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Journal of Drainage and Irrigation Machinery Engin
 
2023 Vol.41 Issue.7
Published 2023-07-25
1
2023 Vol. 41 (7): 1- [Abstract] ( 3 ) [HTML 1KB] [ PDF 57526KB] ( 83 )
2
2023 Vol. 41 (7): 2- [Abstract] ( 4 ) [HTML 1KB] [ PDF 874KB] ( 98 )
649 Fault prediction model of centrifugal pump based on external magnetic field
LUO Yin*,CHEN Yinwei,QIN Xuecong,CHEN Yunfei
Aiming at the lack of universality and timeliness of traditional fault malfunction diagnosis method for centrifugal pumps in the complex and changeable engineering environment, a fault malfunction prediction model of centrifugal pumps based on improved KNN algorithm by Mahalanobis distance was proposed. At first, the external magnetic field signals under fault malfunction condition were processed. Accordingly, the corresponding working condition indexes were obtained. Afterwards, the weight analysis was implemented by ReliefF algorithm to extract features, providing a database of malfunction prediction and classification for KNN algorithm. During the process, original Euclidean distance in KNN algorithm was replaced by Mahalanobis distance to eliminate the dimensional influence between feature indexes, so as to improve the accuracy of the prediction results. The key value K of KNN algorithm was sifted by the 10-fold cross validation method. Consequently, the operation result of the prediction model was proved to be the best when the value of K was 120. When the centrifugal pump was running off-design point, the malfunction prediction model established by the improved KNN algorithm could accurately predict the possible failures or faults according to the external magnetic field signals, effectively solving the serious hysteresis of traditional monitoring methods. The model training data contained the external magnetic field signals under various working conditions of 0.2Qd~1.2Qd full flow. The test results show that the malfunction prediction accuracy of the fault prediction model is 0.831 5 at 0.4Qd, 0.799 9 at 0.8Qd, 0.852 7 at 1.0Qd and 0.874 1 at 1.2Qd working condition, respectively, which basically realizes the accurate prediction of centrifugal pump malfunction.
2023 Vol. 41 (7): 649-654 [Abstract] ( 7 ) [HTML 1KB] [ PDF 31613KB] ( 127 )
655 Modification and experimental verification of guide vanes hydraulic model for large vertical axial-flow pumps
CHEN Yueting,TANG Fangping*,ZHANG Xiaowen,WANG Lin,LIU Yuxi,DAI Jian,WANG Hai
In order to improve the matching between the guide vanes and impellers of the axial-flow pumps, a vertical axial-flow pump was taken as the research object. The guide vane of the hydraulic models were modified by an orthogonal experiments. The hydraulic models of axial-flow pumps with different guide blades were compared and optimized by using computational fluid dynamics software(CFD)and model tests. The results show that the maximum error between the numerical calculation results and the model test results is less than 5%. The overall trend of the performance curve is relatively good. The numerical calculation method is reasonable and reliable. Under the design flow condition, the optimized guide vane can reduce the hydraulic loss of the guide vane body and the outlet circulation of the guide vane, and the kinetic energy recovery effect is better. It can effectively reduce the design head and ensure the efficient operation of the pump station with 80.7% efficiency. Different guide vanes have a significant impact on the performance of the vertical axial flow pump device. The optimized guide vanes can change the design flow rate of the device, so that the efficient area of the device is biased towards large flow rate. Simultaneously increase the device head of the pump under small flow conditions and reduce the device head under large flow conditions.
