Journal of Hydroelectric Engineering

水力发电学报

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2020 Vol. 39, No. 6 Published: 2020-06-25

	1	Progress and developing trends in pump technology ^Hot!
		LUO Xingqi, WU Dazhuan
		DOI: 10.11660/slfdxb.20200601
		As typical hydraulic machines, pumps play an important role in the national economy, and progress in pump technology attracts concerns from many industries. Driven by various application requirements on the modern pump, significant advances have been achieved in its theory and technology along with the rapid development in the related disciplines such as materials science, mechanics, informatics, and computer science. At present, its internal flow mechanisms and operating characteristics are understood more deeply, information technology is widely used in its design, operation and maintenance, and new pump products are gradually becoming eco-friendly and intelligent. This article focuses on the progress in the technology of various vane pumps achieved over the last two decades, including vortex pumps, centrifugal pumps, mixed flow pumps, axial flow pumps, and tubular pumps. Based on the requirements of product applications, this paper summarize the developing trends in the hydrodynamics, design technology, vibration and noise, and operation and maintenance technology of the modern pumps.
		2020 Vol. 39 (6): 1-17 [Abstract] ( 274 ) PDF (4583 KB) ( 839 )

	18	Vibration feature extraction for hydropower units based on ensemble empirical mode decomposition and approximate entropy
		JIANG Wenjun, HU Xiao, ZHANG Pei, DENG Shengming, XIAO Zhihuai
		DOI: 10.11660/slfdxb.20200602
		In recent years, research on the feature extraction method of non-stationary nonlinear vibration signals has been a hot spot in the fault diagnosis of hydropower units, and its effectiveness is a key factor of fault diagnosis accuracy. This paper describes a new feature extraction method based on ensemble empirical mode decomposition (EEMD) and approximate entropy for vibration signals from hydropower units. It uses EEMD to obtain approximate entropy eigenvalues of the intrinsic mode function (IMF), and then inputs them into a probability neural network (PNN) for pattern identification. Results show this method can effectively distinguish the difference in the operation modes of a unit, laying a basis for fault diagnosis in engineering applications.
		2020 Vol. 39 (6): 18-27 [Abstract] ( 267 ) PDF (1617 KB) ( 510 )

	28	Quantitative evaluation on spatial heterogeneity of water resources in China
		QI Hongwei, SHANG Songhao, LI Jiang
		DOI: 10.11660/slfdxb.20200603
		Spatial heterogeneity is an essential property of precipitation and water resources. Based on the results of the second integrated assessment to water resources in China, the Lorenz curve is used to calculate Gini coefficients and Lorenz asymmetric coefficients, which represent the degree and source of spatial heterogeneity respectively. Results indicate that different types of water resources in China show considerable or strong spatial heterogeneity. And the heterogeneity across different water resources divisions increases from east and south coasts to northwest, depending on the area, average precipitation, and other natural conditions. For each division, the heterogeneity in precipitation is the smallest, followed by groundwater resource, total water resources, and surface water resource; and water resources heterogeneity is featured with asymmetry dominated by those sub-divisions with less amount of water resources, or relative symmetry.
		2020 Vol. 39 (6): 28-38 [Abstract] ( 555 ) PDF (3007 KB) ( 588 )

	39	Runoff forecasting and dynamic parameter identification using probability distributed model
		HAO Ruonan, LIU Dengsong, SUN Yingjun, CHIANG Yenming
		DOI: 10.11660/slfdxb.20200604
		Studies on applicability of the probability distributed model (PDM) to the river basins in China and investigation of its parameter change across different flood stages are limited. This study compares the performance of PDM-based runoff forecasting for two typical basins in Zhejiang Province, and examines model parameter changes through dynamic identifiability analysis (DYNIA) to infer dominant controlling factors in rainfall-runoff process under different time windows. The results show that forecasting performance for the two basins is generally satisfactory with the Nash-Sutcliffe efficiency coefficient both over 0.7, and the model performs better in the Longquan basin dominated by low flows than the Jinhua basin dominated by high flows. Three parameters (empirical coefficientss α, b and maximum storage capacity Smax) of various flood events are negatively correlated to antecedent soil moisture. The recession slope-related b is positively correlated to average evaporation in the Jinhua basin but negatively to mean rainfall in the Longquan basin. Identifiability of α, a coefficient controlled by soil moisture at a depth of 28 cm, is generally higher for flood peak and recession periods.
		2020 Vol. 39 (6): 39-48 [Abstract] ( 121 ) PDF (1384 KB) ( 268 )

