What Are Water Turbines?

Hydraulic turbine is a power machine that converts the energy of water flow into rotating mechanical energy. It belongs to turbine machinery in fluid machinery. As early as around 100 BC, the embryonic form of water turbineswater wheelswas used to raise irrigation and drive grain processing equipment. Modern water turbines are mostly installed in hydropower stations to drive generators to generate electricity. In a hydropower station, the water in the upstream reservoir is directed to the turbine through a water diversion pipe, pushing the turbine runner to rotate and driving the generator to generate electricity. The finished water is discharged downstream through the tailpipe. The higher the head and the greater the flow, the greater the output of the turbine. ^[1]

Hydraulic turbine is a power machine that converts the energy of water flow into rotating mechanical energy. It belongs to turbine machinery in fluid machinery. As early as around 100 BC, the embryonic form of water turbineswater turbineswas used to raise irrigation and drive grain processing equipment. Modern water turbines are mostly installed in hydropower stations to drive generators to generate electricity. In a hydropower station, the water in the upstream reservoir is directed to the turbine through a water diversion pipe, pushing the turbine runner to rotate and driving the generator to generate electricity. The finished water is discharged downstream through the tailpipe. The higher the head and the greater the flow, the greater the output of the turbine. ^[1]

Chinese name: Water turbine
Foreign name: hydroturbine

Function: Converting the energy of water flow into rotating mechanical energy
Use: Power generation
Nature: Mechanical engineering terminology

Turbine development

Water turbines and auxiliary equipment are important hydropower equipments, an indispensable component of the hydropower industry, and important equipment that make full use of clean and renewable energy to achieve energy conservation, emission reduction, and environmental pollution reduction. Its technological development is in line with the development scale of China's hydropower industry. adapt. Driven by the strong demand of China's electric power, China's water turbine and auxiliary machinery manufacturing industry has entered a period of rapid development, and its economic scale and technical level have significantly improved. China's water turbine manufacturing technology has reached the world's advanced level. ^[1]

The comprehensive strength of China's hydraulic turbine and auxiliary machinery manufacturing industry has increased significantly, and the entire industry has shown a booming and vibrant situation. The improvement of the industry is reflected in the improvement in the quality of economic operations and the significant increase in economic benefits. In 2010, there were 68 enterprises in China's hydro turbine and auxiliary machinery manufacturing industry above the designated size (with annual sales revenue of more than 5 million yuan), achieving sales revenue of 4.470 billion yuan, a year-on-year increase of 2.35%; total profit of 323 million yuan, a year-on-year increase of 4.16% . ^[1]

In 2010, China s hydropower installed capacity reached 211 million kilowatts, with a newly-approved hydropower scale of 13.22 million kilowatts and a construction scale of 77 million kilowatts. According to China's commitment to the international community that "non-petrochemical energy will reach 15% of total energy in 2020", China's hydropower industry must have an installed capacity of 380 million kilowatts in 2020. And even in accordance with the Medium and Long-Term Development Plan for Renewable Energy announced by China, it is determined that the installed hydropower capacity will reach 300 million kilowatts by 2020, and there will be nearly 300 large hydropower units with a single unit capacity of more than 50 kilowatts in China in 11 years, with an average annual Newly installed 25 large hydropower units of 500,000 kilowatts and above. If the installed capacity of 380 million kilowatts is reached in 2020, China's required water turbines and auxiliary equipment will further increase, and China's water turbine and auxiliary machinery industry has a bright future. ^[1]

Historical development of water turbines

When the water flow of the early impact turbines hit the blades, the kinetic energy was lost and the efficiency was not high. 1889

Turbines (2 photos)

In the year, American engineer Pelton invented the water bucket turbine, which has a streamlined convergent nozzle, which can efficiently convert the energy of the water stream into the kinetic energy of a high-speed jet. The best of water turbines (the entire paragraph can be omitted, 80% of the paragraph above is outdated and replaced. Very old information, the reference value is not great, so it is recommended to remove this paragraph) In the early 1980s, The world's largest stand-alone water bucket turbine was installed at the Sisma power station in Norway. It has a stand-alone capacity of 315 MW, a head of 885 meters, and a speed of 300 rpm. It was put into operation in 1980. The bucket head turbine with the highest head is installed at the Reiserk Mountain Power Station in Austria. Its single power is 22.8 MW, the speed is 750 rpm, and the head is 1763.5 meters. It was put into operation in 1959. ^[1]

