CN101173610A - Heated wall cooling structure and gas turbine blade using the cooling structure - Google Patents

Abstract

A heated wall surface cooling structure and a gas turbine blade using the cooling structure, the cooling structure has a dense wall surface layer, the dense wall surface layer is opened with a plurality of discrete through holes for coolant to pass through; the heated side of the dense wall surface layer is covered with a porous medium layer , making the porous medium layer and the dense wall surface layer with a plurality of discrete through-holes form a double-layer stacked structure, and the outlets of the discrete through-holes communicate with the porous medium layer. The porous medium layer can cover the dense wall surface layer continuously, or only cover the partial area of the outlet of the discrete through-hole. The invention combines the characteristics of air film cooling and sweat cooling, fully combines the advantages of the two cooling methods, can effectively improve the cooling efficiency on the wall surface, reduce the temperature gradient of the wall surface, and avoid the continuous increase of material thermal stress. At the same time, the strength of the cooling structure of the present invention is sufficient for common impeller machines.

Description

Heated wall cooling structure and gas turbine blade using the cooling structure

technical field

The invention relates to a cooling structure for a heated wall surface and a gas turbine blade using the cooling structure, belonging to the technical field of thermal engineering.

Background technique

Necessary cooling of mechanical structures in high-temperature environments to ensure safe operation of structures has always been a common problem in production and life. In applications involving heat engines, high-temperature surfaces that need to be cooled abound, such as cylinder walls of diesel and gasoline engines for vehicles, thrust chambers of rockets, blades of gas turbines, outer walls of ultra-high-speed aircraft, inner cylinders of super-combustion engines, etc. For gas turbines, increasing thermal efficiency and power means increasing turbine inlet temperature. The turbine inlet temperature, which has been increasing year by year, has exceeded 2000°C, while the maximum heat-resistant temperature of metal parts such as blades is generally only around 1000°C. Therefore, efficient cooling of gas turbine blades is a key factor that determines the future development of gas turbines.

According to the application position, the cooling of high-temperature surfaces includes two types: internal cooling and external cooling. Internal cooling refers to taking cooling measures on the inner side of the heated wall (that is, the opposite side of the high-temperature environment) to quickly take away the heat transferred from the high-temperature environment to the surface, such as regenerative cooling through convective heat exchange; external cooling refers to the cooling of the heated surface. Cooling measures are taken on the outside (that is, the side that is in contact with the high-temperature environment) to separate the high-temperature gas from the wall to reduce heat transfer between the two, such as gas/liquid film cooling, sweating cooling, shielding cooling, ablation cool down. Both air film cooling and sweat cooling use relatively low-temperature fluid as a coolant, which is discharged from a certain form of wall opening to form a cooling protection layer, thereby forming an effective active cooling of the high-temperature wall. But there is a big difference between the two: film cooling is generally done by opening discrete through holes with a diameter of millimeters on the dense wall, or even a straight groove with a width of millimeters; Formation of porous media with pores, such as sintered metal particle porous media with pores ranging from tens to hundreds of microns, and wire mesh with porosities ranging from tens to hundreds of PPI.

Common heated walls such as gas turbine blades, rocket thrust chambers, flame tubes of aeroengines, etc., one of the common points of these heated walls is that one side is washed by the high temperature mainstream, so the other side is usually cooled by coolant, or the cooling The agent is sprayed into the high-temperature main flow from a certain type of outlet on the heated wall surface, and directly cools the wall surface washed by the high-temperature main flow forcibly. Fig. 1 shows a schematic diagram of a conventional film cooling structure. One side of the dense wall surface layer 1 (the upper side in the figure) receives the scour of the high-temperature fluid 5, for example, for the gas turbine blade, it is the high-temperature gas at the outlet of the combustion chamber, The dense wall layer 1 is thus heated by the high temperature environment 6 on this side. Using methods such as laser drilling, a plurality of discrete through-holes 3 are formed on the dense wall surface layer 1 to be cooled, or air film holes. Cooling channel 8, so that coolant 7 is ejected from discrete through-holes 3, and a film-like coolant protection layer is formed on the heated side of dense wall surface layer 1, and the dense wall surface layer 1 is cooled and protected to prevent it from being burned. From the structural characteristics of this cooling method, it can be seen that since the air film holes for spraying out the coolant are discretely distributed, the film coolant on the heated side of the dense wall is also discretely distributed. When the temperature of the high-temperature environment is high, the dense wall surface Due to the existence of a large temperature gradient, the large thermal stress will cause the fatigue failure of the compact wall surface, which is very unfavorable for the gas turbine blades that use film cooling as the main cooling method, because the gas turbine blades are often subjected to high temperature Mainstream thermal shock etc.

