EP1715250A1 - Heat shield element for covering the wall of a combustion chamber, combustion chamber and gas turbine - Google Patents

Abstract

The heat shield element (15) for lining a combustion chamber wall with a hot zone (17) is provided with a number of grooves (23) constituted so that the thermally induced stresses within this zone are reduced. Independent claims are also included for: (A) a combustion chamber with a number of the proposed heat shield elements; (B) a gas turbine with such a combustion chamber.

Description

The invention relates to a heat shield element, in particular for lining a combustion chamber wall, with a hot side which can be exposed to a hot medium, a wall side opposite the hot side and a peripheral side adjoining the hot side and the wall side. The invention further relates to a combustion chamber with a combustion chamber wall and a gas turbine.

Ceramic or metallic elements are often used to line thermally highly stressed combustion chambers, such as e.g. a furnace, a hot gas duct or a combustion chamber of a gas turbine used.

Such a lining consisting of ceramic heat shield elements is in the EP 0 419 487 B1 described. The heat shield elements are designed so that the occurrence of mechanical stresses under thermal stress is largely avoided. The heat shield elements are mechanically held on a metallic wall of the combustion chamber and touch the metallic wall directly. To avoid excessive heating of the wall, for example as a result of direct heat transfer from the heat shield element or by introducing hot medium into the gaps formed by the adjacent heat shield elements, the space formed by the wall of the combustion chamber and the heat shield element with cooling air, the so-called Blocking air applied. The blocking air prevents the penetration of hot medium up to the wall and at the same time cools the wall and the heat shield element.

From the EP 1 064 510 B1 goes out a wall segment for a combustion chamber, which is acted upon by a hot fluid.

The wall segment consists of a metallic support structure and a heat protection element attached to the metallic support structure. Between the metallic support structure and the heat protection element, an elastic or plastically deformable separating layer is attached, which should accommodate and largely compensate for possible relative movements of the heat protection element and the support structure. Such relative movements can be caused, for example, in the combustion chamber of a gas turbine, in particular an annular combustion chamber, by different thermal expansion behavior of the materials used or by pulsations in the combustion chamber, as may occur in an irregular combustion to produce the hot working medium or by resonance effects. In this case, the separating layer causes the relatively inelastic heat protection element rests overall flat on the release layer and the metallic support structure, since the heat protection element partially penetrates into the release layer. The release layer can compensate for manufacturing due to unevenness of the support structure and / or the heat protection element, which can lead locally to an unfavorable force input compensate.

Another type of ceramic lining for combustion chambers, which are to absorb very high mechanical and thermal loads, is in the EP 0 724 116 A2 specified. The lining consists of wall elements of high-temperature-resistant structural ceramics, such as silicon carbide (SiC) or silicon nitride (Si ₃ N ₄ ). The wall elements are mechanically fixed by means of a central fastening bolt to a metallic support structure (wall) of the combustion chamber. Between the wall element and the wall of the combustion chamber, a thick thermal insulation layer is provided, so that the wall element is spaced correspondingly from the wall of the combustion chamber. About three times as thick in relation to the wall element insulation layer consists of a ceramic fiber material, which is prefabricated in blocks. The dimensions and the external shape of the wall elements are adaptable to the geometry of the space to be lined.

When applying the surface of a heat shield element to a hot medium, e.g. a hot gas whose temperature rises rapidly in a short time. The resulting relative thermal expansions lead to thermally induced stresses, which can lead to the formation of cracks in the material of the heat shield element. Depending on the presence of other loads such as vibrations or chemical effects, the damage effect can be further enhanced, so that the service life of the heat shield element is limited by the formation of cracks. The heat shield elements must therefore, especially in combustion chambers of gas turbine plants, regularly visually inspected for cracks and be diagnosed and are exchanged cyclically for operational safety reasons.

The invention is based on the observation that, in particular, ceramic heat shield elements are often inadequately protected against the occurring thermomechanical loads, in particular as a result of thermal cycling, due to their necessary flexibility with respect to thermal expansions.

Accordingly, the object of the invention is to specify a heat shield element with an increased service life, in particular with respect to thermomechanical loads. It is another object of the invention to provide a combustion chamber with a long service life and a gas turbine with a combustion chamber.

