Journal of Hydroelectric Engineering

水力发电学报

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2020 Vol. 39, No. 8 Published: 2020-08-25

	1	Progress and development trends in hydraulic turbine technology ^Hot!
		LUO Xingqi, ZHU Guojun, FENG Jianjun
		DOI: 10.11660/slfdxb.20200801
		The performance of hydraulic turbines, as the core mechanical equipment for developing hydropower, determines the development and utilization rate of hydropower. Driven by the progress of modern science and technology, hydraulic turbine technology has made a great progress in China, it has experienced the developing stages of introduction, absorption, digestion and recreation, and now has reached an internationally advanced level after a rapid development over recent two decades. This paper focuses on the key research advances made in the field of turbine technology in the past two decades, based on a comprehensive synthesis of research achievements in this field in China and abroad. The progress is summarized in three parts: hydrodynamic foundation of hydraulic turbines, optimal design theory of hydraulic turbine flow components, and development of new hydraulic turbines. This paper also discuss the problems in some of the research fields and present a prospect for the development trends in hydraulic turbine technology.
		2020 Vol. 39 (8): 1-18 [Abstract] ( 618 ) PDF (1059 KB) ( 1501 )

	19	Study on explicit analytical solution of surge waves in air cushion surge chamber based on KBM method
		OU Chuanqi, LIU Deyou, ZHOU Ling
		DOI: 10.11660/slfdxb.20200802
		Calculation of surge waves in the surge chamber of a hydropower station is an important part of its water conveyance system design and optimization. This paper describes a unified relationship of indoor gas volume versus water level in an air cushion surge chamber (ASC) to overcome the difficulty in calculation of the existing implicit formula of surge waves and its poor universality. We consider the flow rate changes and the characteristics of system resistance and impedance in the transient process, and derive a water level equation of ASC applicable to different chamber shapes. Based on the start time and end time of transient, we use the KBM asymptotic method to derive an analytical formula for calculating the ASC water levels and related extremums and evaluate its errors at different time benchmarks. Results show that these formulae are easy to calculate and applicable to the ASCs with various shapes and the open surge chambers, with calculation errors within the range of 1% at the end time of transient.
		2020 Vol. 39 (8): 19-27 [Abstract] ( 100 ) PDF (814 KB) ( 306 )

	28	Layered electrical measurement of early hydration process of thin cement paste
		WANG Bohao, WANG Wei, JIN Feng, TAN Handong, HUANG Duruo
		DOI: 10.11660/slfdxb.20200803
		The internal environment of cemented granular materials formed by gravity control grouting is different from that of ordinary concrete. To investigate the influence of internal environment on hydration reaction, this study conducts subtle layered electrical measurements of the early hydration stage of thin cement paste using an embedded electrode array and other equipment, and uses thermogravimetric analysis to verify the measurements. Results show that in the initial hydrolysis stage and dormant stage of the reaction, the hydration process of test samples is basically uniform along vertical direction and the hydration process of samples of different thickness is also basically the same. Starting from the accelerating stage, pore saturation in the shallow layer of a sample becomes smaller than that in the deep layer. Therefore, after a certain curing age, the degree of hydration in the shallow layer is lower than that in the deep layer; and its value in the shallow layer of a thinner sample is smaller than that at the same depth in a thicker sample. This study would help quality control in the construction of cemented granular materials. K
		2020 Vol. 39 (8): 28-35 [Abstract] ( 101 ) PDF (1065 KB) ( 286 )

	36	Failure analysis of concrete with initial defects based on acoustic emission technologys
		CUI Wei, LIU Manman, SONG Huifang, YAN Jianghua, YAN Hongmei, GUAN Wei
		DOI: 10.11660/slfdxb.20200804
		Initial defects of concrete material play a great role in its deformation and failure properties. We conduct a series of uniaxial compression tests on the initial defects of different sizes and different inclination angles to explore their influence on the deformation behaviors and failure mechanism of concrete, and analyze stress-strain curves, acoustic emission characteristics, and images of crack propagation. The test results show that: (1) Compared with an intact specimen, the peak stress and peak strain in a concrete specimen with initial defects are reduced; the stress-strain curve shows a more obvious concave trend in initial loading stage, and a gentler slope in unloading stage. However, the influence on residual strength presents no obvious pattern. (2) The failure process of concrete with initial defects has four stages of crack development: initiation, propagation, coalescence, and through crack failure. (3) Tensile failure dominates at inclination angles of 0° and 90°, while initial defects at 30°, 45° or 60° cause shear failure along their paths.
		2020 Vol. 39 (8): 36-45 [Abstract] ( 152 ) PDF (5946 KB) ( 333 )