2023 Vol. 41 (7): 655-662 [Abstract] ( 5 ) [HTML 1KB] [ PDF 5534KB] ( 140 )
663 Influence of impeller inlet diameter on multiphase flow performance of sewage pump
ZHANG Yanlu,XU Yunfeng,WANG Zhen,YANG Chen,XU Bin,*
To study the effect of impeller inlet diameter on the multiphase flow performance of sewage pump, three double-blade impellers with different inlet diameters(100, 120, 140 mm)were employed as the research object. The mixture multiphase model, Rayleigh-Plesset cavitation model and Gidaspow drag model were used to conduct steady numerical calculation of solid-liquid-gas three-phase flow in the pump, and the hydraulic characteristics of the sewage pump also be predicted. The research results show that increasing the diameter of the impeller inlet will cause the high-efficiency area of the sewage pump to shift to a small flow rate, but it will help to suppress the degradation of the hydraulic characteristics under the condition of multiphase flow. The efficiency of multiphase flow in the pump with impeller diameter of 100 mm is 10.27% lower than that of single-phase flow, while the efficiency of multiphase flow in the pump with impeller diameter of 120 mm and the pump with impeller diameter of 140 mm are 6.54% and 8.20% lower than that of single-phase flow, respectively. This indicates that increasing the impeller inlet diameter can significantly improve the anti-cavitation characteristics of the pump, and the critical net positive suction head of the sewage pump corresponding to the three impeller diameters are 4.03, 2.06 and 1.95 m, respectively. The flow blockage effect caused by cavitation can be effectively mitigated. Solid particles with high flow velocity are monitored in the pump with an inlet diameter of 100 mm, and the solid phase volume distribution on the impeller surface decreases with the increase of inlet diameter, and the solid phase flow velocity in the pump also decreases. The research shows that appropriately increasing the diameter of the impeller inlet is helpful to improve the multiphase flow performance of the sewage pump.
2023 Vol. 41 (7): 663-669 [Abstract] ( 7 ) [HTML 1KB] [ PDF 15085KB] ( 149 )
670 Influence of pump valve on discharge performance of reciprocating pump
LI Bin*,LI Yi,GAO Yaning
Aiming at the problems of poor discharge performance of reciprocating pump caused by delayed closing lag of the pump valve and the excessive opening resistance of the pump valve, the pump valve of a certain type of reciprocating pump was taken as the research object. The influence of the spring stiffness of the pump valve, the mass of the valve disc and the diameter of the inner hole of the valve seat on the maximum opening residence of the valve, the opening and closing lag angel of the valve, and the discharge flow and pressure of the pump were studied through multi-disciplinary coupling numerical calculation of the mechanical, mechanical and flow field. The accuracy of the numerical calculation method was verified by bench test of reciprocating pump. The research results show that the inner hole diameter of the valve seat has more obvious effects on the maximum opening resis-tance, opening and closing lag angle, the pump discharge flow and discharge pressure are more obvious than the spring stiffness and disc quality. The maximum change value of the opening resistance and opening and closing lag angle caused by the change of valve seat inner hole diameter is 0.684 0 MPa and 28°, respectively. The opening and closing lag angle of valve seat increases with the inner hole diameter of valve seat. The pump discharge flow and discharge pressure decrease with the increase of the inner hole diameter of the valve seat. The maximum change value of the pump discharge flow and discharge pressure caused by the change of the inner hole diameter of the valve seat is 10.558 7 L/min and 0.187 8 MPa, respectively. The research results can provide some reference for optimizing the design of pump valve and improving the discharge performance of reciprocating pump.
2023 Vol. 41 (7): 670-676 [Abstract] ( 5 ) [HTML 1KB] [ PDF 3216KB] ( 117 )
677 Experimental study on mechanical properties of concrete with cold joints
QIN Yuan,LIANG Da*,WANG Yulong,CHAI Junrui,ZHOU Heng
Cold joints in concrete directly affect the overall performance of concrete structures. In this paper, compressive tests and splitting tensile tests were conducted on the concrete with cold joints formed by the cold joints at different ages and the concrete with cold joints formed by the superimposed concrete with different elastic modulus, the variation law of its mechanical properties was studied. The results show that the overall compressive strength of concrete specimens with cold joints and the bonding strength of the cold joints bonding surface are gradually decrease with the growth of age. The strength of new concrete is increased, which can effectively improve the compressive strength of concrete with cold joints. However, the improvement of the bonding surface strength is relatively limited. By calculating the rock brittleness characteristic coefficient, it is found that the strength improvement of new concrete can effectively improve the deformation resistance of old and new concrete. A formula for calculating the strength of cold joint bonding surface is established, which can predict the bonding strength of cold joint bonding surface well. When the age interval is about 7 to 14 day, and when the ratio of elastic modulus of new and old concrete is 1.10, the mechanical properties are better. When the age interval is more than 28 days, the ratio of elastic modulus of new and old concrete should not be more than 1.10.
