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Journal of Drainage and Irrigation Machinery Engin
 
2021 Vol.39 Issue.1
Published 2021-01-25
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2021 Vol. 39 (1): 0- [Abstract] ( 18 ) [HTML 1KB] [ PDF 7958KB] ( 421 )
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2021 Vol. 39 (1): 0- [Abstract] ( 18 ) [HTML 1KB] [ PDF 1238KB] ( 463 )
1 Structural optimization design of impeller vane of shaft seal pump based on CFD
MU Zhenwei,GUI Xinwei*,XIA Qingcheng,ZHANG Zhishan
In order to study the leakage water flow characteristics in the shaft seal of the pump impeller in the Francis turbine, CFD software was used to explore the feasibility of improving hydraulic efficiency and pressure reduction effect in the shaft seal in term of turbine four in the Xinjiang Hongshanzui 1st cascade hydropower station based on different pump impellers.The impeller vane angle and height are varied on the basis of model accuracy,respectively; 22 improved geometric models are numerically si-mulated in total.The results show that the impeller with 45° vane angle and 0.081 5 height ratio can increase the vacuum degree in the shaft seal by 60.9%.The change in vane height is more favorable to the hydraulic efficiency improvement of the impeller than that in vane angle.There is a most unfavorable height ratio for the impeller shroud. In the position determination of the shroud,the most unfavorable height ratio of 0.135 9 must be avoided.Since the study is based on parameterization of model structure, the universality of conclusion is improved in some extent, and a certain theoretical basis is providedfor the shaft seal design and transformation in engineering.

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2021 Vol. 39 (1): 1-7 [Abstract] ( 55 ) [HTML 1KB] [ PDF 2824KB] ( 594 )
8 Review of research in hydrodynamic noise of centrifugal pump
LANG Tao,LIU Yutao,CHEN Keqiang,XU Enxiang,JIN Licheng,JIANG Xiaoping
The research status of hydrodynamic noise of centrifugal pump is introduced from four aspects: component, theoretical analysis, numerical simulation, and experiment.Based on the research work in the world, the current research status of the components and influencing factors of the hydrodynamic noise is summarized in detail in terms of internal sound field and external sound field.The internal sound field can be divided into discrete noise and broadband noise from the spectrum characteristics of the noise. The discrete noise is mainly caused by the dynamic static interference, and the energy is concentrated in the blade passing frequency and its harmonic frequencies.In the research of broadband noise, a lot of work still need to be done.FW-H equation is the basic equation for calculating the hydrodynamic noise of centrifugal pump in the theory of acoustic analogy, which is extensively used. At the same time, the theory of vortex sound also shows a quite good development prospect. At present, the hybrid numerical simulation based on the acoustic analogy method is the mainstream approach for simulating the hydrodynamic noise of centrifugal pump, thus, the application of the acoustic propagation equation method such as the linear Euler method(LEE)is less adopted. Nevertheless, the acoustic propagation equation method will be applied with continuously unfolding study on the high-frequency noise of centrifugal pump in the future.The hydrophone-based dual port model can measure the low-frequency noise of centrifugal pump accurately, but this method requires higher standard testing conditions and is costly. The microphone array method has a better prospect in measuring the high-frequency noise in the internal sound field of centrifugal pump. Finally, the problems to be solved in the future and the topics worthy of being noted are put forward.
2021 Vol. 39 (1): 8-15 [Abstract] ( 29 ) [HTML 1KB] [ PDF 1475KB] ( 837 )
16 Influence of relative position of diffuser leading edge on pressure pulsation in mixed-flow pump
HU Bo,ZHANG Shuangquan*,SUN Zhixiang
A mixed-flow pump is taken as the research object, and the influence of relative position of diffuser leading edge on the hydraulic performance and internal pressure fluctuation of the pump is investigated. Steady and unsteady flow simulations were performed based on ANSYS CFX software using the k-ω turbulence model. When the relative position of diffuser inlet edge is changed, the hydraulic performance of the pump was predicted by using numerical simulation and four cases were selected to analyze the pressure pulsation in the pump. The results show that the hydraulic performance of the pump rises firstly and then decreases with increasing angle α between the impeller trailing edge and the diffuser leading edge. Especially, at α=5°, the hydraulic performance is the optimal. The change of angle α has an influence on the pressure pulsation amplitude inside the pump. The larger the angle α, the smaller the pressure pulsation. The change of the angle α also affects the pressure pulsation amplitude of the main frequency inside the pump. At the impeller inlet and outlet, the larger the angle α, the smaller the amplitude of them in frequency; inside the volute, however, there is not an obvious rule. With the increase of angle α, the pressure pulsation near the volute tongue is less affected by the impeller rotation but more by the tongue. These results can provide a reference for optimal design of the diffuser in a mixed-flow pump.
