毕业设计水利水电工程英文文献翻译
水利水电工程毕业设计英文翻译,混凝土重力坝
Concrete Gravity DamThe type of dam selected for a site depends principally on topographic, geologic,hydrologic, and climatic conditions. Where more than one type can be built, alternative economic estimates are prepared and selection is based on economica considerations.Safety and performance are primary requirements, but construction time and materials often affect economic comparisons.Dam ClassificationDams are classified according to construction materials such as concrete or earth. Concrete dams are further classified as gravity, arch, buttress, or a combination of these. Earthfill dams are gravity dams built of either earth or rock materials, with particular provisions for spillways and seepage control.A concrete gravity dam depends on its own weight for structural stability. The dam may be straight or slightly curved, with the water load transmitted through the dam to the foundation material. Ordinarily, gravity dams have a base width of 0.7 to 0.9 the height of the dam. Solid rock provides the best foundation condition. However, many small concrete dams are built on previous or soft foundations and perform satisfactorily. A concrete gravity dam is well suited for use with an overflow spillway crest. Because of this advantage, it is often combined with an earthfill dam in wide flood plain sites.Arch dams are well suited to narrow V- or U-shaped canyons. Canyon walls must be of rock suitable for carrying the transmitted water load to the sides of the canyon by arch action. Arch sections carry the greatest part of the load; vertical elements carry sufficient load through cantilever action to produce cantilever deflections equal to arch deflections. Ordinarily, the crest length-to-height ratio should be less than 5, although greater ratios have been used. Generally, the base width of modern arch dams is 0.1 to 0.3 the height of the impounded water. A spillway may be designed into the crest of an arch dam.Multiple arches similarly transmit loads to the abutment or ends of the arch. This type of dam is suited to wider valleys. The main thrust and radial shears are transmitted to massive buttresses and then into the foundation material.Buttress dams include flat-slab, multiple-arch, roundhead-buttress, and multiple-dome types. The buttress dam adapts to all site locations. Downstream face slabs and aprons are used for overflow spillways similar to gravity dam spillways. Inclined sliding gates or light-weight low-head gates control the flow.The water loads are transmitted to the foundation by two systems of load-carrying members. The flat slabs, arches, or domes support the direct water load. The face slabs are supported by vertical buttresses. In most flat-slab buttress dams, steel reinforcement is used to carry thetension forces developed in the face slabs and buttress supports. Massive-head buttresses eliminate most tension forces and steel is not necessary.Combiantion designs may utilize one or more of the previously mentioned types of dams. For example, studies may indicate that an earthfill dam with a center concrete gravity overflow spillway section is the most economial in a wide, flat valley. Other design conditions may dictate a multiple-arch and buttress dam section or a buttress and gravity dam combination.Site ExplorationThe dam location is determined by the project’s functions. The exact site within the general location must be determined by careful project consideration and systematic studies.In preliminary studies, two primary factors must be determined-the topography at the site and characteristics of the foundation materials. The first choice of the type of dam is based primarily on these two factors. However, the final choice will usually be controlled by construction cost if other site factors are also considered.Asite exploration requires the preparation of an accurate topographic map for each possible site in the general location. The scale of the maps should be large enough for layout. Exploration primarily determines the conditions that make sites usable or unusable.From the site explorations, tentative sketches can be made of the dam location and project features such as power plants. Physical features at the site must be ascertained in order to make a sketch of the dam and determine the position of materials and work plant during construction. Other factors that may affect dam selection are roadways,fishways, locks, and log passages.TopographyTopography often determines the type of dam. For example, a narrow V-shaped channel may dictate an arch dam. The topography indicates surface characteristics of the valley and the relation of the contours to the various requirements of the structure. Soundness of the rock surface must be included in the topographic study.In a location study, one should select the best position for the dam. An accurate sketch of the dam and how it fits into the topographic features of the valley are often sufficient to permit initial cost estimates. The tentative location of the other dam features should be included in this sketch since items such as spillways can influence the type and location of the dam.Topographic maps can be made from aerial surveys and subsequent contour plotting or they can be obtained from governmental agencies. The topographic survey should be correlated with the site exploration to ensure accuracy. Topographic maps give only the surface profile at thesite. Further geological and foundation analyses are necessary for a final determination of dam feasibility.Foundation and Geological InvestigationFoundation and geological conditions determine the factors that support the weight of the dam. The foundation materials limit the type of dam to a great extent, although such limitations can be compensated for in design.Initial exploration may consist of a few core holes drilled along the tentatively selected site location. Their analysis in relation to the general geology of the area often rules out certain sites as unfeasible, particularly as dam height increases. Once the number of possible site locations has been narrowed down, more detailed geological investiagtions should be considered.The location of all faults, contacts, zones of permeability, fissures, and other underground conditions must be accurately defined. The probable required excavation depth at all points should be derived from the core drill analysis. Extensive drilling into rock formations isn’t necessary for small dams. However, as dam height and safety requirements increase, investigations should be increased in depth and number. If foundation materials are soft, extensive investigations should determine their depth,permeability, and bearing capacity. It is not always necessary orpossible to put a concrete dam on solid rock.The different foundations commonly encountered for dam construction are: (1)solid rock foundations, (2) gravel foundations, (3) silt or fine sand foundations, (4) clay foundations, and (5) nonuniform foundation materials. Small dams on soft foundation ( item 2 through item 5 ) present some additonal design problems such as settlement, prevention of piping, excessive percolation, and protection of foundation from downstream toe erosion. These conditions are above the normal design forces of a concrete dam on a rock foundation. The same problems also exist for earth dams.Geological formations can often be pictured in cross-section by a qualified geologist if he has certain core drill holes upon which to base his overall concept of the geology. However, the plans and specifications should not contain this overall geological concept. Only the logs of the core drill holes should be included for the contractor’s estimates. However, the geological picture of the underlying