Arrangement for rear impact cooling of an impact plate exposed to a hot medium at its front

Abstract

An arrangement (1) for the rear impact cooling of an impact plate (2) thermally stressed on its front side (3) by a hot medium (4) comprises the impact plate (2), a perforated plate (6) arranged at a distance from the rear side (5) of the impact plate (2), cooling fluid passage holes in the perforated plate (6) directed towards the rear side (5) of the impact plate (2), a cooling fluid outflow channel (9) formed between the rear side (5) of the impact plate (2) and the perforated plate (6), open in a transverse flow direction (10) at a cooling fluid outlet opening, and a cooling fluid supply channel (13) to which the cooling fluid passage holes are fluidically connected. The cooling fluid supply channel (13), the cooling fluid passage holes, and the cooling fluid outflow channel (9) form a cooling fluid passage through the arrangement (1) that is closed up to the cooling fluid outlet opening.To increase heat transfer from the baffle plate (2) to a cooling fluid (15) flowing through the cooling fluid passage, fluidic oscillators (19) are arranged in the cooling fluid passage.

Description

TECHNICAL AREA OF INVENTION

[0001] The invention relates to an arrangement for the rearward impact cooling of an impact plate whose front surface is exposed to a hot medium. In particular, the invention relates to an arrangement for impact cooling with the features of the preamble of independent claim 1.

[0002] The baffle plate can, for example, be the inner wall of a cooled turbine blade in a gas turbine. In various gas turbines, operating conditions can occur under which the gas striking the turbine blades has a higher temperature than the melting point of the blade material. Effective cooling of the turbine blades exposed to the hot gases is particularly necessary under these operating conditions.

[0003] The so-called impact cooling is an established method for achieving high heat transfer rates to a cooling fluid. STATE OF THE ART

[0004] In impact cooling for an impact plate, a cooling fluid is directed through a perforated plate onto the back of the impact plate. This results in the formation of only a thin thermal boundary layer on the back of the impact plate, leading to a high heat transfer rate. Specifically, a cooling fluid outflow channel with a substantially rectangular cross-section is formed between the back of the impact plate and the front of the perforated plate. Except for the cooling fluid passage holes in the perforated plate, the cooling fluid outflow channel is open only at one end, at a cooling fluid outlet. The cooling fluid enters the outflow channel through the passage holes, forming impact jets directed perpendicularly towards the back of the impact plate. These impact jets entrain some of the cooling fluid already present in the outflow channel. At stagnation points on the back of the impact plate, the cooling fluid's velocity is reduced to zero.After impacting the baffle plate, the pressure field prevailing in the cooling fluid outflow channel accelerates the cooling fluid radially, leading to the formation of so-called wall jets. These wall jets collide with the wall jets of adjacent impact jets, resulting in fountain flows. The cooling medium is displaced by the adjacent jets towards the channel's side walls and flows back along these walls to the perforated plate. Some of the cooling fluid is carried away by impact jets exiting from the plate, while the remainder merges into a transverse flow through the cooling fluid outflow channel. This transverse flow travels in a corkscrew motion towards the cooling fluid outlet. The corkscrew-shaped transverse flow deflects the cooling fluid impact jets directed towards the back of the baffle plate, increasing shear forces and consequently reducing the heat transfer from the baffle plate to the cooling fluid.Furthermore, the crossflow around the impact jets induces vortex pairs with vortex axes parallel to the axis of the respective impact jet.

[0005] It is known to use impact cooling in the cooling of turbine blades.

[0006] From EP 2 284 392, an arrangement with the features of the preamble of independent claim 1 is known. In this arrangement, conical or pyramidal pins project perpendicularly from the back of the baffle plate. The impact jets of the cooling fluid collide between the spaces formed by the pins in such a way that this collision creates a turbulent flow acting on the baffle plate, which causes additional heat transfer. However, there is a risk that the pins may impede the flow over the back of the baffle plate in practice and lead to an undesirable thickening of the thermal boundary layer on the back of the baffle plate. TASK OF INVENTION

[0007] The invention is based on the objective of demonstrating an arrangement for impact cooling with the features of the preamble of independent claim 1, in which the cooling effect is significantly improved by flow bodies arranged in the fluid passage. SOLUTION