2023 Vol. 41 (7): 677-681 [Abstract] ( 7 ) [HTML 1KB] [ PDF 1331KB] ( 149 )
682 Analysis of permeability characteristics of biochar amended clay based on nuclear magnetic resonance technique
YANG Haili,LI Mingyu*,NIAN Tengfei
Among the microscopic pore structure testing methods, nuclear magnetic resonance(NMR)testing technology has the advantages of wide testing pore range and fast testing speed. The mercury intrusion test technology can quantitatively study the soil pore distribution and pore size, but the test period is long. Therefore, a method based on mercury intrusion data to calibrate the NMR T2 spectral curve was proposed, and this method was used to quantitatively study the pore structure characteristics of modified clay with different biochar contents and its influence mechanism on permeability characte-ristics. The results show that with the increase of biochar content, the saturated permeability coefficient of the biochar-clay mixture increases gradually. Adding biochar to clay changed the pore structure of the clay. For pure clay, the T2 distribution curve has a unimodal structure. With the increase in biochar content, the T2 distribution curve showed a bimodal structure, the T2 spectrum shifted to the right, and the peak T2 gradually increased. Combined with the proportional relationship between T2 value and pore radius, it can be qualitatively judged that with the increase of biochar content, the most probable pore size of soil samples increases. Through the conversion coefficient C value between mercury intrusion data and NMR T2 spectrum, the most probable pore size corresponding to peak T2 was obtained, and the influence of the change of pore structure characteristics of biochar modified soil on the change of macroscopic permeability coefficient was quantitatively analyzed.
2023 Vol. 41 (7): 682-688 [Abstract] ( 6 ) [HTML 1KB] [ PDF 2419KB] ( 124 )
689 Effect of rotation speed on mode of fan blades and its Weibull fitting
ZHANG Jianping*,LIU Ming,ZHANG Zhiwei,WANG Mingqiang,HAN Yi
To investigate the effect of rotation effect on the mode of wind turbine blades, the finite element model of the blades was established and imported into ANSYS software for calculation. The modes of the blades under static and rotating conditions were obtained, and the relationship between rotational speed and blade modal frequency was obtained by Weibull function fitting. The results show that the vibration mode of stationary blades basically keeps the mixed mode of swing and shimmy or one of the dominant modes with the increase of modal order, while the torsional mode does not appear until the tenth order mode. The vibration mode frequencies and modes of the rotating blade are significantly different from those of the stationary blade. The first and second order vibration modes exhibit the swing vibration in the opposite direction, while the vibration form of the third to tenth order are similar to that of the first to seventh order under the static conditions. The rotating blade have stronger resistance to bending and torsion. With the increase of rotation speed, the blade modal frequencies from the third to the seventh order show a non-linear decreasing trend, while those from the eighth to tenth order present an opposite trend. The Weibull function fitting model can not only describe the variation law of blade modal with rotation speed, but also has high fitting accuracy. The research results provide a theoretical basis and technical guidance for the safe operation and reliability design of wind turbines.
