KR20110079075A - A gas turbine blade and method for forming an internal cooling passage thereof - Google Patents

Abstract

PURPOSE: A gas turbine blade and a method for forming an internal cooling passage thereof are provided to improve the overall cooling performance because a spiral rib is formed in the internal cooling passage to create vortex. CONSTITUTION: A gas turbine blade(100) comprises an internal cooling passage(110) which receives cooling liquid. The internal cooling passage has a spiral rib(120) which is formed through ECM(Electro Chemical Machining).

Description

A gas turbine blade and method for forming an internal cooling passage

The present invention relates to a method for forming an internal flow path of a gas turbine blade for improving cooling performance. More specifically, the cooling performance by turbulent flow while minimizing the flow friction loss during the flow of the cooling fluid through the internal flow path of the gas turbine blade. It relates to a gas turbine blade that can improve the and a method for forming an internal flow path in the gas turbine blade.

Typically it is necessary to increase the turbine inlet temperature in order to increase the efficiency of the gas turbine, but if the turbine inlet temperature is increased, the turbine blade material is damaged due to the limitation of the turbine blade material. In order to improve such a problem, studies are recently underway to improve the heat resistance of elements in terms of processing such as surface treatment.

However, attempting to apply various cooling schemes is also parallel because protecting the blades only by this method also presents a limit to the fundamental problem. At this time, as the cooling method, film cooling, impingement jet cooling, forced convection cooling, etc. may be considered. Among these, forced convection cooling is an effective cooling method without loss caused by the cooling fluid as in the case of membrane cooling, as it is cooled through the flow path inside the blade, without further processing on the blade surface, compared to other cooling methods. .

In forced convection cooling, turbulence accelerators in the form of irregularities, fins and delta taps are sometimes used to improve cooling performance. Among these, the cooling method using the unevenness | corrugation especially is used a lot. Here, the unevenness is an apparatus used for disturbing the flow in the flow path to improve heat transfer.

First, a description of a conventional turbine blade, the main part of the gas turbine engine is largely divided into a compressor, a combustor, a turbine, wherein the turbine is composed of a stator blade and a rotor blade. The fixed blade serves to redirect the flow out of the combustor and to accelerate the flow, while the rotor blade generates work from the flow.

FIG. 1 is a perspective view illustrating an internal cooling flow path and an inclined unevenness by terminating a blade and a blade of a conventional turbine blade, and FIG. 2 is a schematic view illustrating a cross-sectional view taken along line II ′ of the general turbine blade illustrated in FIG. 1.

Fig. 1 shows one of these gas turbine blades, in which A represents a cooling passage (duct) and B represents inclined unevenness. As shown in Fig. 2, a plurality of cooling passages are formed in one rotor blade, and a plurality of inclined unevennesses are formed in parallel on the surface facing each cooling passage. These irregularities are formed in side by side and staggered arrangement, and have a structure having a constant angle of attack with respect to the flow on the cooling flow path. The method of forming the inclined unevenness in the cooling passage is manufactured by inserting the ceramic core in the gas turbine blade casting process to form the inclined unevenness and the flow path, and then melting and removing the ceramic core.

On the other hand, as another uneven form formed in the cooling passage of the conventional gas turbine blade, the gas turbine blade shown in US Patent No. 5,413,463 has a structure in which an annular recess is formed on the cooling passage. . That is, as shown in Figure 3, the cooling passage of the gas turbine blade has a structure in which a plurality of vertical recesses (annular recess) is formed at regular intervals along the axial path.

The forced convection cooling by the vertical unevenness or the inclined unevenness of the cooling channel has various factors such as the shape of the cooling channel, the height of the unevenness installed, the collision angle between the unevenness and the main flow, the distance between the unevenness and unevenness, and whether the unevenness is shorted. The cooling performance of the gas turbine blade flow path depends on.

The locally nonuniform cooling effect causes nonuniform temperature distribution on the blade surface and the resulting thermal stress, so it is important to improve the uniformity of the heat transfer coefficient as much as possible with the improvement of the average cooling performance. In addition, the smaller the pump (compressor) power to supply the cooling fluid is effective, the power is determined by the pressure drop (flow friction loss) increased by the unevenness installed in the duct. Therefore, it is necessary to design in consideration of frictional loss as well as improving cooling performance during uneven installation.

As described above, the arrangement of the concavities and convexities or the collision angles installed in the flow path of the gas turbine blade are very important factors for the cooling performance. At this time, it should be considered that not only the improvement of cooling performance but the overall heat transfer performance should be shown. In general, if the collision angle between the main flow and the unevenness is less than 90˚ or the unevenness is shortened, this will result in greater frictional loss, so that the same power can be used to achieve higher cooling performance. Design is necessary.