[0008] According to the invention, this problem is solved by an arrangement for impact cooling with the features of independent claim 1. Dependent claims 2 to 12 relate to preferred embodiments of the arrangement according to the invention. Claim 13 relates to a turbine blade with an arrangement for impact cooling according to the invention. DESCRIPTION OF THE INVENTION

[0009] An arrangement according to the invention for the rearward impact cooling of an impact plate exposed to a hot medium at its front surface comprises the impact plate, a perforated plate arranged at a distance from the rear of the impact plate, cooling fluid passage holes in the perforated plate directed towards the rear of the impact plate, a cooling fluid outflow channel formed between the rear of the impact plate and the perforated plate, open exclusively in a transverse flow direction at a cooling fluid outlet opening except for the cooling fluid passage holes in the perforated plate, and a cooling fluid supply channel to which the cooling fluid passage holes are fluidically connected. The cooling fluid supply channel, the cooling fluid passage holes, and the cooling fluid outflow channel form a cooling fluid passage through the arrangement that is closed up to the cooling fluid outlet opening.To increase heat transfer from the baffle plate to a cooling fluid flowing through the cooling fluid passage, fluidic oscillators are arranged in the cooling fluid passage.

[0010] Fluidic oscillators are flow bodies in which a fluid flowing through them changes its flow direction by oscillating. Fluidic oscillators are known in several embodiments. They belong to the fluidic components, which, due to their belonging to the technical field of "fluidics," are also referred to as "fluidic" in English. Specific fluidic oscillators are known, for example, from EP 0 381 344 A2, WO 2000 / 023197 A1, and DE 10 2010 010 790 A1.

[0011] Fluidic oscillators, as used in the arrangement according to the invention, each have a fluid inlet and a fluid outlet, wherein the cooling fluid flowing into the fluid inlet alternately flows out of the cooling fluid outlet in two different outflow directions. The outflowing cooling fluid sweeps back and forth between the two different outlet directions at a frequency that depends on its volumetric flow rate and the dimensions of the fluidic oscillator. In the arrangement according to the invention, the fluidic oscillators can be arranged at various points in the fluid passage. However, this generally does not include the through-holes in the perforated plate, because there is insufficient space available there for the formation of fluidic oscillators.

[0012] Preferably, at least some of the fluidic oscillators are arranged on the back side of the baffle plate within the cooling fluid outflow channel, but without spanning the cooling fluid outflow channel over its entire height up to the perforated plate or its entire width along the baffle plate. On the contrary, in the arrangement according to the invention, the fluidic oscillators are each provided only locally, and in the preferred embodiment, locally on the back side of the baffle plate. The different outflow directions of the fluidic oscillators run along the back side of the baffle plate. The cooling fluid flowing out of the fluid outlet of the respective fluidic oscillator then sweeps across the back side of the baffle plate. This improves the heat transfer from the baffle plate to the cooling fluid.

[0013] A further improvement in heat transfer is achieved by arranging the fluidic oscillators on the back side of the baffle plate between two stagnation points of the cooling fluid exiting the baffle plate as impact jets from two adjacent cooling fluid passages in the transverse flow direction. The arrangement is such that a wall jet, generated by the impact jet exiting the upstream cooling fluid passage, flows through the fluidic oscillator. This wall jet, exiting the fluidic oscillator alternately in different outflow directions, periodically impinges on the impact jet of the cooling fluid exiting the downstream cooling fluid passage from different directions, thus exciting it to oscillation.

[0014] Alternatively or additionally, at least some of the fluidic oscillators can be arranged on the front of the perforated plate in the cooling fluid outflow channel, with the different outflow directions running along the front of the perforated plate so that the outflowing cooling fluid sweeps across the front of the perforated plate. In this case, the fluidic oscillators can each be arranged between two cooling fluid passage holes adjacent in the transverse flow direction.

[0015] Both the fluidic oscillators formed on the back of the baffle plate and the fluidic oscillators formed on the front of the perforated plate can be open towards the cooling fluid outflow channel. This is a significant advantage in the manufacture and operation of the arrangement according to the invention. Closed fluidic oscillators would be very complex to manufacture and would be susceptible to clogging during operation of the arrangement.

