Patent Application
20060269393
This application claims priority under 35 U.S.C. ยง 119 to German application number 10 2005 015 150.7, filed 31 Mar. 2005, the entirety of which is incorporated by reference herein.
1. Field of the Invention
The invention relates to a housing for a machine, in particular virtually rotationally symmetrical housings, for example for a turbomachine, with a first housing shell which is connected to a second housing shell along a parting plane passing mostly through the machine axis or axes.
2. Brief Description of the Related Art
In a housing of this type, in the region of the parting plane, at least one flange is formed, by means of which the two housing shells are fastened to one another. Conventionally, this flange extends in the parting plane and there forms a housing widening which extends radially with respect to a longitudinal direction of the housing and which usually reaches over the entire axial length or circumference of the housing. The two housing shells are screwed directly to one another in the region of the flange, the respective screw connection passing through the parting plane preferably perpendicularly.
The housing shells thus conventionally possess contact faces extending in the parting plane, which lie against one another along the parting plane and are pressed against one another within the respective flange by means of the respective screw connection.
Furthermore, a housing of this type, at least in a turbomachine, such as, for example, a turbine or a compressor, may have a rotationally symmetrical or virtually rotationally symmetrical form. The radially projecting flanges cause a disturbance in such a housing in two respects: on the one hand, the rigidity of the flange region in respect of a moment of flexion in the circumferential direction, for example a thermal moment as a result of a radial temperature gradient over the wall, is locally markedly different from the rest of the circumference, and, on the other hand, the additional masses and the radial extent of the flanges lead to a changed temperature behavior of the housing in the region of the flange. Both disturbances have an adverse effect on the deformation behavior of the housing, in that, even when the pressure and/or thermal load is constant in the circumferential direction, locally different curvatures and distortions occur. As a result, during operation, a rotationally symmetrical housing acquires a cross section which is no longer circular.
In order to keep the circumferential rigidity constant, the flanges must have a width of approximately 2-3 times the wall thickness. What opposes this is that they should ideally not project beyond the (rotational) contour of the remaining housing for reasons of as uniform a thermal behavior as possible and a reduction in overall size. For these contradictory requirements, on the one hand, sufficient flexural rigidity in the circumferential direction and, on the other hand, a low radial extent, a satisfactory compromise has been difficult to find with the design principles known hitherto.
In this regard, the various known solutions of the prior art for alternative principles for the connection of housing flanges also do not constitute a solution which is satisfactory in this respect, because these are mainly aimed at increasing the closing forces, sometimes at the expense of lower circumferential rigidity and without regard to the necessary installation space.
Thus, DE 853 451 describes clamps which generate markedly higher closing forces from relatively low horizontal tension bolt forces via wedge or toggle lever mechanisms. So that these closing forces can be applied without excessively high circumferential moments as a result of wall tension and the distance of the clamps from the wall center line, the flanges must be kept particularly narrow, thus further reducing their circumferential rigidity, even though the necessary radial installation space is very large.
An alternative proposal with a similar aim is the subject of Swiss publication CH 319 355, in which the closing forces are generated from lower bolt tension forces via a lever mechanism. In contrast to the previous solution proposal, the circumferential rigidity is likewise increased on account of the large radial width of the flange, but at the expense of a high space requirement with correspondingly problematic thermal behavior.
U.S. Pat. No. 2,457,073 illustrates a combination of the two principles discussed above: a clamp with a lever mechanism acts on a narrow nose in a cylindrical wall of virtually constant thickness. Consequently, transient thermal processes should cause highly uniform temperature distributions, but the flexural rigidity of the parting plane is minimal.
U.S. Pat. No. 2,276,603 likewise proposes clamps with a wedge mechanism for generating the closing forces, similar to the abovementioned DE 853 451. However, because of the small vertical bearing faces remaining between the clamp and the housing half, the circumferential stiffening is only minor. The aim is obviously solely to achieve greater closing forces.
Finally, U.S. Pat. No. 2,169,092 proposes use of double T-shaped shrunk-in ties instead of bolts.
In may be stated, overall, that the solutions presented here are directed primarily at sealing of the housing shells and at generating high closing forces, but ignore the problems of circumferential rigidity and mass distribution and the risk of asymmetric deformation.
This has the unavoidable consequence that a high flexural rigidity in the circumferential direction, with as uniform a mass distribution as possible in the flange region, to ensure the highest possible rotational symmetry, along with high mechanical and thermal load-bearing capacity, is not achieved according to these solutions.