Fig. 2 is a schematic diagram of a conventional sweat cooling structure. The part of the dense wall surface layer 1 that is strongly heated is replaced by a porous medium layer 2, and a cooling channel 8 is formed on the opposite side that is heated, so that the coolant 7 flows from the porous medium layer 2. It sprays out from the pores in the dense wall surface layer 1 and forms a sweat-like coolant protection layer on the heated side of the dense wall surface layer 1 to cool and protect the dense wall surface layer 1 to prevent it from being burned. The advantage of this cooling method is that it can provide uniform cooling protection for the entire cooled area, and in the case of using the same flow rate of coolant, the cooling efficiency is generally higher than that of the aforementioned film cooling. However, since sweat cooling requires a porous material as a whole, and the pores are relatively small, the biggest disadvantage is that the structural strength of the wall is not only much inferior to the dense wall without cooling measures, but also far inferior to the wall with air film holes. At the same time, another shortcoming that makes it still unable to be effectively used in complex situations is that it is easy to block, and local blockage is likely to cause local high-temperature failure, and then the entire cooling wall will be burned quickly.

The cooling structure adopted by the existing gas turbine blade is as follows: the inside of the blade has a convective cooling channel with enhanced heat exchange measures, and the wall surface is provided with discrete through holes for film cooling. Fig. 7 shows the cooling structure of the existing gas turbine blade, the coolant flows in the internal coolant channel 4 of the blade, and is sprayed through the discrete through-holes 3 opened on the blade surface, thereby forming a cooling gas film layer on the blade surface , effectively protect the blades washed by high temperature gas. Fig. 8 is a cross-sectional view of an existing film-cooled gas turbine blade. The coolant flows through the blade internal coolant channel 4 in the center of the blade, and is sprayed out through the discrete through-holes 3 provided on the dense wall surface layer 1 of the blade. Formed as a cooling air film around the dense wall of the blade. Some scholars have proposed to use porous media to construct blades to use sweat cooling to further improve the cooling capacity. In short, the existing film cooling of gas turbines has the following deficiencies: the cooling capacity is limited; the use of discrete through holes leads to uneven cooling, correspondingly large thermal stress, and the material is prone to fatigue failure. Sweating cooling has the following disadvantages: the strength of the porous medium forming sweating cooling is poor; it is easy to cause overall failure due to local blockage.

Contents of the invention

In order to overcome the deficiencies and defects of air film cooling and sweat cooling, the present invention proposes a cooling structure for the heated surface and a gas turbine blade using the cooling structure. Cooling, to ensure that the wall surface of the cooling structure has a certain strength, try to make the strength of the cooling wall surface close to the original dense wall surface; further improve the cooling efficiency of the heated wall surface, try to make the cooling efficiency of the heated wall surface close to sweat cooling; Under the premise of efficiency, the strength of the wall surface is guaranteed.

In order to solve the problems of the technologies described above, the present invention takes the following technical solutions:

A cooling structure for a heated wall surface, which has a dense wall surface layer, and the dense wall surface layer is provided with a plurality of discrete through holes for coolant to pass through, and is characterized in that: the heated side of the dense wall surface layer is covered with a porous medium layer, making the porous medium layer The medium layer and the dense wall surface layer with a plurality of discrete through-holes form a double-layered structure, and the porous medium layer covers the outlets of all the discrete through-holes; the porous medium layer is a whole piece of continuous distribution, continuous completely cover the heated side of the dense wall surface layer, so that the outlets of all the discrete through holes are covered by the whole porous medium layer; On the heated side of the dense wall surface layer, the outlets of all the discrete through holes are respectively covered by the multi-piece porous medium layer.

The cooling structure of the heated wall surface of the present invention is characterized in that: the diameter of the discrete through-holes is 0.1-5mm; the arrangement of the discrete through-holes is arranged in parallel or forked rows; the discrete through-holes are inclined holes, cylindrical holes or outlets Diffusion holes with local diffusion.

The cooling structure of the heated wall surface of the present invention is characterized in that: the thickness of the porous medium layer is 0.5 to 3 times the diameter of the discrete through holes or 0.4 to 10 mm. The porous medium layer is made of sintered bronze, stainless steel or nickel-based alloy particles, the particle diameter is 10-5000 microns, and the porosity is between 0.2-0.5; another option for the porous medium layer is ceramic porous structure , the pore size of the ceramic porous structure is equal to between 5 and 500 microns; another selection of the porous medium layer is copper, copper alloy, stainless steel or nickel-based alloy material, and the structure is woven wire mesh or foam metal, and the woven wire mesh Or the pore size of the metal foam is equal to 100-1000 microns.

The technical feature of the present invention is also: each sheet of the discontinuously distributed porous medium layer extends along the upstream and downstream directions of the high-temperature main flow, so that the distance between the edge of the porous medium layer and the edge of the nearest row of discrete through-hole outlets is 0.5 to 10 times the diameter of the discrete through-holes; the porous medium layer covers the outlets of the entire row of discrete through-holes in strips. The distance that the porous medium layer extends along the downstream direction of the high-temperature main flow is greater than the distance along the upstream direction of the high-temperature main flow.

