DE8618859U1 - Heat shield - Google Patents

Description

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Kraftwerk Union Aktiengesellschaft Our reference Mülheim VPA 85 P 6112 DE 01

Heat shield

The present invention relates to a heat shield arrangement for protecting a supporting structure against a hot fluid according to the preamble of claim 1. * Such a heat shield arrangement is known, for example, for lining the inner wall of the combustion chamber of a gas turbine plant from DE-PS 11 73 734. The heat shield elements consist of profiled stones which are attached to the combustion chamber walls at a distance from one another, forming cooling air gaps, by means of retaining clips made of aesthetic material. The retaining clips are in turn held by bolts which penetrate the combustion chamber wall. The bolts are held adjustable in the combustion chamber wall by means of eccentric bushings so that the attachment can be adapted to the dimensions of the combustion chamber stones, _which do not always match.

The object of the present invention is to create an improved heat shield arrangement of the generic type, which is suitable for lining complex-shaped structures. The cooling air consumption should be as low as possible and distributed as evenly as possible over the area to be protected, without large thermal stresses occurring on the heat shield elements and their anchors. The heat shield arrangement should, if possible, consist only of metallic components.

35

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-2- VPA 85 P 6T12 PE 01

According to the invention, this object is achieved in a generic heat shield arrangement by the features specified in the characterizing part of claim 1. Advantageous further developments are specified in claims 2 to 15. As will be explained in more detail with reference to the drawing, the invention offers various advantages. By constructing a single heat shield element in the manner of a mushroom, its cap parts can expand freely in all directions away from the shaft part without significant thermal stresses occurring. If necessary, the cap parts can expand more on their hotter surface than on their underside, which leads to a slight curvature of the cap parts, but not to thermal stresses.

Furthermore, it is easily possible to cover any spatial surface of load-bearing structures with such heat shield elements. Such surfaces can always be broken down into segments of suitable size, whereby it depends on the specific shape whether triangles, polygons or segments of a rotational body surface are the best solution. It is also possible in principle to use curved hat parts in space. However, it is particularly advantageous to approximate given structural surfaces using flat triangles wherever possible, whereby the size of the triangles depends on the desired accuracy of the approximation. The triangles created in this way are generally not equilateral and not completely equal to one another, but it is desirable to use triangles that are almost equilateral wherever possible. This can lead to difficulties in some places, but in principle it is desirable to use triangles with angles that are not too acute, since otherwise the long tips could have an increased tendency to bend. The individual heat shield elements do not necessarily have to be anchored exactly at their center of gravity.

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^, however, this is generally the most cost-effective solution. The type of anchoring depends on the respective requirements, so that various complex solutions can be considered. The simplest solution is anchoring with an anchor bolt which penetrates the supporting structure in a through hole and is braced against the supporting structure with at least one fastening nut screwed onto its free end.

TO means, for example a spacer ring or a ring shoulder, a defined distance is created between the support structure and the hat part. However, such an arrangement (can only be dismantled if the back of the

supporting structure is accessible, which is for example the case of hot

T5 gas ducts of gas turbines is not always possible. Another method of fastening, as will be explained in more detail in the drawing, is to screw the heat shield elements from the hot gas side using countersunk anchor bolts, which of course requires appropriately fastened nuts on the back of the supporting structure.

The decisive effect of the heat shield arrangement is achieved by the type of cooling of the heat shield elements. A cooling fluid, preferably air, is directed through a large number of holes in the support structure against the underside of the hat parts. This air hits the surface to be cooled almost vertically and flows along it to the sides (so-called impact cooling). This effect alone cools the hat parts considerably. The cooling fluid also flows to the edges of the hat parts and through the gaps between the hat parts and, diverted by the hot fluid flowing past, forms an additional cooling film on the top of the hat parts.

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Since most of the gaps do not run in the direction of flow, a very uniform, effective cooling film can form.

5 Since the cooling fluid gaps between the heat shield elements have different and changing widths depending on the temperature and other parameters, these gaps are only of limited use as defined throttling points for the cooling fluid flow. It is therefore advantageous to install base plates opposite these gaps on the supporting structure.

strips which form a defined distance from the hat parts. These skirting boards can also have defined recesses on their upper side which are perpendicular to the course of the skirting board and which ensure a minimum flow of cooling fluid even when heat shield elements are in place. It can even be advantageous to dimension the skirting boards and heat shield elements in such a way that they lie against one another during initial assembly and that a gap 20 only forms during commissioning due to heat influences.

&iacgr; Further details of the invention are shown in the drawing

explained in more detail using individual examples.

