MOUNTING OF AXIAL TURBO-MACHINERY

Abstract: The invention relates to a method and a device for mounting an axial turbo-machine, preferably a low-pressure compressor for a gas turbine, constructed without a parting line with a whole or constructed rotor. From the design point of view, problems arise regarding the mounting of the stationary guide vane rings in the case of a design without a parting line and a whole rotor. The problem is solved by dividing the guide vane rings into sectors in a number greater than two. These sectors are brought radially into position and are guided and fixed in the correct position by guide rings which are applied around each guide vane ring composed from sectors. Each composed guide vane ring with the surrounding guide ring is guided and fixed to the preceding guide ring and all the guide vane rings are successively built up around the whole or constructed rotor. The guide rings mounted together constitute a stiff annular element.

Description: Mounting of axial turbo-machinery. TECHNICAL FIELD The invention relates to axial turbo-machines, preferably low-pressure compressors for gas turbines and to a method and a device for mounting of a machine concept without a parting line and with a non-divisible rotor. BACKGROUND ART When designing axial turbo-machines comprising a bladed rotor in several stages and partitions comprising stationary guide vanes, an axial parting line is preferably chosen. The housing of the turbo-machine is thus given a top half and a bottom half, which are bolted together in the parting line by means of flanges. The partitions, which contain the stationary guide vanes, are divided into two halves, one half being placed in the bottom half of the housing where it is aligned and centered by means arranged between the wall half and the housing. The bladed rotor is placed in its bearing positions in the ends of the bottom half, the rotor discs then being situated between the mounted partitions of the bottom half. The other partition halves are mounted in the top half of the housing. The principle described above is the most frequently used. However, depending on the type of turbo-machine, it is a question of partitions in the form of plates with a rela- tively low (a small radial extent) guide vane channel to the extreme case involving guide vane lattices attached to the inside of the housing without any wall construction. Action type steam turbines have marked partitions whereas guide vane lattices for a gas turbine compressor can only comprise guide vanes attached to the inner walls of the compressor housing with or without any connecting element at the inner limit of the guide vanes nearest the rotor shaft. The parting line entails an accumulation of material and a departure from the rotational symmetry, which is a drawback upon start-up and load changes. Uneven temperature heating arises, which above all causes ovalities. To prevent this from giving rise to cutting between stationary parts and parts of the rotating rotor, enlarged clearances in the flow channel are required, which causes major leakage and inferior performance of the machine. The negative effect of parting lines is minimized either by minimizing the amount of material in the parting line by constructing in high- strength material with thin thicknesses (gas turbines for aircraft) or choosing to change the load of the turbine slowly (large steam turbines for high pressures and cast housings) . Parting lines are sensitive to leakage, which means that the necessary stiffness requires a certain amount of material in the flanges. Consequently, there is a reason for designing turbo-machinery completely rotationally symmetrically with- out parting lines. From the design point of view the problem then arises how to proceed to mount the stationary lattices between the rotor stages. One known turbine concept compri¬ ses high-pressure turbines which are of the so-called barrel type, that is, they have no parting lines. Such a turbine is composed of an inner housing, composed of axially mounted rings screwed together, which fix the partitions which in turn are divided into two halves and inserted radially into their positions and locked there by the above-mentioned rings. The ring package is guided by guiding elements in the surrounding cast turbine housing. When designing an axial turbo-machine, preferably a gas turbine, it is advantageous also to avoid parting lines to obtain a rotationally symmetrical design. Constructively, the mounting problem has been solved by using built rotors, which when mounting the machine are built up step-by-step successively with whole guide vane rings sandwiched in between (in the above steam turbine application referred to as partitions) . This method is technically applicable. However, it would entail technical and economic advantages if it were possible to use non-divisible rotors while at the same time utilizing a design without a parting line. For axial turbo-machines, preferably high-pressure com- pressors for gas turbines, this is possible since it is possible to mount the guide vane rings guide vane by guide vane in the housing, the boundary of the guide vane nearest the rotor shaft being free and without any structural member which interconnects the guide vane tips. The limitation that this design entails has to do with oscillations and is dealt with by the guide vanes being short as compared with their chord. With regard to an axial turbo-machine, preferably a low- pressure compressor for a gas turbine, the guide vanes are of such a length that the free attachment mentioned above creates problems from the point of view of oscillation. A constructive design could be guide vanes with