The invention provides a gas turbine blade with a heated wall surface cooling structure, which contains a dense wall surface layer that constitutes the basic structure of the blade. The dense wall surface layer is provided with a plurality of discrete through holes for coolant to pass through. It is characterized in that: the dense wall surface layer The outer side is covered with a porous medium layer, so that the porous medium layer and the dense wall surface layer with a plurality of discrete through-holes form a double-layered structure, and the porous medium layer covers the outlets of all the discrete through-holes; the porous medium The thickness of the layer is 0.5 to 3 times the diameter of the discrete through holes or 0.4 to 10mm; the porous medium layer is a whole piece of continuous distribution, which continuously and completely covers the heated outer surface of the dense wall surface layer, so that all the discrete through holes The outlet of the hole is covered by the whole piece of porous medium layer; or the porous medium layer is composed of discontinuously distributed multi-pieces, which are discretely and partially covered on the heated outer surface of the dense wall surface layer, so that the outlets of all discrete through holes are respectively Covered by the multi-piece porous medium layer.

The gas turbine blade with a heated wall surface cooling structure according to the present invention is characterized in that: the diameter of the discrete through holes is 0.1-5mm; the arrangement of the discrete through holes is arranged in parallel or fork; the discrete through holes are inclined holes , Cylindrical holes or diffuser holes with localized diffusion at the exit.

The gas turbine blade with a heated wall surface cooling structure according to the present invention is also characterized in that: each piece of the discontinuously distributed porous medium layer extends along the upstream and downstream directions of the high-temperature main flow, so that the edge distance of the porous medium layer The distance from the exit edge of the nearest row of discrete through holes is 0.5 to 10 times the diameter of the discrete through holes. The distance that the porous medium layer extends along the downstream direction of the high-temperature main flow is greater than the distance along the upstream direction of the high-temperature main flow; the porous medium layer covers the outlets of the entire row of discrete through holes in strips. The porous medium layer is made of sintered bronze, stainless steel, and nickel-based alloy particles, the particle diameter is 10-5000 microns, and the porosity is between 0.2-0.5; another option for the porous medium layer is ceramic porous structure , the pore size is between 5 and 500 microns; another choice of the porous medium layer is copper, copper alloy, stainless steel or nickel-based alloy, and the structure is woven wire mesh or foam metal.

The present invention combines the characteristics of air film cooling and sweating cooling, uses a structure in which a porous medium layer is partially covered at the outlet of the discrete through hole, fully combines the advantages of the two cooling methods, and can effectively provide cooling efficiency on the wall surface and reduce The temperature gradient of the wall surface avoids continuous increase of material thermal stress, and meanwhile, the strength of the cooling structure of the present invention is sufficient to be used in common impeller machines.

Description of drawings

Figure 1: Schematic diagram of conventional film cooling.

Figure 2: Schematic diagram of conventional sweat cooling.

Figure 3: The cooling structure of the present invention.

Fig. 4: The cooling structure of the present invention, wherein the porous medium layer is distributed continuously and completely covers the heated side of the dense wall surface layer.

Fig. 5: The cooling structure of the present invention, in which the porous medium layer is discretely distributed and discretely partially covers the heated side of the dense wall surface layer.

Fig. 6: The cooling structure of the present invention, wherein the distance that the porous medium layer extends along the downstream direction of the high-temperature main flow is greater than the distance along the upstream direction of the high-temperature main flow.

Figure 7: Schematic diagram of existing gas turbine blade film cooling.

Figure 8: Schematic diagram of existing gas turbine blade film cooling, blade cross-section.

Fig. 9: A cross-sectional view of a gas turbine blade applying the cooling structure of the present invention.

Figure 10: Schematic diagram of the distribution of film holes on the surface of the existing film-cooled gas turbine blade.

Fig. 11: Schematic diagram of the coverage of the porous medium layer on the surface of the gas turbine blade of the present invention.

Fig. 12(a): Simulation results of temperature gradient on a conventional film cooling surface.

Figure 12(b): Simulation results of the surface temperature gradient of the present invention.

In the figure: 1. Dense wall surface layer; 2. Discrete through holes; 3. Porous medium layer; 4. Coolant channel inside the blade; 5. High temperature fluid; 6. High temperature environment; 7. Coolant; 8. Cooling flow channel.

Detailed ways

The principle and specific structure of the present invention will be further described below.

The heated wall surface cooling structure provided by the present invention has a dense wall surface layer 1, and the dense wall surface layer 1 is provided with a plurality of discrete through holes 3 for coolant to pass through, and the heated side of the dense wall surface layer 1 is covered with a porous medium layer 2, Thereby the porous medium layer 2 and the dense wall surface layer 1 having a plurality of discrete through-holes 3 form a double-layer stacked structure, and the described porous medium layer 2 covers the outlets of all the discrete through-holes 3; the described porous medium layer 2 is A whole piece of continuous distribution is continuously and completely covered on the heated side of the dense wall surface layer 1, so that the outlets of all the discrete through holes 3 are covered by the whole piece of porous medium layer 2; or the porous medium layer 2 is not composed of Continuously distributed multi-piece composition, discretely partially covered on the heated side of the dense wall surface layer 1, so that the outlets of all discrete through holes 3 are covered by the multi-piece porous medium layer 2 respectively; the diameter of the discrete through holes 3 is 0.1-5mm; the discrete through-holes 3 are arranged in a straight row or a fork row; the discrete through-holes 3 are inclined, and are cylindrical holes or diffusion holes with local diffusion at the outlet.

