EP0566478B2 - High pressure steam turbine casing - Google Patents

Description

The present invention relates to improvements high pressure turbine modules comprising an intake for very high characteristics steam, a steam exhaust, a rotor supporting movable wheels consisting of movable fins and stator parts comprising an external body and an internal body supporting fixed stages arranged between the movable wheels, the internal body being provided with the inlet side of a seal holder ensuring sealing inlet steam (see for example FR-A-1 320 174).

High pressure stator parts of turbines in addition to the two envelopes constituted by the internal body and the external body a third intake envelope when pressures and the temperatures are very high.

Thanks to this multiplicity of envelopes we can reduce the pressure and temperature difference between them.

In addition, the internal and external bodies are in two parts and have flanges in the plane of horizontal joint to allow bolting.

• à une augmentation des dimensions transversales des enveloppes du stator
• à une non isotropie de ces mêmes enveloppes.

The multiplication of envelopes, the presence of a flange at the horizontal joint for bolting the bodies leads to:

• an increase in the transverse dimensions of the stator casings
• to a non isotropy of these same envelopes.

This causes increased effort and affects the mechanical and thermal behavior of the envelopes and hardware.

This problem is critical in the admission area where the pressure and the temperature are very high.

Furthermore in the case of steam turbines with action the rotor is provided with discs supporting the fins which results in an increase large transverse dimensions of the finned rotor and therefore stator parts.

The turbine module according to the invention of simplified design and whose dimensions have been reduced while ensuring good mechanical behavior and thermal includes an inlet for very high steam features, steam exhaust, rotor supporting wheels movable consisting of movable fins, and stator parts comprising a external body and an internal body supporting fixed parts (diaphragms and fixed guide vanes) constituting with the movable wheels of the stages, the body internal being provided on the intake side with a seal carrier surrounding the rotor and independent of the internal body, i.e. free expansion with respect to said body and is characterized in that the internal body comprises two bodies, the anterior body is disposed on the inlet side in an anterior area and produced as a single piece and the rear body of which is arranged on the side of the exhaust in a posterior zone of the high pressure module and produced in two parts comprising an upper half-body and a lower half-body united in a diametral joint plane, that the anterior zone comprises a plurality of stages, each stage of which has a diaphragm in the form of monobloc crown or a pair of half-crowns, as the posterior body has a front face located on the border between the areas against which comes lean all of the crowns of the anterior area, as the front of the posterior body is extended by a circular rim which is housed in a groove in the periphery of the anterior body, thus coupling together said two bodies, that the one-piece front body surrounds part of the rotor, and that at least the part of the rotor surrounded by the front body is a rotor drum with grooves in which the feet of the fins are fixed

By separating the internal body into two anterior parts and later we can adapt each of the parts to the characteristics of steam.

The anterior part in which the temperature and the vapor pressure are very high has a inner casing and a seal holder to isotropic admission therefore without bolting.

This further has the effect of reducing the radial and transverse dimensions since it removes the thickness of the flange required for bolting.

On the other hand, the use of a drum rotor (therefore without discs) inside the anterior internal body reduces the radial dimension of the vein and correlatively that of the envelopes. Furthermore this reduction of the radial dimension of the vein is favorable with the efficiency in particular for the turbines with action.

Finally, the body no longer comprises on admission that two envelopes, an outer body and an inner body.

This further reduces the dimensions cross.

Note that the third envelope which can be sometimes necessary for operational reasons in partial injection is not in the case of supercritical turbines (250 bars, 565 ° C) or with characteristics even higher (350 bars, 580 ° C) which operate with full sliding pressure injection.

According to a preferred embodiment of the invention the grooves of the drum rotor located in the area of the anterior internal body are longitudinal and the wheels mobile are separated by spacers of the same shape that the feet of the fins slipped in the grooves longitudinal and facing the fixed floors which are made up of monoblock diaphragms.

Regarding the part of the rotor located in the area of the posterior internal body, this can be classic construction with discs for turbines with action to carry the movable fins which presents the advantage of having a limited number of floors.

This rotor part can also be a drum rotor with circumferential grooves which brings the indicated advantages of the drum rotor.

A drum rotor HP module is described in the French patent application No. FR-9104855 in the name of applicant.

The posterior internal body for reasons of simplification is in two parts which can either be bolted either fretted.