formations is a great aid in evaluating the dam safety. The appendix consists of excerpts from a geologic report for the site used in the design examples.HydrologyHydrology studies are necessary to estimate diversion requirements during construction, to establish frequency of use of emergency spillways in conjunction with outlets or spillways, to determine peak dischargeestimates for diversion dams, and to provide the basis for power generation. Hydrologic studies are complex; however, simplified procedures may be used for small dams if certain conservative estimates are made to ensure structural safety.Formulas are only a guide to preliminary plans and design computations. The empirical equations provide only peak discharge estimates. However, the designer is more interested in the runoff volume associated with discharge and the time distribution of the flow. With these data, the designer knows both the peak discharge and the total inflow into the reservoir area. This provides a basis for making reliable diversion estimates for irrigation projects, water supply, or power generation.A reliable study of hydrology enables the designer to select the proper spillway capacity to ensure safety. The importance of a safe spillway cannot be overemphasized. Insufficient spillways have caused failures of dams. Adequate spillway capacity is of paramount importance for earthfill and rockfill dams. Concrete dams may be able to withstand moderate overtopping.Spillways release excess water that cannot be retained in the storage space of the reservoir. In the preliminary site exploration, the designer must consider spillway size and location. Site conditions greatly influence the selection of location, type, and components of a spillway. The design flows that the spillway must carry without endangering the dam areequally important. Therefore, study of streamflow is just as critical as the foundation and geological studies of the site.附录2外文翻译混凝土重力坝一个坝址的坝型选择，主要取决于地形、地质、水文和气候条件。
毕业设计-水利外文翻译
英文原文：Water Resources and Hydropower Engineering ConstructionDesign Layout[Key words] construction layout Fuzzy multiple attribute decisionmaking Water Resources and Hydropower Construction[Abstract] Analysis of affecting factors of the construction layout program characteristics that people value in identifying these indicators fuzzy constraints are difficult to give exact values, while decision-making process has been one of psychological, subjective will and the work experience and other aspects influence decision-making process and therefore there is certainly ambiguity.1, Water Resources and Hydropower Engineering Construction Layout FactorsConstruction advantages and disadvantages of the general layout scheme, involving many factors, from different angles to evaluate the evaluation factors generally have two categories, qualitative factors, and quantitative factors of a class. Qualitative factors are mainly: 1. Favorable production, easy to administer, facilitate the degree of life; 2. During the construction process, the degree of co-ordination; 3. The principal impact of construction and operation; 4. Meet the security, fire, flood prevention, environmental protection requirements; 5. Temporary Works and the combination of permanent works and so on. Indicators are mainly quantitative factors;1. Site preparation earthwork quantity and cost;2. The extent of use of earth excavation;3. Temporary works of construction work quantity and cost;4. Workload and a variety of materials, transport costs;5. Size and cost of land acquisition;6. Made to the area to field, the recovery or recycling construction fees.As the construction is construction planning layout content, is that people under work experience, combined with engineering data on the occurrence of a future prediction about. Therefore, both qualitative factors, and the quantitative factors, there is uncertainty. We know that the uncertainty of two different forms; one is uncertain whether the incident occurred in 11 random, the event itself the state of uncertainty 11 ambiguity. Randomness is an external cause in general uncertain, but ambiguity is an inherent uncertainty of the structure. From the information point of view, therandomness involves only the amount of information, while the ambiguity is related to the meaning of information. We can say that ambiguity is more profound than the randomness, the uncertainty more generally, especially in the subjective understanding of areas of role ambiguity is much more important than the role of randomness. Random people for a lot of research has been carried out, achieved fruitful results; while ambiguity was ongoing and in-depth knowledge and research in the. All people involved in the system, carried out by people planning, feasibility studies, evaluation of decision-making, design and management, and therefore, can not ignore the objective world of things in the human brain, one by one to reflect the uncertainty of ambiguity, it is an objective difference intermediate division caused by the transition of a kind of uncertainty. Construction Layout Design is no exception, in the arrangement of construction there are a large number of objective fuzzy factors. For example, the construction of facilities, coordination between the levels of "good" and "general" is an accurate value can not be described. Therefore, the arrangement can not ignore or avoid the construction of the fuzziness existing in the process, but should be objective and deal with ambiguity of this objective, understand the rules for people planning, demonstration, evaluation and decision, design and management to provide a scientific basis and methods.As the construction layout of the content involved in more programs fuzzy factors exist, the traditional construction arrangement he considered the existence of ambiguity, but in decision-making process has fuzzy information precision, not a real fuzzy optimization. Therefore, the program should focus on optimization of fuzzy factors into account, the ambiguity should be reflected in the decision-making on the index, index weights. For quantitative indicators, mainly the amount and cost of the project issues, its value can be found in engineering materials and design documents to determine by calculation, the results are the values of the parameters and experience. As every engineer's understanding of things is not the same experience in a certain range of parameter changes, the results also in a certain range. For qualitative indicators, according to experts, engineering experience, through expert scoring method, set the value of statistics to determine. Such subjective factors, the knowledge structure and decision-making preferences play a major role. But in practice, due to the complexity of objective things and the people's thinking on the use of fuzzy concept, to describe with precision the number becomes very difficult, but with "some", "left"and the like get fuzzy concept to describe the more reasonable. Determine the weights of evaluation indexes, there are many mathematical ways to determine the accurate calculation. We know, for different projects, in the same factors, their importance is not the same, then the mathematical model is difficult to fully reflect the actual situation, the help of experts in engineering experience must be judged.Since the existence of the above ambiguity, avoid or ignore the ambiguity is unscientific, incomplete. Previous index value that decision-making, decision weights for programs for determining the value of the preferred method, there is bound to sidedness and limitations. As technology develops, people are increasingly demanding of precision, the object of study become more complicated, as complicated to some degree after the