[0016] Alternatively or additionally, at least some of the fluidic oscillators can be arranged on the back side of the perforated plate in the cooling fluid supply channel, with the different outflow directions running along the back side of the perforated plate, meaning the outflowing cooling fluid sweeps across the back side of the perforated plate. While the effect on the flow of the cooling fluid on the back side of the baffle plate is even less direct here than with fluidic oscillators arranged on the front side of the perforated plate, the fluidic oscillators on the back side of the perforated plate still have an effect, extending to the back side of the baffle plate, by significantly influencing the flow through the cooling fluid passage holes in the perforated plate and thus affecting the impact jets of the cooling fluid that strike the back side of the baffle plate.In addition, the fluidic oscillators on the back of the perforated plate cause a pulsating flow through the cooling fluid passage holes in the perforated plate, which counteracts a blockage of the cooling fluid passage holes by sand or dust carried along by the cooling fluid.

[0017] Fluidic oscillators on the back of the perforated plate can also be arranged between two cooling fluid passage holes adjacent in the transverse flow direction and / or be open towards the cooling fluid supply channel.

[0018] The fluidic oscillators of the arrangement according to the invention have a typical length of at least four times and not more than twelve times the diameter of the cooling fluid passage holes in the perforated plate that are located upstream in the transverse flow direction, and a height above the respective back or front of the plate of typically at least one and not more than two times this diameter.

[0019] Specifically, the fluidic oscillators of the arrangement according to the invention can be 3D-printed, either in a separate process on plates already manufactured elsewhere or during the 3D printing of the impact plate or the perforated plate. The 3D printing of the fluidic oscillators can be carried out specifically by metal-based additive manufacturing, in particular direct metal-based additive manufacturing, such as selective laser melting or sintering of a metal powder.

[0020] A turbine blade according to the invention has an arrangement according to the invention for cooling its inner wall which serves as a baffle plate.

[0021] Advantageous further developments of the invention result from the patent claims, the description and the drawings.

[0022] The advantages of features and combinations of features mentioned in the description are merely exemplary and can have an effect alternatively or cumulatively, without the advantages necessarily having to be achieved by embodiments according to the invention.

[0023] Regarding the disclosure content—not the scope of protection—of the original application documents and the patent, the following applies: Further features can be derived from the drawings—in particular, the geometries depicted and the relative dimensions of several components to one another, as well as their relative arrangement and functional connection. The combination of features from different embodiments of the invention or from features of different claims is also possible, deviating from the chosen cross-references of the claims, and is hereby encouraged. This also applies to features that are illustrated in separate drawings or mentioned in their description. These features can also be combined with features from different claims.Likewise, features listed in the patent claims may be omitted for further embodiments of the invention, but this does not apply to the independent patent claims of the granted patent.

[0024] The features mentioned in the claims and the description are to be understood, with regard to their number, as meaning that exactly that number or a greater number than the stated number is present, without the need for the explicit use of the adverb "at least". Thus, for example, if a cooling fluid supply channel is mentioned, this is to be understood as meaning that exactly one cooling fluid supply channel, two cooling fluid supply channels, or more cooling fluid supply channels are present. The features mentioned in the claims may be supplemented by further features or may be the only features that the subject matter of the respective claim possesses.

[0025] The reference numerals contained in the patent claims do not constitute a limitation of the scope of the subject matter protected by the patent claims. They merely serve the purpose of making the patent claims easier to understand. BRIEF DESCRIPTION OF THE FIGURES

[0026] The invention will now be further explained and described with reference to preferred embodiments shown in the figures. Fig. 1 shows a first embodiment of the arrangement according to the invention for impact cooling with fluidic oscillators arranged on a rear side of an impact plate in a vertical section running along a transverse flow direction. Fig. 2 is a top view of the fluidic oscillators on the back of the baffle plate in a horizontal section running along the transverse flow direction. Fig. 3 shows a second embodiment of the arrangement according to the invention for impact cooling with fluidic oscillators arranged on a front side of a perforated plate in a vertical section running along the transverse flow direction. Fig. 4 is a top view of the fluidic oscillators on the front of the perforated plate in a horizontal section running along the transverse flow direction. Fig. 5 shows a third embodiment of the inventive arrangement for impact cooling with fluidic oscillators arranged on a rear side of the perforated plate in a vertical section running along the transverse flow direction; and Fig. 6 is a top view of the fluidic oscillators on the back of the perforated plate in a horizontal section running along the transverse flow direction. FIGURE DESCRIPTION