2021 Vol. 39 (1): 16-22 [Abstract] ( 34 ) [HTML 1KB] [ PDF 3668KB] ( 526 )
23 Pressure fluctuation characteristics of gas-liquid two-phase flow in multiphase pump
SHI Guangtai,LIU Zongku*,LI Helin,YANG Xi,
To perform a thorough investigation into the effect of inlet gas void fraction(IGVF)on the flow structure and pressure fluctuation characteristics in multiphase axial-flow pump, the transient flow field and pressure fluctuation characteristics in a multiphase axial-flow pump were numerically simulated at 5%,10% and 15% IGVFs based on the standard k-ε turbulence model by employing ANSYS CFX. Then, the variation rules of internal flow field structure, frequency domain characteristic, and pressure fluctuation coefficient with IGVFs were analyzed and summarized. The results shown that when the IGVF exceeds a certain extent, the pressure fluctuation was weakened. Meanwhile, the dominant frequency amplitude has a significant effect on the pressure fluctuation. Under the gas-liquid two-phase condition, rotor-stator interaction is still the main cause for pressure fluctuation. Specially, the dominant frequencies of pressure fluctuation in the impeller and diffuser were 11 and 3 times of the impeller rotational frequency, respectively. Further, the maximum amplitude of the dominant frequency and pressure fluctuation coefficient appeared near the rotor-stator interface. The research results can provide some reference for structural optimization, hydraulic design and fatigue analysis of multiphase axial-flow pump.

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2021 Vol. 39 (1): 23-29 [Abstract] ( 40 ) [HTML 1KB] [ PDF 4690KB] ( 889 )
30 Optimization design of hydraulic components of high-pressure pump for ten thousand-ton-scale seawater desalination installations
WANG Yulu,LI Wei,HU Jingning,YE Xiaoyan,GEN Haohan,WANG Xingyuan
In order to design a highpressure pump with a wide range of highefficiency region for ten thousandtonscale seawater desalination installations, an endsuction doughnut multistage structure was adopted,three impellers and three radial diffusers were designed, from them nine design cases were generated for excellent hydraulic model screening. In ANSYS CFX, 9 design cases were numerically simulated, respectively, and the design case with the best hydraulic performance was fabricated and tested.The test results show that the model pump has a wide highefficiency region, and the performance at various operating points meet the design requirements. The errors of head and efficiency between numerical simulation and test are 2.52% and 2.96% at the duty point, and they are all within the allowable range in engineering: Nevertheless, the accuracy of numerical simulation was validated. The matching of the flow field at the impeller outlet and the diffuser inlet was examined.It turned out that with increasing throat area of the diffuser the best efficiency point is shifted towards a high flow rate.The internal flow in the model pump is analyzed, and it is identified that the pump operation is unstable under low flow conditions, and more vortex structures appearin the diffuser, 〖JP2〗resulting in a larger energy loss. As the flow rate gradually is increased, the vortices are reduced and the pump operation tends to be stable, hence the highpressure pump should avoid running at a low flow rate. The results can provide some references for the optimal design of highpressure pump and study of its internal flow.

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2021 Vol. 39 (1): 30-36 [Abstract] ( 34 ) [HTML 1KB] [ PDF 3005KB] ( 471 )
37 Design and numerical simulation of upstream flow channel in gate station based on Star CCM+
XU Jie,SHI Wei,YUAN Shouqi,LI Yanjun,LI Yaling*
In order to study the influence of flow pattern in an upstream flow channel on the operation of gate station, a large gate station was used as the research object, and numerical simulations of flow in the upstream channel of the station were carried out based on Star CCM+ software. It was found that there are many large vortices in the upstream flow channel in pump station operating mode, resulting in a poor uniformity of velocity in the inlet to the pump due to asymmetry of the channel and change in the cross-sectional area. To remove the unfavorable flow patterns in the inlet flow channel, the upstream flow channel was redesigned by altering channel diffusion angle, channel curvature profile, and flow conditioner length. Their effects on the hydraulic performance of channel were analyzed comparatively. The results show that a smaller flow channel diffusion angle in the pump intake can significantly eliminate the vortex in the flow channel. Specially, when the diffusion angle is 10°, the velocity deviation angle is the smallest and the inflow is the most uniform at the pump inlet. A properly extended straight line channel profile can make the streamlines in the flow channel even smooth. A slightly extended flow conditioner length can suppress the dead water vortex area in front of the flow passage, but the flow conditioner can also worsen the pump inlet flow condition and allow the vortex size in the primary flow to be enlarged.