In the 1980s, the world's largest propeller-type turbine was manufactured by China Dongfang Electric Works and installed at the Gezhouba Hydropower Station in the middle reaches of the Yangtze River in China. Its single power is 170 MW, the head is 18.6 meters, and the speed is 54.6 rpm. The wheel has a diameter of 11.3 meters and was put into operation in 1981. The world's highest-head propeller turbine was installed at the Nambia power station in Italy. Its head is 88.4 meters, the stand-alone power is 13.5 MW, and the speed is 375 rpm. It was put into operation in 1959. ^[1]

The mixed-flow turbine with the highest water head in the world was installed at the Rossheim power station in Austria. It has a water head of 672 meters and a single power of 58.4 MW. It was put into operation in 1967. The mixed-flow turbine with the largest power and size is installed in the Takuli Third Power Station in the United States. Its single power is 700 MW, the diameter of the runner is about 9.75 meters, the head is 87 meters, and the speed is 85.7 rpm. It was put into operation in 1978. run. ^[1]

The world's largest mixed-flow pump turbine is installed at the Bremen Energy Storage Power Station in Federal Germany. The water head of the turbine is 237.5 meters, the generator power is 660 MW, and the rotation speed is 125 rpm; the pump head is 247.3 meters, the motor power is 700 MW, and the rotation speed is 125 rpm. ^[1]

The world's largest diagonal flow turbine is installed at the Jieya Power Station in the Soviet Union, with a single power of 215 MW and a water head of 78.5 meters. ^[1]

Hydro Turbine Classification

Hydraulic turbines can be divided into impact turbines and impact turbines according to their working principles. Runner of impact turbine

Turbine performance comparison It is rotated by the impact of water flow, and the pressure of the water flow is constant during the work, mainly due to the conversion of kinetic energy; the runner of the impact turbine is rotated by the reaction force of the water in the water, and the pressure energy and kinetic energy of the water flow are changed during the work , But mainly the conversion of pressure energy. ^[1]

Water Turbine Impact Turbine

Percussion turbines can be divided into two types according to the direction of water flow: cut-type (also known as bucket type) and oblique type. Oblique water

Water turbine The structure of the turbine is basically the same as that of the bucket turbine, except that the jet direction has an inclination angle, which is only used for small units. ^[1]

Theoretical analysis proves that the efficiency is highest when the circumferential velocity at the bucket circle is about half of the jet velocity. When the load of this type of turbine changes, the direction of the inlet water speed of the runner does not change. In addition, this type of turbine is used in high-head power stations. The head change is relatively small and the speed change is not large. Therefore, the efficiency is less affected by the load change. The efficiency curve is relatively smooth, with the highest efficiency exceeding 91%. ^[1]

Impact Turbine

Turbine Overview

Impact turbines can be divided into mixed flow, axial flow, diagonal flow and cross flow. In a mixed-flow turbine, the water flows radially into the water guiding mechanism and flows out of the runner axially; in an axial-flow turbine, the water flows radially into the guide vanes and axially enters and leaves the runner; in an oblique flow turbine, the water flows Radially enter the guide vane and flow into the runner in a direction inclined to the main shaft, or into the guide vane and runner in a direction inclined to the main shaft; in a cross flow turbine, the water flows into the guide vane in the axial direction And runner.

Turbine schematic Axial flow, cross flow and diagonal flow turbines can be further divided into fixed and rotary paddles according to their structure. Fixed paddle type runner blades are fixed; paddle type runner blades can be rotated around the blade axis during operation to adapt to changes in water head and load. ^[1]

Various types of impact water turbines are equipped with water inlet devices. The water inlet devices of large and medium-sized vertical shaft impact water turbines are generally composed of volutes, fixed guide vanes and movable guide vanes. The function of the volute is to evenly distribute the water flow around the runner. When the water head is below 40 meters, the volute of the turbine is usually cast on site. When the water head is higher than 40 meters, tailor-welded or cast metal volutes are often used. ^[1]

In the impact turbine, the water flow fills the entire runner flow path, and all the blades are simultaneously affected by the water flow. Therefore, under the same head, the diameter of the runner is smaller than the impact turbine. Their maximum efficiency is also higher than that of impact turbines, but when the load changes, the efficiency of the turbine is affected to varying degrees. ^[1]

Impact water turbines are equipped with tailpipes, which are used to: recover the kinetic energy of the water flow at the outlet of the runner; drain the water downstream; when the installation position of the runner is higher than the downstream water level, convert this level of energy into pressure energy and recover . For turbines with low head and large flow, the kinetic energy at the outlet of the runner is relatively large, and the recovery performance of the tailpipe has a significant impact on the efficiency of the turbine. ^[1]

