Journal of Hydroelectric Engineering

水力发电学报

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2021 Vol. 40, No. 1 Published: 2021-01-25

	1	Advances in research of lean construction technology of integrated design and construction for hydropower projects: Exploration of digital twin application mode ^Hot!
		ZHANG Sherong, JIANG Peiqi, WU Zhengqiao
		DOI: 10.11660/slfdxb.20210101
		With popularization and application of the project general contracting model in the water conservancy and hydropower industry, the integrated design and construction model led by design has become an effective means of reducing costs and increasing efficiency, unified management, and scientific decision-making. This paper reviews the recent advances in the research of general contracting models, design models, construction models, and design and construction collaboration models for the water conservancy and hydropower industry in China and overseas; and clarifies the current pain points of this industry and its major bottlenecks in developing and implementing such integrated models. We investigate the key roles and concept of applying the informatization technology forefront, deepening technological innovation and practice, and adopting the top-down design and lean construction models in solving the existing problems of low design optimization efficiency in design and construction integration, cumbersome mutual feedback of design and construction information, and low level of intelligent construction. To further develop this concept, taking the digital twin technology as a basic application framework for the future, we expound key research directions for further research, and suggest how to promote the integrated design and construction in hydropower development and overcome the shortcomings in water conservancy informatization.
		2021 Vol. 40 (1): 1-12 [Abstract] ( 525 ) PDF (569 KB) ( 2067 )

	13	IBAS-BP dynamic evaluation of gravelly soil blending quality under real-time monitoring
		QIAO Tiancheng, WU Binping, WANG Jiajun, YU Jia, CUI Bo, LIU Minghui
		DOI: 10.11660/slfdxb.20210102
		The traditional method of gravelly soil blending quality evaluation mainly uses supervision of the side station to control its blending construction parameters, and takes the P5 content of a randomly sampled point as the blending quality evaluation index. It is not only subjected to human factors but also limited to the poor timeliness and great randomness, and is hard to truly reflect the uniformity of blending. To solve these problems, we present a new dynamic method for evaluating gravelly soil blending quality based on an IBAS-BP neural network. First, a blending uniformity value (BUV) is worked out to reflect blending quality through a comprehensive consideration of the contents of different particle sizes; then, we develop a new method that can achieve real-time monitoring and collection of the construction parameters of gravelly soil blending based on GPS positioning, wireless transmission and so on. Finally, to realize the dynamic evaluation of the whole work unit, we adopt a BP neural network that is optimized by the Beetle Antennae Search (BAS) algorithm using the backtracking idea and the non-linear step adjustment function. Engineering application shows that the blending quality evaluated using BUV agrees with the test results sampled after blending, and our monitoring method is effective and applicable. Comparison of the model predictions with measurements gives a correlation coefficient of 0.953, an average error of 0.23%, and a standard deviation error of 6.17%, thus improving consistency, representativeness and superiority over traditional regression models.
		2021 Vol. 40 (1): 13-23 [Abstract] ( 140 ) PDF (2983 KB) ( 525 )

	24	Repair material of concrete structures and its application to hydraulic flow channels
		CUI Dongwen, ZHANG Guijin, FAN Ming, ZHAO Xueyu
		DOI: 10.11660/slfdxb.20210103
		Erosion damage to concrete structures is often observed in various flow channels, and usually using existing repair materials cannot insure a good durability of the repaired structure. To achieve better repair effect, we develop new composite materials and conduct laboratory tests on their abrasion resistant properties, thermal compatibility, and mechanical properties under hydraulic environment. Mechanical analysis of the repaired structures and field repair tests of a diversion channel and an overflow surface have been carried out. The results show that our new composite materials achieve better performances than the other similar materials in China – wet adhesive strength of up to 3.95 MPa between epoxy interface agent and original concrete, compressive strength of underwater abrasion resistant mortar of up to 85.99 MPa, and abrasion resistant strength of up to 2545.2 h/(kg/m2) when protected with a flexible nano-ceramic coating. And they have good compatibility with concrete and can adapt to the deformation of concrete both in high and low temperature environments; in the range of -20℃~40℃, the structures repaired using them will not crack or be corroded, keeping structural integrity. The site repair effect is considerably fine, and no obvious damage to the surface has been observed after sufficient times of flood discharge. Thus, we suggest that these new composite materials be widely applied to similar projects to achieve a good durability and better effect of concrete structure repair.
		2021 Vol. 40 (1): 24-31 [Abstract] ( 251 ) PDF (2160 KB) ( 556 )