The invention will now be described in more detail. with reference to particular embodiments cited by way of example and represented in FIGS. 3 to 20.

Figure 1 shows a longitudinal half-section of a conventional action turbine HP module.

Figure 2 shows in radial half-section the module of figure 1.

Figure 3 shows in longitudinal half-section a first embodiment of the turbine module according to the invention.

Figure 4 shows a longitudinal section of a variant of FIG. 3.

Figure 5 shows a radial section of the figure 4.

FIG. 6 represents a second embodiment of the turbine module according to the invention.

Figure 7 shows a section of a moving wheel of the module in Figure 6.

Figure 8 shows a section through a diaphragm of the module in Figure 6.

Figure 9 shows the circumferential arrangement fins.

Figures 10, 12, 14 show the three stages of the assembly of the module of figure 3.

Figures 11, 13, 15 show the three stages of the assembly of the module of figure 6.

FIG. 16 represents a third embodiment of the turbine module according to the invention.

Figure 17 is a detailed view of the front in Figure 3.

Figure 18 is a detailed view of the front in Figure 6.

Figure 19 is a variant of the posterior part of the rotor of Figures 3 and 6.

Figure 20 shows the air conditioning of the modules Figures 3 and 6.

The conventional action turbine module HP (figure 1) comprises a rotor 1 provided with discs 2 supporting movable fins 3 constituting movable wheels 4 and stator parts 5. Stator parts 5 have an external body 6 in two bolted parts in the horizontal joint plane and an internal body 7 supported by the external body 6 which is also in two parts bolted in the joint plane. In the internal body 7 are mounted diaphragms 8 also in two parts including guide vanes fixed 9 of the vein 10. Each diaphragm 8 constitutes the fixed part of a stage 40 with the movable wheel 4 which follows him.

The diaphragms 8 produced in two parts for allow their mounting are the seat of constraints and different deformations depending on the azimuth considered. They must be axially oversized especially for the first floors so as to take into counts this cut at the horizontal joint.

The module has intake pipes 11 opening into an internal envelope 12 inside of the internal body used for the distribution of steam in the vein 10 which ends in the exhaust 13.

This envelope 12 can be produced in different ways. It can be made in two closed parts to the joint and assembled by bolting or it can be made up of several injection nozzle holders steam fixed to the internal body 7.

On the internal body 7 around the rotor 1 intake side is mounted at free expansion, a packing holder 14 made in two parts and bolted. It has fittings 15 ensuring the seal between the internal body 7 and rotor 1 on the intake side.

A first realization of the action turbine module is shown in Figure 3.

The rotor 1 of the module is a drum rotor, that is to say without discs. It has circumferential grooves 16 in which the feet 17 of the movable fins 3. Such a rotor is described in the application FR-A-9104855 in the name of the applicant.

The external body 6 of the stator parts 5 of the module is of classical construction and has two bolted parts.

The internal body 7 of the stator parts is separated in two bodies coupled a front body 18 on the side admission arranged in the anterior zone (zone A) and a rear body 19 on the side of the exhaust 13 in the posterior zone (zone P).

The front body 18 is in one piece, that is to say without radial cut so perfectly isotropic. he comprises two half-crowns 20 provided with grooves 21 in which guide vanes are inserted 9 individually, each set of guide vanes 9 with the movable wheel 4 which follows it constitutes a stage 40.

The front body 18 surrounds a packing holder 14 mounted at free expansion which comprises an external tube 22 'monobloc that is to say without radial cut therefore perfectly isotropic which comes to hoop two half-crowns 22 in which seals are mounted retractable 15 each making a half-circumference. There can of course be more than one trim 15 serial. These linings 15 seal with rotor shaft 1.

If you don't want to use retractable fittings 15, the packing holder 14 with free expansion does not has more than half crowns and is completely piece.

The posterior body 19 is made in two parts and coupled to the anterior body 18. It is isotropic and shrunk by frets 39. In this design the hooping is total and easy to carry out since the posterior internal body is fully cylindrical and does not have the steam admissions.

As the posterior body 19 is isotropic, the parts vein fixed 10 are guide vanes 9 mounted full hole to the unit at the cut of the horizontal joint in the grooves 23 of the internal body.

