Introduction of Tubular turbine
The Tubular type turbines are usually the best choices for
exploitation of tidal power and hydraulic power with extremely low
heads and extremely large flow rates. They have the advantages such
as large discharge, high flow speed, high efficiency and less
excavation, etc. Their variations have Bulb, Pit, Siphon and S
types according to their structural types.
The water diversion parts, runner and water drainage parts of
Tubular turbine are on one axial line. The water flow directly and
straightly through the runner without spiral casing. The water flow
is axial from the pipe inlet to the draft tube outlet.
Tubular turbine generally has two categories: fully tubular and
half tubular. The half Tubular turbine is divided into bulb, pit
and shaft extension types, etc.
The generator’s rotor of the full tubular type unit is on the outer
circle of turbine’s runner, whose application is less because of
its difficult sealing.
For half Tubular turbine, the generator is separate from the hydro
Tubular type: Generator set is installed inside the airtight bulb
body, which has a compact structure, straight passage shape, high
hydraulic efficiency and so it is widely used.
Shaft extension type tubular unit: The generator is installed
outside, the main shaft of turbine extends to the outside of the
Pit type tubular unit: The generator is installed inside a pit.
Application scope of heads: 2m~25m
Runner diameters: 1.0m ~ 7.2m
Installable capacity: 200KW ~ 200000KW
Tubular type turbine is actually horizontal installed axial flow
turbine. The water from the reservoir flow through bulb head and
then enter into the turbine along the passage between the outer
wall of bulb body and the powerhouse concrete. The structures of
tubular turbine and horizontal type axial flow turbine are
basically similar. The differences between Bulb Tubular Turbine and
axial flow turbine are the water diversion chamber, water
distributor and draft tube.
Tubular turbine adopts conical water distributor that mainly
includes the inner and outer chambers of the guide vane, guide
vane, guide vane arm, connecting rod and control ring, etc. The
guide blade axis of conical water distributor is layout into 60 ~
70 degree angle with the unit axis. The bearings supporting the
guide vane are seated on the guide vane inner and outer chamber.
The guide vane composes a conical surface for adjusting the water
flow or stooping the unit. In order to reduce the water leakage
losses on the guide vane end surface, the surface of the guide vane
inner and outer chamber are spherical surface.
Bulb or tubular turbines are designed into the water delivery tube.
A large bulb is centered in the water pipe which holds the
generator, wicket gate and runner. Tubular turbines are a fully
axial design, whereas Kaplan turbines have a radial wicket gate.
Pit turbines are bulb turbines with a gear box. This allows for a
smaller generator and bulb.
S- turbines eliminate the need for a bulb housing by placing the
generator outside of the water channel. This is accomplished with a
jog in the water channel and a shaft connecting the runner and