	32	Calculation method of bending moments and crack openings of steel fiber reinforced concrete beams with longitudinal reinforcement
		BI Jihong, WANG Zhaoyao, HUO Linying, ZHAO Yun
		DOI: 10.11660/slfdxb.20210104
		The purpose of this paper is to establish a mechanical model that can predict the width of crack opening in steel fiber reinforced concrete (SFRC) beams with longitudinal steel bar reinforcement (R-SFRC) under loading. We develop a tensile stress-crack width constitutive model of SFRC beams considering the effective width of cracks and the effective pull-out angle of steel fibers, and then a SFRC flexural strength model based on fracture mechanics. And we formulate a calculation model that, taking the effect of reinforcement into account, can be used to analyze the bending moments and crack widths of R-SFRC beams and simulate their bending failure process. This calculation model, along with the standard methods of CECS 38—2004 and RILEM TC 162-TDF, is used to calculate the crack width of the collected 12 R-SFRC beams at service loads. The results demonstrate that the calculation results of the two standard methods are conservative and discrete, while our method gives predictions in a good agreement with experimental measurements and can effectively predict the crack width of R-SFRC beams and its variation over the loading process with a good accuracy and small coefficients of variations.
		2021 Vol. 40 (1): 32-42 [Abstract] ( 142 ) PDF (1027 KB) ( 418 )

	43	Study on three methods for controlling year-end water stage in Lianghekou Reservoir
		JIANG Zhiqiang, LIAO Xiang, JI Changming, QIN Hui
		DOI: 10.11660/slfdxb.20210105
		This paper examines the influence of different control methods of the year-end water stage in a multi-year regulating reservoir and the inter-annual variations in its inflow on the resulted operation of the cascade system, through a case study of the cascade reservoirs in the middle and lower Yalong River. We conduct optimization calculations of multi-dimensional dynamic programming and compare three operating methods - fixed stages, stage variations by a specified function, and stage variations under dynamic bounds - for controlling the year-end stage in the Lianghekou Reservoir, and work out a new optimal control method that can achieve coupling optimization with inflow frequency variations. This study is useful to improve the joint operation and the social and economic benefits of the cascade reservoirs with multi-year regulating reservoirs.
		2021 Vol. 40 (1): 43-53 [Abstract] ( 216 ) PDF (1102 KB) ( 363 )

	54	Method of short-term scheduling for high-proportion hydropower grid considering energy decomposition
		XIE Mengfei, JIA Zebin, ZHANG Fan, MA Gaoquan, HE Peishan, SHEN Jianjian
		DOI: 10.11660/slfdxb.20210106
		Improper connection between medium and long-term trading energy and short-term power generation scheduling is a key problem that may cause structural water abandonment or power shortage. How to decompose the 96-point curve of trading energy is crucial for the power generation scheduling of high-proportion hydropower grids. This study develops a new method for short-term power generation scheduling based on the decomposition of energy curve and a practical project of the Yunnan power grid, applies power station classification strategy in determination of the standard load curve in sequence, and formulates a decomposition method of daily energy that couples with standard load curve and considers fairness. And aiming at minimizing the relative deviation from the planned decomposition energy completion degree, we integrate the check strategies for hydropower station restricted area and power grid transmission section, and optimize iteratively the initial decomposition curve to quickly obtain a feasible power generation process of power stations. This method is verified using examples of short-term scheduling of the power grid, and the results show it can effectively reduce the deviation of implemented generation scheduling, satisfying the practical and timely requirements of generation scheduling for high-proportion hydropower grids.
		2021 Vol. 40 (1): 54-64 [Abstract] ( 155 ) PDF (1218 KB) ( 790 )