2023 Vol. 41 (7): 689-694 [Abstract] ( 8 ) [HTML 1KB] [ PDF 2703KB] ( 149 )
695
2023 Vol. 41 (7): 695-700 [Abstract] ( 7 ) [HTML 1KB] [ PDF 2826KB] ( 114 )
701 Design of accelerated blade passage centrifugal impeller based on compound line
GAO Zongfei,ZHU Yunming,SHEN Chungen*,LIU Jiang,GUO Erkuo
In order to improve the heating efficiency of integrated ceiling heaters used in bathrooms, a multi blade centrifugal impeller blade structure and its design method were studied using a certain brand of bathroom electric heating equipment as an example under the blowing condition. Using CFX commercial fluid simulation software, and based on the results of CFD simulation, the shortcomings and defects of the original impeller in aerodynamic design are analyzed. Based on the design method of the original impeller blade profile formed by fiting logarithmic spiral lines and small arcs was proposed and designed. and the acceleration of the complex line of wind channel impeller, After comparing and analyzing the aerodynamic performance of the composite profile impeller with the original impeller through 3D printing, it was concluded that the air flow rate at the blower outlet was 216.2 m3/h, which increased by 13.9%, and the airflow speed at the outlet was more uniform and stable. In addition, the noise of the fan has decreased by 2.3 dB, which significantly improving the aerodynamic performance and heating efficiency of the heater. The numerical simulation and experimental study in this paper has theoretical significance and important engineering application value for the performance optimization and noise reduction design of multi-wing centrifugal heaters.
2023 Vol. 41 (7): 701-708 [Abstract] ( 10 ) [HTML 1KB] [ PDF 9609KB] ( 164 )
709 Distribution of water and nitrogen in soil infiltration by fertilizer film hole irrigation under formation of dense soil layer
ZHAO Penghui,FEI Liangjun*,LIU Dayou
To study the distribution characteristics of water and nitrogen in soil infiltrated by fertilizer liquid film hole irrigation under the conditions of dense layer formation on the surface, a two-stage indoor film hole irrigation infiltration test was carried out. In the first stage of the test, when muddy water infiltration formed a dense layer, four fertilizer liquid(calcium ammonium nitrate)mass concentration levels(0, 200, 500, and 800 mg/L)were set up for the second stage infiltration. The cumulative infiltration per unit film hole area, soil moisture content, nitrate nitrogen, ammonium nitrogen mass ratio distribution, and distribution characteristics were studied. Fertilizer solution can promote soil water infiltration. The improved Kostiakov model and the improved Philip model can well represent the relationship between cumulative infiltration per unit film hole area and infiltration time(R2>0.95), and obtain the empirical model of cumulative infiltration per unit film hole area and infiltration time with fertilizer solution concentration parameters. The high water content area volume(θ>25%)of the wetting body increases with the increase of the concentration of the fertilizer solution, and the water content is the highest near the center of the film hole. However, the fertilizer solution has little effect on the water content distribution along the radial direction of the surface soil of the film hole. The higher the concentration of the fertilizer solution, the greater the content of nitrate nitrogen and ammonium nitrogen in the soil-wetting body. The distribution of nitrate nitrogen in the wetting body is similar to the distribution of water content in the wetting body, both of which are relatively higher quality in the upper layer of the soil. The mass ratio of ammonium nitrogen in the wetting body decreases gradually with the increase of infiltration distance.
