1. Field of the Invention
The present invention relates to a gas turbine that is rotationally driven using combusted gas from a combustor, and more specifically, to a gas turbine in which power is effectively increased by bleeding from tangential on board injection (TOBI) nozzles to rotor disks.
2. Description of Related Art
In a gas turbine plant, compressed air from a compressor is guided into a combustor, and the high-temperature gas generated when this compressed air is combusted along with a fuel is guided into the gas turbine to drive it. A typical design is one in which a portion of the compressed air is introduced into a cooling device as bleed air and cooled. The cooled bleed air is subsequently guided to stationary and moving blades on the gas turbine side, and used as cooling for these blades and as sealing air between the moving and stationary blades.
An example of a design for bleeding to the first stage unit of the moving and stationary blades in a conventional gas turbine will be explained below with reference to FIG. 4. FIG. 4 is a partial cross-sectional view showing the flow path of bleed air to the first stage unit. A compressor, which would be to the left on the page but is not shown in the figure, is coaxially disposed to the gas turbine.
In FIG. 4, the numerals 1 and 2 indicate first stage moving blades and first stage stationary blades, respectively. A plurality of first stage moving blades 1 are disposed in a circle around rotor disk 3 which is coaxial to the compressor. First stage moving blades 1 receive combustion gas HF from the compressor, and thereby turn first stage rotor disk 3. A plurality of first stage stationary blades 2 are disposed in a circle on the interior side of a vehicle so as to be coaxial to first stage rotor disk 3. First stage moving blades 1, first stage rotor disk 3 and first stage stationary blades 2 are provided in this way to form a first stage unit. A seal disk 7 is connected to the same shaft upstream from first stage unit. A plurality of disk holes 7a, which are penetrating holes through which bleed air from upstream passes to first stage unit, are formed centered about this shaft and at equal angle intervals from one another.
The numeral 5 in FIG. 4 is a bleeding chamber that takes up cooled bleed air f1 from the cooling device. Bleed air f1 which has been taken up into bleed air chamber 5 passes through disk holes 7a in seal disk 7, and is supplied into first stage rotor disk 3. This bleed air f1 is guided into each first stage moving blade and cools these blades from the inside. A plurality of tangential on board injection (TOBI) nozzles 10 are formed centered around the aforementioned shaft at the discharge port of bleeding chamber 5. Bleed air f1 is ejected along the direction of rotation of seal disk 7. By providing each TOBI nozzle 10 to impart swirling flow to bleed air f1 in this way, it is possible to reduce pumping losses.
The symbol f2 in FIG. 4 is sealing air from the compressor. After passing through labyrinths 8a, 8b, 8c and brass seal 9, this sealing air f2 crosses in front of the discharge port of each TOBI nozzle 10, passes through brass seal 12 and labyrinths 13a, 13b, and is supplied into space interval C between first stage moving blades 1 and first stage stationary blades 2. The sealing air f2 supplied to space interval C prevents combustion gas HF from leaking inside via this space interval C.
However, this conventional gas turbine has the problems explained below.
Namely, sealing air f2 on its way from the compressor to space interval C interferes with the swirling flow of bleed air f1 discharged from each TOBI nozzle 10 toward seal disk 7. For this reason, the circumferential speed component is reduced. The reduction in this circumferential speed component invites an increase in pumping losses. As a result, the effect of providing the TOBI nozzles 10 is lost. In other words, the gas turbine losses power.
If the reduction in this circumferential speed component is anticipated from the beginning, however, one might consider increasing this component by increasing the tilt angle of the TOBI nozzles. However, the delivery pressure from TOBI nozzles 10 is reduced when the circumferential speed component is increased. In this case, the difference between the delivery pressure of each TOBI nozzle 10 and the pressure of combustion gas HF becomes smaller, and the flow rate of sealing air f2 decreases. The sealing structure in space interval C may not function normally as a result. Infiltration of combustion gas HF from space interval C is linked to a reduction in the power for rotating each first stage moving blade 1. Thus, the turbine also losses power.
As explained above, when a circumferential speed component is added to the flow passing through seal disk 7 in order to increase the power of the gas turbine, then, conversely, the power drops.