JPS585403A - gas turbine rotor blades - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a gas turbine rotor blade, and more particularly to a gas turbine rotor blade suitable for cooling the rotor blade using a cooling fluid. In gas turbines, improvements in efficiency are being pursued by increasing the turbine inlet temperature. In response to high temperatures, it is necessary to cool the high-temperature components of the gas turbine to keep them below an allowable temperature, but cooling generally induces a decrease in the mainstream gas temperature and a mixing loss between the mainstream gas and the refrigerant. Therefore, in order to fully utilize the benefits of increasing the turbine inlet temperature, a technology is required to effectively cool the turbine with as little amount of refrigerant as possible. Cooling of rotating rotor blades is particularly important from the viewpoint of strength and reliability, as large centrifugal force acts on them. Conventionally, the so-called simple convection cooling method, in which internal pressure refrigerant is passed through a cooling tube opened inside the blade and discharged from the tip of the blade, has been widely used for gas turbine rotor blades due to its simple structure. 1 to 3 are a plan view, a front view, and a side view showing a conventional simple convection cooling structure for gas turbine rotor blades.

In the figure, the gas turbine rotor blades are blades! , Shroud 2. Plant form 3. Shank 4. It is composed of a dovetail 5, and a seal fin 6 is attached to the tip of the shroud 2. A plurality of rotor blades are attached to a rotating disk (not shown) via daptills 5, and a casing 7
The rotary movement is caused by the working gas flowing inside. To cool the rotor blades, the coolant is supplied from the lower end of the doptail or the lower part of the platform 3, passes through the walls of the plurality of cooling pipes 8 bored inside the shank 4 and the blade part 1p while cooling, and is discharged from the tip of the rotor blade. This is done by Air, vapor, liquid, etc. are used as the refrigerant. The cooling pipes 8 are optimally designed to have two diameters and one position in order to uniformly and effectively cool the rotor blades. Although this cooling method has a simple structure and high design reliability, its cooling efficiency for a constant flow rate of refrigerant is usually inferior to, for example, a film cooling method in which refrigerant is blown out from the blade surface. For this reason, in order to apply convection cooling to blades with a high heat load, it was necessary to sacrifice some aerodynamic performance and increase the coolant flow rate.

An object of the present invention is to provide a gas turbine blade that dramatically improves cooling efficiency by promoting the cooling effect on the flow rate of refrigerant.

The feature of the present invention is to utilize the phenomenon that when a pulsation component is given to the fluid flowing inside the pipe, the average heat transfer coefficient within the pipe increases under the condition of a constant average flow velocity. As a means to give pulsation to the fluid, an uneven part whose inner diameter changes in the circumferential direction is provided on the inner surface of the stationary body facing the tip of the rotor blade, and the gap between the tip of the rotor blade and the casing from which refrigerant is discharged is The purpose is to change the direction of rotation of the refrigerant, and to give pulsations to the flow of the refrigerant due to fluctuations in the discharge resistance accompanying the rotation.

Next, a gas turbine blade □ which is an embodiment of the present invention will be explained.

In FIG. 4 to FIG. 6, the gas turbine rotor blade has a blade section 1.
, the shroud 2 which is its tip, and the platform 3 which is its base. A large number of discs, each consisting of a shank 4 and a dovetail 5, are fitted onto the outer periphery of a rotating disc (not shown) and are rotated by a high-temperature working fluid flowing within a casing 7 having a cylindrical or conical inner peripheral surface.

The refrigerant for cooling the gas turbine rotor blades is supplied from the lower part of the rotor blades, and the shank 3. The air is discharged into the working fluid from the tip of the blade through cooling holes 8 (only some of the cooling holes are shown) that penetrate the blade 1. The flow rate of the refrigerant is determined by the pressure difference between the entrance and exit of the cooling hole 8 and the inflow of the cooling hole 8.

Determined by the flow resistance of the outlet and pipe sections. This gas turbine rotor blade is characterized in that the refrigerant has a pulsation component, and the function of the pulsation in the refrigerant to improve cooling performance will be explained here. As an illustrative example, the phenomenon in which the internal heat transfer coefficient increases due to flow pulsation will be explained in more detail with reference to FIG. FIG. 7(a) is a schematic diagram showing a cooling pipe, and the average heat transfer coefficient within the pipe is determined by the pipe diameter, pipe length, physical property values of the cooling fluid, flow rate, etc. Now, if a pulsation component is given to the flow velocity of this cooling fluid as shown in Figure 7(b), the heat transfer coefficient in the tube will be compared to the case where the pulsation frequency is 0, that is, a uniform flow, as shown in Figure 7(C). increases as the pulsation frequency increases;
When the frequency becomes large enough, it approaches a constant value. In addition, as the amplitude of the pulsation increases, the heat transfer coefficient within the root canal increases as the amplitude increases. This phenomenon is thought to be due to the fact that the temperature boundary layer of the flow inside the tube is peeled off from the tube wall due to pulsation and becomes thinner, increasing the heat flow rate and increasing the heat transfer coefficient. Therefore, as a means for imparting a pulsating component to the refrigerant, in this embodiment shown in FIGS. 4 to 6, the refrigerant outflow resistance changes in the rotational direction at the refrigerant outflow portion at the tip of the gas turbine rotor blade. This is what I did. This refrigerant outflow resistance is determined by the gaps g, g' between the casing 7 and the inlet/outlet 8a of the cooling hole 8 at the tip of the gas turbine rotor blade, and the rotational speed of the rotor blade. Therefore, in this embodiment, by providing one or more protrusions 9 on the inner surface of the cage/gua, the protrusions 9 close the gap between the inner surface of the casing 7 and the cooling hole outlet 8a at the tip of the rotor blade. The part is g1, and the part without the protruding piece is g'. As a result, the outflow resistance changes with the rotation of the rotor blades, so the flow of refrigerant flowing through the cooling holes 8 becomes a pulsating flow with a frequency equal to the number of rotations times the number of protrusions. Further, the amplitude of the pulsation is determined by the gap g between the inner surface of the projection piece 9 and the cooling hole outlet portion 8a, and the smaller the gap g is, the larger the pulsation amplitude of the flow velocity can be. Therefore, obtaining an appropriate pulsating flow can be easily achieved by adjusting the number of protrusions and the gap g.

