JPH0372801B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a double pressure turbine driven by a work fluid such as steam.

Such a double pressure turbine is described in Japanese Patent Laid-Open No. 127004/1985, which includes a high pressure section with at least one radial impulse turbine stage, a low pressure section with at least one axial turbine stage, and a low pressure section with at least one radial impulse turbine stage. a device for introducing a work fluid at one pressure into the high pressure section to drive the directional impulse stage; and a device for introducing a work fluid at a lower pressure into the low pressure section to drive the axial flow stage. Has equipment.

Radial impulse turbines have been well developed in recent decades. The latest form of the turbine includes a rotor with a bucket oriented transversely to the direction of wheel rotation and opening at the periphery of the wheel. An elastic working fluid is supplied to the bucket, for example through a nozzle ring surrounding the rotor.

According to the invention, a radial impulse stage is arranged on the rotor having a bucket belt spaced around the periphery of the rotor and opening into the periphery, and injecting a higher pressure into the bucket belt for turning the rotor. a nozzle ring including an annular array of nozzles for introducing work fluid, the nozzle ring also including vanes separating adjacent nozzles and partially defining the profile of the nozzles; It has an axially directed surface that curves continuously from the edge at the nozzle outlet to a portion located radially outward of the edge of the adjacent vane.

The edges at the nozzle outlet of each vane have a wedge angle of less than 3°. The wedge angle in the conventional design is
11° or more is typical. However, the inventors have found that efficiency can be significantly increased by reducing the angle to a maximum of 3 degrees.
It also reduces wake and relative flow disturbance. Reducing the wedge angle also reduces the stress exerted on the rotor by the work fluid distributed from the turbine nozzle to the rotor.

Two embodiments constructed in accordance with the invention will now be described in conjunction with the accompanying drawings.

Turbine 6 shown in FIGS. 1 to 4
comprises an elongated outer casing 7 consisting of a plurality of casing elements having a generally circular cross section and assembled together by bolts.

The interior of the casing 7 is divided into a high pressure section 8 and a low pressure section 9 (see FIGS. 2 and 3).

The high pressure section 8 has two impulse turbine stages 10
and 11. The low pressure section 9 has six conventional axial turbine stages 12, 13, 14, 15, 1
6,17.

The high pressure turbine stage and the low pressure turbine stage each include a rotor. These rotors are designated with the same reference numerals as the stages concerned, with the letter R appended.

The eight rotors 10R . The elements of the assembly thus produced are held together by a single tension bolt 19, and the assembly is rotatably supported within the casing 7 by suitable bearings. The upstream (or front) end of the assembly is provided with splines (not shown) that receive the drive couplings to provide power take-off upstream of the high pressure section.

As shown in FIG. 2, the first and second stage rotors 10R and 11R in the high pressure section 8 of the turbine 6 are cast from steam grade 17-4PH stainless steel or equivalent material.

The first stage rotor 10R is surrounded by an annular nozzle ring 20. The nozzle 21 of this ring has a converging shape as shown in FIG. These nozzles have vanes 2 made of metal left over in the milling of the ring 20 forming the nozzles.
1A. The vanes have sharp edges 21C and curved surfaces 21B exhibiting a wedge angle of less than 3 degrees. This curved surface faces radially inward toward the rotor axis and extends from edge 21C to a location where it overlaps the edge 21C of the next blade. The curvature of surface 21B is similar to the curvature of the outer circumference of the rotor (ie, plus or minus 10%). Each nozzle has an inlet port 2 that opens on the outer periphery of the nozzle ring.
2, and a delivery port 23 opening on the inner periphery thereof,
The cross section in the direction perpendicular to the fluid flow at the discharge end is square. The outlet of the nozzle 21 is the first one, as shown in FIG.
It is radially aligned with the inlet 24 to the bucket 25 at the peripheral flange 26 of the stage rotor 10R.

The buckets are equiangularly spaced and are typically formed by milling with a cutter inclined at an angle of 18° to the radial direction.

A cross-section of bucket 25 perpendicular to the fluid flow has substantially right-angled corners 27 (see FIG. 4);
The buckets then have an inlet 24 close to the upstream side of the rotor, an outlet 28 close to the downstream side of the rotor, and a semicircular impulse surface 29 between the inlet and the outlet.

