Support Arrangements for Turbomachines

This invention relates to support arrangements for turbomachines. In this specification the term "turbomachine" is intended to cover turbines, rotodynamic pumps, and rotodynamic compressors.

It is desirable for the axis of the casing of a turbomachine to remain fixed in vertical position despite changes in the temperature of the turbomachine. In many constructions, for example, variations in the position of the axis may cause the relatively small labyrinth clearances in the dummy or thrust-balancing pistons or glands to be upset, where the bearings of the turbomachine are supported separately from the casing, while if the bearing housings are integral with the casing, difficulties may occur in the input or output shaft coupling.

According to the present invention, a turbomachine includes a support arrangement including vertically-extending rods to each of which a part of the weight of the turbomachine is transferred at a point near the horizontal median plane of the turbomachine, the coefficient of thermal expansion of the material of the rods being less than that of the material of the turbomachine casing, and the support arrangement also being arranged to define the longitudinal position of the adjacent part of the turbomachine.

By appropriately selecting the materials and dimensions of the rods and the casing, it can be arranged that the axis of the casing remains in substantially the same place despite changes in temperature.

The support arrangement may be such that the weight of the turbomachine is transferred to the rods at points above the horizontal median plane of the turbomachine. Preferably the coefficient of thermal expansion of the rods is not more than one-third of that of the casing of the turbomachine.

Where the casing of the turbomachine is split along the horizontal median plane, the lower half of the casing may be provided with lugs having apertures through which the rods extend, and the weight of the turbomachine may be transferred to the rods by covers secured to the upper surfaces of the lugs and resting on the upper ends of the rods. Conveniently the covers are vertically adjustable relative to the lugs.

Preferably the turbomachine includes at least one guide member extending downwards from one of the lugs, the coefficient of thermal expansion of the guide member being substantially the same as that of the turbomachine casing. The or each guide member may be a sleeve surrounding the associated rod. Preferably also there is associated with each rod a sliding member which supports the rod on a base member, the sliding member being constrained to slide only in the horizontal direction transverse of the turbomachine. The turbomachine may be so arranged that horizontal movements are transmitted by the or each guide member to the associated sliding member. This arrangement ensures that the the loads on the rods are purely vertical, so that the rods cannot be tilted.

The position of the turbomachine casing in the transverse horizontal direction may be defined by a connection in the vertical median plane of the turbomachine.

The invention may be carried into practice in various ways, but one embodiment will now be described by way of example, with reference to the accompanying drawings, in which:-

FIG. 1 is a diagrammatic plan view of the delivery end of a turbomachine with the upper half of the casing removed, showing part of the support arrangements for the casing;

FIG. 2 is a section on the line II--II of FIG. 1 to an enlarged scale, and also shows part of the upper half of the casing; and

FIG. 3 is a section on the line III--III of FIG. 2.

FIG. 1 shows the delivery end of the bottom half 1 of a turbomachine casing, including a volute 2. The joint face of the bottom half 1 is horizontal and contains the axis of the rotor of the machine when this is in place. The bottom half 1 of the casing is supported at the delivery end by two lugs 5 which form part of the casing and are supported on a bed plate 6 through two bearing blocks 7. The bearing blocks 7 are so arranged that the bottom half of the casing can slide on the blocks 7 in the horizontal direction normal to the axis of the turbomachine i.e. sideways. The position of the turbomachine in the horizontal direction relative to the bed plate 6 is fixed by a T-shaped member 4 which is secured to the bed plate 6, and which engages in a forked projection 8 provided on the bottom half 1 of the casing below the axis of the turbomachine. The arrangement is such that only forces directed horizontally and normal to the axis of the turbomachine can be transferred from the projection 8 to the member 4; all other forces are transferred through the lugs 5.

The other end of the turbomachine is supported in a broadly similar manner, but since its longitudinal position is fixed by the bearing blocks 7, the lugs at the other end of the machine are supported by horizontally resilient supports of conventional design.

The arrangement of the connections between the lugs 5 and the bearing blocks 7 will now be described in greater detail.

The weight of the turbomachine is transferred from each lug 5 to the associated bearing block 7 by a rod 10, which is made of a material having a very low coefficient of thermal expansion for example, of a coefficient not more than one-third of that of the turbomachine casing. The rod 10 bears on the block 7 by way of various intermediate elements 11 - 13 which will be described in detail hereinafter and which are mounted in a recess 14 in the block 7.

The plane 16 of the top end of the rod 10 is some distance above and parallel to the plane of the joint face 9 of a lug 5 and bottom casing half 1. To this end, a cover 17 made of a material having the same coefficient of thermal expansion as the material used for the turbomachine casing is secured by screws 18 to the lug 5 and is formed on the underside with a recess 19 which receives the rod 10. The separation between the plane 16 and the plane of the joint face 9 can be varied to some extent by means of shims 20 which are disposed between the cover 17 and the lug 5. The shims 20 thus position the plane 9 at a particular level, for example relative to a rotor supported on separate bearing blocks. During operation, the increase in the distance between the planes 9 and 16 due to thermal expansion can be made to cancel out the corresponding increase in the length of the rod 10, so that there is substantially no displacement of the plane 9. That is, when heated, the rod 10 expands upwardly, as viewed in FIG. 2, from the sliding member 11. Thus, the cover 17 and plane 16 become displaced upwardly. The upward displacement of the cover 17 would also move the plane 9 upwardly, however, because of the thermal expansion of the cover 17 the plane 9 moves downwardly relative to the plane 16. In this way, the downward displacement of the plane 9 caused by the cover 17 cancels the upward displacement of the plane 9 caused by the rod 10.

A sleeve 21 made of a material having the same heat expansion coefficient as the material used for the turbomachine casing is fitted in the lug 5, and surrounds the rod 10. The sleeve 21, which extends downwardly into a bore in a sliding member 11, has various tasks. The sleeve 21 serves to prevent horizontal backlash from occurring between the lug 5 and the rod 10 when thermal expansion or contraction occurs. Also, the sleeve 21 receives the thrusts axial of the turbomachine and transmits them to the bearing block 7; the sleeve 21 also transmits transverse movements of the lug 5, so that the transverse movement of the bearing system takes place in a plane perpendicular to the machine axis. Consequently, all force components which act other than vertically are kept away from the weight-bearing rod 10, which always remains in a vertical position so that the plane 16 of the top surface always remains horizontal.

The rod 10 is supported on the sliding member 11 and the transverse forces applied to the sleeve 21 are transmitted to the sliding member 11 mounted in the recess 14 in the block 7. The member 11 rests on a slipper 13 secured in the recess 14 by screws 23; a low-friction insert 12 facilitates the transverse movements described. As FIG. 3 shows, the recess 14 and the insert 12 are so devised that the member 11 is free to move transversely. However, the member 11 is located axially of the turbomachine by spacer elements 24 which are secured to the side edges as shown. The axial position of the member 11 can be adjusted by means of shims 25.