2021 Vol. 39 (1): 37-43 [Abstract] ( 46 ) [HTML 1KB] [ PDF 4703KB] ( 1374 )
44 Study on orthogonal optimization design of hydro-turbine used in hydraulic fume exhausters
CHEN Huilong,XIE Xiaofeng,LIAO Wenyan,GUI Kai,XIE Yuntong,ZHANG Jie,ZHAO Binjuan*
In order to improve efficiency of the hydro-turbine used in hydraulic fume exhausters, numerical simulations of flow in a whole hydro-turbine were carried out, and the simulated results were compared with the experimental data. The orthogonal experiment method was used to optimize the primary geometric parameters of the turbine. By applying L9(33)orthogonal table, three parameters such as nozzle exit area, nozzle diameter and nozzle length were selected to be experimental factors. The orthogonal optimization design was performed in terms of turbine efficiency, and the range analysis method was used to analyze the experimental results. The orthogonal experiments result show that the nozzle length has the most significant effect on the turbine efficiency, followed by the nozzle diameter and the nozzle exit area. The optimized nozzle length is 389.7 mm, the nozzle diameter is 30 mm, and the nozzle exit area is 92.57 mm2. Compared with the reference hydro-turbine before optimization, the nozzle length is reduced by 10% after optimization, the efficiency is increased by 7.67%, the velocity distribution inside the turbine is even more uniform. Consequently, operating cost of the hydraulic fume exhauster will be reduced. The feasibility of orthogonal experiment method in the hydro-turbine optimization is verified.
2021 Vol. 39 (1): 44-49 [Abstract] ( 40 ) [HTML 1KB] [ PDF 2270KB] ( 458 )
50 Moving speed of tandem two-pipe vehicles in pressure pipeline
JIA Xiaomeng,SUN Xihuan*,LI Yongye
In order to improve and develop the hydraulic transportation technology of tube loading pipeline, the influence factors of double vehicle transport velocity of tandem pipeline in pressure pipeline are studied by combining physical model test and theoretical analysis. The results show that: with the increase of Reynolds number, pipe vehicle diameter and vehicle length, the transportation velocity of two-pipe vehicles increases gradually. However, with the increase of the load, the transportation velo-city of two-pipe vehicles will gradually decrease. The results shown that the transportation velocity of two-pipe vehicles is less than that of single pipeline vehicle under different vehicle spacing, and with the increase of vehicle spacing, the transportation velocity of two-pipe vehicle gradually increases and approaches to that of single pipeline vehicle. The standard regression coefficient method in multiple regression analysis was used to analyze the influencing factors. The results showed that the influence of Reynolds number, vehicle diameter, vehicle length, load and distance between two vehicles on the transportation velocity of pipeline vehicles decreased in turn. The research results provide a certain re-ference and basis for optimizing the structure of the pipeline vehicle, increasing the transportation velocity of the two-pipe vehicles, and reducing the transportation energy consumption of pipeline vehicle.
2021 Vol. 39 (1): 50-55 [Abstract] ( 23 ) [HTML 1KB] [ PDF 1835KB] ( 438 )
56 Influence of micro-texture direction of seal lip on sealing performance of oil seal
ZHANG Fuying,YANG Junmei*,SHUI Haoche,DONG Chengcheng,
Based on the pumping mechanism of rotating shaft seals, considering the influence of triangular texture direction on the sealing lip surface, a numerical model of oil seal sealing area was established. The model coupled the energy conservation equation for temperature solution. By solving the numerical equation iteratively, the pump suction rate, oil film thickness, friction torque, lip sealing pressure, lip average temperature and lip opening were obtained when the lip surface triangle texture was rotated in different directions(with the center of gravity of the triangle as the rotation center, and rotated to the right at 0 degree, 45 degree, 90 degree, 135 degree, 180 degree, 225 degree, 270 degree, 315 degree, respectively). The results show that the pump suction rate is the most affected by the direction of triangular texture, and the difference is 0.783 6 mL/h. The variation of other sealing performance parameters is smaller. In surface texture design, the influence of triangular texture direction on pump suction rate should be given priority. Considering all the sealing performance parameters, when the triangle texture direction is 135 degrees, the pump suction rate, friction torque, average lip temperature and maximum lip temperature of the oil seal are all better, the sealing performance is the best among eight groups of oil seals with different texture directions.