This rear body 19 has a front face 24 located on the border between zones A and P against which all the half-crowns 20 of zone A comes lean.

The front face 24 is extended by a circular rim 25, which is housed in a groove 26 formed in the periphery of the anterior body 18, thus coupling the two bodies 18, 19 together.

The half-crowns 20 (fig. 17) have for each stage 40 a sealing segment 41 to prevent or slow the steam flow in the annular space between the crown 20 and the anterior body. This possible leak is immediately recovered upstairs following by holes 42 so as to be sure to have the temperature of the top floor of zone A on the face before 24.

If zone A has too many floors 40 important (see figures 4 and 5), it is planned to introduce a intermediate support 27 produced by a crown 28 comprising several sectors which are pushed from the outside from the anterior body 18 towards the inside thereof the sectors then being astride a circumferential groove 29 formed inside the anterior body 18 and on a groove 30 formed on the outside of the half crowns 20.

According to a variant of the invention (see fig. 6) the area A comprises a drum rotor 1, the grooves 31 of which are longitudinal.

In this design we use as on turbines with action as fixed parts of stages 40 of 8 monobloc diaphragms without cut at the horizontal joint therefore perfectly isotropic and of dimensions reduced axial.

The fins 3 are mounted axially on the rotor 1 in the grooves 31; spacers 32 carrying the seals against the diaphragms ensure filling of the groove between the moving wheels 4. This allows mounting of 8 monobloc diaphragms to the continuation of each movable wheel 4 and spacer 32.

An end spacer 33 located under the seal holder intake 14 blocks the fin-spacer assembly in the axial direction through a crown 34 screwed onto the rotor.

In Figure 7 there is shown a section aa of movable wheel 4 of zone A.

The feet 17 of the fins 3 have at the base a development and are exactly complementary to longitudinal grooves 31.

The feet 17 of the fins 3 of the same moving wheel 4 are joined above the grooves 31 and the caps 35 of the same wheel 4 are mounted in contact with each other with the others.

Between two movable wheels 4 fins 3 we slid the spacers 32 which have the same shape as the feet 17 of the fins 3 in each groove (see FIG. 8).

The spacers 32 can be separated or joined in packs of three, four or five. These spacers 32 or packets of spacers are in contact with each other above the grooves 31.

The spacers 32 carry the seals 36 opposite hubs 37 of diaphragms 8.

Each diaphragm 8 in zone A (see fig. 18) includes for each stage 40 a sealing segment 41 to prevent or slow down the flow of steam into the annular space between the diaphragm 8 and the anterior body 18. This possible leak is immediately recovered on the next floor by grooves 43 so to be sure to have the temperature of the last stage of zone A on the front face 24 (see fig. 18).

An action turbine with drum rotor having longitudinal grooves is described in application FR-A-9200948 filed January 29, 1992 in the name of the applicant.

The posterior body 19 is constituted like that of figure 3 except that instead of being shrunk it is bolted therefore not isotropic.

The diaphragms 8 constituting the fixed parts of the vein 10 are made in two parts and mounted at free expansion. This arrangement makes it possible to better conserve the radial rotor / stator clearances when the latter is not isotropic.
We will now describe the assemblies of zones A and P for the modules in Figures 3 and 6.

1 - Assembly of fins and fixed parts of the stages ZONE A

Two cases arise depending on whether the grooves of the drum rotor are circumferential or axial.

A - Case of circumferential mounting of the fins (Figure 3)

The movable fins 3 have a foot 17 in the form of T overturned. The foot 17 of the fin 3 is introduced in the circumferential groove 16 in the shape of an inverted T then swivels. When all the fins 3 are in place shims 38 are introduced having the same section as foot 17 of fins 3 but much thinner (see figure 9). The last shims 38 are cut in two vertically to be able to be inserted and the last in three.

In the general case there remains a play between the hats. Then we mount the fixed vanes 9 in the half-crowns 20 then we mount these half-crowns 20 around the finned rotor 1 and while temporarily holding them by screws before mounting in the front body 18. (see figure 10).

B - Case of axial mounting of the fins (Figure 6)

Each movable wheel 4 is assembled in its entirety with its self-tightening on rotor 1 by sliding it axially, between the moving wheels 4 the spacers are mounted 32 in the longitudinal grooves 31 and the monoblock diaphragms 8 (see figures 7 and 8).

