghum, a field experiments was conducted to study the effect of the irrigation quota(2 400, 3 000, 3 600, 4 200, 4 800 m3/hm2respectively)on growth and biomass of two crops of feeding sweet sorghum. Results showed that the peak of stems diameter and plant height of sweet sorghum appeared respectively at 62th days and 158th d after sowing. Plant height increased with increasing irrigation quota, while stems diameter had a reducing with increasing irrigation quota. Daily growth rate of sweet sorghum appeared at 76th days after sowing was the biggest, which were between 4.00-4.89 cm/d. With different irrigation quota, fresh or dry biomass of sweet sorghum was 63.9-115.5 t/hm2 and 12.7-21.4 t/hm2 respectively, water consumption of that in the whole growth stage was 326.95-504.24 mm, WUE of fresh and dry biomass was 15.53-24.63 kg/m3 and 3.89-4.51 kg/m3 respectively. When irrigation quota was 4 200 m3/hm2, Fresh or dry biomass of two crops of sweet sorghum were all the biggest, and no significant increase was achieved by adding irrigation quota. In conclusion, for water-saving and increasing the biomass, irrigation schedule with irrigation quota of 4 200 m3/hm2(irrigation frequency was 4 times)was thereby recommended as an optimized irrigation to increase the biomass of two crops of feeding sweet sorghum.
2018 Vol. 36 (12): 1312-1316 [Abstract] ( 289 ) [HTML 1KB] [ PDF 3290KB] ( 496 )
1317 Hydraulic performance of subsurface trace tape
YANG Bin, ZHAO Yuefen, CHEN Yanyu, WANG Haitao, MO Yan, WANG Jiandong*
The main objective of this research is to obtain the design parameters and hydraulic perfor-mance of the trace drip tape in the field.The hydraulic performance of the trace drip tape,characterized with the discharge of 900 mL/h, were evaluated by laboratory and field trials. The results revealed that the manufacturing deviation coefficient of the test tape is 0.04, and the relationship between the pressure and the discharge of the trace drip emitter is in accord with the function used for traditional drip emitter.The discharge rate of the trace emitter under the buried condition is more sensitive to the pressure change compared with that under surface free flow condition, and the decrement of discharge is not obvious when the trace drip tape was buried in field, and the average discharge rate of buried trace emitter under nominal working pressure(10 m)is reduced by 3%-8%. In addition, when the flow rate deviation coefficient of drip irrigation system is less than 20%,and combined with research results concerning spatial variability of soil moisture in the field, the limit laying distance of the trace drip tape is about 150 m used for subsurface drip irrigation.
2018 Vol. 36 (12): 1317-1322 [Abstract] ( 323 ) [HTML 1KB] [ PDF 4330KB] ( 487 )
1323 Application of optical modulation and demodulation technology in weed spectral identification
WEI Xinhua, BAO Sheng*, TAO Tao, LI Lin
In order to identify weeds from crops rapidly and nondestructively, a spectral sensor based on spectral analysis technology was developed. In this paper, winter rape in seedling stage was served as study crop, and a prototype experimental system with the spectral sensor was designed according to four characteristic wavelengths(590, 710, 750 and 940 nm), which already had been extracted. On basis of the traditional spectral sensor, the system could eliminate the interference of the environmental stray light in detected results by using optical modulation and demodulation technology. This system included experimental equipment(optical signal modulation equipment and photoelectric signal acquisition equipment)and experimental data processing LabVIEW program. Validation experiments were performed on four different bands using winter rape leaves. When the DC component variation amplitudes, which were caused from the change in the intensity of external environmental stray light, were 10.00%, 6.40%, 1.17%, 1.34%, 22.60%, 38.90%, 56.00% and 59.50%, respectively, the reflectance always was stable. The experimental results show that the system can stably measure the reflectance of measured samples when the ambient light intensity varies either slowly or rapidly. The system confirms that the optical modulation and demodulation technology can effectively improve the signal-to-noise ratio of the measured samples.
