EP1056932A1

EP1056932A1 - Turbine housing

Info

Publication number: EP1056932A1
Application number: EP98966202A
Authority: EP
Inventors: Norbert Henkel; Uwe Zander; Edwin Gobrecht
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 1998-02-18
Filing date: 1998-12-08
Publication date: 2000-12-06
Anticipated expiration: 2018-12-08
Also published as: US6345953B1; WO1999042705A1; KR20010041053A; CN1286739A; CN1119509C; DE19806809C1; JP2002504641A; EP1056932B1; JP4213863B2; DE59805746D1

Abstract

The present invention relates to a turbine housing (1) which comprises an inner housing (2) surrounded by an outer housing (3), wherein said inner (2) and outer (3) housings each have a first upper partial region (5) as well as a second lower partial region (6) with the outer surface (7) of the inner housing facing from a distance the inner surface (8) of the outer housing. The outer surface (7) of the inner housing, in a portion at least of the first partial region (5), is used for the radiation transmission of heat to the inner surface (8) of the opposite outer housing, wherein said heat transmission is lower than that occurring in a portion at least of the second partial region (6) on the outer surface (7) of the inner housing. This can be achieved due to appropriate surface coatings which are applied in the corresponding regions and which have different absorption and/or emission indices (a1, a2). A temperature equilibrium can thus be obtained between the upper surface and the lower surface of the respective housings (2, 3) so as to prevent any buckling thereof upon cooling.

Description

1 description

turbine housing

The present invention relates to a turbine housing with an inner housing which is surrounded by an outer housing, in particular for steam turbines. The inner housing and the outer housing each have a first, upper section and a second, lower section. These sections are often designed as separate housing parts.

An inner housing outer surface is spaced apart from an outer housing inner surface.

In the article "Temperature determination in turbine housings" by Robert Erich, in: Allgemeine Wärmetechnik, Zeitschrift für

Heat, refrigeration and process engineering, Vol. 9, 1959, pages 163 to 182, the different heating of individual structural elements of a steam turbine when starting up and at

Different temperatures cause deformations of the material and stresses that overlap the stresses caused by the vapor pressure. The aim of the article is to obtain selection criteria for the steels to be used based on calculated and determined temperature distributions. From the thermal expansions determined, all the necessary clearances and gaps can then be suitably dimensioned, which is of particular importance when two workpieces with different expansion coefficients are stepped on. In addition, the temperature distributions determined in this way should be able to derive guidelines on how to heat known turbines from the cold state and at what speed load changes are to be made without creeping processes in the material being caused by excessive stress.

The object of the present invention is to keep a curvature of the turbine housing low during cooling. 2

This object is achieved according to the invention with a turbine housing with the features of claim 1. Advantageous refinements and developments are specified in the dependent claims.

The invention is based on the knowledge that be a steam turbine, which has a turbine outer casing and a turbine inner casing or a guide vane carrier, occur after the turbine has been switched off and between the respective housings or between the outer housing and a vane carrier on. These can lead to the fact that both housings bend, which leads to undesirable tensions and bridging of the game. This means that in unfavorable cases turbine blades can graze the housing and cause rubbing damage. The curvature that occurs when the outer house cools naturally is also referred to as "cat hump" because of its appearance.

The turbine case has an inner case that is one

Outer house is surrounded. In the following, "inner housing" is also understood to mean a guide vane carrier. The inner housing and the outer housing are each divided into a first, upper section and a second, lower section. An inner housing outer surface and an outer housing inner surface are spaced apart from one another. The inner housing outer surface and the opposite outer housing inner surface ^{0 σ are designed in} at least part of their respective first subarea so that there is less heat transfer due to radiation have as at least in a part of their respective second partial area. As a result, after the turbine has been switched off, it is avoided that the outer housing cools too quickly compared to the inner housing. If the inner housing outer surface had approximately the same heat transfer to the opposite outer housing inner surface in the first and in the second partial area, a not inconsiderable 3 significant buoyancy flow can be initiated in the space formed by two opposite surfaces. This buoyancy flow would result in a higher heat input in the first, upper part of the outer housing. When cooling by natural convection, temperature compensation can now be achieved according to the invention due to the lower heat transfer in the first partial area, so that the temperature difference between the first, upper partial area and the second, lower partial area is considerably lower than previously known temperature differences of over 50 Kelvin with natural cooling without Additional measures may lie.