We end with the end spacer 33 and the crown 34 screwed onto rotor 1 (see figure 11).

ZONE P - see figures 3 and 6)

In zone P we have chosen a circumferential arrangement fins 3, the grooves 16 of the drum rotor 1 in this area are therefore circumferential.

Axial mounting of the fins in this area would have been possible but in fact more complex.

The assembly takes place as indicated above (see figure 9).

In zone P we can foresee as described two realizations for the fixed parts of the vein 10, according to that the posterior body 19 is bolted or shrunk and the mounting fixed floors will be different as shown below for mounting the stators.

One can provide for the last movable wheel 4 of the rotor 1 (therefore exhaust side) axial mounting in grooves 31 '(see fig. 19) which improves the problems vibration.

2 - Assembly of the stators ZONE A - (see figures 12, 13)

In zone A, the mounting of the internal body 18 and of the packing holder 14 are identical whatever the mounting principle of the fin (axial or circumferential).

These two pieces have been said to be isotropic and without radial cut.

The fins 4 and the diaphragms 8 or guide vanes 9 of zone A are mounted on rotor 1 as seen previously.

The seal holder 22 'which has an outer tube fretting two half-crowns 22 carrying the linings retractable 15 is threaded and centered on the body internal 18 by keys external to the internal body 18.

This set is then threaded onto the rotor on one side admission.

The diaphragms 8 (fig. 13) or the crown 20 bearing the guidelines 9 (fig.12) are then centered from the outside of the anterior body 18 by pawns and are thus mounted at free expansion.

This type of mounting is necessary for the construction but taking into account the anterior isotropic body 18 is not necessary from the point of view of the design.
Note that if the lining holder 14 does not have retractable linings 15 it is entirely in one piece (fig. 16).

ZONE P (Figures 3, 10, 12, 14) and (Figures 6, 11, 13, 15).

The lower front half-body 18 comprising its half-diaphragms 8 (fig. 6) or the guide 9 (fig. 3) is in place in the lower external half-body 6.

• rotor 1 en appui sur ses coussinets
• corps antérieur 18 en appui dans le corps externe 6 côté admission et attelé au demi-corps postérieur 9.

The rotor assembly 1 front body 18 of zone A is mounted in the lower external body 6, taking the following precautions:

• rotor 1 resting on its bearings
• front body 18 resting in the external body 6 on the intake side and coupled to the rear half-body 9.

We then come to style this set by the half-body posterior superior which includes its half-diaphragms 8 (fig. 6) or its guidelines 9 (fig. 3).

We bolt (fig. 15) or we hoop (fig. 14) the half-body posterior superior 2 according to the chosen design.

The upper external half-body is then mounted and bolted.

As a variant for action steam turbines we can for zone P take a rotor 1 with discs 2 quite classic.

This arrangement makes it possible to reduce the number of floors 4, 8 of zone P.

On the other hand, of course, the rotor of zone A is a drum rotor with axial or circumferential mounting; on the figure 16 the fins 3 are shown for mounting axial.

On the other hand the posterior body 19 of the zone P can be as for zone P of the modules already described either bolted to be shrunk.

We can provide (see fig. 20) for sweeping with cold vapor of interstatoric space 44. For this purpose samples are taken from one of the last floors 40 of zone P by slots 45.

One takes at the front of the lining holder 14 by slots 46 made in this seal holder leaks hot steam having passed the linings 25.

The slots 46 are continued by slots 47 passing through the one-piece anterior body 18 and by pipes 48 crossing the interstatoric space and supplying through slots 49 a floor in zone P, we avoid thus the escape of hot steam from the part front of the anterior body and moreover we work the hot steam escaping. You can pay by means 50, a cold vapor leak outside interstatoric space 44, which makes it possible to adjust the temperature of this space and possibly cool the rotor of another module (MP for example).