	65	Distributed hydrological model of Heilongjiang River basin
		LI Mingliang, YANG Dawen, HOU Jie, XIAO Peng, XING Xigang
		DOI: 10.11660/slfdxb.20210107
		Heilongjiang (Amur) River is a boundary river in high latitude cold region with prominent flood control problems, yet few studies have been carried out from the perspective of the river basin. This paper establishes a spatial information database of the Heilongjiang basin and constructs a physically-based distributed hydrological model or GBHM-HLJ model. This model uses a generalized model, featured with an exponential variation in the hydraulic conductivity of frozen soil with temperature, to simulate the influence of soil freezing and thawing cycles on water flow. For model calibration and validation periods, the Nash-Sutcliffe efficiency coefficients of daily discharge at the ten main stations are all greater than 0.73, and the coefficients of determination of monthly discharge all greater than 0.82. The simulated monthly average of snow precipitations over the basin is compared with the FY-3C satellite remote sensing data of 2014-2019, showing a coefficient of determination of 0.83. For the main stream control station Khabarovsk in the period of 1960-1990, this efficiency coefficients of its daily discharge and annual maximum daily discharge simulations are 0.90 and 0.72, respectively. Our model lays a basis for further hydrological study of the basin and its main and tributary streams.
		2021 Vol. 40 (1): 65-75 [Abstract] ( 187 ) PDF (4964 KB) ( 621 )

	76	Hydrological ensemble forecasting method based on stochastic combination of multiple models
		ZHAO Zeqian, HUANG Qiang, MING Bo, CHEN Jing, LIU Dengfeng, CHEN Xi
		DOI: 10.11660/slfdxb.20210108
		Accurate and reliable hydrological forecasting plays an important role in water resources development and utilization. Ensemble forecasting could characterize forecast uncertainty in the form of probability distributions or intervals, which is a key issue in hydrological forecasting. In this paper, we describe a new hydrological ensemble forecasting method, namely a stochastic combination of multiple models (SCMM) that integrates several hydrological models together with linear weights and then optimizes the upper and lower limits of the weights using a multi-objective evolutionary algorithm. Finally, it creates ensemble forecasting samples through stochastically generating the weights within the optimized interval. In a case study of the medium-long-term runoff forecasting of the Huangjinxia reservoir located on the Han River, we construct six statistical forecast models considering two lead times of a month and ten days, and optimize the limits of the weights using the improved nondominated sorting genetic algorithm (NSGA-II) algorithm, yielding the ensemble forecast samples. Results show our method can better reflect the forecast uncertainty and improve significantly the average forecasts over those of the Bayesian model averaging method or a deterministic forecast model, thus providing a promising hydrological forecasting technique.
		2021 Vol. 40 (1): 76-87 [Abstract] ( 336 ) PDF (3569 KB) ( 559 )

	88	Neural network estimation methods for varying output coefficients of hydropower stations
		JIA Benjun, ZHOU Jianzhong, CHEN Xiao, HE Zhongzheng, ZHANG Yongchuan, TIAN Mengqi
		DOI: 10.11660/slfdxb.20210109
		Focusing on how to improve the accuracy in estimating power output coefficients and power generation process of a hydropower station for its medium-long-term generation dispatching, this study develops three neural network models with an output of power output coefficient K and three alternative inputs–water head, generation flow, and inflow rate. These models adopt the neural network data mining technology and consider the influence of the station’s key status information comprehensively. And we formulate three neural network methods for estimating the varying K values in the station’s output calculations and compare the methods with traditional methods, in a case study of the many years’ operation data of the Three Gorges hydropower station. The results show our methods are more accurate in the estimations of K value, power output, and power generation, providing a new practical approach to the refined output calculation of medium-long-term power generation dispatching of hydropower stations.
		2021 Vol. 40 (1): 88-96 [Abstract] ( 177 ) PDF (1437 KB) ( 387 )