meaning of the precise cognitive declines and the appropriate fuzzy but accurate. Here, the introduction of fuzzy mathematical tools, the use of modern fuzzy multiple attribute decision making theory, Fuzzy multiple attribute decision making model, can exist for people to consider the ambiguity of the objective, to provide strong support for rational decision-making.2, Water Resources and Hydropower Engineering Construction Design LayoutConstruction Layout as a focus of the system around the concrete layout of the temporary structures. There are 1. All kinds of storage, stockpile and Spoil; 2. Mechanical repair system; 3. Metal structure, mechanical and electrical equipment and construction equipment installed base; 4. Wind, water and electricity supply systems; 5. Other construction plant, such as steel processing, wood processing, prefabricated factory; 6. Office and living space, such as offices, laboratories, dormitories, hospitals, schools, etc.; 7. Fire safety facilities and other, such as fire stations, guard, and security cordon so. At this time, various types of temporary structures should be put forward, the construction of facilities furnished a list of partial pressure, their area, building area and volume of construction and installation; on fertilization with an estimate of land acquisition, land area and the proposed land use plan, the study to reclaiming land in the use of the measures, site preparation earthwork volume calculations, the integrated cut and fill balance of the proposed excavation of the use of effective planning.Construction of facilities in order to avoid conflict between the layouts, construction of facilities in the analysis of adjacency relations, is to analyze the relationship between the construction of facilities, strength of correlation andrelationship. Usually based on the adjacency relationship, consider the construction schedule, construction strength, facilities operation and logistics. Analysis of the size and layout of the construction of facilities present at the location of the ground between the site controlled the indicators are: 1. The scale of construction facilities layout, the main considerations to meet the construction requirements of the case, the construction of facilities, capacity and layout area. 2. Foundation bearing capacity of the construction of facilities to consider geology, slope stability and so on. 3. Hydrological requirements and construction guide closure of the case, consider the different construction periods, flood, water table, water level changes in the construction site layout planning of construction restrictions and impact. 4. The height difference logistics constraints, considering logistics and vertical elevation gradient lines, logistics of import and export. 5. Construction of the distance between these facilities and restrictions, mainly refers to the construction of facilities necessary for running the minimum operating radius, the minimum limit transportation question, minimum import and export logistics, construction and facilities, the safety distance between. 6. Construction site area of internal and external traffic conditions, construction equipment, consider the minimum safe height and width of the transport, building materials inside the transport requirements.To be concrete system facilities arranged in a prominent position, so that interference by the other facilities as small as possible, the need for construction of facilities at this time analysis of the relationship between the adjacent, as many facilities for Hydropower Construction, different facilities have a clear focus on functionality, such as depots, gas stations, etc., if not for the neighbor relations analysis, because the construction of facilities for the inter-functional conflict, construction and project management to bring incalculable damage and safety hazards buried.References:[1] Lu Yu Mei editor of the Three Gorges Dam Construction [M]. Beijing: China Electric Power Press, 2003[2] Wei-Jun Zhu, Zhang Xiaojun and so the overall layout design of the Three Gorges Project Construction [J]. The people of the Yangtze River, 2001.32 (10) :4-5.译文：水利水电工程施工的布置方案设计[关键词]施工布置模糊多属性决策水利水电施工[论文摘要]分析施工布置方案的影响因素特点，指出人们在确定这些指标值时受到模糊性因素的限制很难给出精确值，同时决策过程还受到人们心理、主观意愿和工作经验等多方面的影响，因而决策过程也必然存在模糊性。
毕业设计毕业论文水电站文献翻译中国水利发电的现状和前景中英文对照
外文资料China's hydroelectric power the current situation and prospectsAbstract: The electricity is a modern industrial production and the life of an essential driving force for energy, hydroelectric power industry is a category. The founding of the past 50 years, China's hydropower industry has developed by leaps and bounds, has made remarkable achievements. The rise of hydropower in China there is a profound background.Key words: Hydro-electric power Status ProspectsFirst, China has a large-scale utilization of water resources and the need for the conditions. China's abundant hydropower resources, whether they are reserves of hydropower resources, or the possible development of hydropower resources in the countries in the world in the first rank. But China's energy utilization rate is only 13 percent, hydropower prospects are bright. As China's rapid economic growth, total energy consumption is also up sharply, coal, oil and gas these conventional energy consumption growing, or even need to rely on imports. It is estimated that by 2010 China's need to import about 100 million t of oil, and its dependence on imports will reach 40 percent or even higher. In such a situation, the development of new energy was particularly important and urgent. The water is a renewable and new energy, an inexhaustible supply of it.Second, the development of hydropower is also the need for environmental protection. Conventional power generation, coal combustion emissions in the course of a large number of hazardous substances so that the atmospheric environment is seriously contaminated, and acid rain caused "greenhouse effect", and many other environmental problems. And nuclear power generation have great potential risk, once the pollution caused by leakage, damage to the environment is immeasurable role. Hydro-electric power is not emissions of harmful gases,dust and ash, and no nuclear radiation pollution, is a clean power production, has obvious advantages.Third, hydro-electric power after more than a century of development, construction technology, manufacturing technology and hydro-generator groups in the transmission technology improved, stand-alone capacity has been increased. And low-cost hydro-electric power, running the high reliability, the extremely rapid development.1 Overview of China's hydropower resourcesChina's many rivers, rich runoff, huge gap, contains abundant hydropower resources. According to statistics, China's river water resources reserves 676 million kw, the generating capacity of 592.2 billion kwh; possible development of hydropower resources of the installed capacity of 378 million kw, the generating capacity of 920 billion kwh.Due to climate and topographical factors such as topography of the impact of China's hydropower resources in different regions and different distribution is very uneven Basin; China's hydropower resources of the river is a prominent characteristic of the steep river, the huge gap, originated the "roof of the world" Qinghai-Tibet Plateau of the Yangtze River, Yellow River and Yarlung Zangbo River, Lancang River, Nujiang River, the natural differences are about as high as 5000 m, forming a series of the world's largest rivers divide, which is not found in other countries. Full understanding of the characteristics of China's hydropower resources can be in the development process in light of local conditions, reasonably full use of hydropower resources.2 status quo of China's hydropower developmentA century, particularly since 1949, after several generations of hydropower builders of hard work, China's hydropower construction from small to large and from weak to strong continue to grow and develop. Since reform and opening up, utilities are building more rapid development of projects have been expanding. 