	49	Fast algorithm for solving optimal power generation model of reservoir operation and its application
		ZHI Yue, AI Xueshan, DONG Zuo, CHEN Senlin
		DOI: 10.11660/slfdxb.20200605
		In solving models for optimal power generation of reservoir operation in a plan of regulating power generation by water supply, traditional dynamic programming are easy to fall into a dimension disaster; while modern intelligent algorithms using random search are inefficient and easy to fall into a local optimum. To overcome these shortages, this paper develops a floater algorithm, a fast solution method for reservoir dispatching model, based on the characteristic that the water consumption rate of power generation is relatively low at a high operating reservoir stage. This method directly finds the optimal solution by keeping the reservoir stage as high as possible during operation, while satisfying the requirements of guaranteed output and minimum generation discharge. A case study and comparison with the results of discrete differential dynamic programming (DDDP) shows this algorithm has the advantages of achieving high power generation and fast computation (two times as fast as DDDP) for general situations. Thus, our floater algorithm improves the optimization results and solving efficiency for reservoir operation, helping formulate a regulating-power-generation-by-water-supply operation plan and rapid decision-making.
		2020 Vol. 39 (6): 49-61 [Abstract] ( 330 ) PDF (1393 KB) ( 575 )

	62	Study on purification efficiency of integrated device with membrane aeration biofilm reactor and ecological floating bed in flowing water
		YUAN Ximin, ZHANG Zichang, MA Chao, XU Kui, SUN Yanan
		DOI: 10.11660/slfdxb.20200606
		To explore the effects of ecological floating bed (EFB), a membrane aerated biofilm reactor (MABR), and an integrated device, an experimental study is conducted on their purification efficiency of four types of pollutants–NH4+-N, permanganate index (CODMn), total phosphorus (TP), and total nitrogen (TN) – in water flows with different velocities (2.5, 10 and 20 m/h). The results show that this MABR-EFB integrated device significantly improves purification effect, and its removal rates of the four pollutants are increased by 40% - 44%, 17% - 34%, 13% - 21% and 14% - 30% respectively compared with those of river water self-purification. A comprehensive consideration of all these pollutants indicates that the device performs best under the hydrodynamic condition at the flow velocity of 10m/h, and MABR buffering effect helps widen the flow velocity range applicable to aquatic plants. Under the hydrodynamic conditions tested in our experiment, the device behaves differently in removing different pollutants: in relatively high pollutant concentration, it purification rate increases with the increasing flow velocity for NH4+-N but reaches the maximum at 10 m/h for CODMn, TP and TN; in low concentration in the later stage of the experiment, it has a low purification rate for all the pollutants tested.
		2020 Vol. 39 (6): 62-71 [Abstract] ( 104 ) PDF (1964 KB) ( 244 )

	72	Experimental study on mechanics and durability of cemented gravel-mixed soil of core wall
		LIU Donghai, ZHANG Zhao
		DOI: 10.11660/slfdxb.20200607
		How to reduce the arch effect of a soil core wall effectively has become an important issue for high rock-fill dams. A common solution is to mix a certain amount of gravel into the clay soil of the core wall to increase its deformation modulus. However, the arch effect of such core walls is still significant for 300 m high dams. If more gravel is mixed, the modulus would undoubtedly be improved, but its impermeability may inevitably be weakened. This paper evaluates the feasibility of a new core wall material for high earth-rock dams–a cemented gravel-mixed soil mixed with three different soil solidifiers, examines the effects of solidifier type and content on its mechanics and durability, and demonstrates the causes of differences in its performance of different types through scanning electron microscope tests. We found the HAS type has the advantages of higher compressive and tensile strengths, larger deformation modulus and toughness, and better impermeability, frost resistance and compactness. Thus, the mixed soil of this type increases the deformation modulus of core walls without increasing the amount of gravel, helping reduce the arch effect of core walls and providing a new alternative for core wall improvement.
		2020 Vol. 39 (6): 72-82 [Abstract] ( 133 ) PDF (3580 KB) ( 379 )