Therefore, the coolant enters the porous medium after flowing through the discrete through-holes. Due to the divergent effect of the porous medium on the fluid, the coolant finally forms a cooling protection similar to sweating on the heated side of the porous medium.

In the heated wall surface cooling structure of the present invention, the diameter of the discrete through-holes is 0.1-5mm, the discrete through-holes 3 are distributed in parallel or forked rows, and the discrete through-holes 3 can be inclined, which are cylindrical holes or outlets with Diffusion pores for local diffusion. The diameter of the discrete through-holes 3 of the present invention has the same order of magnitude as the existing film cooling holes, which is about several millimeters; the arrangement of the discrete through-holes 3 can also be arranged in a row and fork as conventional gas film holes; consider To the flow direction of the high-temperature main flow on the heated side, setting the discrete through-holes 3 to form an acute angle with the flow direction of the high-temperature main flow is helpful to improve cooling efficiency; the conventional discrete through-holes formed by mechanical means are generally cylindrical holes, that is, horizontal The cross-section is a circular hole, but in order to improve the distribution of the outlet coolant, a diffusion outlet can be provided at the outlet of the discrete through hole, and the diffusion outlet can be in the shape of a dustpan, a funnel, or the like, thereby forming a diffusion hole.

In the heated wall surface cooling structure of the present invention, the porous medium layer is formed by sintering bronze, stainless steel, and nickel-based alloy particles, the particle diameter is 10-5000 microns, and the porosity is between 0.2-0.5, preferably the particle diameter is 80 Micron and 200 micron, preferably get porosity 0.33 and 0.36; As another option, this porous medium layer also can be ceramic porous structure, and its pore size is equal to between 5～500 micron, preferably gets 20 micron; As another choice , the porous medium layer is a wire mesh structure of copper, copper alloy, stainless steel or nickel-based alloy, and its pore size is equal to 100-1000 microns, preferably 100 microns, 200 microns and 500 microns. The thickness of the porous medium layer is 0.5 to 3 times the diameter of the discrete through hole or 0.4 to 10 mm, preferably 1 and 1.8 times the diameter of the discrete through hole, or preferably the thickness of the porous medium layer is 1.2 mm and 2 mm, so that the porous The dielectric layer is thick enough to provide effective sweat cooling without unnecessarily increasing the thickness of the cooling structure.

In the cooling structure of the heated wall surface of the present invention, the porous medium layer can be continuously distributed and completely cover the heated side of the dense wall surface layer, which is equivalent to the protection of the dense wall surface covered with a layer of porous medium layer, so that the coolant can In the porous medium layer, it flows to any area that needs to be protected on the dense wall surface; the porous medium layer can also be discontinuously distributed on the heated side of the dense wall surface layer, partially covering the discrete through-hole area. Considering the actual situation, The heat flux density of each area of the heated wall is not the same, and usually only need special cooling protection for some intensely heated areas, so discrete through holes can be set in these individual areas, and locally between the dense walls of these areas The outer cover is covered with a porous medium layer, so that the coolant can be used in a targeted manner.

In the cooling structure of the heated wall surface of the present invention, in addition to covering the outlets of the discrete through-holes, the porous medium layer also extends along the upstream and downstream directions of the high-temperature main flow, and the distance from the edge of the nearest row of discrete through-hole outlets is 0.5 to 10 times The diameter of the discrete through hole, preferably take this distance as 5 times and 10 times the diameter of the discrete through hole, in order to make the coolant fully diffuse in the porous medium layer after flowing out from the discrete through hole, the area of the porous medium layer should be It is larger than the outlet of the discrete through hole, and a certain margin is guaranteed. For example, as mentioned above, after covering the outlet of the discrete through hole, the edge of the porous medium layer should be about 0.5 to 10 times away from the edge of the nearest row of discrete through hole outlets. The distance of the discrete via diameters. Since the coolant can diffuse in the porous medium layer along the downstream direction, the distance that the porous medium layer extends along the downstream direction of the high-temperature main flow is greater than the distance along the upstream direction of the high-temperature main flow.

In the heated wall surface cooling structure of the present invention, the porous medium layer is strip-shaped, covering the outlets of the entire row of discrete through holes. As mentioned above, the porous medium layer can be discontinuously distributed according to local conditions, and the discrete through-holes can be distributed in rows, so the porous medium layer covering the outlets can be strip-shaped.

In the heating wall cooling structure of the present invention, the heating wall adopts different cooling methods in different areas, and it is characterized in that: at least a part of the area adopts the structure of combining the aforementioned discrete through-holes with the porous medium layer, and at least another part of the area adopts sweating Cooling or film cooling, so that multiple cooling structures coexist on the heated wall.