The first object is achieved according to the invention by a heat shield element, in particular for lining a combustion chamber wall, with a hot medium exposable hot side, one of the hot side opposite wall side and adjacent to the hot side and the wall side peripheral side, wherein to increase the effective surface in a thermally loaded A number of notches in the material is introduced, which are designed such that the thermally induced stress forces in this area are reduced.

The invention is based on the finding that, because of the material-typical thermal expansion properties and the temperature differences typically occurring during operation (ambient temperature at standstill, maximum temperature at full load), sufficient thermal mobility of heat shield elements, in particular in gas turbine combustors, must be ensured as a result of temperature-dependent expansion in no case component destructive thermal stresses due to expansion inhibition occur. This can be known to be achieved by lining the wall to be protected from hot gas attack with a plurality of individual heat shield elements limited in size, such as a combustor wall of a gas turbine combustor. In this case, corresponding expansion gaps are provided between the individual ceramic heat shield elements which, for safety reasons, must never be completely closed, even in hot conditions. It must be ensured that no hot gas penetrates into the expansion column, because otherwise the wall structure is excessively heated. The simplest and safest way to do this, e.g. to avoid in a gas turbine combustor, the flushing of the expansion gaps with air (sealing air).

With the invention, a new way is shown to limit the life-limiting cracking, which manifests itself in the operation of the heat shield element, and thus significantly increase the service life of the heat shield element. This is achieved by deliberately introducing notches in the material in the area of the heat shield element that tends to cause the formation of thermal stress. If a crack occurs, this leads to a total reduction in tension. Short thermal cracks have no appreciable effect on the remaining bearing capacity of the heat shield element with respect to mechanical forces. To step However, cracks larger than a critical length, the mechanical load capacity of the heat shield element is significantly reduced and there is an acute danger of failure.

To avoid all this, a number of notches are introduced into the surface of the region susceptible to thermal stress-induced material cracking. This increases the surface area of this area and the tension forces affect this enlarged surface. Surface tension is generally defined as force per unit length [N / m], i. if the area on which the forces act is increased, with the effective surface also the length of the surface is increased, then the tension generated on the surface is correspondingly reduced. By this measure, a lifetime extension of the heat shield element is given directly, so that correspondingly longer lifetimes are achieved.

In a particularly advantageous embodiment, the hot side has a hot side surface, with a plurality of notches extending over the hot side surface. Studies have shown that crack formation and crack growth are particularly pronounced due to the high temperature of the hot medium in the region of the hot side surface. Therefore, the mechanical load capacity of the heat shield element damaging material weakening due to cracking and crack growth in areas or portions of the hot side surface is particularly serious and life-limiting. The cracking effects on the hot side surface therefore contribute to a considerable extent to the weakening of the mechanical load carrying capacity of the heat shield element in the application. The weakening of the material can assume dimensions such that the material separates out from the hot-side surface in areas of high crack density or is increasingly removed as a result of the application of the hot flowing medium. Therefore, it is particularly beneficial when the notches extend as possible over the entire hot side surface.

Furthermore, it is preferred that the notches in their course have a curved, in particular a curved shape. This means that the notches are at least partially curved. The advantage of the curved or curved shape is that very long notches can be formed by this shape. A long run of notches, combined with a dense network of notches on the surface, leads to a particularly effective enlargement of this surface. Thus, the above advantages result, by which the formation of long thermo-voltage-induced cracks in the material can be avoided.

The introduction of a number of notches with curved or curved shape in the material in a thermally stressed area also has other very important advantages. In the event that a rift occurs anyway, he will reach a notch as he grows and continue to follow the course of the score. Since the notches are preferably designed to be very long and the crack must travel a very long distance before he reached two sides of the heat shield element and the heat shield element could break into two fragments. This long distance means that the time between the occurrence of the crack and the breakage of the heat shield element also becomes larger. In this greater period of time, there is also a greater likelihood that during a regular inspection of the combustion chamber the crack will be detected and the heat shield element replaced. Even if the damaged heat shield element is not detected in time and breaks into pieces, the likelihood of further cracks and their paths intersecting increases in the longer term. Then the heat shield element breaks into several smaller pieces. Experience has shown that when a heat shield element breaks into just two pieces and separates from the combustion liner, it only takes a few minutes takes until the turbine blades are so damaged by the hard fragments that a failure of the entire gas turbine plant is to be feared. On the other hand, when the heat shield element in the form of several small pieces separates from the combustion chamber wall and enters the gas turbine space, the turbine blades are not so severely affected. An immediate compulsory interruption or shutdown of the gas turbine plant is then advantageously not given, but a shutdown process can be performed gradually and controlled with the gas turbine plant.

