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Counter-turbine of Hydraulic Turbines Classification
Author: source: date: 2020-06-03 10:01:47
As hydropower generation matures today, the technology of water wheels is also developing and advancing. The main function of a water turbine is to convert water energy into mechanical energy. According to the different ways in which the runner converts the energy of the water, the turbines can be divided into two categories: impact turbines and impact turbines. However, under the two major categories, there are specific categories of turbines. Today we will introduce the classification of counter-turbine.
The water flow in the runner area of the counter-turbine is always a pressure flow that continuously fills the entire runner when it passes through the runner blade flow path. Direction, which produces a reaction force on the runner blades, driving the runner to rotate. After the water flows through the turbine, most of its kinetic energy and potential energy are converted into rotating mechanical energy of the runner.
Francis turbineThe water flow enters the runner in the radial direction from around, and then flows out of the runner approximately in the axial direction. Francis turbine has a wide range of application heads, about 20-700m, simple structure, stable operation and high efficiency. It is the most widely used modern turbine.
Francis turbineAlso known as Francis turbine, it is a type of impact turbine. It was invented by American engineer Francis in 1849. It is also known as Francis turbine, or radial axial turbine. The water flows into the runner radially from the surroundings, and then flows out of the runner approximately axially. The runner is composed of an upper crown, a lower ring and blades. The development trends in recent years are high head, large capacity, high specific speed and high efficiency.
Axial turbineThe water flow changes from radial flow to axial flow between the guide vane and the runner, and the water flow maintains the axial flow in the runner area. The application head of the axial flow turbine is about 3 ~ 80m. Axial-flow turbines are widely used in low-head and high-flow hydropower stations. According to whether the runner blade can rotate during operation, it can be divided into two types: axial flow fixed paddle type and axial flow rotary paddle type turbine. The runner blades of an axial-flow fixed-paddle turbine are fixed, so the structure is simple and the cost is low, but its efficiency will drop sharply when it deviates from the design conditions. Therefore, this type of turbine is generally used for low head, Hydropower stations with small output and small head changes. The runner blades of the axial flow paddle turbine can rotate according to changes in operating conditions, thereby expanding the range of the high efficiency area and improving the stability of operation. However, this type of hydraulic turbine requires a mechanism to operate the blade rotation, so the structure is more complicated and the cost is higher. It is generally used in large and medium-sized hydropower stations with large changes in the head and output.
Diagonal flow turbineThe water flow flows in the direction of an angle with the main axis in the runner area. The runner blades of diagonal flow turbines are mostly made in a rotatable form, with a wide high efficiency area, suitable for the water head between axial flow and Francis turbines, about 40 ~ 200m. It is a new model based on the improvement of the axial flow turbine in the early 1950s to improve the head of the axial flow turbine. Its structural form and performance characteristics are similar to the axial flow turbine, but due to its tilt The structure of the blade operating mechanism is particularly complex, and the processing technology requirements and cost are relatively high, so it is generally only used in large and medium-sized hydropower stations. At present, the application of this type of turbine is not common.
Tubular turbineTubular turbine is a horizontal shaft turbine with a flow path approximately straight. It does not have a water diversion volute, and the blades can be made into two types, fixed and rotatable. According to the different types of generators, it is divided into two types: full-flow and semi-flow.
The generator rotor of a full-flow turbine is directly mounted on the outer edge of the runner blade. Its advantage is that the flow channel is straight, the flow is large, and the efficiency is high. However, due to the high linear velocity and long circumference of the outer edge of the runner blade, rotary sealing is difficult. At present, this model has been rarely used.
Semi-turbine turbines have shaft extension, shaft type and light bulb type devices. Among them, shaft extension and shaft type are simple in structure and easy to maintain, but their efficiency is low, and they are generally only used for small hydropower stations. At present, the bulb tubular turbine is widely used. Its compact structure, good stability and high efficiency. Its generator is arranged in the steel bulb body surrounded by water. The turbine and the generator can be directly connected or can be increased. Speed device connection.The applicable head of the tubular turbine is 1-25m, which is suitable for low-head and large-flow hydropower stations. Due to its horizontal shaft arrangement and simple flow channel form, it has less civil engineering and simple construction, and is therefore widely used in the development of hydraulic resources such as rivers and tides in coastal areas. At present, the largest bulb tubular turbine with a diameter of 5.5m and a single output of 15MW has been independently developed in my country.
These are the specific classifications of impact turbines, which are turbomachinery in fluid machinery. It is very different from the impact turbine, for example, in terms of flow channel, the pressure of the water flow in the counterattack turbine is different and not equal to the atmospheric pressure, so a closed channel is required. However, in impulse turbines, there is no need to provide a closed channel.