A first, particularly advantageous embodiment for the formation of a lower heat transfer due to radiation provides that the inner housing in the first partial area on the inner housing outer surface has a first emission number that has a smaller value than a second emission number of the second partial area on the inner housing outer surface . It has proven to be advantageous for temperature compensation if the first emission number has a value below 0, t> and the second emission number has a value above 0.5. The s is also to be considered depending on the material used for the inner and outer housing. In order to avoid stresses in the housings themselves, both housings mostly consist of a similar material. The emission number of the respective material can still be decisively influenced by suitable surface treatment, e.g. by roughening the surface in order to obtain a suitable emission number. The surface is preferably processed in such a way that the material properties such as strength and corrosion behavior are at most insignificantly influenced.

A development of the use of different emission numbers in the first, upper partial area and second, lower partial area provides for the inner housing outer surface that a material in the first partial area has a smaller emission 4 has number as a further material, but which is now applied to the inner housing outer surface in the second partial area. This makes it possible to continue to use the materials previously used for the inner and outer housing. A material to be applied is used which has a higher emission number than the inner housing. A desired positive radiation effect can be amplified in this way. An oxide ceramic, for example zirconium oxide, is preferably used as the material to be applied. Furthermore, other coating materials with a suitable radiation property and connectivity to the material of the housing can also be used. A coating material preferably also has corrosion resistance in water vapor. The layer thickness with which the coating material is applied can be, for example, in the range between 50 μm and 100 μm. On the one hand, this offers the property of a particularly high emission number, for example of e = 0.8 or higher. On the other hand, the oxide ceramic can be applied reliably and in a manner that is durable over a long period of time, using common housing material 1 ~ I, for example GGG-40. A suitable technique for applying a thin layer of oxide ceramic is, for example, plasma spraying. _The type of application, as well as the oxide ceramic itself, further ensure that a high chemical resistance to the media occurring in the turbine housing is ensured. The coating material in this case preferably has a coefficient of thermal expansion, which is also suitable with regard to transient temperature conditions to keep the risk of chipping from the housing material small.

A further embodiment for achieving a lower heat transfer by radiation in a part of the first partial area of the inner housing outer surface to the opposite outer housing surface in relation to a part of the second partial area of the inner housing outer surface is achieved in that at least part of the second partial area of the outer 5 housing inner surface has a larger absorption number than a part of the first portion of the outer housing inner surface. This also results in increased heat input into the second, lower section of the outer housing. This also leads to an equalization of the outer housing temperatures. Since the driving temperature gradient for natural convection between the inner housing and the outer housing is thereby reduced, this design also counteracts natural convection.

A further development of the configuration of the second partial area with a larger absorption number has a third material in the second partial area on the inner surface of the outer housing. This third material has a higher absorption number than a fourth material of the outer housing inner surface in the first partial area. This third material is either the material of the outer housing inner surface in the second partial area itself, the surface of which has been processed accordingly, or d- ;. ^The material can also be an appropriate material which is applied to the inner surface of the outer housing in the second partial area. Another possibility for changing the absorption numbers between the first, upper partial area and the second, lower partial area of the outer housing inner surface is to change the outer housing inner surface in the first, upper partial area so that it has a lower absorption number than the outer housing. Inner surface of the second, lower section.

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

1 shows a preferred embodiment of the invention in which a material is applied to an inner surface of the outer housing, FIG. 2 shows 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 is a schematic perspective view of an outer housing and

Figure 4 shows a further embodiment of the invention, in which a further material is applied to an inner surface of the outer housing.

FIG. 1 shows a schematic illustration of a turbine housing 1. The turbine housing 1 has an inner housing 2 and, preferably concentrically thereto, an outer housing 3. Instead of an inner housing 2, a guide vane carrier could also be provided. The inner housing 2 and the outer housing 3 are spaced apart from one another in such a way that an intermediate h ri u 1 results. This intermediate space 4 is filled with a gaseous medium, in particular steam in a steam turbine, which is capable of convection. The inner housing 2 and the outer housing 3 each open into a first, upper subarea 5 and a second, lower subarea 6.