Preferably, the course of the notches is circular arc and / or parabolic and / or serpentine and / or spiral. These shapes ensure a particularly long course of the notches and thereby also a significant increase in the effective surface.

In the case of the spiral course, a single notch extending over the entire surface could suffice. The notch then begins in a central region of the hot side surface and spirals out toward the hot side edges.

Preferably, the notches are aligned with respect to the main flow direction of the hot medium so that the flow resistance at the hot side surface is reduced by the alignment of the notches. In the case of the circular-arc or parabolic course of the notches, this means that the course is aligned concavely with respect to the inflowing hot medium. By this configuration, the resistance is reduced, the hot medium experiences on the hot side surface, because the hot medium enters the notches in the inflection point and is equal to split into two streams without the hot medium accumulates in the inflection point.

In a serpentine course, the notches are preferably oriented so that the hot medium does not encounter any inflection points on its way.

In a helical course, the orientation of the hot side relative to the main flow direction of the hot medium does not play a major role, because the spread of the hot medium on the hot side surface is the same, regardless of which direction the hot side is flowing.

Further explanations to this claim are given based on the embodiments in Figures 5 to 8.

It is further preferred that the notches on the base have a fillet with a radius of curvature for setting a predetermined notch effect. Investigations have shown that the introduction of a fillet at the bottom achieves high stability and low notch effect. In particular, locally high thermomechanical stresses can be avoided in this way.

Preferably, the number, the spacing, the arrangement and the geometry of the notches are set so that the mechanical carrying capacity of the heat shield element is only slightly affected by the notches themselves. By introducing a plurality of notches, the thermal stress can be reduced as well, as is done in an analogous manner by the operational formation of one or less thermo-voltage-induced cracks. The cross-sectional shape of the notch can preferably be adjusted in a targeted manner so that maximum stress relief is achieved with minimal weakening of the load-carrying capacity of the heat shield element. This solution is advantageously used in many cases in which caused by chemical or physical effects Dehnungsgradienten from one side into the interior of a component of a material. Instead of causing thermo-voltage-induced cracks in an uncontrolled manner and allowing them to be reproduced, notches are deliberately introduced with defined depth and geometry and defined distances to each other.

Preferably, the heat shield element has a height and the notches have a depth such that the depth of the notches is about 2% to 10%, in particular 4% of the height of the heat shield element. The deeper the notches are, the larger the area on which the tension forces will act, and that will reduce the stresses on the heat shield element surface. However, the notches can not be made arbitrarily deep because of the mechanical stability of the heat shield element and its thermal insulation effect. For the accomplishment of their task, notches with a depth of typically 2% to 10%, preferably up to 4%, of the heat shield element height are sufficient. To further increase the surface area, the notches could be brought closer together, i. with a smaller distance from each other.

The advantage here is that the notches have a width and the distance between two notches is 2 times to 3 times the notch width. In order to increase the surface area as much as possible, the notches should be placed very close to each other in the heat shield element material, e.g. cut, etched or in a cast heat shield element, the notches may already be provided in the mold. At the same time, the mechanical stability and the thermal insulation effect of the heat shield element must be considered again. In this case, a distance between the notches of 2 times to 3 times the notch width has been found to be particularly suitable.

Another advantage is that the distance along the course of two adjacent notches is almost constant. If small and, above all, uniform distances between the individual notches are present, are also induced in this range Distributing stresses evenly reduces the likelihood of cracking.

Another advantage is that the notches do not intersect in their course. At the intersections of two or more notches, the uniform distribution of the induced voltages is disturbed, so such interfaces must be avoided.