	97	Decision making for multi-objective reservoir operation schemes based on marginal substitution rate
		WU Yueqiu, WANG Liping, ZHAGN Yanke, WU Jiajie, ZHANG Pei
		DOI: 10.11660/slfdxb.20210110
		To obtain multi-objective optimal operation schemes of reservoirs under the condition of uncertain inflow runoff, this study examines the Three Gorges reservoir with a combined storage capacity for flood control and power generation. The forecast error of reservoir inflow process is quantified and the principle of benefit maximization by coupling output and cost isolines in microeconomics is applied. Then, the marginal substitution rate is used in multi-objective reservoir optimization and decision to seek the best point balancing flood control with power generation. The results show that this model can directly describe the mutual feedback transformation relationship between flood control benefit and power generation benefit under different inflow scenarios, and it also obtains the optimal reservoir operation stage for the early flood period when the inflow forecasting error is considered, theoretically and practically helping make full use of reservoir benefits while ensuring flood control safety.
		2021 Vol. 40 (1): 97-106 [Abstract] ( 145 ) PDF (493 KB) ( 676 )

	107	Study on structural stability of Francis turbine impellers under partial load conditions
		FENG Jinhai, LING Zuguang, ZHAO Ziwen, LI Huanhuan, CHEN Diyi
		DOI: 10.11660/slfdxb.20210111
		For flexible operation of hydro-generator sets, structural stability of Francis turbine impellers under partial load operation is extremely important. This paper presents a static analysis and a modal analysis of the impeller under three typical partial load conditions, based on the one-way fluid-structure coupling method. The results show that under load conditions of 80%, 60% and 40%, large deformation is located at the impeller lower ring, the middle of the tail edge, and the middle of the head edge of the impeller blades respectively. Prestressing has less influence on the runner structure such as an increase of only about 1Hz in its natural frequency, while water mass has a great impact including a frequency reduction of 15% to 36% but the reduced natural frequencies agree better with the real values. Under the influence of flow disturbance at the outlet of guide blades, the impeller will resonate under these three partial loads, largely in the modes of radial, bending, bending and torsion, and axial rotation deformation. Of all the modes, bending and torsion deformation has the greatest influence likely causing blade fracture. The results are significant to theoretical stability analysis of the flexible operation of Francis turbines.
		2021 Vol. 40 (1): 107-114 [Abstract] ( 227 ) PDF (3047 KB) ( 824 )

	115	Effect of operating condition variations on tip clearance flow characteristics of tubular turbines
		ZHU Guojun, LIU Jiamin, FENG Jianjun, LI Chenhao, WU Guangkuan, LUO Xingqi
		DOI: 10.11660/slfdxb.20210112
		The tubular turbine is a main type of the hydraulic turbines for low head hydropower development, but its tip clearance flow is the key factor controlling its cavitation and stability performances. Using CFD simulations, this paper examines the mechanism of the initial location variation and shape variation of the tip leakage vortices (TLVs) that are induced by a variation in the operating condition, and evaluates the vortices’ influence on the cavitation and stability of the turbine. Results support the major conclusion that a variation in guide vane opening alters the angle of attack at the leading edge of runner blades and further affects the initial locations and three-dimensional shapes of TLVs. And we find these variations are the cause of variations in runner cavitation performance, and verify TLVs can increase the amplitude of pressure fluctuations over the regions they swept, leading to the amplitudes doubled or more.
		2021 Vol. 40 (1): 115-122 [Abstract] ( 140 ) PDF (1969 KB) ( 478 )