Precisely where turbomachines are concerned, however, an asymmetric deformation of the housing presents problems, since, as a rule, the housing serves for carrying guide blades and sealing zones for moving blades. An asymmetric deformation of the housing disturbs the throughflow of the turbomachine. In particular, radial gaps may be formed or enlarged between the moving blades and the housing-side sealing zones and between the guide blades and rotor-side sealing zones, thus causing the flow to pass around the blades at their tip. The efficiency of a turbomachine is significantly reduced, however, when the high-energy flow flows around the blades at their tip and therefore does not transmit any work to the respective blade.
This is where the invention comes in. One aspect of the present invention is concerned with the problem of specifying, for a housing of the type initially mentioned, an improved embodiment which, in particular, significantly improves the dimensional stability of the housing, in that the circumferential rigidity, even in the region of the parting plane, is virtually constantly equal to that of the rest of the housing circumference, while at the same time the radial extent in the region of the parting plane can be largely adapted to the remaining rotational contour of the housing.
Another aspect of the present invention includes attaching, instead of the respective, in particular horizontal flanges, at least one bridge which extends perpendicularly with respect to the parting plane and which is connected firmly, and rigidly in terms of moment of deflection in the circumferential direction, on both sides of the parting plane, in each case in a corresponding bridge portion, both to one housing shell and to the other shell. A bridge of this type forms, transversely with respect to the parting plane, a tie which connects the two housing halves in the parting plane firmly to one another such that they bear against one another. In this case, the local flexural rigidity achievable at the parting plane with the aid of the bridge can be made virtually ideally equal to the rest of the circumference. In addition, if necessary, by appropriate dimensioning and/or additional structural elements, the tensile strength of the bridge can be many times higher than in the case of a conventional screw connection which passes through the flange perpendicularly with respect to the parting plane. A particularly advantageous feature, however, is the connection in the circumferential direction which is rigid in terms of moment of deflection, at the same time with a reduction in the radial extent in the parting plane.
The bridge may be screwed or otherwise connected on one of the bridge portions or on both bridge portions to the housing half associated in each case. With the aid of a screw connection of this type, a suitable selection of the screwing points in terms of positioning and/or number and/or dimensioning, particularly high flexural rigidity and, if necessary, also strength can be produced for the respective connection between the respective housing shell and the respective bridge portion.
It is likewise basically possible to integrate one of the two bridge portions into the associated housing shell, that is to say the bridge then forms an integral part of the respective housing shell. This results particularly simply in a firm connection between the housing shell and the bridge formed integrally on it or in one piece or in one part with it, and only one side of the bridge is connected releasably to the other housing shell.
Additionally or alternatively, at least one of the bridge portions may be connected to the associated housing shell via a positive connection. Suitable positive connections are, for example, a dovetail coupling, a hammerhead coupling or a clamp coupling. As a result of form fit, particularly high moments and forces can be transmitted directly between the bridge and the respective housing shell, while, basically, screws for the transmission of pairs of forces of circumferential moments and/or shear forces between the bridge and the respective housing shell may be dispensed with.
Further important features and advantages of the housing according to the invention may be gathered from the drawings and from the associated figure description with reference to the drawings.
Preferred exemplary embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description, the same reference symbols referring to identical or similar or functionally identical components. In the drawings, in each case diagrammatically,
According to
So that the bridge 6 does not lead to an asymmetric deformation of the housing 1 on account of the loads occurring, it should have essentially the same strength and rigidity values and, in particular, the same thermal properties (mass, wall thickness, radial extent) as the remaining region of the housing shells 2, 3.
This bridge 6 extends perpendicularly with respect to the parting plane 4 and is arranged such that it passes through the parting plane 4. The bridge 6 correspondingly has a first bridge portion 7 which is located on the same side of the parting plane 4 as the first housing shell 2. Furthermore, the bridge 6 has a second bridge portion 8 which is located on the outer side of the parting plane 4 in the same way as the second housing shell 3. The first bridge portion 7 is connected firmly to the first housing shell 2. The second bridge portion 8 is connected firmly to the second housing shell 3.