1950s to the early 1960s, mainly repairing the dam and power station fullness, Dragon River. Gutian, and other minor works, initiated the development of small and medium hydropower (such as 114-8508, the Huaihe River, Huangtankou, Liuxihe, such as power stations). In the late 1950s in terms gradually mature, a number of rivers cascade development, such as Shizitan, salt Yanguoxia, Tuo River,Xinfengjiang, Xin'anjiang, the West-and cat jumping into a river to river at the works. The mid-1960s to the late 1970s during the period has started Gongzui, Yingxiuwan, Wujiangdu, Bikou, Fung Beach, Longyangxia, Baishan, Dahua and other projects. The early 1970s first 1000 MW installed capacity of the Liujiaxia Hydropower Station production. 2715 MW capacity of the 1980s the completion of the Gezhouba Hydropower Station, after a series of big hydropower stations have been building, 18200 MW capacity of the Three Gorges Project has started in 1994 and by the end of 2000, the 1000 MW larger than the largest hydropower station (not including Storage Power Station) has 18.In addition to conventional hydropower station, China's pumped-storage power station building has made great achievements. Pumped Storage Power Station was built in the main hydraulic fewer resources, to meet the needs of the power system peak load regulation. The construction of the main Pumped Storage Power Station are as follows:Guangzhou Pumped Storage Power Station to the total capacity of 2.4 million kw, is the first Block is currently the world's largest pumped-storage power station. Power station construction in two phases with a total capacity of eight, each lasting four and a capacity of 300,000 kw reversible high parameters of pumped storage units, the design of head 535 m, rated speed 500 r / min, comprehensive efficiency of 76 percent.Jiang Tianhuangping Pumped Storage Power Station, a total installed capacity of 1.8 million kw, a regulation on pure pumped storage power station, power consumption, pumping 4.28 billion kwh. North China Power Grid's largest pumped-storage power plant Ming Tombs Pumped Storage Power Station, "the Ming Tombs Reservoir" for the next pool, using plastic concrete cutoff wall hanging seepage control technology, power plants to install four 200,000 kw Francis River inverse-turbine pumps, an electric generating units, the installed capacity of 800,000 kw.Hebei Panjiakou hybrid pumped-storage power station, equipped with a conventional Taiwan 150,000 kw hydro-generator group, there are three pumped-storage units, each of 90,000 kw, total installed capacity of 420,000 kw.In addition, China's construction in Tibet also has the world's highest Pumped Storage Power Station Yangzhuoyong Lake pumped-storage power station. Pumped Storage PowerStation is also available in other Baoquan pumped storage power plant in Henan, Anhui Langyashan Pumped Storage Power Station, Shandong Taian Pumped Storage Power Station, Tongbai Pumped Storage Power Station in Zhejiang, Yixing in Jiangsu Pumped Storage Power Station, Hebei Zhang Nihewan Pumped Storage Power Station.3 China's hydropower development problems facing theChina's hydropower industry in nation-building after a considerable development, but there are still many problems. For example, the Ertan Hydropower Station in Sichuan Province since 1949 is the most intensive investment, the largest engineering, technical difficulty of the highest building projects, but an operation on the face of the enormous waste of resources and enterprises to huge losses this embarrassing position. The situation prevailing in China's hydropower station. The reasons were mainly the following points.First, the management system, a high degree of monopoly power industry system hindered the development of hydropower. China's Ministry of Water Resources and Ministry of Water and Power and management, and water conservancy and hydroelectric power is the power of the integrated projects, but the Ministry and its subordinate electric power throughout the production and scheduling system none of the staff from thermal power systems, power industry from nature Or that a high degree of monopoly industries, enterprises full control of a single power scheduling, power distribution, electricity sales, electricity billing and other powers. At the same time the electricity market in the period of relative surplus of hydroelectric power, thermal power contradiction between the very sharp and in China under the present circumstances, the priority use of hydropower resources can not be guaranteed, a large number of hydropower resources have been wasted. Hydropower and the Internet generally low tariffs, we can imagine the state of hydropower stations. Opening up the electricity market, breaking the monopoly of the power industry system, water and electricity problem is to solve the fundamental way. At the same time, the Internet tariff for water and electricity reform, "debt service tariff" that electricity tariff structure to a single bi-use electricity price of the electricity tariff structure.Secondly, in the current economic interests, the number of thermal power production, with the size of the economic benefits are directly related to mine. China's long-term mainly to thermal power, thermal power plants with their long-established fixed in a coal mine, if weuse water and electricity to replace thermal power, thermal power plants will face not only the pressure, coal will face great pressure, resulting in thermal power plants and coal mines Two aspects of the economic difficulties. Therefore, departments or units by the economic interests of the drive to form a "protective thermal power and hydropower light" situation, and this caused a lot of hydropower resources have been wasted, and even disposable loss of electricity consumption significantly higher than the actual Internet.Third, technically, since the peak shaving or water and electricity load rejection is relatively easy, even a few minutes to complete the start-up of large hydropower generating units and electricity networks, or stopping, and at the same level of capacity thermal power unit may need a few 10 hours to complete the start or stop. Therefore, in the scheduling grid, the hydropower generating units are often used to peak shaving or backup units, in sufficient water to flood when the power generation, but its importance in the era of conventional power generation applications, resulting in the huge waste of water and electricity.In short, the cause of China's water and electricity problems faced by people in the final analysis is ideologically not aware of the need for the development of hydropower and urgency of water and electricity often because there are one-time investment objective, long construction period, less completed early return The characteristics, and only on the immediate economic interests, water and electricity to the development of multiple objective of the resistance. Therefore, we should vigorously promote the development of hydropower in China is by the great significance of changing the concept of water and electricity, essentially wiping out all kinds of obstacles.4 China's hydropower development prospectsWith the deepening of reform and national economic development, China's electricity market situation has undergone fundamental changes from the previous power and capacity of the "double vacancy" into a relative surplus of