EP1056932B1 - Turbine housing - Google Patents

Description

The present invention relates to a turbine housing an inner housing which is surrounded by an outer housing, especially for steam turbines. The inner case and that Outer housings each have a first, upper partial area and a second, lower section. Often are these sub-areas are designed as separate housing parts. An inner housing outer surface lies on an outer housing inner surface spaced from each other.

In the article "Temperature determination in turbine housings" by Robert Erich, in: General Heat Technology, Journal for Heating, cooling and process engineering, Vol. 9, 1959, pages 163 to 182, the different heating of individual construction elements a steam turbine when starting up and at Load changes handled during operation, by such Different temperatures cause deformation of the material on as well as tensions that are caused by the vapor pressure superimposed tensions. The aim of the article is based on calculated and determined temperature distributions Get selection criteria for the steels to be used. All can then be determined from the thermal expansions determined required games and columns appropriately sized what when two workpieces meet with different expansion coefficients is of particular importance. About that In addition, the temperature distributions determined in this way should Guidelines can be derived, such as known turbines from the warm up cold state and at what speed Load changes should be made without creeping caused by overstressing in the material.

The object of the present invention is a curvature to keep the turbine housing low when cooling down.

An arrangement to reduce Temperature differences in a turbine housing is from JP-A-03054302 (abstract) known.

This object is achieved with a turbine housing solved with the features of claim 1. Advantageous configurations and further developments are in the dependent claims specified.

The invention is based on the knowledge that at a steam turbine that has a turbine outer shell and a Turbine inner casing or a vane carrier, occur after the turbine is switched off and between the respective housings or between the outer housing and a Guide vane carrier temperature differences. these can cause both housings to twist, causing undesirable Tensions and game bridges. This means that in unfavorable cases turbine blades the housing can rub and cause rubbing damage. The one that occurs when the outer casing cools naturally Warping is also due to its appearance with "cat humps" designated.

The turbine casing has an inner casing that is made by a Outer casing is surrounded. Under "Inner Housing" is the following also understood a vane carrier. The inner case and the outer case are each in a first, upper Sub-area and a second, lower sub-area divided. An inner case outer surface and an outer case inner surface are opposite each other. The inner case outer surface and the opposite outer case inner surface are at least in part of their respective the first section designed so that there one have less heat transfer by radiation than at least in a part of their respective second sub-area. This enables the turbine to be switched off it is avoided that. the outer housing opposite the inner housing cools down too quickly. Would the inner case outer surface namely an approximately equal heat transfer to the opposite Outer case inner surface in the first and second Partial area would be a not insignificant in the upper area Buoyancy flow in the opposite of both Space formed space can be initiated. This buoyancy flow would result in a higher heat input in the cause first, upper portion of the outer housing. at Cooling by natural convection can now be done according to the invention due to the lower heat transfer in the first section create a temperature compensation so that the temperature difference between the first, upper section and the second, lower section considerably below previously known temperature differences of over 50 Kelvin with natural cooling can lie without additional measures.

A first, particularly advantageous embodiment for training less heat transfer due to radiation provides that the inner housing in the first section on the Inner housing outer surface has a first emission number, which has a smaller value than a second emission number of the second section on the inner housing outer surface. It has proven to be advantageous for temperature compensation if the first emission number is below 0.5 and the second emission number has a value above 0.5. This also depends on the material used to consider for the inner or outer housing. About tensions To avoid namely in the housings themselves, both exist Housing mostly made of a similar material. The Emission number of the respective material can be determined by suitable Surface processing are still decisively influenced, e.g. by deliberately roughening the surface, thereby to get a suitable emission number. Preferably done the processing of the surface so that the material properties such as strength and corrosion behavior at most be influenced insignificantly.

Further training in the use of different emission numbers in the first, upper section and second, lower Sub-area provides for the inner housing outer surface that a material in the first section has a lower emission number has as a further material, but now on the Inner housing outer surface applied in the second section is. This makes it possible to use the materials previously used continue to use for inner and outer housing can. A material to be applied is used that has a higher emission number than the inner housing. A desired positive radiation effect is on reinforceable in this way. Is preferred as to be applied Material an oxide ceramic, e.g. Zirconia. Farther can also use other coating materials with a suitable radiation properties and connectivity the material of the housing can be used. A coating material preferably also has corrosion resistance in water vapor. The layer thickness with which the coating material applied, e.g. in the area are between 50 µm and 100 µm. This offers the one Property of a particularly high emission number, for example of e = 0.8 or higher. On the other hand, the oxide ceramic on common housing material, for example GGG-40, reliably and permanently applied. A suitable one Technique for applying a thin layer of oxide ceramics is, for example, plasma spraying. The type of application, as well as the oxide ceramic itself, continue to represent sure that also high chemical resistance to the media occurring in the turbine housing is. The coating material preferably has a coefficient of thermal expansion that also suitable with regard to transient temperature conditions is the risk of chipping from the housing material to keep small.