Although the above-mentioned embodiment is a case in which a shroud is attached to the tip of the gas turbine rotor blade, an embodiment in which a shroud is not attached to the tip of the rotor blade is shown in FIGS. 8 to 10. In the figure, if the gas turbine rotor blade does not have a shroud, one or more grooves 10- are provided on the inner surface of the cage/gua instead of the protruding pieces of the previous embodiment, thereby determining the outflow resistance of the refrigerant. 7 and the outflow part 8a of the cooling hole 8 from g to g as the rotor blade rotates.
' is made to change periodically.

Note that the flow of refrigerant in the cooling holes of the gas turbine rotor blades described above pulsates, but the overall cooling refrigerant flow is averaged by the sum of the pulsating flow rates of the individual blades due to the large number of blades. It doesn't change much. Therefore, the fluctuating flow does not affect the refrigerant supply source.

Furthermore, although the above-described embodiments have been described assuming that the refrigerant of the gas turbine rotor blades is gas, similar effects can be expected when a liquid such as water is used as the refrigerant. Figures 11(a) and 11(b) show the flow situation in the pipe when the refrigerant is liquid. FIG. 11 is a sectional view of the cooling holes 8 provided inside the blade. Further, 12 indicates the refrigerant inlet side, and 13 indicates the refrigerant outlet side.

FIG. 11(a) shows the case where no pulsation component is given to the refrigerant. In this case, part of the liquid refrigerant evaporates, resulting in a liquid phase 15 and a gas phase 1.
The liquid, which is divided into 6 parts and has a large specific gravity, is pressed onto some parts by Coriolika as it rotates. For this reason, the cooling effect is reduced in the tube wall of the cooling hole 8 only in the gas phase portion opposite to the source side, and thermal stress is likely to occur due to non-uniform cooling.

FIG. 11) is a schematic diagram showing a flow situation in a pipe when a pulsating component according to the present invention is given to a refrigerant by liquid cooling. In this case, the liquid phase is divided by the fluctuation of the discharge resistance, and the liquid phase 15 and the gas phase 16 become uniform and exist alternately on the tube wall of the cooling hole 8, and the evaporation of the liquid phase is promoted and a large boiling occurs. The heat transfer coefficient is obtained. In addition, since the amount of liquid discharged is reduced by the evaporation promotion gate, the generation of two lotions due to collision between the liquid and the casing and the adverse effects on performance are alleviated.

As described above, according to the embodiments of the present invention, by adding a pulsating component to the flow of refrigerant in the cooling holes, it is possible to increase the in-pipe heat transfer coefficient by 30% or more under the condition that the average cooling flow rate is constant, thereby improving the cooling efficiency. High gas turbine blades can be provided.

In other words, since the cooling target can be achieved with a small flow rate of refrigerant, it is possible to provide a high-performance turbine blade with low aerodynamic and thermal losses.

Therefore, according to the present invention, by providing a pulsating action to the refrigerant flow rate, the cooling effect is promoted, the cooling efficiency is dramatically improved, and the next generation gas turbine blade can be realized.

[Brief explanation of the drawing]

Fig. 1 is a plan view showing a conventional convection-cooled rotor blade, Fig. 2 is a front view showing a conventional casing and convection-cooled rotor blade, and Fig. 3 is a front view showing a conventional convection-cooled rotor blade.
The figure is a side view of Fig. 2, and Fig. 4 is a developed view from the inner circumferential side showing a casing structure showing one embodiment of the present invention. 6 is a side view of FIG. 5, and FIG. 7 (a
) is a schematic diagram of a cooling pipe, Figure 7(b) is a diagram showing the tendency of change in flow velocity with a pulsating component over time, and Figure 7(C) is a diagram showing the heat transfer coefficient in the pipe with respect to the frequency and amplitude of pulsation. , FIG. 8 is a developed view of the casing structure seen from the inner peripheral side showing another embodiment of the present invention, and FIG. 9 shows the casing and rotor blade section of FIG. 8 which is another embodiment of the present invention. Front view, No. 10
The figure is a side view of FIG. 9, FIG. 11(a) is a schematic diagram illustrating the flow situation in the cooling holes of a conventional liquid-cooled blade, and (inside FIG. 11) is the cooling hole of the liquid-cooled blade according to the present invention. FIG. DESCRIPTION OF SYMBOLS 1... Wing part, 2... Shroud, 7... Casing, 8... Cooling hole, 8a... Cooling hole outflow part, 9...
・Protrusion piece,' Fig. 7 (Phantom Fig. 7 (b) Tsubama Eki 8 Tsuba No. 99 I$IO Fig. ll) ↑12 v, ll -↓- Fig. Crin\-l -/6 Fig. b)

Claims (1)

[Claims] 1. In a gas turbine rotor blade having a cooling channel that allows a coolant to flow down inside the shrine, an annular stationary inner circumferential surface close to the cooling channel opening at the tip of the rotor blade has an inner diameter that changes in the circumferential direction. A gas turbine moxibustion device characterized in that a concavo-convex portion is provided to impart pulsation to a refrigerant flowing through a cooling flow.