electricity and peak shaving a serious shortage of capacity, to the development of hydropower A good opportunity.4.l general principleNow and in the future some time, China's hydropower development should be the main priority and good regulation of hydropower stations and power industry from all socio-economic development point of view and consider comprehensive study on hydropower development and strength and to prevent waste; reasonable evaluation Pumped Storage Utility economic benefits, fully aware of the pumped-storage power station filled valley, peak shaving, FM, PM, incidents such as back-up role in the importance of coordinated development in the eastern part of the pumped-storage power station; further strengthen water and electricity "basins, Cascade, and rolling, comprehensive "way of development; pay more attention to ecological problems.4.2 ladder to development and construction of hydropower baseChina's hydropower resources are mainly located in the western region, accounting for more than three quarters, but the current development rate of eight percent. Especially Yunnan Province, the province's total installed hydropower capacity can be developed about 90 million kw, the country's total installed capacity of hydropower development can be 23.8 percent, ranking the second in the provincial water resources are mainly located in the Jinsha River, Lancang River, Nujiang River, Pearl River, Red River and the Irrawaddy, such as Jiang's six major river systems, in western China is the most potential for hydropower development of the main provinces. However, Yunnan Province's industrial base is relatively backward, electricity and water resources are mainly located in the inconvenience of cross mountains, the development more difficult. With the great western development strategy for the implementation of the West, East project will lose the activation of the rich hydropower resources, and promote the cause of China's hydropower development. Yunnan Province to play the regional advantages, to build China's hydropower energy base, and the West, East lose, both local economic development to meet the demand for electricity, but also optimize the country's energy structure.At present, Chuan Xinan than the total installed capacity of the Three Gorges Power Station is also a 600,000 kw of the Xiluodu and Xiangjiaba hydropower station two giant project formally approved by the State Council, which will be China's largest hydropower base. Luobo River Power Station in Leibo County in Sichuan Province and Yongshan County in Yunnan Province at the junction of the design capacity of 12.6 million kw, the average annual generating capacity of 57.12 billion kwh; Xiangjiaba Hydropower Station located in Yibin County, Sichuan Province and Yunnan Province Fuxian water at the junction, thecapacity of 6 million kw, the average annual generating capacity of 30.7 billion kwh. That the construction of two power stations with a strong ability to adjust, less farmland inundated, immigration and other less one of the advantages of large-scale hydropower stations. The two giant hydropower station project marks the official start of China's large-scale development of hydropower resources of the upper reaches of the Yangtze River, the upper reaches of the Yangtze River hydropower resources development will greatly improve China's power structure, lay the West, the East lost the general pattern of nationwide The energy balance and optimize the allocation.4.3 continue to attach importance to the development of small hydropowerChina's small hydropower resources are very rich reserves of around 150 million kw, to develop capacity is about more than 70 million kw, in the corresponding generation of about 200 billion - 250 billion kwh. Small Hydropower in addition to large-sized hydropower is not the atmospheric pollution, the use of renewable energy without the worry of energy depletion, low-cost advantages of its resources, He scattered on the negative impact on the ecological environment, the technology is mature, less investment, easy to build, Therefore suitable for the rural and mountainous areas, especially rural and mountainous areas in developing countries.China, as developing countries, small hydropower construction has made great achievements, to the end of 1997, China's total installed capacity of small hydropower has reached 20.52 million kw, the generating capacity of 68.3 billion kwh. Small hydropower construction in most cases can be the local building materials to absorb the local labor force building, thereby reducing construction costs, and easier to standardize their equipment, can reduce the cost and shorten the construction period, no complicated expensive technology is conducive to China's economic underdevelopment in the mountains and Achieving rural electrification, which should continue to attach importance to its development and construction.中国水利发电的现状和前景摘要：电力是现代化工业生产和生活不可或缺的动力能量，水力发电是电力工业的一个门类。
水利水电英语课文翻译
水利水电英语课文翻译水利水电英语课文翻译课文翻译需要掌握一定的词汇和技巧，当然英语课文翻译可以帮助提高学生的英语水平。
以下是店铺整理的水利水电英语课文翻译，欢迎阅读。
水利水电英语课文翻译1：Lesson 1 importance of water 水的重要性Water is best known and most abundant of all chemical compounds occurring in relatively pure form on the earth‘s surface. Oxygen, the most abundant chemical element, is present in combination with hydrogen to the extent of 89 percent in water. Water covers about three fourths of the earth's surface and permeates cracks of much solid land. The Polar Regions are overlaid with vast quantities of ice, and the atmosphere of the earth carries water vapor in quantities from 0.1 percent to 2 percent by weight. It has been estimated that the amount of water in the atmosphere above a square mile of land on a mild summer day is of the order of 50,000 tons.在地球表面以相对纯的形式存在的一切化合物中，水是人们最熟悉的、最丰富的一种化合物。
水利水电毕业设计外文文献翻译
水工建筑物，29卷，9号，1995旋涡隧道溢洪道。
液压操作条件M . A .戈蓝，B. zhivotovskii，我·诺维科娃，V . B .罗季奥诺夫，和NN罗萨娜娃隧道式溢洪道，广泛应用于中、高压液压工程。
因此研究这类溢洪道这是一个重要的和紧迫的任务，帮助在水工建筑中使用这些类型的溢洪道可以帮助制定最佳的和可靠的溢洪道结构。
有鉴于此，我们希望引起读者的注意，基本上是新的概念（即，在配置和操作条件），利用旋涡流溢洪道[1，2，3，4 ]。
一方面，这些类型的溢洪道可能大规模的耗散的动能的流动的尾段。
因此，流量稍涡旋式和轴向流经溢洪道的尾端，不会产生汽蚀损害。
另一方面，在危险的影响下，高流量的流线型面下降超过长度时，最初的尾水管增加的压力在墙上所造成的离心力的影响。
一些结构性的研究隧道溢洪道液压等工程rogunskii，泰瑞，tel'mamskii，和tupolangskii液压工程的基础上存在的不同的经营原则现在已经完成了。
这些结构可能是分为以下基本组：-涡旋式（或所谓的single-vortex型）与光滑溢洪道水流的消能在隧道的长度时的研究的直径和高度的隧道；参看。
图1），而横截面的隧道是圆或近圆其整个长度。
涡旋式溢洪道-与越来越大的能量耗散的旋涡流在较短的长度- <（60——80）高温非圆断面导流洞（马蹄形，方形，三角形），连接到涡室或通过一个耗能（扩大）室（图2）[ 5，6 ]或手段顺利过渡断[ 7]；-溢洪道两根或更多互动旋涡流动耗能放电室[ 8 ]或特殊耗能器，被称为“counter-vortex耗能”[ 2，4 ]。
终端部分尾水洞涡流溢洪道可以构造的形式，一个挑斗，消力池，或特殊结构取决于流量的出口从隧道和条件的下游航道。
液压系统用于的流量的尾管可能涉及可以使用overflowtype或自由落体式结构。
涡旋式溢洪道光滑或加速[ 7 ]能量耗散的整个长度的水管道是最简单和最有前途的各类液压结构。
水利水电专业毕业设计外文翻译