Maximum efficiency can be obtained by milling the buckets with transition surfaces on the inlet and outlet sides of the buckets. Such a transition surface reduces losses due to fluid impingement on the rotor when the work fluid changes flow direction in the bucket.

The profile of the trailing edge surface 30 of each bucket is
High efficiency can be obtained by fabricating a smooth curved surface ending in sharp edges as shown in the figure. The appropriate curved surface can be easily manufactured by casting. Alternatively, such a surface is
It could also be fabricated by milling to form a sharp wedge-shaped plane forming an angle of about 3 degrees with the adjacent surface of the next bracket. This removes excess metal from the rotor and also matches well with the relative jet velocity of the work fluid discharged from the nozzle ring. This, together with the sharp leading edge created by planar milling, contributes to less irregular flow and better efficiency.

Before the bucket 25 is milled, one groove is milled into the rotor. The groove extends continuously around the rotor, opens at the periphery of the rotor, and creates a slot at the leading edge of the bucket.
Although this groove is primarily provided to not interfere with the shank of the cutter used to form the bucket, it also eliminates excess metal from the rotor and reduces stress between the rotor and bucket.

The outlet 23 of the nozzle 21 forms an almost continuous circle around the rotor 10R. This, together with the sharp edges between adjacent buckets, creates a substantially perfect circular jet of work fluid into the bucket and ensures smooth filling of the bucket. This contributes significantly to the efficiency of the turbine.

The nozzle ring 20 is an annular high pressure feed manifold 3
3 by an anti-rotation pin 31 to a radial flange 32 at the downstream end of the rotor. Manifold 33
is bolted between casing elements 34 and 35 on the upstream side of the high pressure section first stage rotor 10R.

The nozzle ring 20 is gripped against a flange 32 and the downstream wall of the nozzle 21 is formed by a plate-like inner covering 36 of the casing element 35 . Casing element 35 is bolted between manifold 33 and outer casing element 37.

Work fluid is supplied to the first stage 10 of the turbine 6 from an inlet 38 that communicates with the interior of the high pressure inlet manifold 33 . The working fluid flows axially from the manifold 33 through an annular inlet 39 between the outer periphery of the nozzle ring 20 and the inner wall of the manifold 33 . The fluid then flows radially inwardly into the nozzles 21 of the nozzle ring 20, as shown by arrows 40 in FIG.

The work fluid is discharged from the nozzle 21 to the rotor 1
It enters the 0R bucket 25 and drives the rotor while flowing inside the bucket. The fluid then flows radially outward as indicated by arrows 41. The incoming and outgoing flow vectors of the work fluid are parallel.

Efficiency is also enhanced by completely covering the area between the inlet 24 and outlet 28 of the bucket 25 with a shroud 36 that completely surrounds the rotor 10R. This complete shroud reduces power loss and turbulence. Efficiency is also enhanced by maintaining a free surface on the exit side of each bucket. Furthermore, since the work fluid flowing out from the bucket outlet does not collide with the cover 36,
That outflow moment is maintained. This is an important advantage especially in multi-stage turbines.

The work fluid exiting the buckets of rotor 10R and flowing outwardly is first axially and then radially inwardly (arrowed 42) can be bent. The guide plate 43 is mounted upstream of a radially inwardly extending annular flange 44 on the casing element 37 by fixing screws 45 .

Flow guide plate 43 and turbine rotor 10R...
17R assembly and joint seal 4
Blocked by 6 and 47. These seals are located on the inner periphery of the flow director plate and on the first and second high pressure sections.
It is supported by stage rotors 10R and 11R.

The work fluid discharged from the first stage 10 flows into a nozzle 48 formed in a nozzle ring 49 surrounding the second stage rotor 11R. Here again, the nozzle outlet is a bucket 51 similar to the bucket 25.
It is aligned with the entrance 50 of.

The nozzle ring 49 is connected to the recess 52 of the flow guide plate 43.
seated within and its flow guide plate and fasteners 45
It is fixed on the upstream side of the flange 44 by.
The upstream side of this flange becomes the rear or downstream wall of the nozzle.