The cooling structure of the gas turbine blade of the present invention has a dense wall surface layer 1 constituting the basic structure of the blade. The dense wall surface layer 1 is provided with a plurality of discrete through holes 3 for coolant to pass through. It is characterized in that: the outer side of the dense wall surface layer 1 Covered with a porous medium layer 2, so that the porous medium layer 2 and the dense wall surface layer 1 with a plurality of discrete through holes 3 form a double-layered structure, and the porous medium layer 2 covers the outlets of all the discrete through holes 3; The thickness of the porous medium layer 2 is 0.5 to 3 times the diameter of the discrete through holes 3 or 0.4 to 10mm; the porous medium layer 3 is a whole piece of continuous distribution, which continuously and completely covers the dense wall surface layer 1 and is heated. so that the outlets of all the discrete through-holes 3 are covered by the whole piece of porous medium layer 3; or the porous medium layer 3 is composed of discontinuously distributed pieces, which are discretely and partially covered on the dense wall surface layer 1 to be heated so that the outlets of all the discrete through-holes 3 are covered by the multi-piece porous medium layer 2; the diameter of the discrete through-holes 3 is 0.1-5mm; ; The discrete through hole 3 is inclined, and is a cylindrical hole or a diffusion hole with local diffusion at the outlet.

As a preferred embodiment of the cooling structure of the gas turbine blade of the present invention, the diameter of the discrete through-holes is 0.1 to 5mm, preferably selected as 0.4mm, 0.8mm and 1.2mm; the discrete through-holes are arranged in a straight row or fork row According to actual needs, the discrete through-holes can be arranged in parallel and fork rows; the discrete through-holes are cylindrical holes or diffusion holes with local diffusion at the outlet; the thickness of the porous medium layer is 0.5- 3 times the diameter of the discrete through holes is either 0.4-10 mm, preferably 1 and 1.8 times the diameter of the discrete through holes, or preferably the thickness of the porous medium layer is 1.2 mm and 2 mm.

As a preferred embodiment of the cooling structure of the gas turbine blade of the present invention, the porous medium layer is distributed continuously and completely covers the outside of the dense wall surface layer; the porous medium layer can also be distributed discontinuously. The heated side of the dense wall layer partially covers the discrete via regions.

As a preferred embodiment of the cooling structure of the gas turbine blade of the present invention, the porous medium layer extends along the upstream and downstream directions of the high-temperature main flow, so that after the coolant flows out from the discrete through holes, it can cool the discrete through holes in the porous medium layer. Both the upstream and downstream areas of the hole outlet form cooling protection, and the distance between the porous medium layer and the edge of the nearest row of discrete through-hole outlets is 0.5 to 10 times the diameter of the discrete through-hole, preferably 5 times and 10 times the distance Discrete the diameter of the through hole, so as to ensure that the coolant can be sufficiently diffused by the porous medium layer.

As a preferred embodiment of the cooling structure of the gas turbine blade of the present invention, the distance that the porous medium layer extends along the downstream direction of the high-temperature main flow is greater than the distance extending along the upstream direction of the high-temperature main flow, thereby considering the cooling of the high-temperature main flow near the wall The influence of the agent, so that the downstream area is fully cooled.

As a preferred embodiment of the cooling structure of the gas turbine blade of the present invention, the porous medium layer covers the outlets of the entire row of discrete through holes in strips.

As a preferred embodiment of the cooling structure of the gas turbine blade of the present invention, the porous medium layer is made of sintered bronze, stainless steel or nickel-based alloy particles, the particle diameter is 10-5000 microns, and the porosity is between 0.2-0.5, Preferably, the particle diameter is 80 microns and 200 microns, and the porosity is preferably 0.33 and 0.36; the porous medium layer can also be a ceramic porous structure, and its pore size is between 5 and 500 microns, preferably 20 microns; The porous medium layer described above can also be a woven wire mesh or a metal foam structure, and its material is copper, copper alloy, stainless steel or nickel-based alloy, and its pore size is equal to 100-1000 microns, preferably 100 microns, 200 microns and 500 microns. Microns.

Another gas turbine blade cooling structure of the present invention, the gas turbine blade adopts different cooling methods in different areas, characterized in that: at least a part of the area adopts the structure covered by the above-mentioned discrete through holes and porous medium layer, and at least another part Zones are either film cooled or sweat cooled, allowing multiple cooling structures to co-exist on the heated wall.

Both air film cooling and sweat cooling use relatively low temperature fluid as a coolant, which is discharged from a certain form of wall opening to form a cooling protection layer, thereby forming an effective active cooling of the high temperature wall, but both have their own characteristics. Film cooling is widely used to protect turbine blades by injecting compressor air as coolant through discrete through-holes on the surface of the airfoil to ensure safe operation of high-temperature components such as blades. With the need to further increase the power and thermal efficiency of gas turbines, the cooling capacity of film cooling can no longer fully meet the increasing turbine inlet temperature. In addition, conventional discrete through-hole film cooling still has the problem of large temperature gradients on the blade surface .