毕业设计（论文）外文翻译题目水库及电力系统简介专业水利水电工程班级2007级四班学生陈剑锋指导教师杨忠超重庆交通大学2011 年RESERVOIRSWhen a barrier is constructed across some river in the form of a dam, water gets stored up on the upstream side of the barrier, forming a pool of water, generally called a reservoir.Broadly speaking, any water collected in a pool or a lake may be termed as a reservoir. The water stored in reservoir may be used for various purposes. Depending upon the purposes served, the reservoirs may be classified as follows: Storage or Conservation Reservoirs.Flood Control Reservoirs.Distribution Reservoirs.Multipurpose reservoirs.(1) Storage or Conservation Reservoirs. A city water supply, irrigation water supply or a hydroelectric project drawing water directly from a river or a stream may fail to satisfy the consumers’ demands during extremely low flows, while during high flows; it may become difficult to carry out their operation due to devastating floods. A storage or a conservation reservoir can retain such excess supplies during periods of peak flows and can release them gradually during low flows as and when the need arise.Incidentally, in addition to conserving water for later use, the storage of flood water may also reduce flood damage below the reservoir. Hence, a reservoir can be used for controlling floods either solely or in addition to other purposes. In the former case, it is known as ‘Flood Control Reservoir’or ‘Single Purpose Flood Control Reservoir’, and in the later case, it is called a ‘Multipurpose Reservoir’.(2) Flood Control Reservoirs A flood control reservoir or generally called flood-mitigation reservoir, stores a portion of the flood flows in such a way as to minimize the flood peaks at the areas to be protected downstream. To accomplish this, the entire inflow entering the reservoir is discharge till the outflow reaches the safe capacity of the channel downstream. The inflow in excess of this rate is stored in stored in the reservoir, which is then gradually released so as to recover the storage capacity for next flood.The flood peaks at the points just downstream of the reservoir are thus reduced by an amount AB. A flood control reservoir differs from a conservation reservoir only in its need for a large sluice-way capacity to permit rapid drawdown before or after a flood.Types of flood control reservoirs. There are tow basic types of flood-mitigation reservoir.Storage Reservoir or Detention basins.Retarding basins or retarding reservoirs.A reservoir with gates and valves installation at the spillway and at the sluice outlets is known as a storage-reservoir, while on the other hand, a reservoir with ungated outlet is known as a retarding basin.Functioning and advantages of a retarding basin:A retarding basin is usually provided with an uncontrolled spillway and anuncontrolled orifice type sluiceway. The automatic regulation of outflow depending upon the availability of water takes place from such a reservoir. The maximum discharging capacity of such a reservoir should be equal to the maximum safe carrying capacity of the channel downstream. As flood occurs, the reservoir gets filled and discharges through sluiceways. As the reservoir elevation increases, outflow discharge increases. The water level goes on rising until the flood has subsided and the inflow becomes equal to or less than the outflow. After this, water gets automatically withdrawn from the reservoir until the stored water is completely discharged. The advantages of a retarding basin over a gate controlled detention basin are:①Cost of gate installations is save.②There are no fates and hence, the possibility of human error and negligence in their operation is eliminated.Since such a reservoir is not always filled, much of land below the maximum reservoir level will be submerged only temporarily and occasionally and can be successfully used for agriculture, although no permanent habitation can be allowed on this land.Functioning and advantages of a storage reservoir:A storage reservoir with gated spillway and gated sluiceway, provides more flexibility of operation, and thus gives us better control and increased usefulness of the reservoir. Storage reservoirs are, therefore, preferred on large rivers which require batter controlled and regulated properly so as not to cause their coincidence. This is the biggest advantage of such a reservoir and outweighs its disadvantages of being costly and involving risk of human error in installation and operation of gates.(3) Distribution Reservoirs A distribution reservoir is a small storage reservoir constructed within a city water supply system. Such a reservoir can be filled by pumping water at a certain rate and can be used to supply water even at rates higher than the inflow rate during periods of maximum demands (called critical periods of demand). Such reservoirs are, therefore, helpful in permitting the pumps or water treatment plants to work at a uniform rate, and they store water during the hours of no demand or less demand and supply water from their ‘storage’ during the critical periods of maximum demand.(4) Multipurpose Reservoirs A reservoir planned and constructed to serve not only one purpose but various purposes together is called a multipurpose reservoir. Reservoir, designed for one purpose, incidentally serving other purpose, shall not be called a multipurpose reservoir, but will be called so, only if designed to serve those purposes also in addition to its main purpose. Hence, a reservoir designed to protect the downstream areas from floods and also to conserve water for water supply, irrigation, industrial needs, hydroelectric purposes, etc. shall be called a multipurpose reservoir.水库拦河筑一条像坝的障碍时，水就被拦蓄在障碍物的上游并形成水塘．通常称之为水库。
建筑设计：水利水电工程专业(水文与水资源篇)中英文对照翻译
水利水电工程专业〔水文与水资源篇〕中英文对照翻译水利水电工程专业〔水文与水资源篇〕中英文对照翻译1. Hydrological Cycle and BudgetHydrology is an earth science. It encompasses the occurrence, distribution, movement, and properties of the waters of the earth and theirenvironmental relations. Closely allied fields include geology, climatology, meteorology and oceanography.水文学是一门地球科学。
它包含地球水资源的发生、分布、运动和特质，以及其环境关系。
与之密切相关领域包括地质学，气候学，气象学和海洋学。
The hydrologic cycle is a continuous process by which water is transported from the oceans to the atmosphere to the land and back to the sea. Manysub-cycles exist. The evaporation of inland water and its subsequent precipitation over land before returning to the ocean is one example. The driving force for the global water transport system is provided by the sun, which furnishes the energy required for evaporation. Note that the water quality also changes during passage through the cycle; for example, sea water is converted to fresh water through evaporation.水文循环是一个连续的过程，在这个过程中水从海洋被运输到大气中，降落到陆地，然后回到海洋。
华北水利水电大学水利水电工程毕业设计外文翻译
DESIGN CONSIDERATIONS OF A HIGH ROCKFILL DAMNAM NGUM 2 CFRD, LAO PDRRuedi Straubaar1, Eva van Gunsteren2 and Stephen Moll31Geotechnical and Dam Engineering Expert, Pöyry Energy Ltd. (formerly Electrowatt Engineering Ltd.)Hardturmstrasse 161, CH-8037 Zurich, SwitzerlandE-mail: ruedi.straubhaar@2 Project Engineer and Assistant Project Manager for Nam Ngum 2, Pöyry Energy Ltd. (formerly Electrowatt Engineering Ltd.) Hardturmstrasse 161, CH-8037 Zurich, SwitzerlandE-mail: eva.van-gunsteren@3 Dam Engineer, Pöyry Energy Ltd. (formerly Electrowatt Engineering Ltd.) Hardturmstrasse 161,CH-8037 Zurich, SwitzerlandE-mail: stephen.moll@Abstract: Nam Ngum 2 dam, a large concrete face rock fill dam (CFRD) of 182 m height, is under construction and impounding is scheduled to start at beginning of April 2010. The dam is situated in a narrow valley and founded on sedimentary rock of variable strength.Dam design principles comprising dam zoning, face slab design and instrumentation are outlined. Foundation treatment including groutingand measures below the plinth are presented. The properties of the available rockfill materials and their influence on the dam zoning are discussed.Emphasis is given to the rockfill properties and placement procedures which influence dam behaviour during construction, impounding and operation.Key words: CFRD, Rockfill, Face Slab, Instrumentation1Nam Ngum 2 Hydropower SchemeThe Nam Ngum 2 (NN2) hydropower scheme is located on the Nam Ngum river in Lao PDR, about90 km north of the capital city of Vientiane and some 35 km upstream of the existing Nam Ngum 1dam and powerhouse. With an installed capacity of 615 MW, the project will produce energy for the Thai electricity grid. A significant component of the scheme is the 182 m high concrete face rock fill dam, with a volume of 9.5 M m3 and a crest length of 500 m. The dam will impound a reservoir with a volume of approximately 4.2 M m3.Construction of the NN2 Project commenced in late 2005 and is scheduled for completion in the second half of 2010. Rock fill placement in the dam body commenced in January 2008, and will be finished in early