Accordingly, the present invention has been made to solve the above problems, the object of the present invention relates to a method for forming an internal flow path of the gas turbine blade for improving the cooling performance, the spiral (螺 旋) continuous to the internal flow path of the gas turbine blade By forming a spiral rib having a helical structure to generate a vortex-shaped turbulent flow in the internal flow path when the cooling fluid flows, a gas turbine blade capable of improving cooling performance by turbulent flow while minimizing flow friction loss. And a method of forming an internal flow path in the gas turbine blade.

Gas turbine blades according to the present invention for achieving the above object, in the gas turbine blades formed with an internal flow path for the cooling fluid flow, the inner circumferential surface of the inner flow passage is continuous spiral along the inner flow path It is characterized in that a spiral rib having an uneven structure is formed.

In this case, the spiral rib may be formed through electrochemical machining (ECM).

On the other hand, the present invention for achieving the above object, in the method for forming an internal flow path for the cooling fluid can flow in the gas turbine blade, a hole (hole) for the formation of the internal flow path in the gas turbine blade Making a step; Inserting an electrode into the hole and injecting an electrolyte into the electrode and transferring the electrode at a constant speed in the axial direction and rotating the same to form a spiral rib of a continuous spiral uneven structure on the inner circumferential surface of the hole; Characterized in that it comprises a.

In this case, the pitch between the ribs may be adjusted through the axial running speed and the rotational speed of the electrode.

According to the present invention having the above-described configuration, by forming a spiral rib having a continuous spiral structure in the internal flow path of the gas turbine blade through which the cooling fluid enters and exits, the spiral rib in the flow of the cooling fluid. As a result, the turbulence in the form of a vortex may be generated to improve the overall cooling performance of the gas turbine blade.

Hereinafter, with reference to the accompanying drawings for a preferred embodiment of the present invention will be described in detail.

4 is a perspective view illustrating an internal flow path structure of a gas turbine blade having a spiral uneven structure according to an embodiment of the present invention, and FIG. 5 is a cross-sectional view of the internal flow path of FIG. 4. 6 is a cross-sectional view illustrating an electrode structure used in forming a spiral internal flow path by ECM processing, and FIG. 7 sequentially illustrates a process of forming a spiral uneven structure in the internal flow path by ECM processing using the electrode of FIG. 6. It is a process chart explaining.

4 to 7, in the gas turbine blade 100 according to the present invention, a spiral uneven structure is formed on the internal flow path 110 of the gas turbine blade 100 through which a cooling fluid flows. The spiral rib 120 is formed in a continuous spiral shape along the internal flow path 110 of the gas turbine blade 100.

The spiral rib 120 is formed to protrude from the inner wall surface of the inner flow path 110 of the gas turbine blade 100 to a predetermined height (H) as shown in the detailed view of FIG.

In this case, since the spiral rib 120 has a predetermined inclination angle along the axial direction of the internal flow path 110 and is formed in a spiral shape, the cooling fluid flows in the process of cooling fluid flowing into the internal flow path 110. It is configured to collide with the helical rib 120 at a constant collision angle.

Here, the shape of the spiral rib 120 may be variously formed by appropriately adjusting the pitch between the height of the protrusion from the inner wall surface 110 of the inner channel 110 and the spiral rib 120 according to the design requirements. have.

The spiral rib 120 may be formed to have various cross-sectional shapes, such as rounded corners or rectangular corners.

Meanwhile, the spiral rib 120 may form the internal flow path 110 of the gas turbine blade 100 by using electrochemical machining (ECM), which is an electrochemical machining method.

The ECM processing is a method of electrochemically dissolving (corrosing) a metal material using electrolysis, and is used to form an internal flow path 110 having a spiral uneven structure through the ECM processing. Electrode 140 is used.

The electrode 140 has a three-dimensional pipe (pipe) shape, the inside is formed with a hollow 141 into which the electrolyte is injected, the side portion at least one discharge hole so that the electrolyte injected into the hollow 141 is discharged 142 is formed.

FIG. 7 illustrates a process of forming a spiral concave-convex structure in the internal flow path 110 using the electrode 140 having the above-described structure. As shown in FIG. 7, first, a predetermined diameter of the gas turbine blade 100 is shown. After processing the smooth hole (hole) of the internal flow path 110 is formed, the electrode 140 is inserted into the hole 110 to perform ECM processing on the electrode 140.