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\ 25 Figure 1 is a schematic view from above of a heat shield arrangement according to the invention,

Figure 2 shows a section through this arrangement, also in a simplified representation, along the line H-II, Figure 3 shows a section through a special embodiment of the invention with countersunk anchor bolts, Figure U shows a schematic section along the line IV-IV

by Fig. 3,

Figure 5 is a top view of a heat shield element according to Figure 4 and
Figure 6 an example of a triangle divided

Supporting structure j namely a part of a hot gas duct of a ! j gas turbine*

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The heat shield arrangement shown schematically in Figure t and 2 is particularly suitable for gas turbine systems, and in particular for the turbine inner casings, which

are flowed through by the hot gases coming from the combustion chamber. Up to now it has been difficult to cool such support structures 1 or to protect them by means of heat shield arrangements. Therefore, such support structures have mostly been used without cooling shields, despite the disadvantages. According to the present invention, the support structure 1 is now provided with cooling air openings 2, which are distributed over the support structure 1 evenly or in accordance with the cooling requirement. To illustrate the arrangement of the cooling air openings 2, a heat shield element has been removed in Figure 1 so that the details underneath can be seen. HG designates the hot gas side, KG the cold gas side; from the latter, cooling air is pressed through the openings 2 under excess pressure, as indicated by arrows. Heat shield elements are anchored to the support structure 1, which have a hat part 3 and a shaft part 5 in the manner of a mushroom. In the present embodiment, the shaft part consists of an anchor bolt 5 which penetrates the support structure 1 in a through hole 8. It is held at a distance from the hot gas side HG of the support structure 1 by means of an annular shoulder 5.2 on its reinforced head 5.1 and is clamped against the support structure T by a fastening nut 5.3 screwed onto its free end, whereby the fastening nuts are connected to the cold gas side KG of the support structure 1 in a rotationally secure manner by a welding point (not shown). The cooling air flowing through the cooling air openings 2 reaches the gap 6 between the support structure and the hat part and strikes the underside 3.1

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of the hat part 3 and then flows along this underside 3*1 to the cooling air gaps H between the individual hat parts Jj.- Baseboards 1*4 in the gap 6 below the cooling gap 4 create defined throttling points and prevent hot gas from penetrating the gap 6. The cooling air emerging from the cooling air gaps M is diverted on the hot gas side HG by the gas flow prevailing there and thus forms a cooling air film on the top side of the hat parts 3*, which creates an additional cooling effect. The hat parts 3 of the individual heat shield elements and their anchor bolts 5 are preferably both made of high-temperature-resistant steel, for example ₁ , so that they can be welded together without any problems. Accordingly, the anchor bolts 5 are each welded to the cell region 7. In the present embodiment, it is initially assumed for the sake of simplicity, in order to illustrate the principle of the invention, that the heat shield elements are similar hat parts of the same shape.

I sided triangles - In the general case, as in Fig. |

6, an irregularly curved surface |

of different polygons, preferably triangles, J

Although such polygons or f

Triangles always have a precisely defined center of gravity, ; however, the anchor bolts do not necessarily have to be exactly in

( 25 be fixed to this centre of gravity. This is indeed the case in all- ]

common advantage, but for reasons of )

Vibration tendency of individual sections of the polygons, an anchoring outside the center of gravity may be advantageous, I

The presence of only one anchoring point for each 3 heat shield elements has the advantage that thermal expansion of the heat shield elements is not hindered and therefore extreme thermal stresses cannot occur. :■

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Since on the cold gas side KG there is an average temperature of, for example, about ^{100 °} C during operation and on the underside 3 * 1 of the cap parts 3 there is an average temperature of, for example, 750° C, differential expansions occur between the supporting structure and the heat shield elements, which are not hindered, however, since the cap parts 3 can expand freely in all directions, as can the bolt heads 5.1. The anchor bolts 5 are screwed tight under pre-tension, so that there is no risk of them becoming loose even when heated to operating temperature. The cap parts themselves, too.

, which has a higher temperature on the hot gas side HG than on

^v their underside 3.1 are not hindered in their thermal expansion. They may take on a convex curvature as seen from the hot gas side HG, but this is possible without hindrance. The baseboards 1.4 create defined throttling points for the cooling gas, which, as explained above, adjust themselves to uniform cross-sections. The exact width of the cooling air gaps 4 between the hat parts 3 is therefore not important, provided they are wide enough. This is also an advantage, since these gaps are constantly changing in different operating conditions.