Axial flow turbine

Suitable for power stations with lower heads. At the same head, the specific rotation speed is higher than that of the mixed flow turbine. ^[1]

The blades of the axial-flow fixed-paddle turbine are fixed on the runner body. The general installation height is 3-50m. The blade placement angle cannot be changed during operation, the structure is simple, and the efficiency is low. It is suitable for power stations with small load changes or by adjusting the number of generating units to adapt to load changes. ^[1]

Axial-flow propeller turbine was invented by the Austrian engineer Kaplan in 1920, so it is also called Kaplan turbine. The general installation height is 3-80m. The runner blades are generally operated by hydraulic pressure relays installed in the runner body, which can be rotated according to changes in water head and load to maintain the optimal cooperation between the movable guide blade angle and the blade angle, thereby improving the average efficiency. The highest efficiency of hydraulic turbines has exceeded 94%. A typical example is Gezhouba. ^[1]

Hydro -turbine

The water flow between the guide vane and the runner is basically non-reversing. With the use of a straight cone tailpipe, the discharge does not have to turn in the tailpipe, so it has high efficiency, large flow capacity, and high specific speed. It is particularly suitable. It is a small riverbed power station with a low head of 3 to 20 meters.

Turbine installation drawing This turbine is installed in a tidal power station and can also realize bidirectional power generation. This type of turbine has various structures, and the most commonly used is a bulb type turbine. ^[1]

The generator of the bulb-type unit is housed in a water-tight bulb body. The runner can be designed as a fixed paddle or a paddle. Which can be subdivided into cross-flow and semi-flow. The world's largest bulb-type turbine (rotor-type semi-throughflow) is installed at the Rock Island Second Power Station in the United States, with a water head of 12.1 meters, a rotation speed of 85.7 rpm, a rotor diameter of 7.4 meters, and a single power of 54 MW , Put into operation in 1978. ^[1]

Francis turbine

It is the most widely used water turbine in the world. It was invented by American engineer Francis in 1849, so it is also called Francis water turbine. Compared with the axial-flow propeller type, its structure is simpler, the operation is stable, and the highest efficiency is higher than the axial-flow type. Some of the highest efficiency has exceeded 95%. Mixed-flow turbines have a wide range of heads, ranging from 5 to 700 meters, but the most widely used are 40 to 300 meters. ^[1]

Mixed flow runners are generally made of low-carbon steel or low-alloy steel castings or cast-welded structures. In order to improve the anti-cavitation and anti-sand wear performance, stainless steel can be deposited on cavitation-prone parts, or stainless steel blades, and sometimes the entire runner can be stainless steel. The use of a cast-welded structure can reduce costs, make the runner size more accurate, and the runner surface smoother, which is conducive to improving the efficiency of the turbine. It is also possible to use different materials to make the blades, upper crowns and lower rings. A typical example is Liujiaxia in China. ^[1]

Turbine oblique flow turbine

It was invented by Swiss engineer Delia in 1956, so it is also called Delia water turbine. Its blades are mounted on the runner body at an angle

Water turbine As the water head and load change, the hydraulic pressure relay relay operating blade in the runner body rotates around its axis accordingly. Its highest efficiency is slightly lower than that of mixed-flow turbines, but the average efficiency is much higher than that of mixed-flow turbines. Compared with axial-flow propeller turbines, it has better anti-cavitation performance and lower flying speed. . ^[1]

Due to the complicated structure and high cost of the oblique flow turbine, it is generally used only when the mixed flow or axial flow turbine is not suitable or not ideal. This turbine can also be used as a reversible pump turbine. When it is started in the pump working condition, the runner blade can be closed into a close-closed cone so that the starting load of the motor can be reduced. ^[2]

Basic concepts and development history of water turbines

A water turbine is a power machine that converts water energy into mechanical energy. In most cases, this mechanical energy is converted into electrical energy by a generator, so the water turbine is used for water energy utilization and power generation. ^[1]

Water is one of the most important natural resources that human beings can rely on in life and production. Our ancestors have fought against floods and learned to use water energy long ago. Dayu s water management for more than 2,000 years in the park is still praised. In 37 AD, the Chinese invented a blower driven by a water wheel-water row. In 260-270 AD, the Chinese created a water mill. In 220-300 AD, a water mill driven by a water wheel was invented. These hydraulic machines have simple structures and are easy to manufacture. . The disadvantages are bulky, low output and low efficiency. The true large-scale rational development and utilization of hydropower resources comes after the development of modern industry and the development of technologies related to power generation and shipping. ^[1]