Sweating cooling can provide high cooling efficiency by expelling coolant from porous walls. Existing studies have shown that to obtain the same cooling effect, the blowing ratio of sweat cooling is only about 1/50 of that of air film cooling. The use of wire mesh porous walls combined with steam cooling is considered to be one of the solutions for blade cooling of high-efficiency turbines in the future. However, since sweat cooling uses a porous wall, the strength of the material is far inferior to the dense wall with discrete through-holes required by film cooling, and the cooling effect is easily deteriorated due to local defects such as blockage, which in turn leads to overall burnout, so that It has not yet entered the practical stage of blade cooling.

The present invention will be described below in conjunction with the accompanying drawings, so as to further understand the present invention.

Fig. 3 shows the cooling structure of the heated wall surface of the present invention, which has a dense wall surface layer 1, which is provided with a plurality of discrete through holes 3 for coolant to pass through, and the heated side of the dense wall surface layer 1 is covered with The porous medium layer 2, thus the porous medium layer 2 and the dense wall surface layer 1 with a plurality of discrete through-holes 3 form a double-layer stacked structure, and the porous medium layer 2 completely covers the outlets of all the discrete through-holes 3 . From the structural characteristics of the cooling method of the present invention, it can be seen that since the outlet of the discrete holes is covered with a porous medium layer, the coolant sprayed from the discrete holes can be dispersed by the porous medium layer, so that its spatial distribution tends to be uniform, thereby Improve the problem of uneven cooling rate and large temperature gradient of the original film cooling. At the same time, because there is a dense wall layer 1 with only discrete holes under the porous medium layer 2 with low strength, the overall wall surface Compared with the simple porous medium layer, the strength is greatly improved, and because the coolant ejected from the discrete holes has a higher local velocity, it can also reduce the probability of the overall failure of the porous medium layer due to local defects.

A kind of cooling structure of the heated wall surface of the present invention shown in Fig. 3, the size of described discrete through-hole 3 is similar to the size of the air film hole of existing gas turbine blade air film cooling, and its diameter can be taken as 0.1～5mm, preferably The selection is 0.4mm, 0.8mm and 1.2mm, which are generally larger than the pore diameter of the pores of the porous medium layer; the discrete through-holes 3 are distributed in a straight row or a fork row, and these two arrangements are consistent with the typical arrangement of the gas film holes in the existing gas film cooling In the same way, it can also be mixed and coexisted according to actual needs; the discrete through-holes can be inclined, that is, form an acute angle with the direction of the outer high-temperature fluid 5, and be cylindrical holes or diffusion holes with local diffusion at the outlet .

For sweat cooling, the porous medium layer 2 that forms sweat is generally a layer of sintered metal particles. In the heating wall surface cooling structure of the present invention, the porous medium layer 2 is made of sintered bronze, stainless steel, and nickel-based alloy particles, the particle diameter is 10-5000 microns, and the porosity is between 0.2-0.5; as another option, the porous The medium layer 2 can also be a ceramic porous structure, and its pore size is equal to between 5 and 500 microns; as another option, the porous medium layer 2 is a copper, copper alloy, stainless steel or nickel-based alloy wire mesh structure, and its pore size is equal to 100-1000 microns. The thickness of the porous medium layer 2 is 0.5 to 3 times the diameter of the discrete through holes or 0.4 to 10 mm, so that the thickness of the porous medium layer is sufficient to form effective perspiration cooling without unnecessary increase in the thickness of the cooling structure.

Figure 4 shows an embodiment in which the porous medium layer 2 can be continuously distributed, and the porous medium layer 2 completely covers the heated side of the dense wall surface layer 1, which is equivalent to the side where the dense wall surface layer 1 is washed by the high-temperature fluid 5 A layer of protection covering the porous medium layer 2 allows the coolant 7 to flow in the porous medium layer 2 to any area of the dense wall surface layer 1 that needs to be protected.

As an embodiment corresponding to the embodiment in FIG. 4 , as shown in FIG. 5 , the porous medium layer 2 is discontinuously distributed on the heated side of the dense wall surface layer 1 , partially covering the area of the discrete through holes 3 . Considering the actual situation, the heat flux density of each area of the heated wall is not the same, and usually only need special cooling protection for some intensely heated areas, so discrete through holes can be set in these individual areas, and locally The dense wall surfaces of these regions are covered with the porous medium layer 2, so that the coolant can be used intensively. As an example of the discontinuous distribution of the porous medium layer 2, in addition to covering the outlets of the discrete through-holes 3, the porous medium layer 2 also extends along the upstream and downstream directions of the high-temperature main flow. The distance is 0.5 to 10 times the diameter of the discrete through-holes. This is to allow the coolant 7 to fully diffuse in the porous medium layer 2 after flowing out from the discrete through-holes 3. The area of the porous medium layer 2 is larger than that of the discrete through-holes 3. The export, and guarantee a certain margin.

Figure 6 shows a preferred embodiment of the discontinuous distribution of the porous medium layer 2 in the present invention. Taking the outlet of the discrete through hole 3 as a reference point, the distance that the porous medium layer 2 extends along the downstream direction of the high-temperature main flow is greater than that along the high-temperature fluid 5, since the flow directions of the high-temperature fluid 5 and the coolant 7 are relatively uniform, more distribution of the porous medium layer 2 downstream of the discrete through holes 3 is conducive to better dispersion of the coolant 7.