Claims (11)

1. A high pressure module for a turbine, the module including an admission (11) for steam having very high characteristics, an exhaust (13) for steam, a rotor (1) supporting moving wheels (4) constituted by moving blades (3), and stator portions (5) including an external body (6) and an internal body (7, 18, 19) supporting stationary portions (diaphragms 8 and stationary guide vanes 9) co-operating with the moving wheels (4) to constitute stages (40), the internal body (7, 18, 19) being provided at its admission end (11) with a baffle carrier (14) surrounding the rotor (1) and independent of the internal body (7, 18, 19), i.e. being free to expand relative to said body, the module being characterized in that the internal body (18, 19) comprises two bodies, namely: an anterior body (18) disposed at the admission end (11) in an anterior zone (A) and made as a single piece; and a posterior body (19) disposed at the exhaust end (13) in a posterior zone (P) of the high pressure module and made in two portions comprising an upper half-body and a lower half-body connected together in the diametral join plane, in that the anterior zone (A) comprises a plurality of stages, each stage (40) having a diaphragm (8) in the form of single-piece ring or a pair of half-rings (20), in that the posterior body (19) includes a front face (24) situated at the boundary between the zones (A and P) and against which the set of rings (20) in the zone (A) bears, in that the front face (24) of the posterior body (19) is extended by a circular rim (25) which is received in a groove (26) formed in the periphery of the anterior body (18), thereby coupling said two bodies (18, 19) together, in that the single-piece anterior body (18) surrounds a portion of the rotor (1), and in that at least the portion of the rotor (1) surrounded by the anterior body (18) is a drum rotor provided with grooves (16, 31) in which the roots (17) of the blades (3) are fixed.
2. A high pressure module for a turbine according to claim 1, characterized in that the turbine is an impulse turbine, in that the grooves (31) of the drum rotor (1) situated in the zone of the anterior internal body (18) are longitudinal, and in that the moving wheels (4) are separated by spacers (32) having the same shape as the roots (17) of the blades (3) slid into the longitudinal grooves (31) and facing the stationary stages which are constituted by single-piece diaphragms (8).
3. A high pressure module for an impulse turbine according to claim 2, characterized in that each diaphragm (8) of a stage (40) is provided with a sealing segment (41) providing sealing between said diaphragm (8) and the anterior body (18), and in that said diaphragm (8) is provided with a groove (43) for delivering any steam that may leak into the following stage (40).
4. A high pressure module for a turbine according to claim 1, characterized in that the grooves (16) of the drum rotor surrounded by the anterior internal body (18) are circumferential, and in that the anterior internal body (18) surrounds two pairs of half-rings (20) in which independent guide vanes (9) constituting the stationary portions of the stages (40) are installed.
5. A high pressure module for a turbine according to claim 4, characterized in that the half-rings (20) for each stage (40) are provided with sealing segments (41) that provide sealing between said half-rings (20) and the anterior body (18), and in that said half-rings (20) are provided with holes (42) that send any steam that may leak into the following stage (40).
6. A high pressure module for a turbine according to any preceding claim, characterized in that the portion of the rotor (1) surrounded by the posterior internal body (19) is a drum rotor provided with circumferential grooves (18) in which the roots (17) of the moving blades (3) constituting the moving wheels (4) are received.
7. A high pressure module for a turbine according to claim 4, characterized in that the last moving wheel (4) of the rotor portion (1) surrounded by the posterior internal body (19) is installed in longitudinal grooves (31') formed in said rotor (1).
8. A high pressure module for a turbine according to any one of claims 1 to 5, characterized in that the turbine is an impulse turbine, and in that the portion of the rotor situated in the zone of the posterior internal body (19) is provided with disks (2) on which the moving blades (3) constituting the moving wheels (4) are mounted.
9. A high pressure module for a turbine according to any one of claims 6 to 8, characterized in that the posterior internal body (19) is made up of two portions bolted together in the join plane in which portions diaphragms (8) made in two portions and constituting the stationary stages are mounted so as to be free to expand.
10. A high pressure module for a turbine according to any one of claims 6 to 8, characterized in that the posterior internal body (19) is constituted by banded portions in which the fixed vanes (9) constituting the stationary stages are threaded.
11. A high pressure module for a turbine according to any preceding claim, characterized in that it includes means (46, 47) for taking leaks of hot steam that escape from the baffle carrier (14) and means (48, 49) for injecting said hot steam into the posterior body (19), and means (44) for taking relatively cold steam from inside the posterior body (19) to inject it into the inter-stator space (44) situated between the anterior body (18) and the posterior body (19) on the one hand and the external body (6) on the other hand, said cold steam being suitable for cooling the rotor of another module.

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