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2021 Vol. 39 (1): 56-60 [Abstract] ( 45 ) [HTML 1KB] [ PDF 1758KB] ( 736 )
61 Analysis of horizontal drainage well effect of improved saline soil based on Modflow-Hydrus coupling model
DAI Fenggang,WANG Xiaoyan*,GU Mingxu,YU Wanlu,LIAN Pengda,
In order to improve the amelioration improvement level of saline-alkaline soil, and determine the scientific and reasonable design scheme of irrigation and drainage engineering, the Modflow-Hydrus coupling model of saturated -unsaturated soil water transport was established, and the drainage effect of horizontal wells in different scenarios in the test area was simulated and analyzed. The results show that: 1)when the depth of groundwater level is shallow, the seasonal variation has an obvious influence on the comprehensive recharge intensity of groundwater; when the groundwater depth is greater than 6 m, the comprehensive recharge intensity of groundwater tends to be constant in different periods; when the groundwater depth level is large, the precipitation supply through the thick vadose zone is uniform. When intermittent drainage occurs, the phreatic water level of a single horizontal well decreases significantly within the control range of 400 m, which has a good drainage effect. The drawdown is positively correlated with the annual pumping intensity of horizontal wells. Under the natural environment, the precipitation infiltration and phreatic water evaporation keep balance, and extend outward from the center of the test area. The drainage test can effectively improve the precipitation infiltration and phreatic evaporation environment within 8 times of the experimental area, so that the soil moisture in the vadose zone enters the saturated zone, and the phreatic water level shown a downward trend. The research results provide theoretical reference for horizontal well construction design of saline alkali soil improvement.
2021 Vol. 39 (1): 61-67 [Abstract] ( 32 ) [HTML 1KB] [ PDF 4053KB] ( 588 )
68 Effects of negative pressure irrigation on growth and water use efficiency of spinach
XIANG Yanyan,HUANG Yunxiang*,LONG Huaiyu,YANG Leijing,HUANG Huang,YU Kang,OUYANG Ningxiang
In order to select a suitable negative pressure to growth of spinach(Spinacia oleracea L.)in Southern China, a pot experiment was conducted to investigate effects of three levels of negative pressure(-5.0 kPa, -10.0 kPa and -15.0 kPa)on spinach growth, physiological index, quality index, water use efficiency and nutrient uptake by using artificial irrigation as the control(CK). The results showed that the yield of spinach was 178.2 g/pot in -5.0 kPa treatment, significantly higher than that in -10.0 kPa or -15.0 kPa treatment, but without significant difference from CK. The underground biomass was 9.99 g/pot in -5.0 kPa treatment, significantly higher than that in CK and -15.0 kPa treatment. The root activity was 419.0 μg/g·h in -5.0 kPa treatment, which was significantly higher than that in CK, -10.0 and -15.0 kPa treatments, with increase by 65.3%, 51.5% and 91.0%, respectively. The vitamin C and soluble sugar contents were 50.72 mg/100 g and 1.74% in -5.0 kPa treatment, increased by 18.3%, 10.5%, 44.9% and 6.1%, 23.4%, 47.5%, respectively, comparing with CK, -10.0 kPa, and -15.0 kPa treatments. The water use efficiency was 3.89 g/kg in -5.0 kPa treatment, which was significantly higher than that in CK and -15.0 kPa treatment but had no significant difference from that in -10.0 kPa treatment. The cumulative absorption of aboveground nitrogen in spinach was significantly higher than that in CK, -10.0 kPa and -15.0 kPa treatments, and phospho-rus and potassium uptakes had no significant difference from CK, but significantly higher than that in -15.0 kPa. In terms of spinach yield and water use efficiency, the negative pressure water supply in -5.0 kPa is suitable to spinach growth in Southern China.