In the embodiment according to
So that particularly high moments and even forces can be transmitted between the bridge 6 and the housing shells 2, 3, the respective bridge portion 7, 8 has provided on it an associated contact face, to be precise a first contact face 10 on the first bridge portion 7 and a second contact face 11 on the second bridge portion 8. Complementarily to this, the first housing shell 2 has a first contact counterface 12, while the second housing shell 3 possesses a second contact counterface 13. In the mounted state, the contact faces 10, 11 bear over their area against the respective contact counterface 12, 13. The tie-up of the bridge 6 to the housing shells 2, 3 expediently takes place such that the respective contact face 10, 11 is pressed against the respective contact counterface 12, 13. In the variant according to
In the embodiment shown here, the contact faces 10, 11 and the contact counterfaces 12, 13 extend in a plane 14 which stands on the parting plane 4. In the embodiment shown here, this plane 14 stands perpendicularly on the parting plane 4. The invention also includes embodiments with contact faces standing slightly obliquely, in particular with contact faces standing obliquely mirror-symmetrically to the plane of symmetry of the housing, similarly to a lift-out slope, which, in particular, simplify the operation of mounting and demounting (
In the embodiment according to
The bridge 6 may be dimensioned particularly simply such that the tensile forces consequently transmittable are considerably higher than tensile forces which can be transmitted by means of conventional screw connections. In addition, the moment rigidity is increased. At the same time, a bridge 6 of this type has comparatively compact build, with the result that the outer contour of the housing 1 is undisturbed or disturbed only slightly in terms of it symmetry.
The bridge 6 may be configured, for example, as a plate. It is likewise possible to configure the bridge 6 as a bar. In the case of a plate-shaped bridge 6, a longitudinal dimension of the bridge 6, which is measured in the parting plane 4 and in the longitudinal direction of the housing 1, is greater than a transverse dimension of the bridge 6, which is measured transversely with respect to the parting plane 4, that is to say along the plane 14. A plate-shaped bridge 6 can be anchored with sufficient strength to the housing shells 2, 3 by means of a corresponding number of screw connections 9. In contrast to this, in the case of a bar-shaped bridge 6, the longitudinal dimension of the bridge 6 is in any event smaller than the transverse dimension of the bridge 6. Preferably, in the case of a bar-shaped bridge 6, the longitudinal dimension of the bridge 6 lies in the region of a thickness which is measured in the parting plane 4 and transversely with respect to the longitudinal direction of the housing 1.
According to
Preferably, the bridge 6 is designed such that an essentially constant mass distribution is obtained over the region of the parting plane 4 in the cross section of the housing 1 in the circumferential direction of the latter. The housing thus possesses largely constant flexural rigidity and, furthermore, essentially the same thermal properties over the entire circumference, with the result that, under the loads occurring when the machine is in operation, a symmetrical deformation of the housing 1 is achieved particularly simply.
While
In the embodiment according to
Similarly to
In the embodiments of
Such additional positive connections 17 are advantageous when high forces also have to be transmitted in addition to the circumferential moments. In particular, they make it possible to dimension the screw connection solely according to the moment transmission, this usually requiring only relatively small bolts on account of the relatively large height of the contact faces and consequently large screw spacings, without surcharges on account of an additional shear load to the screws having to be taken into account.
In particular, the variant shown in
In the variant according to
In the embodiment according to
In this type of positive connection 17, the screw connections 9 could basically be dispensed with or be further reduced if either the positive connection is placed approximately in the middle of the respective contact faces, so that the moment can be transmitted by means of the large-area support on both sides, or in that, instead of this, in each case a second row of such connections is arranged nearer to the parting plane 4, so that the pairs of forces arising from the circumferential moments can also be transmitted in the radial direction via the contact faces by means of suitable positive connections (
In the embodiment according to
It is clear, in this case, that the embodiments, shown in
Whereas, in the embodiments of
The embodiments illustrated here are purely by way of example and therefore without any restriction in generality. Thus, types of housing construction other than rotationally symmetrical likewise come under the invention. Also, such types of construction with a horizontal parting plane and bridges arranged perpendicularly with respect to this, that is to say vertically, are also a very frequent embodiment, although any other spatial orientation is likewise possible, for example a vertical parting plane and horizontal bridges.
Furthermore, it goes without saying that individual features of some embodiments can be combined with features of other embodiments, without departing from the scope of the invention. In particular, the additional features explained with reference to
In particular, the various positive connections 17 and the screw connections 9 can be combined. For example, one bridge portion 7, 8 may be provided with a first positive connection 17, while the other bridge portion 8 or 7 is fastened to the respective housing shell 2, 3 by means of a second positive connection 17 or solely by means of screw connections 9.
List of Reference Symbols
While the invention has been described in detail with reference to exemplary embodiments thereof, it will be apparent to one skilled in the art that various changes can be made, and equivalents employed, without departing from the scope of the invention. The foregoing description of the preferred embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed, and modifications and variations are possible in light of the above teachings or may be acquired from practice of the invention. The embodiments were chosen and described in order to explain the principles of the invention and its practical application to enable one skilled in the art to utilize the invention in various embodiments as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto, and their equivalents. The entirety of each of the aforementioned documents is incorporated by reference herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2005 015 150.7 | May 2005 | DE | national |