2018 Vol. 36 (12): 1323-1329 [Abstract] ( 294 ) [HTML 1KB] [ PDF 5147KB] ( 433 )
1330 Barbed labyrinth channel optimization based on constrained multi-objective particle swarm algorithm
MA Ruijia, WEI Zhengying*, CHEN Xueli, MA Shengli
In order to improve the comprehensive performance of drip irrigation emitter, a barbed labyrinth path was designed according to the boundary layer separation condition, and the channel structure was optimized. The same size channel model was fabricated and the water flow in the model was experimented by Particle Image Velocimetry(PIV)to validate the accuracy of numerical simulation. In view of the hydraulic performance and anti-blockage performance, the three geometrical variables were taken as experimental factors, and the flow rate, flow pattern index and particle-passing rate as performance parameters were examined, then 25 orthogonal experiments were carried out. The influences of these structural variables on the performance parameters were summarized. Three empirical correlations between the structural variables and performance parameters were obtained by regression analysis. The streamline plots were investigated and the effects of vortices in the corners and downstream the barbs on both internal flow field and particle motion were analyzed. In the end, the flow was taken as the constraint condition, and the flow pattern index and particle passing rate, which were with the minimum and maximum polarity respectively, were taken as the objective function. As a result, the labyrinth path was optimized by using constrained particle swarm optimization algorithm under a multi-objective condition. The unique solution of the Pareto solution set was obtained in equal weights, which was subject to 0.483 flow pattern index, 0.955 particle-passing rate and 2.17 L/h flow rate. By using the constrained optimization design method, the optimized channel structure satisfies the flow constraint condition and has the optimal comprehensive performance.
2018 Vol. 36 (12): 1330-1336 [Abstract] ( 370 ) [HTML 1KB] [ PDF 6676KB] ( 498 )
1337 Effects of water-retaining agent dose on soil water and nutrient contents, maize yield and economic benefit under drip irrigation
LI Rong*, XIA Lei, WANG Yanli, WU Pengnian, YU Lin, YE Xubo, QIAN Peng
In the Yellow River pumping irrigation areas in Ningxia, the land in the areas is subject to a severe lack of water, lean soil and low fertility, etc. To solve this problem, water-retaining agents can be applied potentially in the land. In the paper, Wote super absorbent polymers(SAP)was used as the water-retaining agent. A field study was conducted to investigate effects of SAP dose(0, 30, 60, 90, and 120 kg/hm2)applied in maize seedling stage on soil nutrient, water content and maize growth in various growth stages, and to decide the optimum SAP dosage in sandy soil under drip irrigation. The case without SAP was specified to be control group. The results show that the soil water storage capacity in 0-100 cm soil layer is increased with increasing SAP dose in the whole growth period. Particularly, the capacities are considerably increased by 14.0% and 17.1% at 90 kg/hm2 and 120 kg/hm2 doses, respectively, compared with the control group. At 60 kg/hm2 SAP dose, nutrient content in the soil tilth is enriched obviously, suggesting SAP has played a most important role in keeping and supplying fertilizer. Whatever SAP dose is applied can significantly promote maize growth, especially the 90 kg/hm2 dose can improve the growth in the silking period of maize significantly. At 60 kg/hm2 SAP dose, the maize yield, water use efficiency and economic benefit are 41.8%, 22.2% and 33.9% higher than in the control group, indicating this dosage is the best. Thus, properly using SAP can effectively improve soil water moisture and fertilizer conditions, promote the growth, and raise the maize yield and economic benefit. The optimum dosage of SAP is in the range of 60-90 kg/hm2 for the Yellow River pumping irrigation areas in Ningxia and it should be popularized in the future.
2018 Vol. 36 (12): 1337-1344 [Abstract] ( 417 ) [HTML 1KB] [ PDF 5215KB] ( 455 )
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