Considering the convenience of processing, the generally discrete through-holes 3 can be set to be distributed in rows. Therefore, as a preferred embodiment of the heated wall cooling structure in the case of the discontinuous distribution of the porous medium layer 2 of the present invention, the porous medium layer 2 is striped. shape, covering the outlets of the entire row of discrete through holes 3, the porous medium layer 2 can be discontinuously distributed according to local conditions, and the discrete through holes 3 can be distributed in rows, so the porous medium layer 2 covering the outlets can be strip-shaped.

As a preferred embodiment of the present invention, considering the complex situation of the existing heated wall, usually the heat flux received by different areas on the wall and other working conditions are quite different, so it is possible to adopt multiple cooling structures according to local conditions. For example, in some areas, the cooling structure of the present invention is adopted, that is, discrete through-holes are opened on the dense wall surface, and a porous medium layer is covered on the heated side of the dense wall surface, so that the porous medium layer completely covers the outlet of the discrete through-holes , and open film holes in another part of the area to form film cooling, and optionally replace the dense wall surface layer with a porous medium layer in another part of the area to form sweat cooling.

Fig. 9 shows an embodiment of a gas turbine blade applying the cooling structure of the present invention. Compared with the existing film cooling gas turbine blade, in the gas turbine blade cooling structure of the present invention, discrete channels are provided on the dense wall surface layer 1 of the blade. holes 3, but a layer of porous medium layer 2 is covered on the outer side of the dense wall surface layer 1, and the porous medium layer 2 completely covers the outlets of these discrete through holes 3, so that when the coolant flows through the coolant passage 4 inside the blade, it can flow from the discrete The through hole 3 sprays out, and due to the dispersion effect of the porous medium layer 2, a uniform protective layer similar to sweat cooling is formed on the outer surface of the blade. At the same time, compared with the original film cooling, the cooling structure of the present invention can effectively overcome the shortcomings of large temperature gradient on the dense wall surface of the blade and insufficient cooling efficiency, and compared with the proposed integral porous medium blade, its structural strength is much higher. Big improvement.

Fig. 10 is a schematic diagram of film cooling of an existing gas turbine blade. Discrete through-holes are distributed in rows on the dense wall layer of the blade, so that film cooling protection layers connected in sheets can be formed at different positions.

Fig. 11 is the cooling structure of the gas turbine blade of the present invention, similar to the film cooling shown in Fig. 10, the discrete through-holes on the dense wall surface layer of the blade are distributed in rows, and the outer side of the blade is discontinuously covered with a porous medium layer, in the form of A strip-shaped layer of porous medium covers the outlets of the discrete through-holes. And as a preferred embodiment, for different regions, different porous medium layers can be selected, such as different porosity, or even different types of porous medium layers. In some areas with low heat flux density, or some areas where film cooling is already competent, such as the blade trailing edge area, the discrete through-holes may not be covered by the porous medium layer, thus forming a gas turbine blade with multiple cooling structures.

The results of computer numerical simulation show that the cooling effect of the invention is better than that of conventional air film cooling, and the temperature gradient of the wall surface is much smaller during cooling. Fig. 12 (a) and Fig. 12 (b) respectively have represented the surface temperature gradient distribution of conventional film cooling and the cooling structure of the present application under a certain cooling capacity, can obtain from the figure, adopt the cooling structure of the present invention to reduce the surface temperature Areas with high temperature gradients. Moreover, the computer simulation structure shows that: 1) when the blowing ratio is 0.6, the maximum surface temperature gradient of conventional air film cooling is 329007 K/m, and the average surface temperature gradient of the local cooling area is 3293 K/m. The maximum surface temperature gradient of the invented cooling structure is 16046 K/m, and the average surface temperature gradient of the local cooling area is 1373 K/m; 2) When the blowing ratio is 0.9, the surface temperature gradient of conventional air film cooling The maximum value is 351654K/m, the average value of the surface temperature gradient of the local cooling area is 1790 K/m, the maximum value of the surface temperature gradient of the cooling structure of the present invention is 16816 K/m, and the average value of the surface temperature gradient of the local cooling area is 1301 K/m. It can be seen that under the same blowing ratio (ie, the same coolant flow rate), the cooling structure of the present invention can greatly reduce the temperature gradient on the surface, thereby avoiding too high thermal stress.

Claims (11)

1. the cooling structure of a heated wall surface, has fine and close wall layer (1), this densification wall layer (1) has a plurality of discrete through hole (3) that passes through for freezing mixture, it is characterized in that: the side of being heated of this densification wall layer (1) is coated with porous medium layer (2), the fine and close wall layer (1) that makes porous medium layer (2) and have a plurality of discrete through holes (3) constitutes double-deck stacked structure, and described porous medium layer (2) covers the outlet of all discrete through holes (3); Described porous medium layer (3) is the whole piece of continuous distributed, completely continuously covers the side that fine and close wall layer (1) is heated, and the outlet of all discrete through holes (3) is covered by this whole piece porous medium layer (3); Perhaps described porous medium layer (3) is made up of discontinuously arranged multi-disc, and the part covers the side that fine and close wall layer (1) is heated discretely, and the outlet of all discrete through holes (3) is covered by this multi-disc porous medium layer (3) respectively.

