Kaplan turbine

Axial Flow Turbine Kaplan Hydro Turbine / Kaplan Water Turbine for Water Head 2m - 70m Hydropower Project

The Kaplan (axial-flow) turbine for low head from 2m to 70m. This type of turbine is mostly suitable for hydropower stations with low water head and big flow.
lts feature is that the water flow passes through the runner axially. The axial-flow turbine can be classified into two forms according to the runner construction: one is fixed blades (Propeller) for small variation of head and power, the other is movable blades (Kaplan) for large variation of head and power.
The kaplan turbine with vertical shaft arrangement , with three types as open flume, pressure flume, and seal off (concrete spiral case).
Generally, Kaplan turbine is composed of distributor, guide vane, runner, draft tube etc. 

Main Structure of Kaplan Water Turbine

This hydraulic turbine is axial flow turbine with a vertical shaft. And its spiral case is made of metal or concrete.
The water flows through the channeling pipe, and then into the spiral case, which ensure that the water enter the turbine circumferentially and symmetrically, forming certain circumfluence quantum.
The water flows through the stay ring into the distributor, whose guide vanes can regulate the turbine discharge and the flow direction and thus make the water flow into the runner circumferentially and symmetrically. Consequently, the runner revolves and converts hydraulic energy into mechanical energy and then drives the rotor of the generator revolve by the force of the main shaft of the hydraulic turbine, thus converting the mechanical energy into electrical energy. The water, which has gotten out of the runner, flows to the downstream of river through the draft tube.
Because of the restoration of the draft tube, the energy of the water flowing out of the outlet, is partly reused, thus loss is reduced and efficiency is improved.

Main structures of the hydraulic turbine are described in the following.

Draft tube assembly

It includes draft tube straight cone and metal bend tube. Because of the restoration of the draft tube, the energy of the water flowing out of the outlet is partly reused, thus loss is reduced and efficiency is improved.

Rotating parts assembly

Rotating department is mainly composed of a runner, main shaft, radial turbine bearing and seals of main shaft. Runner with the blades of stainless steel of 06Cr13Ni4Mo assembled and welded. After having been mould into shape, all the  blades must be processed to the required degree of roughness and precision.
To ensure the stable operation of runner, a test for still balance is performed in the manufactory. Shared by the hydraulic turbine and hydro generator, the vertical main shaft, connects the runner with pins. The main shaft seal is of the type with soft graphite packing
The radial turbine bearing is water-lubricating elastic metal-plastics bearing,clean water,0.15~0.2Mpa.

kaplan turbine runner

Distributor assembly

Distributor consists of head cover, bottom ring, guide vanes, the regulating ring, transmission departments and any other parts. They are divided into two parts. One part includes guide vanes and supporters of three parts of shaft sleeves, namely bottom ring and head cover. The other part includes guide vane arm, conjunction rod, regulating ring, and pull-push rod of transmission departments.

distributor

a. Guide vane and its supporting parts.

There are  guide vanes spreading in a circle equally.

Guide vane is standard blade-shaped with positive curvature This enables the guide vanes to have the virtues of little hydraulic loss and high degree of strength as guide vanes’ opening varies. The Guide vanes are made of 20SiMn.On the bottom of guide vane, shaft sleeves are fixed with the bottom ring and they are self-lubricating bearings of thin plates of Fluon. In the head cover, shaft sleeves are fixed with the bottom ring and they are self-lubricating bearings of thin plates of Fluon.

Guide vanes

b. Transmission department.

Control ring is welded with steel plates, supported by head cover. On the joint surface are anti-grinding plates of nylon, which are used for guide in direction. There is pressing plate so that control ring won’t go up. On the top, control ring are connected with two connecting rods. Below, there are 24 holes to pins, spreading in a circle equally. Control ring is connected with guide vanes through pins, connecting plates and guide vane arms.

The shear pins between the guide vane arms and connecting plates are the weakest part in the transmission department of guide vane. If guide vanes close with great difficulty, the shear pins are immediately sheared to protect other parts. Consequently the signaling equipment is sheared, and signal is sent.

Francis Turbine

Horizontal Francis Hydro Turbine / Francis Water Turbine with Water Head From 20m to 300m

Francis turbines are most widely used among water head from 20m to 700mm. A Francis turbine has a runner with fixed blade, usually nine or more. Water is introduced just above the runner and all around it and then falls through, causing it to spin. Besides the runner, the other major components are the spiral case, wicket gates, and draft tube. Most small Francis turbine are horizontal shaft and metallic spiral case, it has two bearing assembled on the generator seat.

Water flows through penstock of the power station, Butterfly valve, expansion pipe, inlet tube, spiral case and wicket gates into the runner, and then it drives the runner to revolve and convert hydraulic energy into mechanical energy and drives the rotor of generator revolution by the force of the main shaft of turbine, thus converting the mechanical energy into electric energy.

Franics Turbine runner compose of the  blade, upper crown, bend and cone.
The whole rotating part is mainly composed of the runner, main shaft, flywheel and main sealing assembly etc. The main shaft is laid in horizontal or vertical  position. The runner cone is keyed on the end of the main shaft, and locked with bolt, The other  end of the main shaft is connected to the flywheel. The runner is the principal component of the turbine convert hydraulic energy into mechanical energy. The main sealing assembly adopts polyethylene packing structure to prevent water leaking out, and should be connected the clean and pressure water which pressure is 0.15~0.25MPa.

Spiral case

The spiral casing is the largest part of the hydraulic turbine and erecting bench- mark. It is made of steel-welding structure. Together with spiral casing and stay ring. Some stay vanes are equipped on the inner of stay ring. A pressure gauge is equipped to measure the pressure of the inlet water there. On the top of the spiral casing, it presents an air-discharge valve, which is used to expel out the residual air in the shell, when the shell is filled with water before starting up the turbine.

Distributor
The distributor consists of wicket gates, guide vane arms, shear pins, regulating ring, head cover, bottom ring etc.
 The wicket gates  function is to regulate the discharge of water flow. so as to suit the regulation on various loads.
 The opening of wicket gates can be regulated by the governor servomotor, to guarantee the revolving speed constant when the load changes. When the turbine is shut down all openings between the wicket from flowing into the runner. Each wicket gate swivels in bushing along, the axial line of its stem. The lower bushing seats in the head cover, the middle and upper bushing seat in the bottom ring. The connecting rod mechanism is equipped between the wicket gates and regulating ring in order to transfers their move and force.
Also the  shear pins are equipped on the distributor. When the turbine is shut down if the closing of the wicket gates exists obstacles, the shear pin related to the opening will be shorn so that the other pats of distributor many not be damaged. The regulating ring is connected with the servomotor by way of the connecting rod.

The draft tube  consists of draft tube, draft tube cone and draft tube bend etc. It’s function is to guide water current and receive some hydraulic energy.