Introduction of Water Turbine

1.Composition of water turbine

It is composed of buried part, water guide mechanism part, rotating part and so on.The buried part mainly includes spiral case, stay ring, draft tube and other parts; the water guide mechanism part mainly includes top cover, bottom ring, guide vane, control ring, transmission mechanism and servomotor and other parts; the rotating part mainly includes runner, main shaft, hydraulic turbine guide bearing and main shaft seal and other parts.

2.Working principle of water turbine 

The water flows through the pressure steel pipe and enters the turbine spiral case after passing through the inlet valve.The spiral case has a circular cross-section, which ensures the water flow enters evenly along the circumference and forms a certain amount of ring. The stay ring connected with the spiral case bears the self-weight of the unit, the water pressure and the load transmitted from the upper concrete and the worm casing to the stay ring, and transmits these loads to the concrete foundation through the fixed guide vane.The water flow enters the water guide mechanism through the stay ring, and through the opening and closing of the guide vane, the flow rate and direction of water flow into the turbine are controlled, so that the water flow enters the runner evenly along the circumference, and the energy of the water flow is converted into mechanical energy of the runner rotation through the runner vane, and the water flow out of the runner flows downstream through the draft tube, and the recovery effect of the draft tube recovers part of the kinetic energy of the water flow out of the runner, so as to reduce the export loss of the turbine and improve the efficiency of the turbine.

3.Our water turbines are divided into three categories:

Cross-flow turbines,

Mixed-flow turbines,

Axial-flow turbines,

(1).Cross-flow turbines are divided into:

-Bulb turbine,

-Pit turbine,

-Tubular turbine

-Bulb turbine:

The bulb turbine is the most important type of cross-flow turbines generator set,which has some differences from other cross-flow type.In general, it shares a main shaft with the generator, which is arranged horizontally, and the two ends are directly connected with the runner and rotor respectively, with a straight conical draft tube.The rotating part of the unit adopts two pivot points and double cantilever structure.The direction of rotation of the unit is clockwise from the generator end to the downstream direction.The generator is housed in a completely sealed bulb body, which becomes part of the turbine runner.The unit is supported by two vertical shafts on a tubular base, with horizontal and vertical vibration prevention support for the generator as auxiliary support to ensure sufficient rigidity and stability of the unit.

-Pit turbine:

The Pit turbine is another type of Cross-flow turbines in which the generator is arranged in the hollow gate pier in the front flow passage of the runner.Since the space provided by the hollow gate pier is much larger than the sealed bin provided by the bulb turbine, the speed increasing gear can be arranged to increase the speed of the generator, thus reducing the lower head.

Advantages: 

The structure is simple, the generator can adopt standard models, with low cost, convenient installation, maintenance, and monitoring of the generator, and the moisture-proof and sealing conditions are better.

Disadvantages:

 Large unit spacing, large amount of civil construction work, poor overflow conditions, generally used only for small and medium-sized power stations.

-Tubular turbine:

The Tubular turbine generally have slightly curved water passage, and the turbine is installed inside the passage.The turbine shaft passes through the pipe wall and is connected to the generator arranged outside the passage through a transmission device.Due to the water flow channel is like "S", it is called S-type turbine. According to the arrangement of the shaft, it can be divided into three types: forward-extending shaft type, backward-extending shaft type and inclined-extending shaft type.

(2).Mixed-flow turbines are divided into:

-Vertical mixed-flow turbine,

-Horizontal mixed-flow turbine

(3).Axial-flow turbines are divided into:

-Kaplan turbine,

-Propeller turbine

-Kaplan turbine

Compared with the Propeller turbine, When the load changes, the Kaplan turbine it not only adjusts the rotation of the guide vanes, but also adjusts the runner blades to form an optimal coordinated relationship with the rotation of the guide vanes, which improves the average efficiency of the turbine, expands the operating range, and obtains stable operating characteristics, which is a model worthy of wide use.