large chords, which, however, entails a longer machine. In the case of non-constant speed machines, the oscillation problems in blade and guide vane lattices are difficult to overcome and require accurate calculations and advanced design solutions. Design solutions with good damping properties are desired. SUMMARY OF THE INVENTION An axial turbo-machine, preferably a low-pressure compressor for a gas turbine, is constructed without parting lines and the rotor 24 is mounted together with the static components in undivided state. The guide vane rings are divided into sectors 9 of a number greater than two. The sectors are inserted radially into their correct position. By means of axial guide pins 12 or other fixing elements, the sectors are fixed in the correct angular position in the plane perpendicularly to the direction of the rotor shaft. Between the sectors, space is provided for the thermal expansion of the sectors. Axially and radially the sectors are fixed by whole guide rings (e.g. 13, 14), which are mounted axially in relation to each other, fixed via axial bolts or other types of fixing elements and guided towards each other radially by means of guide surfaces (e.g. 15, 26) or some other guiding principle, for example by axial pins. The amount of material in the guide rings is adapted such that the heating rate and the thermal expansion thus obtained follow the corresponding heating and thermal expansion of the rotor upon start-up and load changes. Since the guide rings constitute a stiff structural member, the faster heating of the sectors following a load change, and the thermal expansion thus obtained, will not give rise to the sectors expanding radially outwards, but they will make use of the above-mentioned gaps between the sectors and will expand inwards towards the rotor shaft. The limiting surface towards the rotor shaft, commonly formed by the sectors, exhibits small deviations from the circular shape, which appears in a uniformly heated machine. The sectors, the outer and inner boundaries of which consist of interconnecting elements 6, 7, create oscillation-damping units and, in addition, at the attachment of the guide vanes to the interconnecting elements, damping material can be enclosed to further improve the damping ability of the sectors. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a sectional view of an axial low-pressure compressor for a gas turbine with an air inlet at 1, a flow channel at 2 and an outlet at 3. The centre line of the rotor shaft is designated 4. The rotor 24 is, according to the figure, constructed from individual units which are bolted together to form a rotor body. According to the invention, the rotor may be made in one piece. Figure 2 shows an enlarged part of the flow channel in Figure 1 (dash-dotted square) . The figure shows a design example with such an embodiment that the inventive concept can be applied. Figure 3 shows a sector of guide vanes with outer and inner interconnecting structural members. Figure 4 shows the sector according to Figure 3, seen axially in the direction of the arrow 25. The sector shown comprises five guide vanes. APPLICATION OF THE INVENTION After manufacture, guide vanes 5 and attachment elements 6, 7 at both their ends constitute a whole in the form of an annular structural member. This is referred to as a guide vane ring. This ring is divided by means of radial sections into a number of sectors 9, the number being greater than two. Figures 3 and 4 show such a sector in two views. In this example the sector comprises five guide vanes 5a-5e, held together by an outer structural member 6 and an inner structural member 7. The structural members 6, 7 enclose a damping material 8. Figure 2 shows a sector 9 of a guide vane ring in a position A, from which position A the sector 9 is inserted radially according to the arrow 10 into a position B. The insertion also comprises an axial displacement into a guide means 11 and in over a guide pin 12. The guide pin 12 fixes the sec¬ tor in the correct angular position in the plane perpendi¬ cular to the direction of the rotor shaft. The guide means 11 fixes the sector radially. The guide vane sector 9 is fixed radially by the guide means 11 in the guide ring 13. After all the sectors of the guide vane ring have been fixed in relation to the guide ring 13, the guide ring 14 is moved axially in the direction of the arrow C in over the mounted sectors, is guided against the guide surfaces 15, 16 and pressed against the guide ring 13. Thereby, the sectors 9 are now fixed radially in the two guide surfaces 29 and 16 of the structural member 6 in the guide surface 11 of the guide ring 13 and the guide surface 27 of the guide ring 14. The guide ring 14 is guided with its guide surface 26 against the guide surface 15 on the guide ring 13 and is thus radially guided against the preceding guide ring, here guide ring 13. With guide ring 14 axially in contact with guide ring 13, the sectors 9 are axially fixed. With guide ring 14 in mounted position, the mounting of the sectors included in the next guide vane ring is started, which is performed in the same way as described above. The guide rings included in the compressor are bolted together axially in groups of rings or individually, which fixes the guide rings axially. This is clear from Figure 1, in which the bolted joint 17 interconnects three guide rings whereas the bolted joint 18 only fixes the succeeding guide ring to the preceding one. Figure 2 shows a bolted joint 19 which interconnects guide rings 13, 20, 21 and further ring elements (not shown) . Numeral 22 designates a blade mounted on the rotor disc 23. Numeral 24 designates the centre line of the rotor.