The heat shield element preferably consists of a ceramic material, in particular of a refractory ceramic. Refractory ceramic materials are particularly suitable for use as a thermal insulator at very high temperatures and temperature gradients, such as high mechanical strength, high allowable service temperature, dimensional stability, corrosion resistance, wear resistance, and low thermal conductivity, due to their material properties. in a combustion chamber.

The object directed to a combustion chamber is achieved according to the invention by a combustion chamber with an inner combustion chamber lining which has heat shield elements according to the above statements.

The object directed to a gas turbine is achieved by a gas turbine with such a heat shield elements having combustion chamber.

Fig. 1

eine schematische Darstellung einer Gasturbinenanlage,

Fig. 2

in perspektivischer Ansicht ein Hitzeschildelement gemäß der Erfindung,

Fig. 3

einen Schnitt durch das Hitzeschildelement in Fig. 2,

Fig. 4

eine Vergrößerung von zwei Kerben in Fig. 3,

Fig. 5

eine Draufsicht auf die Heißseite eines Hitzeschildelementes mit einem kreisbogenförmigen Verlauf der Kerben,

Fig. 6

eine Draufsicht auf die Heißseite eines Hitzeschildelementes mit einem parabolischen Verlauf der Kerben, und

Fig. 7

eine Draufsicht auf die Heißseite eines Hitzeschildelementes mit einem serpentinenförmigen Verlauf der Kerben.

The invention will be explained in more detail by way of example with reference to the drawing. It shows schematically and partially simplified:

Fig. 1

a schematic representation of a gas turbine plant,

Fig. 2

in perspective view a heat shield element according to the invention,

Fig. 3

a section through the heat shield element in Fig. 2,

Fig. 4

an enlargement of two notches in Fig. 3,

Fig. 5

a top view of the hot side of a heat shield element with a circular arc of the notches,

Fig. 6

a plan view of the hot side of a heat shield element with a parabolic curve of the notches, and

Fig. 7

a plan view of the hot side of a heat shield element with a serpentine course of the notches.

In Fig. 1, a gas turbine plant 1 is shown schematically. It comprises a combustion chamber 3 with a fuel supply system 5 and arranged along an axis 7 air compressor 9, gas turbine 11 and electric generator 13. Ambient air L is sucked by the air compressor 9, compressed and then led to the combustion chamber 3, where they together with the fuel B is mixed and burned, whereby a hot gas M is formed. The combustion chamber 3 is equipped with a heat-resistant combustion chamber lining, which is formed from a number of heat shield elements 15 arranged side by side over the entire area. The gas turbine 11 is driven by the hot gas M, which leaves the combustion chamber 3 under high pressure. The hot medium M flows through the gas turbine 11 drivingly and escapes as exhaust gas A. The exhaust gas A is filtered in a filter system, not shown in detail in Figure 1 and released after the filtration process in the atmosphere. To the gas turbine 11, a generator 13 is coupled, which serves to generate electrical energy. The generator 13 is connected to an electrical network and the electrical energy generated by the generator 13 is fed into this network.

In Fig. 2 is a perspective view of a Hitzschildelement 15 is shown, which is a part of the lining of the combustion chamber 3 in FIG. 1. The heat shield element 15 in this embodiment is cuboid, in particular with a nearly square base. The heat shield element 15 has a hot side 17, a hot side 17 opposite wall side 19, which is not shown in detail in this figure, and on the hot side 17 and the wall side 19 adjacent peripheral side 21. The hot side 17 has a plurality of nearly equidistant notches 23. The notches 23 in this embodiment have a circular arc-shaped course 25 a.

FIG. 3 shows a section through the heat shield element 15 shown in FIG. 2 along the axis SS '. The upper edge represents a section through the hot side 17, the lower edge through the wall side 19 and the two side edges through the peripheral side 21. The heat shield element 15 has a height H. On the hot side surface 17, a plurality of notches 23 is introduced. The depth T of the notches 23 is comparatively small compared to the height H of the heat shield element 15.

FIG. 4 shows an enlargement of the section IV in FIG. 3 with two notches 23. The notches 23 are introduced into the hot side surface 17 and have a depth T, so that locally the effective height H of the material of the heat shield element 15 is reduced. However, as already shown in FIG. 3, the dimension of the depth T of the notches 23 is much smaller than the height H of the heat shield member 15 in comparison. The notches 23 also have a fillet radius R at the bottom 27 , By means of this rounding off, locally high thermo-mechanical stresses at the bottom 27 can be avoided and thus a lower notch effect can be achieved. Furthermore, the notches 23 have a width C. The distance D between the two notches 23 in this embodiment is about 2.5 times the width C.