	46	Tensile creep of dam concrete at early age under variable temperature history
		ZHAO Zhifang, ZHONG Yangfeng, LI Xinyu, SUN Yukun
		DOI: 10.11660/slfdxb.20200805
		To determine the tensile creep of dam concrete at early age, this study conducts an experiment on the development of temperature, deformation, and restraint stress of fly ash dam concrete, using temperature-stress test technology and considering comprehensively its hydration process and restraint state at early age. We test restrained specimens and free specimens of concrete materials with fly ash contents of 35% and 80% under different temperature curing conditions, and obtain their early age tensile creep and developing trends. By the measurements of temperature-stress tests and adiabatic temperature rise tests, we develop and verify a tensile creep model of the concrete materials at early age under variable temperature history based on an improved Kelvin model. The results show the concrete with 80% fly ash has a larger specific tensile creep and slower development of restraint stress, a condition favorable to its crack resistance. The improved Kelvin model, based on a better consideration of the hydration process, can predict the tensile creep of dam concrete at early age under the restraint condition, and is useful to the assessment of early age cracking risk.
		2020 Vol. 39 (8): 46-54 [Abstract] ( 121 ) PDF (789 KB) ( 380 )

	55	Floods encountering risk analysis for upper Yangtze River and Dongting Lake
		ZHANG Chao, PENG Yang, JI Changming, SHI Yulong
		DOI: 10.11660/slfdxb.20200806
		To better understand the encountering patternof floods from the upper Yangtze River and Dongting Lake, this paper presents a fitting analysis of the probability distributions of annual maximum (AM) flood peaks, 15-day flood volumes, flood occurrence dates, and flood occurrence intervals for the two hydrological stations of Yichang and Chenglingji, based on their daily discharge records of the period 1951-2016. We use the Archimedean Copula functions to examine the encountering risk characteristics of the occurrence dates and discharges (including peak discharges and discharge time variations) of the stations’ floods. To analyze flood peak encountering risks, we formulate a joint distribution probability of the flood peaks and flood intervals of the two stations through considering their flood peak correlations and the correlations between each station’s flood peaks and occurrence dates. Finally, influence of the Three Gorges reservoir on the two stations’ floods encountering risks is analyzed to help the optimal operation of the reservoir and the flood prevention and disaster reduction in the middle and lower Yangtze River.
		2020 Vol. 39 (8): 55-68 [Abstract] ( 171 ) PDF (805 KB) ( 456 )

	69	Hydropower development, electric power transformation and energy revolution in China
		ZHANG Boting
		DOI: 10.11660/slfdxb.20200807
		For energy revolution and power transformation, nearly all the countries have recognized one of the most prominent symbols is the retirement of the coal power plants. However, for a long time in China, huge divides existed on this issue. The domestic public opinion had long been dominated by a strong coal community of interests, and a widespread public thought was held in China–the ultra-low coal emission technology has advanced to a level of coal power plant emission lower than gas power plant emission. In such a view, China could deliver on the Paris Agreement without coal power retirement. However, a recently released report, A high ambition coal phaseout in China: feasible strategies through a comprehensive plant-by-plant assessment, revealed that China must retire all the coal power plants by the years of 2040-2055 if the Paris Agreement is to be fulfilled. The author, working on hydropower for decades, well understands the importance of hydropower in power transformation. This paper discusses the importance and feasibility of hydropower development and power transformation in China, reviewing the historical experiences and lessons in the previous hydropower planning that was prepared for power transformation but failed to be implemented.
		2020 Vol. 39 (8): 69-78 [Abstract] ( 193 ) PDF (429 KB) ( 462 )

	79	Flood forecasting method for medium- and small-size rivers short of hydrological data in Liaoning Province
		PENG Anbang, LIU Jiufu, MA Tao, HUANG Dui, WANG Wenzhong
		DOI: 10.11660/slfdxb.20200808
		Most of the medium- and small-size rivers in China are located in hilly areas where hydrological stations are sparse and limited monitoring data are available, but these rivers can generate floods characterized by sudden, strong and great destructiveness. Thus, how to predict the floods in such rivers attracts much attention. This paper presents a flood prediction method for medium and small rivers for better consideration of the characteristics of these rivers in Liaoning Province. We collect and extract the basic data of underlying surface, hydrology, meteorology, etc. , and extract a new set of irrelevant indexes using the principal component analysis that can reduce the dimension and influence of related indexes. Then, a variable fuzzy model is used to classify and identify the hydrological similarity of 30 reference stations and 84 river stations. Finally, we construct a Topmodel model for prediction of distributed floods, and verify its effectiveness and practicability through comparison of its accuracies in flood predictions for the reference stations before and after parameter transplantation. Our results lay a basis for flood prediction of the medium- and small-size rivers in Liaoning Province, and are also useful to flood forecasting of other valleys short of hydrological data.
		2020 Vol. 39 (8): 79-89 [Abstract] ( 176 ) PDF (1536 KB) ( 390 )