2021 Vol. 39 (1): 68-74 [Abstract] ( 33 ) [HTML 1KB] [ PDF 0KB] ( 254 )
75 Experiments on water erosion mechanism of weathered Pisha sandstone slope with different densities
ZHANG Ying,LI Xiaoli*,CHANG Ping,GUO Luomin,WU Shangyun
In order to study the water erosion mechanism of weathered Pisha sandstone and provide data reference for soil erosion control in Ordos,rainfall erosion experiments under different densities and rainfall intensities were carried out by using rainfall simulation system. The friction angle and cohesion of weathered Pisha sandstone with a density of 1.7g/cm3 were measured by a direct shear apparatus. For each slope with a particular density, the causes of infiltration runoff and erosion were revealed.The results show as follow: For the slope with a density of 1.7 g/cm3, the steady infiltration rate increases with increasing rain intensity. For the slope with a density of 1.5 g/cm3, the sensitivity of erosion due to infiltration rate is the highest. The the slope with a density of 1.6 g/cm3, the sensitivity of erosion due to cumulative infiltration depth is the highest; to the slope with a density of 1.7 g/cm3, the sensitivity of erosion due to runoff is the highest.The time-history curves of shear strength and sediment have a negative correlation.From the perspective of direct shear test and sensitivity analysis, the main cause of the erosion of 1.7 g/cm3 weathered Pisha sandstone slope is flow scouring.
2021 Vol. 39 (1): 75-80 [Abstract] ( 30 ) [HTML 1KB] [ PDF 3143KB] ( 496 )
81 Regression correction of Hargreaves equation within a year in China′s agricultural regions
XIA Xingsheng,ZHAO Xizhen,TANG Tong*,PAN Yaozhong,
For the question that there is a lack of research on the linear regression correction of the Hargreaves Equation(HS)for entire mainland China, and the existing correction coefficient of regions or stations is not uniform in spatial and temporal scale and difficult to be popularized and applied. Meteorological data, which was included in the Dataset of Monthly Values of Radiation Data from Chinese Surface Stations and the Dataset of Monthly Values of Climate Data from Chinese Surface Stations, were obtained from 1957 to 2016 at 124 sites. Firstly, based on Penman-Monteith(PM)equation and the HS, the average reference crop evapotranspiration—ET0-PM and ET0-HS in each month were calculated. Secondly, using ET0-PM as the truth value, and based on the average ET0-PM and ET0-HS of each region from 1957 to 2010, the correction coefficients of a and b of the HS from 38 agricultural sub-regions in China were obtained by regression analysis. Finally, taking 2011—2016 as the application verification interval, and the monthly change of 6 a mean relative error(RE)before and after correction of ET0-HS by the coefficients obtained from the corrected data was used to verify the applicability of HS correction method recommended by the Food and Agriculture Organization of the United Nations(FAO)in China′s agriculture regions. Based on the comparative analysis of the error results, the monthly optimal values of correction coefficients a and b of HS in each agricultural region were proposed. The results show that:(1)The correction coefficients a and b of HS calcula-ted by regression have no obvious change regularity in all agricultural regions, but the value of coefficient b is relatively stable around 0.8, and the coefficient a varies greatly from -0.22 to 1.10;(2)Before and after correction of ET0-HS have different degree errors, but ET0-HS error after correction will be significantly reduced, with the average RE was reduced by 20% and the maximum RE was reduced by about 100%. Therefore, after verification, the method of HS correction suggested by FAO is simple and easy to ope-rate, and has a certain popularization value for rapidly obtaining accurate ET0 by using simplified methods in various agricultural regions in China.

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2021 Vol. 39 (1): 81-88 [Abstract] ( 30 ) [HTML 1KB] [ PDF 1846KB] ( 670 )
89 Principal component analysis method for suitable water and fertilizer doses of drip irrigation grape in an extreme arid area
HOU Yusheng,WANG Zhenhua*,LI Wenhao,ZHANG Jifeng,DOU Yunqing,WEN Yue,
In order to identify the appropriate water and fertilizer doses for drip irrigation grape in an extreme arid area, the optimal water and fertilizer doses with higher yield and better efficiency were evaluated comprehensively for a mature seedless white grape in a test field by using the principal component analysis method. In doing so, irrigation and fertilization two factors were selected with four levels 6 000(W1), 6 750(W2), 7 500(W3), 8 250 m3/hm2(W4)for irrigation dose, three levels 450(F1), 750(F2), 1 050 kg/hm2(F3)for fertilization dose. The results showed that effects of water and fertilizer interaction on yield, water and fertilizer utilization efficiency and quality of drip irrigation grape have statistical significance(P<0.01). The influence of irrigation and fertilizer doses on titratable acid is also with statistical significance(P<0.05). The influences on grape yield, water use efficiency, fertilizer partial productivity, soluble solids, and vitamin C are statistically signi-ficant(P<0.01). The maximum yield occurs in treatment W3F2, especially with a 29.76% increment compared with the minimum yield treatment. The highest soluble solid content is achieved in treatment W3F2. The richest titratable acid is reached in treatment W4F2, unfortunately, the difference from treatment W3F2 is not statistically significant(P>0.05). The vitamin C quantity per 100 g was 7.37-8.52 mg across diffe-rent water and fertilizer treatments, and the difference between treatment W3F2 and W4F3 is not statistically significant(P>0.05). The quality index is better in treatment W3F2. The results of principal component analysis showed that the best water and fertilizer treatment for the drip irrigation grape in the extreme arid area is W3F2 in which N, P2O5 and K2O are 300, 150 and 300 kg/hm2, respectively.