2023 Vol. 41 (7): 709-715 [Abstract] ( 8 ) [HTML 1KB] [ PDF 1998KB] ( 118 )
716 Comprehensive drought monitoring model based on spatial distance model and its application in Northeast China
ZHAO Yiyuan,JIANG Hailing*,ZHOU Xingyu,LI Yao,CHEN Guangyi
The Comprehensive drought monitoring model was built by combining the factors of precipitation condition index(PCI), modified energy index(MEI)and vegetation condition index(VCI)with spatial distance model(SDM), which was based on comprehensive drought index(CDI). The PCI, MEI and VCI represent atmospheric precipitation deficit, soil moisture surplus and deficiency and vegetation growth, respectively. The applicability of CDI was verified by using grain yield per unit area, crop disaster area and standardized precipitation evapotranspiration index(SPEI). The results illustrated that the CDI can reflect agricultural and meteorological drought information. The absolute value of correlation coefficients between CDI and grain yield per unit area are all exceeding 0.66(P<0.05), and the highest was 0.82(P<0.01). The absolute value of correlation coefficients between CDI and crop disaster area in Heilongjiang, Jilin and Liaoning provinces are 0.75, 0.74 and 0.74, respectively, which passed the signi-ficance test(P<0.05). The correlation coefficients between CDI and SPEI are between -0.80~-0.67(P<0.01). In addition, based on the CDI, the continuous drought events in spring and summer of 2018 in Northeast China are monitored, and the results are consistent with the actual drought situation, which better reflected the temporal and spatial evolution of the drought situation.
2023 Vol. 41 (7): 716-722 [Abstract] ( 11 ) [HTML 1KB] [ PDF 4216KB] ( 156 )
723 Cultivated land quality improvement path based on carbon neutral background
HE Zhenjia,HE Wei,*,LUO Lintao,XU Yan,HOU Xiandong,DU Yichun,ZHANG Jun,REN Huxing
Facing the increasingly complex international environment and the need for the construction and development of ecological civilization, China has promised to achieve carbon neutrality by 2060. Vigorously promoting the improvement of the quality of arable land in medium and low-yield fields and building high-standard farmland are effective ways to increase grain production capacity and achieve agricultural carbon neutrality. The sources of carbon emissions and the potential of emission reduction in the agricultural field are analyzed, and the result and shows that the agricultural system has great potential for carbon sequestration and emission reduction through scientific and reasonable technologies to improve the quality of cultivated land and optimize field management. Combined with the advanced carbon emission reduction measures that adopted internationally, it is proposed that under the background of agricultural carbon neutrality, China needs to focus on ″reducing the difference in crop yield and efficiency to ensure food security″, ″reducing the energy consumption of nitrogen fertilizer production and improving nitrogen fertilizer use efficiency″, ″inhibiting the Methane emissions from paddy fields, promoting low-carbon rice farming technologies″ and ″increasing the return of rotted straw to the field, and optimizing the fertilizer management model″ and other measures to improve the quality of cultivated land. The necessary suggestions for carbon neutrality in China′s future agricultural field, in order to provide necessary reference for accelerating the improvement of cultivated land production capacity and realizing carbon sequestration, is put forwarded.
2023 Vol. 41 (7): 723-730 [Abstract] ( 4 ) [HTML 1KB] [ PDF 1073KB] ( 156 )
731 Preparation of acoustic microspheres by electrostatic breakup and freeze-drying
WANG Xiaoying,PEI Jingxian*,WANG Dongbao,WANG Junfeng
For the preparation of acoustic microspheres by electrostatic breakup combined with freeze-drying technology, a high-speed digital camera technique was used to visualize the slurry breakup process. The image analysis technique was applied to study the influence of different working parameters on the particle size and sphericity of the microspheres. A theoretical model based on a Back Propagation(BP)neural network was established to analyze the importance of each working parameter. The results show that as the voltage increases, the slurry appears in dripping mode, micro-dripping mode, and oscillating micro-dripping mode. In the dripping mode, microspheres of millimeter size are formed; In the micro-dripping and oscillating micro-dripping modes, the microsphere particle size differs from the dripping mode by an order of magnitude, being 1/4-1/3 of the inner diameter of the ca-pillary tube. In the dripping mode, there is little difference in the size of the microspheres when the flow rate is increased, and in the micro-dripping and oscillating micro-dripping modes, the size of the microspheres gradually increases with increasing flow rate. The particle size of the microspheres prepared in each breakup mode has varying degrees of increase as the nozzle diameter increases. Due to evaporation, the particle size of the microspheres is slightly smaller than the droplet diameter, and when low voltages(0 and 2 kV)are applied, the increase in flow rate has an irregular effect on the particle size of the microspheres The receiving distance is the decisive factor affecting the sphericity of the microspheres. Increasing the receiving distance, which leads to a wider distribution of roundness and a decrease in the sphericity of the microspheres. The BP neural network analysis shows that the effect of voltage, nozzle diameter, and flow rate on the particle size of the microspheres accounted for 87%, 10%, and 3% respectively. Voltage is the determining factor for particle size of microspheres.