Another training to achieve a lower heat transfer by radiation in a part of the first partial area the inner housing outer surface to the opposite Outer housing surface in relation to a part of the second section the inner housing outer surface is achieved that at least part of the second section of the outer housing inner surface has a larger absorption number than part of the first portion of the outer housing inner surface. This also results in increased heat input in the second, lower section of the outer housing. This again leads to an evening of the outer housing temperatures. Because this is the driving temperature gradient for natural convection between the inner casing and this training is also effective towards natural convection.

A further development of the design of the second sub-area with a larger absorption number points in the second Part of a third material on the inner surface of the outer casing on. This third material has a higher absorption number as a fourth material of the outer case inner surface in the first section. This third material is either the material of the outer housing inner surface in the second section itself, with its surface machined accordingly has been, or the third material can also be an additional Material that is on the outer housing inner surface is applied in the second section. One more way for a change in the absorption numbers between the first, upper section and the second, lower section the inner surface of the outer casing is the inner surface of the outer casing to change in the first, upper section so that this has a lower absorption number than the outer housing inner surface of the second, lower section.

Figur 1

eine bevorzugte Ausführung der Erfindung, bei der auf einer Außengehäuse-Innenfläche ein Material aufgetragen ist,

Figur 2

eine Temperaturverteilung, wie sie sich unter Vernachlässigung von Naturkonvektion durch Strahlungseffekte bei der Ausführung nach Figur 1 nach Abstellen der Turbine ergibt,

Figur 3

die schematische perspektivische Ansicht eines Außengehäuses und

Figur 4

eine weitere Ausgestaltung der Erfindung, bei der ein weiteres Material auf einer Außengehäuse-Innenfläche aufgetragen ist.

Exemplary embodiments of the invention and further advantages and features are explained in more detail with reference to the following drawing. Show:

Figure 1

a preferred embodiment of the invention, in which a material is applied to an inner surface of the outer housing,

Figure 2

a temperature distribution as it results from neglecting natural convection due to radiation effects in the embodiment according to FIG. 1 after the turbine has been switched off,

Figure 3

the schematic perspective view of an outer housing and

Figure 4

a further embodiment of the invention, in which a further material is applied to an inner surface of the outer housing.

Figure 1 shows a schematic representation of a turbine housing 1. The turbine housing 1 has an inner housing 2 and preferably concentric with an outer housing 3. Instead of an inner housing 2, a guide vane carrier could also be used be provided. The inner case 2 and the outer case 3 are spaced from each other so that there is a space 4 results. This space 4 is with a gaseous Medium, in particular steam in a steam turbine, filled, which is convection capable. The inner casing 2 and the outer housing 3 can each be in a first, upper Subarea 5 and a second, lower subarea 6 split.

If one now considers a heat flow through the turbine housing 1, an inner heat flow Qi through the inner housing 2 and an outer heat flow Qa through the outer housing 3 result , For example, the outer housing 3 is a cast housing (GGG-40) made using spheroidal graphite. The associated thermal conductivity is approximately 30 W / mK. The thickness of the outer housing 3 is approximately 100 to 150 mm. Between the inner housing 2 and the outer housing 3, heat transfer occurs on the one hand through a heat convection current QK and through a radiant heat flow QS. The latter acts from the inner housing outer surface 7 to the outer housing inner surface 8. The outer housing inner surface 8 in the first, upper part 5 has a first absorption number a1, which is smaller than a second absorption number a2 in part of the second, lower part 6. Either the outer housing inner surface 8 is specially treated in the second, lower partial area 6 or in the first, upper partial area 5. The particularly advantageous solution shown here provides for the application of a first material 9 on the inner surface of the outer housing in the second partial region 6. The first material 9 forms a thin layer with a small material thickness, so that the better absorption of radiant heat due to the second absorption number a2, which is greater than the first absorption number a1, is not canceled out by an excessively high heat conduction resistance. The first material 9 extends here in an angular range of approximately 90 °. However, the angular range can also be considerably smaller or also larger, for example depending on a heat gradient over the length of the turbine. Because the first material 9 absorbs radiant heat better than a second material 10 in the first partial area 5, the second partial area 6 absorbs a considerably larger heat flow than without the first material 9. This counteracts the heat convection current QK in the first partial area 5 and leads to it a lower temperature difference between the first section 5 and the second section 6 when the turbine is switched off. Zirconium oxide (ZrO ₂ ) has proven to be an extremely resilient first material 9, which is advantageously applied by plasma spraying. Even with a small thickness, such a layer is able to withstand even in the case of more aggressive media in the intermediate space 4. At a radiation temperature of approximately 350 ° C., such as occurs for a longer period when a turbine is switched off, this oxide ceramic also has an absorption number of approximately 0.9. This is considerably higher than an absorption number of approximately 0.25 for an outer housing 3 made of the material mentioned above. It should also be noted that the first absorption number a ₁ and also the second absorption number a ₂ are dependent on the temperature. If the temperature changes during the cooling process after the turbine has been switched off, zirconium oxide also fulfills the requirement to have a high absorption number over a wide temperature range.