[0027] The arrangement 1 shown in Fig. 1 serves for the impact cooling of an impact plate 2, for example, the inner wall of a turbine blade of a gas turbine. The impact plate 2 is exposed to a hot medium 4 on its front surface 3, meaning that heat is transferred into the impact plate 2 by the hot medium 4. The hot medium 4 may have a temperature above a critical temperature for the material of the impact plate 2, for example, its melting point. In this case, it is particularly important to cool the impact plate 2 in order to dissipate the transferred heat before the material of the impact plate 2 exceeds its critical temperature, causing the impact plate 2 to lose its structure. A perforated plate 6 is arranged at a distance from a rear surface 5 of the impact plate 2. Cooling fluid passage holes 7 are formed in the perforated plate 6, directed towards the rear surface 5 of the impact plate 2.Between a front face 8 of the perforated plate 6 and the rear face 5 of the baffle plate 2, a cooling fluid outflow channel 9 is formed, which, in addition to the cooling fluid passage holes 7, is only accessible in a transverse flow direction 10 at a point in . Fig. The cooling fluid outlet opening 1 (not shown) is open. Contrary to the transverse flow direction 10, the cooling fluid outflow channel 9 is closed, as it is laterally, where it is bounded on both sides by side walls 11. A cooling fluid supply channel 13 or plenum adjoins a rear side 12 of the perforated plate 6 and is bounded at the rear by an inner wall 14. The cooling fluid supply channel 13, the cooling fluid passage holes 7, and the cooling fluid outflow channel 9 form a closed cooling fluid passage through the arrangement 1 up to the cooling fluid outlet opening. Specifically, cooling fluid 15 is supplied via the cooling fluid supply channel 13. The cooling fluid 15 exits the cooling fluid passage holes 7 in the perforated plate 6 as impact jets 16, initially in the form of free jets. At stagnation points 17, the impact jets 16 collide with the impact plate 2. Afterwards, the cooling fluid 15 flows in the form of wall jets 18 along the back 5 of the impact plate 2.These wall rays 18 pass through fluidic oscillators 19, each formed between two stagnation points 17 on the rear 5 of the baffle plate 2.

[0028] Fig. 2 shows the fluidic oscillators 19 formed on the rear side 5 of the baffle plate 2 and open towards the cooling fluid outflow channel 9. Each fluidic oscillator 19 has a fluid inlet 20 and a fluid outlet 21. When the fluid inlet 20 is supplied with cooling fluid 15, the fluid automatically adheres to one of the two walls 22 and 23 inside the fluidic oscillator 19. From there, the cooling fluid 15 encounters a transverse wall 24 or 25 and divides there. While the main part of the cooling fluid 15 leaves the fluidic oscillator 18 in the form of a free jet, a small portion flows back through one of two side channels 26 and 27 and, at the end of the side channel 26 or 27, pushes the main jet against the opposite wall 23 or 22, respectively. This process repeats itself, and a periodic oscillation is generated between the two. Fig. The two indicated flow states are characterized by the outflow direction of the cooling fluid 15 sweeping over the back side 5 of the baffle plate 2. This causes the impact jet 16 of the cooling fluid 15, which strikes the next stagnation point 17 downstream along the transverse flow direction 10, and the resulting next wall jet 18, to be periodically subjected to different directions and thus also excited into oscillations. Overall, this results in a significantly improved heat transfer from the baffle plate 2 to the cooling fluid 15 and thus a significantly improved impact cooling of the baffle plate 2.

[0029] Fig. 3 shows an embodiment of the arrangement 1 in which the fluidic oscillators 19 are arranged on the front 8 of the perforated plate 6 instead of on the rear 5 of the baffle plate 2. These fluidic oscillators 19 are also open towards the cooling fluid outflow channel 9, as shown in Fig. 4. With the fluidic oscillators 19 arranged on the front 8 of the perforated plate 6, the cooling fluid 15 flows through them, forming a transverse flow in the transverse flow direction 10.

