Fluid reaction surfaces (i.e. – impellers) – With heating – cooling or thermal insulation means – Changing state mass within or fluid flow through working...
Reexamination Certificate
2000-08-22
2002-04-30
Ryznic, John E. (Department: 3745)
Fluid reaction surfaces (i.e., impellers)
With heating, cooling or thermal insulation means
Changing state mass within or fluid flow through working...
Reexamination Certificate
active
06379117
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a cooling air supply system used for rotors operating at a high temperature and requiring cooling air.
2. Description of the Related Art
FIG. 5
shows a typical configuration of a cooling air passage used in a gas turbine rotor.
In the machines having rotors operating at a high temperature, such as gas turbines, the rotors are cooled by supplying cooling air thereto. For example, rotor blades of gas turbines which contact a high temperature combustion gas are cooled by supplying cooling air to the cooling air passages formed within the blade in order to increase durability of the blades. Usually, cooling air is supplied to the rotor blade through axial cooling air passages formed in the rotating shaft of the turbine.
In
FIG. 5
, reference numeral
10
designates a gas turbine rotor as a whole. Rotor
10
includes a rotor shaft
11
and a plurality of turbine disks
13
coupled to the shaft
11
(in
FIG. 5
, only one turbine disk is shown). Rotor blades
15
for receiving energy of high temperature combustion gas in order to rotate the rotor
10
are embedded on the outer periphery of the disks
13
.
As shown in
FIG. 5
, a cylindrical sleeve
31
is disposed around the outer periphery of the rotor shaft
11
. The cylindrical sleeve
31
is attached to the side face of the rotor disk
13
and rotates together with the rotor shaft
11
. The cylindrical sleeve
31
has an inner diameter larger than the outer diameter of the shaft
11
and the clearance between the inner surface of the sleeve
31
and the outer surface of the shaft
11
forms an annular cooling air passage
30
. An end of the cooling air passage
30
opposite to the turbine disk
13
opens to a cooling air supply chamber
20
and acts as an annular air inlet opening
33
.
The cooling air supply chamber
20
is formed in a casing
50
accommodating the rotor
10
as an annular chamber surrounding the open end (i.e., the annular air inlet opening
33
) of the sleeve
31
. Labyrinth seals
51
and
53
of a known type are disposed on both axial ends of the cooling air supply chamber
20
to prevent cooling air in the chamber
20
from escaping through the clearances between a stationary member (i.e., the casing
50
) and a rotating member (i.e., the rotor
11
and the cylindrical sleeve
31
).
Cooling air is supplied from a pressurized air source (typically, from the discharge of the air compressor of the gas turbine) to the cooling air supply chamber
20
through a cooling air piping
23
. From the cooling air supply chamber
20
, cooling air flows into the annular air inlet opening
33
formed around the outer periphery of the shaft
11
and flows through the cooling air passage
30
in the axial direction to the turbine disk
13
. At the turbine disk
13
, a part of the cooling air is supplied to the root portions of each of the blades
15
through radial air passages
13
a
disposed in the turbine disks
13
. Cooling air supplied to the roots of the blade
15
, then, flows through a blade cooling air passage formed within the blades (not shown) to cool the material of the blade
15
and discharged from outlet holes disposed on the leading edges or trailing edges of the blades
15
. The remaining portion of cooling air (i.e., cooling air not flowing into the radial cooling air passage
13
a
) is supplied to other turbine disks (not shown) through an axial passage
13
b
perforating through the turbine disk
13
in order to cool the rotor blades of other rotors.
When cooling air flows through the cooling air passage
30
, a velocity component tangential to the outer periphery of the shaft is given to the flow of cooling air through the contact with the outer surface of the rotor shaft
11
which rotates at a high speed and cooling air in the passage
30
flows in a spiral flow path around the shaft
11
towards the turbine disk
13
. This causes a power loss at the rotor shaft
11
by an amount equal to the kinetic energy, corresponding to the tangential velocity component, given to cooling air at the air inlet
33
of the cooling air passage
30
.
In order to reduce the power loss at the rotor shaft due to the tangential velocity imparted to cooling air, tangential cooling air nozzles are used in some cases. In the cooling air system equipped with tangential cooling air nozzles, air nozzles injecting cooling air to a direction tangential to the outer peripheral of the rotor shaft are disposed in the casing
50
near the inlet
33
of the cooling air passage
30
. Since cooling air is ejected from the tangential air nozzles in the direction tangential to the outer periphery of the shaft
11
, the tangential velocity component is imparted to cooling air before it flows into the cooling air passage
30
. Therefore, the power loss at the rotor shaft due to the tangential velocity component is largely reduced.
The tangential air nozzles consist of a number of nozzle members having aerofoil cross sections and are disposed radially around the rotor shaft
11
at the air inlet
33
of the cooling air passage
30
and air passages are formed by the clearance between the nozzle members. Usually, the tangential nozzles are formed as expansion nozzles, i.e., the air passages of the nozzles are designed in such a manner that cooling air passing through the nozzles expands in the air passages in the nozzles and is ejected in the tangential direction at a predetermined speed. The pressure difference across the nozzles, i.e., the pressure difference between the pressure of the air in the cooling air supply chamber
20
and the pressure of air at the air inlet
33
of the cooling air passage
30
is determined in such a manner that the magnitude of the velocity of cooling air leaving the nozzles is substantially the same as the peripheral speed of the rotating shaft
11
during the operation of the gas turbine. Since cooling air is ejected from the nozzle in the tangential direction at the speed the same as the peripheral speed of the shaft
11
, a difference in the magnitude of the tangential velocity components does not occur when cooling air and the rotor shaft contact each other and power loss at the rotor does not occur.
However, problems occur when nozzle members having aerofoil cross sections are used for tangential air nozzles. When the aerofoil type nozzle members are used, the tangential nozzles are formed by assembling separately manufactured nozzle members by disposing the respective nozzle members around the air inlet of the cooling air passage and securing them to the stationary members in the cooling air supply chamber by welding or brazing. Alternatively, all the tangential nozzles may be made of a one-piece annular member including the aerofoil nozzle members arranged radially therein and may be formed by casting or by machining an annular shaped material by, for example, an electric discharge method.
However, since the shape of the aerofoil nozzle members and the arrangement thereof is complicated, manufacturing and assembly of the tangential nozzles requires many man-hours and, therefore, is costly. Further, when welding or brazing are used for assembling the nozzles, distortion of the nozzle members due o the high temperature used during the assembly may occur. This causes inaccuracy of the direction of cooling air ejected from the nozzles.
Further, if the aerofoil type nozzle members are used, it is necessary to arrange the respective nozzle members in a direction tangential to the outer periphery of the shaft, i.e., the respective nozzle members must be arranged around the outer periphery of the shaft in such a manner that each of the nozzle members is arranged on a plane perpendicular to the axis of the shaft and inclines at a predetermined angle with respect to a radius of the shaft. When the outlets of the nozzles are located in proximity of the outer periphery of the shaft the inclination of the nozzle members becomes larger and, therefore, the manufacturing and assembling of the tangential nozzles becomes more diffi
Mitsubishi Heavy Industries Ltd.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Ryznic John E.
LandOfFree
Cooling air supply system for a rotor does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Cooling air supply system for a rotor, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Cooling air supply system for a rotor will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2817079