Figure 2 shows an XY coordinate system. The X axis indicates a measured temperature of the outer housing inner surface 8 from FIG. 1. The Y axis shows the location of the measurement in degrees. In order to clarify the location of the measurement, a schematic view of the outer housing 3 with a subdivision corresponding to a calculation grid is given in FIG. Corresponding to the Y axis in FIG. 2, the degree is from minus 90 ° starting in the second, lower subarea 6 from FIG. 1 and progressing to the indication of plus 90 ° in the first, upper subarea 5 corresponding to FIG solely due to the changed radiation conditions, a temperature difference between the first partial area 5 and the second partial area 6 of at most Δ T = 27 K. This temperature difference Δ T caused by the radiation equals an otherwise at least 50 K large temperature difference between the first partial area 5 and the second partial area 6 at least partially when different absorption numbers are not used. In order to ensure this result, it is advantageous that the first absorption number a ₁ in the first section 5 has a value below 0.5 and the second absorption number a ₂ in the second section 6 has a value above 0.5.

FIG. 4 shows a further embodiment in order to use the thermal radiation to compensate for temperature differences. For simplification in FIG. 4, the same components as in FIG. 1 are also provided with the same reference symbols. On the one hand, the outer housing inner surface 8 has a third material 11 in the first partial area 5. The third absorption number a _{3 of} this third material 11 is smaller than the absorption number a _{4 of} the outer housing inner surface 8 in the second partial region 6. On the other hand, the inner housing outer surface 7 in the second partial region 6 has a fourth material 12. The inner housing outer surface 7 in the first partial area 5 has a first emission number e ₁ , which has a smaller value than a second emission number e ₂ and this fourth material 12. It is preferred that the first emission number e _{1 has} a value below 0.5 and the second emission number e _{2 have} a value above 0.5. In this way, a higher radiant heat flow QS flows from the inner housing outer surface 7 to the outer housing inner surface 8 in the second partial region 6 than in the first partial region 5 is knitted.

Claims (11)

1. Turbine housing (1)

   having an inner housing (2) which is surrounded by an outer housing (3), the inner housing (2) and the outer housing (3) each having a first, upper partial region (5) and a second, lower partial region (6), and

   having an inner-housing outer surface (7) and an outer-housing inner surface (8) which are positioned opposite one another, with a distance between them,

   characterized in that the inner-housing outer surface (7) and the opposite outer-housing inner surface (8), at least in a part of their respective first partial region (5), are designed in such a way that, in that region, they exhibit a lower heat transfer through radiation than at least in a part of their respective second partial region (6).
2. Turbine housing (1) according to Claim 1, characterized in that at least a part of the second partial region (6) of the outer-housing inner surface (8) has a greater absorption coefficient (a₂) than a part of the first partial region (5) of the outer-housing inner surface (8).
3. Turbine housing (1) according to Claim 2, characterized in that the outer-housing inner surface (8), in the second partial region (6), has a first material (9) which has a greater absorption coefficient (a₂) than the absorption coefficient (a₁) of a second material (10) of the outer-housing inner surface (8) in the first partial region (5).
4. Turbine housing (1) according to Claim 3, characterized in that the first material (9) is applied to the outer-housing inner surface (8).
5. Turbine housing (1) according to Claim 4, characterized in that the first material (9) is an oxide ceramic.
6. Turbine housing (1) according to Claim 2, characterized in that a third material (11), the absorption coefficient (a₃) of which is lower than an absorption coefficient (a₁) of the outer-housing inner surface (8) in the second partial region (6), is applied to the outer-housing inner surface (8) in the first partial region (5).
7. Turbine housing (1) according to Claim 4, 5 or 6, characterized in that the material (9; 11) is applied by means of plasmaspraying.
8. Turbine housing (1) according to one of the preceding claims, characterized in that a first absorption coefficient (a₁) in the first partial region (5) is below 0.5 and a second absorption coefficient (a₂) in the second partial region (6) is above 0.5.
9. Turbine housing (1) according to one of the preceding claims, characterized in that the inner-housing outer surface (7), in the first partial region (5), has a first emission coefficient (e₁) which is lower than a second emission coefficient (e₂) of the second partial region (6) on the inner-housing outer surface (7).
10. Turbine housing (1) according to Claim 9, characterized in that the first emission coefficient (e₁) is below 0.5 and the second emission coefficient (e₂) is above 0.5.
11. Turbine housing (1) according to Claim 9 or 10, characterized in that a fourth material (12) is applied to the inner-housing outer surface (7).

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