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2021 Vol. 39 (1): 89-95 [Abstract] ( 34 ) [HTML 1KB] [ PDF 1516KB] ( 480 )
96 Effects of biodegradable mulch on cotton yield and water use efficiency
ZHAO Jiatao,MA Yuzhao,FAN Yanli,LIU Junmei,LI Quanqi*
In order to explore the feasibility of replacing ordinary mulch with biodegradable one in cotton fields of North China Plain and solve the white pollution problem, four experimental treatments, i.e. 6 μm ordinary mulch(PE), 8 μm biodegradable film 1(M1),6 μm biodegradable film 2(M2), and bared land(control-CK)were set up. Effects of the various treatments on the emergence rate, leaf area index(LAI), agricultural water consumption rate, yield and water use efficiency(WUE)of cotton were analyzed and compared. The results showed that compared with CK, mulching treatments significantly improved the seed emergence rate, but the difference between three films in PE, M1 and M2 was not statistically significant. LAI of two biodegradable films M1 and M2 was significantly lower than PE in the early stage, and PE was the best in seed cotton yield and pre-frost flower rate. There was no significant difference in seed cotton yield and pre-frost flower rate among the three treatments. Likewise, there was no significant difference in WUE among the three mulching treatments, but their WUE was significantly higher than that of CK. Compared with PE, there was no statistically significant difference in seed emergence rate, pre-frost flower rate, seed cotton yield and WUE between the two biodegradable film treatments. Compared with PE, the 6 μm biodegradable film did not increase the cotton water consumption, but the 8 μm biodegradable film did significantly increase the consumption. It is better to replace PE with the 6μm biodegradable mulch.
2021 Vol. 39 (1): 96-101 [Abstract] ( 35 ) [HTML 1KB] [ PDF 1516KB] ( 572 )
102 Monitoring model of SPAD value of winter wheat canopy based on ″three-edge″ parameters
LIN Shaozhe,PENG Zhigong*,WANG Chuntang,ZHANG Baozhong,WEI Zheng,ZHANG Qian,HAN Nana,LIU Lu
In order to provide theoretical basis and technical support for hyperspectral diagnosis of the SPAD value of winter wheat canopy, the hyperspectral estimation model between ″three-edge″ parameters and SPAD value was established. Based on the correlation between canopy reflectance and canopy SPAD value of winter wheat, the linear regression model and principal component regression model of canopy SPAD value of winter wheat based on ″three-edge″ parameters were constructed. The results showed that the correlation coefficients of red valley location,(SDr-SDb)/(SDr+SDb), red valley amplitude,(SDr-SDy)/(SDr+SDy)were the highest at jointing stage, heading stage, filling stage and whole growth period, respectively, and all had statistical significance(P<0.01);compared with the same linear regression model, the spectral model constructed by principal component method increased the determinant coefficients R2 by 49.6%, 54.3%, 14.3%, 8.6% at jointing stage, heading stage, filling stage and whole growth stage, and the root mean square error RMSE and relative error RE decreased by 9.0%, 12.4%, 13.5% and 13.6%, respectively. Therefore, the principal component regression model based on comprehensive spectral information has a high estimation accuracy for the SPAD value of winter wheat canopy in each growth period and the whole growth period, which can provide a basis for monitoring and diagnosing the SPAD value of winter wheat.
2021 Vol. 39 (1): 102-108 [Abstract] ( 35 ) [HTML 1KB] [ PDF 1724KB] ( 625 )
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