In this process, an electrolyte is injected into the hollow 141 of the electrode 140, and a predetermined level of voltage is applied between the gas turbine blade 100 and the electrode 140, and during processing by the electrode 140, As the electrode 140 is rotated at a constant speed and is transported at a constant speed in the axial direction of the internal flow path 110, the internal flow path is caused by electrolysis by the electrolyte discharged through the discharge hole 142 of the electrode 140. As the inner circumferential surface of the 110 is partially dissolved (corrosion), an inner flow path 110 having a continuous spiral uneven structure as shown in FIG. 4 may be formed on the inner circumferential surface of the hole.

When the spiral flow path is formed by the ECM process, the pitch P between the spiral ribs 120 may be adjusted through the axial traveling speed and the rotation speed of the electrode 140.

In addition, according to the number and arrangement of the discharge holes 142 formed on the side of the electrode 140 may be formed differently in the spiral shape of the internal flow path 110, for example, when the discharge hole 142 is one The spiral rib 120 may be formed in a single spiral shape, and when the discharge holes 142 are two, the spiral rib 120 may be formed in a double spiral shape.

In addition, by appropriately adjusting the axial running speed, the rotational speed, etc. of the electrode 140 during ECM processing, it is possible to form a spiral concave-convex structure of the desired shape in the inner flow path (110).

8 is a graph comparing the cooling performance of the spiral recessed and projected internal passage of the present invention and the conventional vertical recessed and projected internal passage as simulation results.

Here, the X-axis is the Reynolds Number (N) dimensionless the flow rate of the cooling fluid flowing through the internal flow path, Nu (Nusselt number) of the Y-axis is dimensionless the heat transfer coefficient, f is a dimensionless pressure drop.

As can be seen in the figure, the Nusselt number divided by the f number under the same Reynolds number condition is shown to increase up to 50% in the case of the spiral coil, it can be seen that the heat transfer performance is increased and the pressure drop is reduced.

In addition, Figure 9 is a simulation showing the flow and velocity distribution of the cooling fluid in the internal flow path of the spiral concave-convex structure according to the present invention.

As can be seen from the comparison graph of FIG. 8 and the simulation diagram of FIG. 9, the flow path loss due to the flow of the cooling fluid is less than that of the conventional annular recess internal flow path structure. It can be seen that the cooling performance of the blade is improved due to the uniform heat transfer by the vortex turbulent flow.

As described above, according to the present invention having the above-described configuration, the cooling fluid flows by forming a spiral rib having a continuous spiral structure in the internal flow path of the gas turbine blade through which the cooling fluid flows in and out. In the spiral ribs, turbulent turbulence may be generated to improve the overall cooling performance of the gas turbine blades.

1 is a perspective view showing an internal cooling passage and inclined unevenness by terminating the outer shape and the blade of a conventional turbine blade.

FIG. 2 is a schematic diagram showing a section line II ′ of the general turbine blade shown in FIG. 1; FIG.

3 is a cross-sectional view showing the internal flow path structure of a conventional gas turbine blade is formed with vertical irregularities.

Figure 4 is a perspective view showing the internal flow path structure of the gas turbine blade is formed spiral structure according to an embodiment of the present invention.

5 is a cross-sectional view of the inner flow passage of FIG. 4.

6 is a cross-sectional view showing an electrode structure used when forming a spiral internal flow path by ECM processing.

FIG. 7 is a process diagram sequentially illustrating a process of forming a spiral uneven structure in an internal flow path by ECM processing using the electrode of FIG. 6.

Figure 8 is a graph comparing the cooling performance of the spiral concave-convex structure inner passage of the present invention and the conventional vertical concave-convex inner passage.

9 is a simulation diagram showing the flow and velocity distribution of the cooling fluid in the inner flow path of the spiral uneven structure according to the present invention

<Description of the symbols for the main parts of the drawings>

100: gas turbine blade 110: internal flow path

120: spiral rib 140: electrode

141: hollow 142: discharge hole

Claims (5)

In the gas turbine blade having an internal flow path through which a cooling fluid can flow, The gas turbine blade, characterized in that the inner circumferential surface of the inner passage is formed with a spiral rib having a continuous spiral concave-convex structure along the inner passage. The gas turbine blade according to claim 1, wherein the helical rib is formed through electro chemical machining (ECM). A method for forming an internal flow path through which a cooling fluid can flow in a gas turbine blade, Machining a hole in the gas turbine blade for forming an internal flow path; Inserting an electrode into the hole and injecting an electrolyte into the electrode and transferring the electrode at a constant speed in the axial direction and rotating the same to form a spiral rib of a continuous spiral uneven structure on the inner circumferential surface of the hole; Method for forming an internal flow path of the gas turbine blade comprising a. 4. The method of claim 3, wherein the pitch between the ribs is controlled through an axial running speed and a rotational speed of the electrode. 4. The method of claim 3, wherein the rib has a semicircular cross section.

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