	83	Deformation analysis and failure mechanism of flexural toppling of high rock slopes
		AN Xiaofan, LI Ning
		DOI: 10.11660/slfdxb.20200608
		Flexural toppling often occurs in anti-dip layered rock slopes, where rock mass shows failure behaviors similar to those of superimposed cantilever beams. Slopes in this failure mode may evolve into large landslides. Taking the left bank slope at the Ecuador’s Delsitanisagua hydropower station as an example, this paper describes its geological and geomorphological characteristics and examines the field data monitored during construction. Generally, typical rock structure (anti-dip and steep-dip) and special lithologic composition (thin-layered gneiss) are prerequisites for flexural toppling, while external factors such as excavation and heavy rainfall trigger and aggravate the deformation of rock layers. Numerical simulation using discrete elements shows that rock mass excavation below elevation 1493 m causes a deep-seated toppling failure of the entire slope; deformation of rock layers is featured with an obvious ductility, and a secondary fracture of reverse buckling develops inside the toppling mass. And in the slope mass, evolution of plastic zones reflects the propagation of rock mass rupture, and a fracture of straight failure with an inclination angle of 21° can be determined from the maximum shear strain and tensile stress distribution. Finally, control over the excavation height and angle at the slope bottom proves an effective way to reduce toppling deformation.
		2020 Vol. 39 (6): 83-98 [Abstract] ( 170 ) PDF (4545 KB) ( 383 )

	99	Deformation compatibility analysis of clay core wall dams based on multi-objective optimization theory
		HUANGFU Zehua, WU Yingli, GUO Wanli
		DOI: 10.11660/slfdxb.20200609
		This paper describes five indexes for evaluating the deformation compatibility of clay core wall dams, i.e., major principal stress, stress level of core wall, maximum settlement of dam body, settlement rate of core wall, and vibration time for compaction. We use these indexes and 3D finite element analysis to examine the deformation compatibility of a core rockfill dam, and come to the conclusions as follows: (1) Functional relationship between each index and the relative density Dr of dam shell material can be summarized by a fitted equation; For each index, an effect function can be obtained using a normalization method. An objective function is obtained by assigning a weight factor to each effect function, and the weighted average value can be used to determine Dr of the optimal dam shell material. (2) Without construction cost taken into account, the Dr obtained by each single index may vary greatly in a wide range of 0.49 to 1.0, while it is reduced to 0.78-0.81 if determined using multi-objective optimization, a reasonable range that meets the design specification. (3) With construction cost considered for a construction elevation of 384 m, Dr of 0.783 is determined for an equal-weight scheme requiring a vibration duration of 90 s. The multi-objective optimization method is beneficial for dam construction .
		2020 Vol. 39 (6): 99-108 [Abstract] ( 139 ) PDF (867 KB) ( 487 )

	109	Effects of reservoir water on simulations of arch dam dynamic characteristics
		QIU Yixiang, WEI Chuhan, WU Zhigang, WANG Jinting
		DOI: 10.11660/slfdxb.20200610
		Water compressibility and dam-water dynamic interaction are important factors that affect the hydrodynamic pressure on dam surface and the dynamic characteristics of an arch dam. This study develops a finite element model of the arch dam-foundation-reservoir water system to evaluate the effects of reservoir water on arch dam dynamic characteristics through a case study of the Laxiwa arch dam. In analysis, we use two reservoir water models, a Westergaard added mass model and a fluid-structure coupling model; three conditions are examined of Westergaard added mass, structure coupling with incompressible water, and structure coupling with compressible water. Results show that water storage behind an arch dam reduces its natural frequencies; compressibility of the water reduces them further, thereby changing its vibration modes. The results help improve the accuracy of high arch dam analysis and seismic response analysis.
		2020 Vol. 39 (6): 109-120 [Abstract] ( 179 ) PDF (2834 KB) ( 407 )