2. the cooling structure of a kind of heated wall surface as claimed in claim 1, it is characterized in that: the diameter of described discrete through hole (3) is 0.1～5mm, preferably gets 0.4mm, 0.8mm and 1.2mm; The arrangement of discrete through hole (3) is in-line arrangement or fork row distributes; Discrete through hole (3) is the diffusion hole that slope hole, cylindrical hole or outlet have local diffusion.

3. the cooling structure of a kind of heated wall surface as claimed in claim 1, it is characterized in that: the thickness of described porous medium layer (2) is the diameter of 0.5～3 times of discrete through hole (3), preferably gets the diameter of 1 times and 1.8 times discrete through hole; Perhaps be taken as 0.4～10mm, preferably be taken as 1.2mm and 2mm.

4. the cooling structure of a kind of heated wall surface as claimed in claim 1 is characterized in that: described porous medium layer (3) forms for bronze, stainless steel or nickel-base alloy particle sintering, and particle diameter is 10～5000 microns, and porosity ratio is between 0.2～0.5; Another selection of described porous medium layer (3) is ceramic porous structure, and the pore size of ceramic porous structure equals between 5～500 microns; The another selection of described porous medium layer (3) is copper, Cuprum alloy, stainless steel or nickel-base alloy material, and structure equals 100～1000 microns for braiding silk screen or foam metal, the pore size of braiding silk screen or foam metal.

5. the cooling structure of a kind of heated wall surface as claimed in claim 1, it is characterized in that: each sheet of described discontinuously arranged porous medium layer (2) all extends along the upstream and downstream direction of high temperature main flow, the edge that makes porous medium layer (2) is the diameter of 0.5～10 times discrete through hole (3) apart from the distance of discrete through hole (3) outlet edge of a nearest row, preferably gets this distance and be the diameter of the discrete through hole of 5 times and 10 times; Described porous medium layer (2) covers the outlet of the discrete through hole (3) of whole row into strips.

6. the cooling structure of heated wall surface as claimed in claim 5, the distance of extending along the downstream direction of high temperature main flow at described porous medium layer (2) is greater than the distance of extending along the updrift side of high temperature main flow.

7. gas turbine blades with heated wall surface cooling structure, contain the fine and close wall layer (1) that constitutes blade basic structure, this densification wall layer (1) has a plurality of discrete through hole (3) that passes through for freezing mixture, it is characterized in that: the outer side covers of this densification wall layer (1) has porous medium layer (2), the fine and close wall layer (1) that makes porous medium layer (2) and have a plurality of discrete through holes (3) constitutes double-deck stacked structure, and described porous medium layer (2) covers the outlet of all discrete through holes (3); The thickness of described porous medium layer (2) is the diameter of 0.5～3 times of discrete through hole (3) or is 0.4～10mm; Described porous medium layer (3) is the whole piece of continuous distributed, completely continuously covers the outer side surface that fine and close wall layer (1) is heated, and the outlet of all discrete through holes (3) is covered by this whole piece porous medium layer (3); Perhaps described porous medium layer (3) is made up of discontinuously arranged multi-disc, and the part covers the outer side surface that fine and close wall layer (1) is heated discretely, and the outlet of all discrete through holes (3) is covered by this multi-disc porous medium layer (2) respectively.

8. the gas turbine blades with heated wall surface cooling structure as claimed in claim 7 is characterized in that: the diameter of described discrete through hole (3) is 0.1～5mm; The arrangement of discrete through hole (3) is in-line arrangement or fork row distributes; Discrete through hole (3) is the diffusion hole that slope hole, cylindrical hole or outlet have local diffusion.

9. as claim 7 or 8 described gas turbine blades with heated wall surface cooling structure, it is characterized in that: each sheet of described discontinuously arranged porous medium layer (2) all extends along the upstream and downstream direction of high temperature main flow, and the edge that makes porous medium layer (2) is the diameter of 0.5～10 times discrete through hole (3) apart from the distance of discrete through hole (3) outlet edge of a nearest row.

10. the gas turbine blades with heated wall surface cooling structure as claimed in claim 9 is characterized in that: the distance that described porous medium layer (2) extends along the downstream direction of high temperature main flow is greater than the distance of extending along the updrift side of high temperature main flow; Described porous medium layer (2) covers the outlet of the discrete through hole (3) of whole row into strips.

11. the gas turbine blades with heated wall surface cooling structure as claimed in claim 7, it is characterized in that: described porous medium layer (3) forms for bronze, stainless steel, nickel-base alloy particle sintering, particle diameter is 10～5000 microns, and porosity ratio is between 0.2～0.5; Another selection of described porous medium layer (3) is ceramic porous structure, and its pore size equals between 5～500 microns; The another selection of described porous medium layer (3) is copper, Cuprum alloy, stainless steel or nickel-base alloy material, and structure is braiding silk screen or foam metal.

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