FIELD OF THE INVENTION
The present invention relates to a method of cooling a rotor of steam turbines in high
pressure (HP) and intermediate pressure (IP) zone, so that conventional material can be
used for the rotor for a much higher inlet/reheat temperatures. More particularly, the
invention relates to a rotor cooling system of a steam turbine with a rotor made of
conventional materials and receiving cooler steam from an external source.
BACKGROUND OF THE INVENTION
The efficiency of steam turbine is dependent upon the inlet and reheat parameters
of the steam turbine. The higher the parameters, the higher the efficiency. However,
turbines with conventional materials are unable to sustain temperature higher than 565
°C. Beyond this temperature, costly materials (high-chromium steels or other materials
which can withstand high temperatures) are required. Moreover, as it becomes
prohibitively expensive to use the costly materials for the entire rotor, and also
technically impossible to achieve the properties for example, high creep strength in HP
zones and high fracture toughness required in the LP zones, It becomes necessary to
have multiple cylinders in the same rotor for the turbine, having high temperature rotors
made of costly materials.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose a system for cooling a high
temperature turbine rotor made of conventional steel materials, which eliminates use of
costly high - chromium materials for forming the rotor.
Another object of the invention is to propose a system for cooling a high temperature
turbine rotor made of conventional steel materials, which allows cooling the rotor and
reduces the number of cylinders required for the turbine.
Yet another object of the invention is to propose a system for cooling a high
temperature turbine rotor made of conventional steel materials, which enables increase
in the efficiency of the turbine by admitting high parameter steam onto a turbine with a
rotor made of conventional material.
SUMMARY OF THE INVENTION
Accordingly, there is provided a rotor cooling system of a steam turbine with a rotor
made of conventional materials and receiving cooler steam from an external source,
comprising a plurality of integral platforms for the moving blades; a ring disposed
between a first guide blade and an inner casing; a plurality of steam passages between
one stage and the next stage formed by holes made in the blade roots; and a plurality
of holes in the inner casing configured and provided with corresponding numbers of
connecting pipes to allow ingress of cold steam from an external source, the rear end of
said connecting pipes extended through an outer casing of the turbine to terminate at
said external source of cold steam.
The turbine is having outer and inner casings and a plurality of fixed and moving blades
with blade guides assembled in the inner casing and rotor. A plurality of connecting
platforms is disposed between the moving blades, the sealing fins and the cooling
passages.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig. 1 - shows a typical partial-section of a turbine with outer and inner casings, and a
plurality of blades with blade guides assembled in the inner casing and rotor according
to the invention.
Fig. 2 - is an enlarged view of the blading portion of the turbine of Fig. 1 in which the
connecting platforms are disposed between the moving blades, the sealing fins and the
cooling passages.
Fig. 3 is an enlarged view of a pair of adjacent blades of a single stage turbine of
Fig. 1, with the platforms and the cooling passages shown in a different view.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
As shown in figure 1, the turbine has an outer casing (1), an inner casing (2) and a
rotor (3). The other components of the turbine are not shown in the partial section, as
they are not particularly relevant in context of the present invention.
Moving blades are mounted on the rotor (3). These blades are provided with
integral platforms (5) on either side, such that the platforms (5) of the adjacent rows
have a very small axial clearance, just sufficient to accommodate thermal expansions
and the distortion of the platforms (5) due to differential temperatures developing
during operations of the turbine and the centrifugal forces.
A ring (4) is assembled between a first guide blade and an inner casing gland portion,
such that the inlet steam is blocked from impinging on the rotor (3). This ring (4)
divides the steam flow path into two parts - a high temperature path of the inlet steam
on its outside, and a low temperature passing inside it.
Cold steam at high pressure is admitted through a plurality of holes (6) drilled in the
inner casing. These holes (6) are connected to pipes by unions (7) and are taken out of
the outer casing, and are connected to a source of lower temperature steam at high
pressure. These holes (6) admit the cold high-pressure steam to the inside of the ring
(4). This steam passes through the passages (8) drilled in the sides of the blades, and
passes on to the last stage. This passing cold steam cools the rotor and the blades, and
does not allow the rotor (3) to be heated up to the high temperature of the steam
passing above the platforms (5).
This makes it possible to use a rotor of conventional material.
WE CLAIM
1. A rotor cooling system of a steam turbine with a rotor made of conventional
materials and receiving cooler steam from an external source, comprising a
plurality of integral platforms for the moving blades; a ring disposed between
a first guide blade and an inner casing; a plurality of steam passages between
one blade stage and the next blade stage formed by holes made in the blade
roots; and a plurality of holes in the inner casing configured and provided
with corresponding numbers of connecting pipes to allow ingress of cold
steam from an external source, the rear end of said connecting pipes
extended through an outer casing of the turbine to terminate at said external
source of cold steam.
2. The system as claimed in claim 1, wherein the connecting pipes are joined to
the holes of the inner casing via pipe couplings.
3. A rotor cooling system of a steam turbine with a rotor made of conventional
materials and receiving cooler steam from an external source substantially as
herein described and illustrated.

A rotor cooling system of a steam turbine with a rotor made of conventional materials
and receiving cooler steam from an external source, comprising a plurality of integral
platforms for the moving blades; a ring disposed between a first guide blade and an
inner casing; a plurality of passages between one blade stage and the next blade stage
formed by holes made in the blade roots; and a plurality of holes in the inner casing
configured and provided with corresponding numbers of connecting pipes to allow
ingress of cold steam from an external source, the rear end of said connecting pipes
extended through an outer casing of the turbine to terminate at said external source of
cold steam.