November 2009. Face slab construction, which is divided into an upper and lower stage, commenced in December 2008 and will becompleted by beginning of April 2010, when impounding will begin. The reservoir will fill during one rainy season, enabling commissioning to take place during the second half of 2010.2Considerations with respect to dam deformationsConcrete face rock fill dams are considered inherently safe for a wide range of weak and strong rock fill (Cooke 1991) and deformation of the rock fill is often assumed not being a governing concern provided the dam is well engineered and the dam foundation is of adequate quality. It is often assumed that dam settlements are a simple function of the dam height and that they are not likely to exceed 1 % of the compacted fill height with horizontal deformations less than 50 % of the settlements. Predictions are also often made based on laboratory tests and dam deformation analyses.2.1 Rock fill testing performed for NN2 CFRDFor the construction of the NN2 dam quarried rock of sedimentary formations are available. The source material, consisting basically of sandstone and siltstone, has been investigated by drilling, quarry trials, laboratory testing and trial embankment construction. The essential tests are index property tests, compressive strength and basic friction angle tests. Tests were also performed on saturated specimen, which normally gives more representative lower values.Of particular interest are always large scale triaxial and compressibility tests, which have been carried out for NN2 by the IWHR1 in China.2.2 Dam analyses and zoning of NN2 CFRDTest results from the IWHR as well as results from the AIT2 and site laboratories were used as basis for dam analyses. Stability as well as 2D and 3D deformation analyses were carried out by the IWHR. Based on the results of the analyses and also based on visual observation which indicated a very high desintegration potential of the siltstone, it had to be concluded that only sandstone is suitable as rock fill for the construction of the high embankment. By using only sandstone for rock fill it was concluded that the dam deformation will be within acceptable and normal limits.During construction it was observed that also fine grained sandstone, porous or weathered sandstone of moderate quality is being obtained from quarrying which can not always completely be separated and wasted. Therefore the dam zoning was adjusted to permit also placement of lower quality rock fill in the central part of the dam embankment. The adjusted dam zoning is shown in Figure 2.3 Observed deformations on constructed damsOften it is assumed that for strong rock fills the settlements are small,less than about 1% of the fill height. It is further commonly assumed that the settlements develop essentially during construction.Although these assumptions were correct for many dams, a few dams did show much more settlements (Kjaernsli et al. 1992). More recent data of observed crest settlements are presented in Figure 3.For the 165 m high Atatürk dam in Turkey high post construction settlements developed. The post construction settlement rate of 0.02 % per year, which can be considered as maximum acceptable creeping pace after impounding, is even 10 years after completion of construction still exceeded.It has to be taken as a fact that deformations often exceed common values and are not always predictable. Laboratory tests are restricted to small maximum particle sizes and do not always reflect the behaviour of large size rock fill.4 Factors influencing the deformations of rock fill damsFactors influencing the magnitude of settlements are discussed in the following. Some information are taken from an unpublished research by Victor Milligan and Lisa Coyne “Review of factors influencing the settlement of rock fill dams”.4.1 Particle size and shapeThere is evidence that the modulus of deformation increases withincreasing particle size. Tests by Marachi et al. (1969) indicated that compressibility is highest for 150 mm particle size and least for 12 mm particle size. It has to be assumed that for particle sizes exceeding 150 mm the compressibility will further increase. A similar effect has to be assumed for the shear strength of rock fill. Increasing particle size somewhat reduces the shear strength depending on the basic characteristics of the source rock.The effect of particle shape on compressibility is well known. McDowell et al. (2004) stated that the “particle shape seems to have a greater effect (on compressibility) than mineralogy”. There is a pronounced reduction in modulus as the particle shape changes from rounded to angular.4.2 Gradation and state of packingIt is well known that uniformly graded rock fill is much more compressible than broadly graded rock fill. In general a uniformity coefficient of 30 is desired to obtain a reasonable gradation.Gradation and density have an essential effect on the state of packing.4.3 Wetting and compactionThe method of rock fill placement has a considerable influence on the compressibility of the rock fill.Water added to the rock fill weakens the rock and induces breakage and crushing of the rock particles, inparticular if the rock fill particles have a relatively high porosity. This will in general cause increased settlement and result in an increase of the long term stiffness of the fill. It is also well known that with smaller lift thicknesses and increased compaction energy the dam deformations are reduced.4.4 Effects of degradationDegradation depends on the stress level and the strength of the rock particles. Under a given stress level, the breakage of rounded particles is much less than that of angular particles. Well graded rounded particles have more contact points and thus experience less stress at contact points. In contrast uniform and sharply shaped particles experience much higher stresses at contact points with an increasing potential for particle breakage and creep.4.5 Predicted versus observed settlementsAlthough the various factors affecting the compressibility of rockfill are well known, it is not always possible to predict the dam deformation with the desired reliability. Laboratory testing and analytical modeling may not be sufficient to conclude on the dam behaviour, in particular the long term creeping of the structure. It is a fact that the observed deformation can exceed the predicted ones.Some of the factors influencing the compressibility can be controlledby the construction methodology. Other factors as the particle shape and strength can not be influenced, they are rather given by the rock type.Important is an adequate instrumentation of the dam and to compare the observed behaviour of the dam with the predictions and observations.4.6 Rock fill used at NN2For NN2, the conditions of the rock fill are as follows:- The particle size of the rock fill is relatively large and the particle shape is quite angular.- The gradation of the rock fill is often uniform and gap-graded, with a lack of rock fragments of gravel size.- The densities obtained after placement are adequate, although segregated areas observed may lead to increased post construction settlements.- Due to the gap grading and the high sand content, wetting of the fill leads to the development of a mud layer on the rock fill surface, which needs to be removed.