If we now consider 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, on the one hand, heat is transferred by a heat convection current QK and by a radiant heat flow QS 7 on. 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 partial area 5 has a first absorption number al, which is smaller than a second absorption number a2 in a part of the second, lower partial area 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 having low material thickness, so that the second due to the opposite to the first absorption number greater al ^Abs' orptionszahl a2 better radiation heat receiving cable resistance not due to excessive heat conduction canceled. 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. By άO -0 ^~ - first material 9 radiant heat absorbs better than a second material 10 in the first portion 5, taking the second portion ^"" a considerably larger heat flow than without the first material 9. This affects the thermal convection current QC in the first portion 5 against and leads to a smaller temperature difference between the first portion 5 and second portion 6 during shutdown of the turbine. As extremely resilient first material 9 has zirconium oxide (Zr0 ₂₎ CrV ieεen which is advantageously applied by plasma spraying. such Even with a small thickness, the layer is able to withstand even more aggressive media in the intermediate space 4. At a radiation temperature of approximately 350 ° C., which occurs for a longer period when a turbine is switched off, this oxide ceramic also has an absorption number of approximately 0.9, which is considerably higher than an absorption number v on about 0.25 for an outer case 3 made of the material mentioned above. It should also be noted that the first absorption number a _x and also the second absorption number a ₂ are dependent on the temperature. If the temperature changes during the cooling process after the turbine is 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. 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 increasing to the indication of plus 90 ° in the first, upper subarea 5 corresponding to FIG. 1. Due to the different absorption numbers, this results in just because of the changed. Radiation conditions ^fj in 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 if different absorption numbers are not used. In order to ensure this result, it is advantageous that the first absorption number ai in the first partial area 5 has a value of less than 0.5 and the second absorption number a ₂ in the second partial area β has a value of more than 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 9 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 ei, 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 ei has a value below 0.5 and that 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. This in turn also leads to the heat convection current QK being made more uniform by the temperatures in the outer housing 3 is counteracted.

Claims

10 claims

1. Turbine housing (1) with 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 section (5) and a second, lower section (6), and with an inner housing outer surface (7) and an outer housing inner surface (8) which are spaced apart from one another, 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 area (5) are designed such that they have a lower heat transfer by radiation than at least in a part of their respective second partial area (6).

? T eng.irhJ "engehäuee (1) according to claim 1, characterized K indicates that at least a part of the second section (β) of the outer housing inner surface (8) has a greater absorption number (a ₂ ) than a part of the first section (5) 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 area (6) has a first material (9) which has a larger absorption number (a ₂ ) than the absorption number (ai) one second material (10) of the outer housing inner surface (8) in the first partial area (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). 11

5. turbine housing (1) according to claim 4, d a d u r c h g e k e n n z e i c h n e t that the first material (9) is an oxide ceramic.

6. Turbine housing (1) according to claim 2, characterized in that a third material (11) is applied to the outer housing inner surface (8) in the first partial region (5), the absorption number (a ₃ ) is smaller than an absorption number (ai) the outer housing inner surface (8) in the second section (6).

7. Turbine housing (1) according to claim 4, 5 or 6, so that the material (9; 11) is applied by means of plasma spraying.

8. Turbine housing (1) according to one of the preceding claims, characterized in that a first absorption number (ai) in the first section (5) has a value below 0.5 and a second absorption number (a ₂ ) in the second section (6) has a value have above 0.5.

9. Turbine housing (1) according to one of the preceding claims, d a d u r c h g e k e n n z e i c h n e t that the

Inner housing outer surface (7) in the first partial area (5) has a first emission number (ei) which has a smaller value than a second emission number (e ₂ ) of the second partial area (6) on the inner housing outer surface (7).

10. Turbine housing (1) according to claim 9, characterized in that the first emission number (ei) has a value below 0.5 and the second emission number (e ₂ ) has a value above 0.5. 12 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).