The comprehensive development and utilization of water resources refers to the comprehensive utilization of river water resources in flood control, irrigation, shipping, power generation, and aquatic inventions through the construction of water conservancy projects. ^[1]

China s hydropower development equipment business also flourished after the founding of New China. In 1975, China was only able to design and manufacture the Xin'anjiang Hydropower Station with a capacity of 75,000 kilowatts. China has been able to design and manufacture mixed-flow turbines with a single capacity of 700,000 kilowatts. Generator sets and axial-flow propeller-type turbine generators with a single capacity of 170,000 kilowatts. The design and manufacturing level of China's hydraulic equipment has reached the world advanced level. The hydropower equipment designed and manufactured in China has been exported to the United States, Canada, the Philippines, Turkey, Yugoslavia, and Vietnam, and has been welcomed by these countries. ^[1]

Hydraulic Turbine Grade

Turbine counterattack

Mixed flow HL

Flow ZZ

Axial ZD

Oblique flow XL

Tubular GZ

Cross-flow fixed-blade GD ^[1]

Turbine impact type

Water bucket CJ

Double-click SJ ^[1]

Water Turbine Application

Pump turbines are mainly used in pumped storage power stations. When the load of the power system is lower than the basic load, it can be used as a pump to use excess power generation capacity to pump water from the downstream reservoir to the upstream reservoir to store energy in the form of potential energy;

Water turbine At this load, it can be used as a water turbine to generate electricity to regulate peak loads. Therefore, a pure pumped storage power station cannot increase the power of the power system, but it can improve the operating economy of the thermal power generating unit and the overall efficiency of the power system. Since the 1950s, pumped storage units have received widespread attention and have developed rapidly in countries around the world. ^[1]

Most of the pump storage units developed in the early days or with high heads are three-machine type, that is, they are composed of a generator motor, a water turbine and a pump connected in series. Its advantage is that the hydraulic turbine and pump are designed separately, which can have higher efficiency, and the rotation direction of the unit is the same when generating and pumping. It can quickly switch from power generation to pumping, or from pumping to power generation. At the same time, the turbine can be used to start the unit. Its disadvantages are high cost and large investment in power stations. ^[1]

The blades of the turbine runner of the oblique flow pump can be rotated, and still have good operating performance when the head and load change, but due to the limitations of hydraulic characteristics and material strength, by the early 1980s, its highest head was only 136.2 meters ( Japan's Takane First Power Station). For higher heads, mixed flow pump turbines are required.

Water turbine The pumped storage power station has two upper and lower reservoirs. Under the condition of storing the same energy, increasing the lift can reduce the storage capacity, increase the unit speed, and reduce the construction cost. Therefore, high-head storage power stations above 300 meters have developed rapidly. The world's highest-head mixed-flow pump turbine was installed at the Bayna Bashta Power Station in Yugoslavia. Its single-unit power is 315 megawatts and the water head of the turbine is 600.3 meters. The pump head is 623.1 meters and the speed is 428.6 rpm. Put into operation. ^[1]

Since the 20th century, hydropower units have been developing towards high parameters and large capacity. With the increase of thermal power capacity in the power system and the development of nuclear power, in order to solve the problem of reasonable peak shaving, countries around the world are actively constructing pumped storage power stations in addition to vigorously developing or expanding large power stations in major water systems. As a result, pump turbines have developed rapidly. ^[1]

In order to make full use of various hydraulic resources, the tide, plain rivers and even waves with very low dropout have also caused widespread

Water turbine Attach importance to the rapid development of tubular turbines and other small units. ^[1] ^[1]

Main working parameters of hydraulic turbine

H Turbine head H (m)

The difference in unit energy between two sections of continuous water flow is called the head. The water head is an important parameter of the turbine. Its size directly affects the output of the turbine and the choice of the turbine model. ^[1]

Turbine flow

The amount of water (volume) flowing through the turbine per unit time is called the flow rate of the turbine and is represented by Q. It is usually expressed in cubic meters per second. ^[1]

Hydraulic turbine output

The energy of the water flow flowing through the turbine per unit time is called the "output of the water flow" through the turbine and is expressed by Np ^ 0. Np ^ 0 = 9.81QH (kw). ^[1]

Turbine efficiency

The ratio of the output N of the water turbine through the output Np ^ 0 of the water flow of the turbine is called the efficiency of the water turbine and is expressed by . Obviously, efficiency is the effective use of water energy by the surface turbine, and it is a dimensionless physical quantity, expressed as a percentage (%). ^[1]

Turbine speed

The number of rotations of the main shaft of the hydraulic turbine in a unit time is called the rotational speed of the hydraulic turbine. ^[1]