- The amount of water effectively added to the fill is around 100-150 l/m3 which is considerably lower than the initially foreseen amount of 250 l/m3.The currently available information from settlement monitoring data indicate that there is a significant increase of settlements at higher stresslevels and also a tendency of quite pronounced creep settlements. The modulus of deformation during construction has decreased from initial values as high as 150 to 200 MPa to currently quite low to moderate values of around 30 to 70 MPa.5 Foundation TreatmentThe geological formations at the dam site consist of medium bedded to massive cliff-forming sandstone and interbedded thin to thick bedded siltstone. Three easterly trending folds whose axes are nearly perpendicular to the Nam Ngum river are present at the dam site. The cliff-forming sandstone is generally slightly jointed to massive, whereas the interbedded siltstone is moderately to closely jointed. The quality of the foundation rock varies within the following limits:- Sandstone: fresh, hard and slightly fractured to weathered and heavily fractured.- Siltstone: fresh and hard to weathered, soft and slaking.The foundation treatment at Nam Ngum 2 mainly aims on:- Positive control of seepage below the plinth.- Providing a stable and non-erodible foundation beneath and around the plinth.- Protection of foundation rock susceptible to erosion.- Levelling of abrupt irregularities in the dam foundation and very steep abutment slopes to reduce differential settlements.With respect to foundation treatment requirements the embankment foundation is divided into three areas. The foundation for the plinth is considered separately since it has more stringent requirements for rock quality and preparation.The upstream third of the embankment is founded on fresh to slightly weathered rock. The central part of the embankment is founded on slightly to moderately weathered rock. The requirements for the downstream third are less rigorous, and the foundation on moderately weathered rock is acceptable. At the riverbed the present dense alluvium of maximum 15 m thickness was left in place only in the central part of the dam body.Particular attention is paid to areas where the foundation of the dam consists of siltstone or highly weathered or intensively fractured sandstone. Such foundation rock is susceptible to erosion requires special protection. For this purpose a 100 mm wire mesh reinforced shotcrete blanket, covered by filters, is provided to cover the erodible rock within the foundation downstream of the plinth up to a distance of 0.3 H (H = reservoir head) from the plinth. In addition, and within the entire dam foundation area up to the downstream slope erodible foundation rock is。
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毕业设计水利水电工程英文文献翻译外文文献：hydraulicturbines and hydro-electric powerAbstractPower may be developed from water by three fundamental processes : by action of its weight, of its pressure, or of its velocity, or by a combination of any or all three. In modern practice the Pelton or impulse wheel is the only type which obtains power by a single process the action of one or more high-velocity jets. This type of wheel is usually found in high-head developments. Faraday had shown that when a coil is rotated in a magnetic field electricity is generated. Thus, in order to produce electrical energy, it is necessary that we should produce mechanical energy, which can be used to rotate the ‘coil’. The mechanical energy is produced by running a prime mover (known as turbine ) by the energy of fuels or flowing water. This mechanical power is converted into electrical power by electric generator which is directly coupled to the shaft of turbine and is thus run by turbine. The electrical power, which is consequently obtained at the terminals of thegenerator, is then transited to the area where it is to be used for doing work.he plant or machinery which is required to produce electricity (i.e. prime mover +electric generator) is collectively known as power plant. The building, in which the entire machinery along with other auxiliary units is installed, is known as power house.Keywords hydraulic turbines hydro-electric power classification of hydel plantshead schemeThere has been practically no increase in the efficiency of hydraulic turbines since about 1925, when maximum efficiencies reached 93% or more. As far as maximum efficiency is concerned, the hydraulic turbine has about reached the practicable limit of development. Nevertheless, in recent years, there has been a rapid and marked increase in the physical size and horsepower capacity of individual units.In addition, there has been considerable research into the cause and prevention of cavitation, which allows the advantages of higher specific speeds to be obtainedat higher heads than formerly were considered advisable. The net effect of this progress with larger units, higher specific speed, and simplification and improvements in design has been to retain for the hydraulic turbine the important place which it has long held at one of the most important prime movers.1. types of hydraulic turbinesHydraulic turbines may be grouped in two general classes: the impulse type which utilizes the kinetic energy of a high-velocity jet which acts upon only a small part of the circumference at any instant, and the reaction type which develops power from the combined action of pressure and velocity of the water that completely fills the runner and water passages. The reaction group is divided into two general types: the Francis, sometimes called the reaction type, and the propeller type. The propeller class is also further subdivided into the fixed-blade propeller type, and the adjustable-blade type of which the Kaplan is representative.1.1 impulse wheelsWith the impulse wheel the potential energy of thewater in the penstock is transformed into kinetic energy in a jet issuing from the orifice of a nozzle. This jet discharge freely into the atmosphere inside the wheel housing and strikes against the bowl-shaped buckets of the runner. At each revolution the bucket enters, passes through, and passes out of the jet, during which time it receives the full impact force of the jet. This produces a rapid hammer blow upon the bucket. At the same time the bucket is subjected to the centrifugal force tending to separate the bucket from its disk. On account of the stresses so produced and also the scouring effects of the water flowing over the working surface of the bowl, material of high quality of resistance against hydraulic wear and fatigue is required. Only for very low heads can cast iron be employed. Bronze and annealed cast steel are normally used.1.2 Francis runnersWith the Francis type the water enters from a casing or flume with a relatively low velocity, passes through guide vanes or gates located around the circumstance, and flows through the runner, from which it discharges into a draft tube sealed below the tail-water level. All therunner passages are completely filled with water, which acts upon the whole circumference of the runner. Only a portion of the power is derived from the dynamic action due to the velocity of the water, a large part of the power being obtained from the difference in pressure acting on the front and back of the runner buckets. The draft tube allows maximum utilization of the available head, both because of the suction created below the runner by the vertical column of water and because the outlet of he draft tube is larger than the throat just below the runner, thus utilizing a part of the kinetic energy of the water leaving the runner blades.1.3 propeller runnersnherently suitable for low-head developments, the propeller-type unit has effected marked economics within the range of head to which it is adapted. The higher speed of this type of turbine results in a lower-cost generator and somewhat smaller powerhouse substructure and superstructure. Propeller-type runners for low heads and small outputs are sometimes constructed of cast iron. For heads above 20 ft, they are made of cast steel, a much more reliable material. Large-diameter propellers。