	90	Analysis on runoff regime in middle Yellow River and its driving factors
		FENG Jiahao, ZHAO Guangju, MU Xingmin, TIAN Peng, TIAN Xiaojing
		DOI: 10.11660/slfdxb.20200809
		This paper presents a systematic analysis on spatiotemporal variations in the runoff in the middle Yellow River and its driving forces, using the methods of Spearman rank correlation test, regime shift index, and double mass curve, based on the 1957-2018 hydrological series at four mainstream stations and eleven typical tributaries in Toudaoguai-Huayuankou reach. The results reveal a significant decreasing trend at the significance level of 0.001 in the annual runoff in the middle Yellow River mainstream and two abrupt changes in its hydrological regime in 1969 and 1987. Since the 1970s, the runoff depth in these tributaries has reduced with time significantly; the runoff proportion of Toudaoguai-Longmen reach to the entire middle Yellow River has decreased from 31% to 23.5% around the year 2000, while the proportions of all the reaches below Longmen have increased obviously. The average contribution rate of human activities to runoff variations was 62.68% in Toudaoguai-Longmen reach and 79.85% in Longmen-Tongguan reach. The major driving forces of runoff reduction are the operation of water conservancy projects and the implementation of soil and water conservation measures, such as reservoirs, check dams, irrigation water diversion works, and terraces.
		2020 Vol. 39 (8): 90-103 [Abstract] ( 190 ) PDF (1997 KB) ( 348 )

	104	Particle size and roughness of Lhasa River bed upstream and downstream of Zhikong Reservoir
		LU Hanyou, LI Zhiwei, HU Xuyue, HU Tiesong, YUAN Xinya
		DOI: 10.11660/slfdxb.20200810
		Since its completion in 2006, the Zhikong Reservoir on the upper Lhasa River has trapped incoming sediment and released clean water, causing a relatively fast coarsening of the gravel riverbed in the downstream channel; but the degree and scope of the coarsening and the equilibrium status of gravel bed are not understood yet. In April 2018, we conducted a field survey of the riverbed around the reservoir focusing on five sites and manually measuring the median particle size of gravels and pebbles on the riverbed surface, and adopted unmanned aerial vehicles (UAV) taking photographs at a height of 30 m. Through image processing and generation of the high-resolution terrain data, we calculated spatial variations in the gravel particle size and relative roughness of the bar surface. Results show that the UAV aerial survey method can extract the particle size of gravel bed surface in good accuracy, and the mean error in median particle size calculations is about 18.7% in comparison with the manual measurements. Owing to flow scour and sorting, the coarsening in the river section of 1 km long below the dam has reached its equilibrium; and the particle size decreases along the course in the 10 km long section below the dam, and gradually recovers to the normal up to a distance of 22 km below the dam.
		2020 Vol. 39 (8): 104-111 [Abstract] ( 146 ) PDF (1869 KB) ( 338 )

	112	Study on correlation of factors affecting saline intrusion length in Modaomen estuary based on field observations
		HUANG Shuqin, YIN Xiaoling, ZENG Ying, ZHAO Xuefeng, REN Jie
		DOI: 10.11660/slfdxb.20200811
		To better understand the characteristics of saltwater intrusion in the Modaomen estuary in dry season, fortnight ship-mounted observations of the waterway were carried out three times in the dry season of 2017-2018, and hydrological and meteorological data of the waterway were collected for this period. This paper presents an analysis of the correlations between the saline intrusion length with inflow discharge, tidal range, sea level, and north wind speed, in combination with analysis of the features of longitudinal and plane topographies for different waterway sections. The results show changes in channel topography impose a significant impact on these correlations. Due to the modulation of the bifurcating reaches, correlation coefficients for the downstream section featured with central bars are smaller than those for the whole section observed. In the upstream section with a narrow, deep single main channel, the location of saltwater upper boundary has higher correlation with runoff discharge and tidal range; and it tends to accelerate saltwater intruding. We also find the influence of runoff on saltwater movement may be weakened and lose its dominating role when the combined action of other factors–such as tide, wind and topography–becomes prominent, although it is usually the most relevant dominant factor.
		2020 Vol. 39 (8): 112-120 [Abstract] ( 99 ) PDF (993 KB) ( 369 )