Nozzle 48 is not shown in detail, but preferably has a convergent shape similar to that shown in FIG.

The second stage rotor 11R is completely covered as described above. In this case the cover is the casing element 37
is formed by a circular radial flange 44 .

After passing through the bucket 51 of the second stage turbine rotor 11R, the work fluid passes through the bucket outlet 53
and enters an annular plenum 54 provided between high and low pressure turbine sections 8 and 9. Here, the work fluid discharged from the high pressure section 8 of the turbine is transferred to the inlet 55
and work fluid that is introduced into the turbine through an annular low pressure inlet manifold 56 surrounding the plenum 54.

Communication between manifold 56 and plenum 54 is provided by an inwardly directed circular opening 57. axially extending circular bosses 58 and 59 that are integral parts of casing element 37 and manifold 5;
6 and the inlet port 55 form a nozzle.

The mixed working fluid is indicated by arrow 6 in Figures 2 and 3.
0, flowing axially to the turbine 6
Enter low pressure section 9 of This section 9 of the turbine 6 is of normal axial construction, with the third
Best shown in fig.

Each turbine stage of the low pressure section has disk 6
1 includes one rotor as described above, which has an annular array of blades 62 attached thereto. A conventional annular array of fixed nozzles 63 is provided upstream of each rotor. The nozzles of each stage are attached to an annular nozzle support 64 fixed to the casing element 37.

Leakage through the nozzles of each stage is prevented by a circular diaphragm 65, a seal 66 on the inner periphery of this diaphragm, and a cooperating seal 67 supported on adjacent rotor discs.

A first supply of mixed work fluid from the annular discharge plenum 54
This first
An axially extending circular flange 68 is fixed to the diaphragm 65 of the axial stage.

As also shown in FIG. 3, each low pressure axial stage preferably includes an annular abradable sliding ring 6 which forms part of the nozzle support for that stage and surrounds its rotor.
Equipped with 9. This sliding ring minimizes the blade tip clearance for the work fluid used and reduces work fluid leakage through the blade tips.

Work fluid flow through the low pressure section is normal, with fluid being discharged from the sixth stage rotor 17R to an annular discharge manifold (not shown).
Work fluid is discharged from the manifold and turbine casing through a discharge duct 70 (see FIG. 1).

One turbine with characteristics as heretofore described, designed to produce an output of 1800 shaft horsepower (136,872 mKg/S) [600 shaft horsepower (45,624 mKg/S) in the high pressure impulse section], is shown in Figs. This is shown in Figure 3.

Typically, this turbine is rated at 14Kg/cm ²
(200 psia) and high pressure steam of 382℃ (720〓)
At a rate of Kg/S (3.23lbs/S) and 2.8Kg/cm ²
(40 psia) and 421℃ (790〓) low pressure steam at 0.35
Supplied at a rate of Kg/S (0.76lbs/S).

The design pressure of the steam discharged from the final stage of the low-pressure axial section of the turbine is 0.046 Kg/cm ²
(0.65 psia).

The rotors of the two impulse stages 10 and 11 in the high-pressure section 8 of the turbine 6 each have a diameter of 0.30.
0.35 m (11.75 and 13.875 in.), and the median chord length of the vanes 62 in the low pressure axial section of the turbine ranges from 0.015 m (0.6 in.) in the first stage 12 to the sixth
The range is up to 0.13 m (5.16 inches) at step 17. The diameter of all disks on which the blades are mounted is 0.34m.
(13.5 inches).

The invention is also applicable to once-through turbines having a combination of radial impulse stages and axial stages. This type of turbine also provides a more efficient arrangement for transferring work fluid from one radial impulse stage to the next, and can employ more than one radial impulse stage. This type of turbine is designated at 71 in FIG.

In many respects, turbine 71 is similar to the turbines previously described. Therefore, in order to avoid the complexity of the explanation,
The turbine 71 will be mainly described with respect to its different features from the turbines described above.

The turbine 71 has an elongated outer casing 72 in which three radial impulse stages 73, 7
4, 75, and seven axial flow stages 76... (only one of which is shown) are accommodated.

Each axial flow stage (which may be of the character previously described in turbine 6) and each impulse turbine stage is designated by the same reference numeral as the stage in question, followed by the letter R.