(^ 25 In Figs. 3, 4 and 5, a further embodiment of the invention is described. The cooling principle remains the same, only the fastening of the individual heat shield elements is changed. In addition, this embodiment shows the arrangement of heat shield elements on an uneven support structure. Fig. 3 shows a longitudinal section through part of the heat shield arrangement, Fig. 4 a section through Fig. 3 along the line IV-IV and Fig. 5 a view from above of a heat shield element. The support structure 31 again has cooling air

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holes 32 and firmly anchored heat shield elements with triangular hat parts 33. Cooling air gaps of width ä33 exist between the individual hat parts 33. Between the support structure 31 and the underside 33*1 of the hat parts 33 there is a gap 36 of width a31. The hat parts 33 have a pot-like shape 33-2, 33-3 in their central area, which has a through hole 33.4 in their underside 33-3. A bolt 35 is inserted through this hole 33=4 and a corresponding through hole 38 in the support structure 31.

through, the bolt head 35.1 being located in the pot-shaped formation 33*2, 33*3, preferably flush with the surface of the hat part 33 on the hot gas side HG. The bolt head 35.1 can have, for example, a hexagon socket or a similar means of engagement for a tool for tightening. This bolt is braced against the cold gas side KG of the support structure 31 by means of a nut, the nut 35.2 having claw-shaped arms 35.3 which are supported against the support structure 31 and are welded to it 35.4. The nut 35.2 itself does not need to touch the support structure 31, so that a suitable preload can be achieved by the claw-shaped arms 35.3. In addition, if the through hole ( > 25 38 in the support structure 31 and the corresponding hole \ 33.4 are at least in some areas significantly wider than

the diameter of the bolt 35, cooling air can flow along the bolt and thus cool it and especially its head 35.1. Suitable drainage channels 33-6 must be provided in the pot-shaped formation 33-2, 33.? Other solutions for maintaining the preload force of the bolt 35 are also conceivable, such as expansion screws, spring plates, etc. For the precise positioning of the heat shield elements, it is advantageous if the pot-shaped formation 33-2, 33-3 is supported in a form-fitting groove 31.3 against the support structure 31.

Additional cooling fluid passages, e.g. in the form of holes 33.6, can be provided in the pot-

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like shape 33*2, 33*3 are provided. AlVsh on

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ti 33 additional cooling fluid passages 33*7 can be provided

I are» which are not connected to the cooling fluid holes 32

< 5 should be aligned. Fig. 3 also shows realistic

\ Regulations for skirting boards 31.4, 31-6, 31.7 as throttle

' represent 39 for the cooling gas flow. These skirting boards can

j nen in the shaping of the supporting structure 31, e.g. by

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\ 31.4, a following the course of the adjacent Hu t-

I , \ parts 33 have adapted surface shape 31-5, which

I is not absolutely necessary, provided that only a defined

\ th throttle point is formed. Difficulties can

j 15 due to excessive accumulation of material, the arrangement of

!' Skirting boards in the area of contact points of several

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'; which is also possible in other ways, if necessary special

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\ 20 31.6, 31.7, a ring-shaped course with

I a hemispherical recess 31·8

Γ inside. This leaves defined throttle points 39 with

I at a suitable distance a32 without too much material being accumulated in one place.

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As indicated in Fig. 4, it may be advantageous to insert a groove in the skirting boards 31.7 on the top side 31.8 transverse to the course

j recesses 31.9 shall be provided in the skirting board,

which also' when the heat shield elements 33 are in contact with a minimum current

' 30 of cooling fluid. Such recesses can also be used to

Underside of the hat parts 33.

Finally, Fig. 6 shows an example of the division of a curved surface into suitable triangles. For example, an inner casing of a gas turbine can be approximated quite well with 35 relatively few triangles, without the

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- 10 - VPA 85 P 6112 EN 01

individual heat shield elements would have to be curved. A better approximation of the shape is basically possible either through a larger number of polygons, especially triangles, or through the use of curved heat shield elements. However, a significant advantage of using triangles is that three points always define a plane, so that the division of a curved surface into triangles causes the least problems during the subsequent manufacture of the heat shield elements.

The present invention is particularly suitable for hot gas ducts, combustion chambers and similar parts of gas turbines, but is not limited to such applications. This heat shield arrangement enables higher temperatures inside a supporting structure or simplifies its construction and reduces its loads.

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Claims (1)