FIGS. 5, 6, 7 and 8 show a plan view of the hot side 17 of a heat shield element 15, wherein four different embodiments of the profile 25 a, 25 b, 25 c and 25 d of the notches 23 are shown in the four figures , On the hot side surface 17 edges 23 are introduced with a curved shape. The notches 23 in FIG. 5 have an arcuate course 25a, in FIG. 6 a parabolic course 25b, in FIG. 7 a serpentine course 25c and in FIG. 8 a helical course. The curves 25a and 25b of the notches 23 in FIGS. 5 and 6 are aligned concavely with respect to the inflowing hot gases M. This embodiment is particularly favorable from a fluid engineering point of view, because this reduces the resistance that the hot gases on the hot side surface 17 experience. In this case, the hot gases M entering the notches 23 at the inflection point W are split into two streams. In contrast, if the arcuate course 25a and the parabolic curve 25b are aligned convex to the hot gases, then the hot gases M will accumulate in the inflection point W. Concerning the serpentine course 25c in Fig. 7, the notches 23 are at best oriented so that when the hot gases M flow into the notches 23, they do not encounter a turning point W on their way, but are redirected only left and right, as well which is shown in Fig. 7. In the case of a spiral course 25d, as shown in FIG. 8, because of the almost symmetrical course 25d of the notches 23, it is insignificant from which direction the hot side 17 of the heat shield element 15 is flown.

Claims (14)

Heat shield element (15), in particular for lining a combustion chamber wall, with a hot side (17) which can be exposed to a hot medium (M), a wall side (19) opposite the hot side (17) and one to the hot side (17) and the wall side (19). adjacent peripheral side (21),
characterized in that, to increase the effective surface area in a thermally stressed area, a number of notches (23) are made in the material, which are designed such that the thermally induced stress forces in this area are reduced. A heat shield element (15) according to claim 1,
characterized in that the hot side (17) has a hot side surface, a plurality of notches (23) extending on the hot side surface (17). Heat shield element (15) according to one of the preceding claims,
characterized in that the notches (23) in their course (25) have a curved, in particular a curved shape. Heat shield element (15) according to one of the preceding claims,
characterized in that the course (25) of the notches (23) is circular arc (25a) and / or parabolic (25b) and / or serpentine (25c) and / or spiral (25d). Heat shield element (15) according to one of the preceding claims,
characterized in that based on the main flow direction of the hot medium (M) the Notches (23) are aligned so that the flow resistance at the hot side surface is reduced by the alignment of the notches (23). Heat shield element (15) according to one of the preceding claims,
characterized in that the notches (23) on the base (27) have a rounding with a radius of curvature (R) for setting a predetermined notch effect. Heat shield element (15) according to one of the preceding claims,
characterized in that the number, the distance (D), the arrangement and the geometry of the notches (23) are set so that the thermal insulation effect of the heat shield element (15) is only insignificantly impaired. Heat shield element (15) according to one of the preceding claims,
characterized in that the heat shield element (15) has a height (H) and the notches (23) have a depth (T) such that the depth (T) of the notches (23) is about 2% to 10%, especially 4% the height (H) of the heat shield element (23) is. Heat shield element (15) according to one of the preceding claims,
characterized in that the notches (23) have a width (C) and the distance (D) between two notches (23) is 2 to 3 times the notch width (C). Heat shield element (15) according to one of the preceding claims,
characterized in that the distance (D) along the course (25) of two adjacent notches (23) is almost constant. Heat shield element (15) according to one of the preceding claims,
characterized in that the notches (23) do not intersect in their course (25). Heat shield element (15) according to one of the preceding claims,
characterized in that it consists of a ceramic material, in particular of a refractory ceramic. Combustion chamber (3) of a combustion chamber wall with a number of heat shield elements (15) according to one of the preceding claims. Gas turbine (11) with a combustion chamber (3) according to claim 13.

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