[0030] Fig. 5 and Fig. Figure 6 illustrates an arrangement of the fluidic oscillators 19 on the back 12 of the perforated plate 6. Here, the coolant supply channel 13 in open fluidic oscillators 19 between the coolant flow holes 7 is traversed by the supplied coolant fluid 15. REFERENCE MARK LIST 1. Arrangement 2 Impact plate 3 Front of the impact plate 2 4 Medium 5 Back of the impact plate 2 6-hole plate 7 Cooling fluid passage holes 8 Front of the perforated plate 6 9 Cooling fluid discharge channel 10 Crossflow direction 11 Side wall 12 Back of the perforated plate 6 13 Cooling fluid supply channel 14 Interior wall 15 Cooling fluid 16 Impact jet 17 Congestion point 18 wall beams 19 fluidic oscillator 20 Fluid inlet 21 Fluid outlet 22 Wall 23 Wall 24 transverse wall 25 transverse wall 26 Side channel 27 Side channel QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] EP 2 284 392

[0006] EP 0 381 344 A2

[0010] WO 2000 / 023197 A1

[0010] DE 10 2010 010 790 A1

[0010]

Claims

Arrangement (1) for rearward impact cooling of an impact plate (2) exposed to a hot medium (4) at its front (3), comprising: the impact plate (2), a perforated plate (6) arranged at a distance from the rear (5) of the impact plate (2), cooling fluid passage holes (7) in the perforated plate (6) directed towards the rear (5) of the impact plate (2), a cooling fluid outflow channel (9) formed between the rear (5) of the impact plate (2) and the perforated plate (6), open in a transverse flow direction (10) at a cooling fluid outlet opening, and a cooling fluid supply channel (13) to which the cooling fluid passage holes (7) are fluidically connected, wherein the cooling fluid supply channel (13), the cooling fluid passage holes (7) and the cooling fluid outflow channel (9) form a cooling fluid passage through the arrangement (1) that is closed up to the cooling fluid outlet opening. form and - wherein flow bodies are arranged in the cooling fluid passage,to increase heat transfer from the baffle plate (2) to a cooling fluid (15) flowing through the cooling fluid passage, characterized in that the flow bodies form fluidic oscillators (19). Arrangement (1) according to claim 1, wherein the fluidic oscillators (19) each have a fluid inlet (20) and a fluid outlet (21), wherein cooling fluid (15) flowing into the fluid inlet (20) alternately flows out of the fluid outlet (21) in two different outflow directions. Arrangement (1) according to claim 1 or 2, wherein at least some first fluidic oscillators (19) are arranged on the rear side (5) of the baffle plate (2) in the cooling fluid outflow channel (9), wherein their first different outflow directions run along the rear side (5) of the baffle plate (2). Arrangement (1) according to claim 3, wherein the at least some first fluidic oscillators (19) are arranged between stagnation points (17) of cooling fluid (15) exiting from two adjacent cooling fluid passage holes (7) in the transverse flow direction (10) onto the baffle plate (2). Arrangement (1) according to one of the preceding claims, wherein at least some second fluidic oscillators (19) are arranged on the front side (8) of the perforated plate (6) in the cooling fluid outflow channel (9), wherein their second different outflow directions run along the front side (8) of the perforated plate (6). Arrangement (1) according to claim 5, wherein the at least some second fluidic oscillators (19) are each arranged between two cooling fluid passage holes (7) adjacent in the transverse flow direction (10). Arrangement (1) according to one of claims 4 to 6, wherein the at least some first and / or second fluidic oscillators (19) are open towards the cooling fluid outflow channel (9). Arrangement (1) according to one of the preceding claims, wherein at least some thirds of the fluidic oscillators (19) are arranged on the rear side (16) of the perforated plate (6) in the cooling fluid supply channel (13), wherein the thirds of their different outflow directions run along the rear side (16) of the perforated plate (6). Arrangement (1) according to claim 8, wherein the at least some third fluidic oscillators (19) are each arranged between two cooling fluid passage holes (7) adjacent in the transverse flow direction (10). Arrangement (1) according to one of claims 8 and 9, wherein the at least some third fluidic oscillators (19) are open to the cooling fluid supply channel (13). Arrangement (1) according to one of the preceding claims, wherein the fluidic oscillators (19) have a length of no more than ten times a local boundary layer thickness and a height of no more than 1.5 times the local boundary layer thickness of the cooling fluid (15). Arrangement (1) according to one of the preceding claims, wherein the fluidic oscillators (19) are 3D printed. Turbine blade with an arrangement (1) according to one of the preceding claims.

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