VPA 85 P 6112 EN 01 Protection claims 1, heat shield for protecting a supporting structure (1; 31) against a hot fluid, in particular for protecting a hot gas duct wall in gas turbine plants and the like, with cooling fluid passages (2; 32) in the supporting structure (1; 31) and with an inner lining made of heat-resistant material, which is composed of &eacgr;&Lgr;&igr; heat shield elements arranged side by side over the entire surface, leaving cooling fluid gaps (4; 34) and anchored to the support structure (1; 31) in a heat-moving manner, characterized in that each heat shield element has a hat part (3? 33) and a shaft part (5; 35) in the manner of a mushroom, the hat part (3; 33) being a flat or three-dimensional, polygonal plate body with straight or curved edge lines, and the shaft part (5; 35) connecting the central region of this plate body to the support structure (1; 31), .<-. 25 2, Heat shield according to claim 1, characterized in that the outline of the hat parts (3i 33) forms a triangle, preferably a triangle in which all angles are greater than 40°, preferably greater than 50°. 30 3, Heat shield according to claim 1, characterized in that the hat parts (3; 33) have approximately the shape of a segment of the surface of a rotating body. 35 Khf/Knl, 12.02.86 * * t i &igr;&kgr; tilt H # » * * 4 t ·· II III S I &iacgr;&iacgr;&igr; i '. '. 11 &iacgr; ! ■ ■: 4 * at III ti II III » » _-|2- VPA 85 P 6112 EN 01 4. Heat shield according to claim 1, 2 or 3, characterized in that the shaft parts (5) are anchor bolts which are grown together with the respective hat parts and which penetrate the support structure (1) in through holes (8) and are braced against the support structure (1) by at least one fastening nut (5.3) screwed onto their free end, whereby an annular shoulder (5.2) or a spacer ring or the like determines the width (al) of the intermediate space (6) between the hat parts (3) and the support structure (1). 5, Heat shield according to claim 1, 2 or 3, characterized by the following features: a) Each hat part (33) has a pot-like shape (33.2, 33.3) in the central area towards the support structure (31) with a bore (33.4) in the underside (33.3). b) The pot-like deformation (33.2, 33.3) is supported against the support structure (31), optionally guided in a form-fitting groove (33.3) or the like, and thus determines the distance (a31) between the hat part (33) and the support structure (31). c) A screw connection (35), consisting of a bolt (35.1) which is guided through the hole (33.4) in the underside (33.3) of the pot-shaped formation (33.2, 33.3) and a through hole (33) in the support structure (31), as well as a nut (35.2) or the like which is supported against the support structure (31), clamps the hat part (33) to the support structure (31), the head of the bolt (35.1) being countersunk in the pot-shaped formation (33.2, 33.3), preferably approximately flush with the surface of the hat part. ti M IfIi ff I I ) t &igr;(&igr; Il If IM I i t ty i &igr; im .· ,·· » » HH &Pgr; it H * · I 11 a >> t &bull; Ml Il · , , , < &igr; t &igr;&igr; ti , .* J -1.3* VPA 85 P 6112 EN 01 6, heat shield according to claim 5, characterized in that the nuts (33*2) are supported by means of claw-shaped arms (35 _V 3) or a collar type of the support structure (31) / Wherein the arms (33,3) are preferably firmly connected to the support structure (31), in particular welded on» 7 4 Heat shield according to one of the preceding claims, characterized in that the hat parts (3·; 33) > anchor bolts (5; 35) and optionally other parts of the heat shield elements consist of high-temperature resistant materials _{, in} particular steel * 8, Heat shield according to one of the preceding claims, characterized in that the support structure (1; 31) has bores (2; 32) through which a cooling _fluid , in particular air, can flow into the intermediate space (6; 36), the bores (2; 32) preferably being arranged perpendicular to the position of the hat parts (3; 33)» 9. Heat shield according to one of the preceding claims, characterized in that a base strip (1.5-j 31.5, 31.6, 31.7) is arranged on the support structure (1; 31) opposite each cooling fluid gap (4; 34) present between the heat shield elements, in the direction of said gap and running approximately over its entire length. i&igr; * · - 14 - VPA 85 P 6112 EN 10. Heat shield according to claim 9, characterized characterized in that the top side (31 * 8) of the skirting board (31 «7) and/or the bottom side of the hat part (33)· are provided with structures (31.9) running in the flow direction of the coolant. 11i Heat shield according to claim 9 or 10, characterized in that the base strips (1*5 j 31.5* 31.6, 31.7) in the upper side are adapted to the course of the adjacent hat parts (3; 33), whereby to avoid excessive accumulation of material, e.g. at corner points of several adjacent heat shield elements, special shapes such as ring-shaped base strips (31.6, 31.7) or double strips with a central groove on the upper side are provided. 12. Heat shield according to one of the preceding claims, characterized in that the edges (33.5) of the hat parts (33) on the hot gas side (HG) are bevelled. 13. Heat shield according to one of the preceding claims, characterized in that additional outlet paths (33-5) for cooling fluid are provided in the region of the anchoring (5; 35). 14. Heat shield according to claim 13, characterized in that the bores (8; 33-8), 38) have additional recesses (33.5) in their side wall. I &igr; Xl I &bull; t Uli » « t 4 · * I · i * Ii 4 j t lie cc Wed . . - 15 - VPA 85 P 6112 EN 01 15 . Heat shield after one of the previous Claims, characterized in that the hat parts (33) have additional cooling fluid outlets (33,7).