Claims: CLAIMS 1. A method of mounting an axial turbo-machine, preferably a low-pressure compressor for a gas turbine constructed with a housing without a parting line and with a whole rotor or a rotor constructed in one piece, characterized in that the guide vane rings divided into radial sectors (9) are mounted by being radially brought into position, the number of sec¬ tors per guide vane ring being greater than two, the sectors being guided and fixed in the correct position by applying guide rings (14) around each guide vane ring composed from sectors. 2. A method according to claim 1, characterized in that the guide rings are fixed axially by means of axial bolts (19) or some other form of fixing element. 3. A method according to claim 1,. characterized in that the sectors, after having been radially brought into posi- tion, are displaced axially towards the previously mounted guide ring (13), the sectors (9) being fixed radially by means of a guide (11) in said previous guide ring (13) . 4. A method according to claim 3, characterized in that each sector (9) is angularly fixed in the plane perpendi¬ cular to the direction of the rotor shaft with the rotor shaft as fulcrum by means of an axial pin (12) or other guide element which is engaged by the sector when being axially fixed to the preceding guide ring (11) . 5. A method according to claim 4, characterized in that guide rings which are fitted over positioned sectors fix these axially. 6. A method according to claim 5, characterized in that guide rings which are fitted over positioned sectors have guide surfaces which are fitted into guide surfaces in the sectors and fix the sectors radially. 7. A method according to claim 6, characterized in that the guide rings are fixed axially by means of axial bolts or another form of fixing elements. 8. A method according to claim 7, characterized in that the guide rings are guided radially against each other. 9. A device in the form of an axial turbo-machine, preferably a low-pressure compressor for a gas turbine, constructed with a housing without a parting line and with a . whole rotor or a rotor constructed in one piece, characterized in that the guide vane rings are radially divided into more than two sectors (9), the sectors being guided and fixed in the correct position by support elements in the form of rings (13, 14) . 10. A device according to claim 9, characterized in that the guide rings are axially fixed by means of bolted joints (19) or some other form of fixing elements. 11. A device according to claim 10, characterized in that the sectors are guided and fixed in the guide ring (13.) of the preceding stage. 12. A device according to claim 11, characterized in that one axial guide pin (12) per sector or another guide element fixes the sectors in the preceding guide ring (13) into a definite angular position in the plane perpendicular to the direction of the rotor shaft with the rotor shaft as fulcrum. 13. A device according to claim 12, characterized in that the guide ring (14) fixes the positioned sectors axially in cooperation with the preceding guide ring (13) . 14. A device according to claim 13, characterized in that the guide ring has guide surfaces which are guided against corresponding guide surfaces on the sectors when the guide ring is axially mounted. 15. A device according to claim 14, characterized in that the guide rings are guided radially against each other via guide surfaces (15, 26) .

Inventors: MAANSSON MARTIN, MAANSSON, MARTIN
Applicants: ABB STAL AB, MAANSSON MARTIN
Application year: 1993
Main classification: F01D9
IPC codes: F01D9, F01D25, F02C7, F04D19, F04D29