2023 Vol. 41 (7): 731-739 [Abstract] ( 9 ) [HTML 1KB] [ PDF 5139KB] ( 124 )
740 Microstructure and property of IN718/WCP composite coating fabricated by electromagnetic compound field-assisted laser cladding
SUN Wei,HUO Kun,DAI Fengze*
The IN718/WCP composite coatings were prepared by electromagnetic compound field-assisted laser cladding. The macrostructure, microstructure, microhardness and wear resistance of the coatings were systematically studied. The results show that the electromagnetic compound field creates a downward Ampere force that enhances Marangoni convection in the molten pool. Enhanced Marangoni convection enables uniform distribution of WC particles in the composite coating. However, excessive Marangoni convection can cause WC particles, especially small WC particles, to escape from the molten pool. The combination of 20 mT steady magnetic field and 100 A direct current works well. The WC particles decompose in the molten pool to form submicron eutectic carbides, feathery eutectic carbides and equiaxed eutectic carbides. The degree of decomposition is related to the spatial location of the WC particles and the distance between particles. The higher the spatial position of the particles(relative to the molten pool), the greater the distance between particles and the more severe the decomposition. In addition, the direct current enhanced the nucleation rate of eutectic carbides and the enhanced Marangoni convection interrupted the long columnar eutectic carbides, which together refined the microstructure of the coatings. Under the action of the compound field(20 mT, 100 A), the diffraction intensity of reinforcing phases is the highest, and the microhardness(530 HV0.2)is greater than that of the coating prepared by unassisted laser cladding(400 HV0.2), which alleviates the adhesive wear during the friction and wear tests.
2023 Vol. 41 (7): 740-748 [Abstract] ( 6 ) [HTML 1KB] [ PDF 10141KB] ( 111 )
749 Structure optimization and droplet deposition characteristics of centrifugal atomizing nozzles
GAO Xueqing,WANG Ding,LI Xinde,CHEN Guopeng,JIANG Zhaoliang*
Aiming to address the issue of uneven nebulization and poor targeting of liquid pesticide caused by the mismatch between the aerial spraying equipment and operating parameters of the current plant protection UAV, the droplet deposition characteristics of the turntable centrifugal atomizing nozzle were optimized. The effects of spray flow and rotation speed of the atomizing disc on the diameter, uniformity and coverage of centrifugally atomized droplets were explored by establishing a variable spray platform. The centrifugal atomizing discs with different structures were constructed by 3D printing technology, and the relative influence of diameter, teeth, and cone angle on droplet deposition characteristics was analyzed by orthogonal tests. The analysis of variance results show that under the same flow rate, the rotation speed of the atomizing disc is negatively correlated with the volume median diameter and relative span of the droplet spectrum. Increasing the rotational speed expands the effective spray area. The spray flow is positively correlated with the droplets coverage rate and volume median diameter, but excessive flow will lead to uneven droplet deposition. The influence of the diameter of the square atomizing disc on the droplet size is statistically significant. With the increase of the diameter, the droplet volume diameter gradually decreases. By estimating the mean boundary value, the optimized atomizing disc diameter is 65 cm, the number of teeth is 180, and the cone angle is 30°. Based on the above optimized results, a UAV spraying experiment in a tea garden is carried out to verify the feasibi-lity of the improved nozzle.
2023 Vol. 41 (7): 749-756 [Abstract] ( 10 ) [HTML 1KB] [ PDF 93464KB] ( 136 )
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