10 rotors 73R, 74R, 75R, 76R
... are joined together by carbic fittings 77 and held in this assembled condition by tension bolts 78. Suitable bearing (not shown)
rotatably supports the assembly within the casing 72.

Radial impulse stage rotors 73R, 74R, 75
R is similar to that in the turbine 6, and the rotors are surrounded by a shroud 79, 80, 81 in order to provide the above-mentioned advantages obtained by completely surrounding it with a shroud. It will be done.

The first stage rotor 73R is surrounded by an annular nozzle ring 82 having nozzles of the type shown in FIG.

Work fluid is supplied to the first stage 73 of the turbine 71 from an inlet 84 that connects with an inlet manifold 83 . Work fluid enters the nozzles of the nozzle ring from manifold 83 through annular inlet 85.

The work fluid flows into the bucket of the rotor 73R from these nozzles, and drives the rotor while flowing through the bucket.

The work fluid that is released from the bucket of the rotor 73R and flows outward is transferred to the turbine casing 7.
2 and the flow director plate 86, first axially and then radially inwardly. Flow director plate 86 is similar to the flow director plate used in turbine 6 shown in FIG. This means that the work fluid is the first stage rotor 73R.
This prevents the fluid flow from spreading as it exits the bucket and is directed toward the nozzle ring 87 of the second impulse stage 74. This is important in order to reduce energy loss during fluid movement.

The operation of the second and third radial impulse stages 74 and 75 and the movement of work fluid between them is essentially the same as in the previous embodiment.

The work fluid from the rotor of the third radial impulse stage 75 flows again against the surface of the shroud 81 and is deflected towards the first of the axial stages 76 .

Work fluid flow through the axial stages is normal, with work fluid being discharged from the final stage rotor to a discharge manifold (not shown). Work fluid is discharged from the manifold and turbine casing through a discharge duct similar to that shown in FIG.

It will be apparent to those skilled in the art that the number of radial impulse stages that can be used in a radial impulse turbine section is not limited to three, and that the greater the number, the higher the efficiency. but,
In most cases, three stages are accepted to be the practical limit, for the simple reason that more stages would result in too large a mass.

[Brief explanation of drawings]

1 is a partial side view of the first turbine; FIG. 2 is a partial axial section of the high pressure section of the first turbine; FIG. 3 is a similar sectional view of the low pressure section of the first turbine; FIG. FIG. 5 is a partial radial cross-sectional view of the rotor and nozzle ring of the radial impulse stage of the high-pressure section of the first turbine, and FIG. 5 is a partial cross-sectional side view of the axial section of the second turbine. 6...Turbine, 7...Casing, 8...High pressure section, 9...Low pressure section, 10,1
1... Impulse turbine stage, 10R, 11R... Same rotor, 12, 13, 14, 15, 16, 17...
Axial flow turbine stage, 12R...17R...same rotor,
19...Tension bolt, 20,49...Nozzle ring, 21,48...Nozzle, 23...Nozzle outlet, 24,50...Bucket inlet, 25,51...
...Bucket, 28,53...Bucket exit, 33
...High pressure feed manifold, 34, 35, 37...
Casing element, 36, 44... rotor surrounding cover, 38... high pressure inlet, 43... flow guide plate,
54...Plinum, 55...Low pressure inlet, 56...
...Low pressure inlet manifold, 61...Low pressure axial flow rotor disk, 62...Axial flow rotor blade, 63...Fixed nozzle, 64...Nozzle support, 65...Diaphragm, 69...Sliding ring, 71...Forcing Fluid type turbine, 72...Casing, 73, 74,
75...Radial impulse stage, 73R, 74R, 75
R...same rotor, 76...axial flow stage, 76R...same rotor, 78...tension bolt, 79, 80, 81
... rotor surrounding cover, 82, 87 ... nozzle ring, 83 ... feed manifold, 84 ... feed port, 86 ... guidance board.

Claims (1)

Claims: 1. A high-pressure section with at least one radial impulse turbine stage, a low-pressure section with at least one axial turbine stage, and into the high-pressure turbine section work fluid from an external source of pressure. and a device for introducing work fluid from the external source at a second low pressure into the low pressure turbine section without passing through the high pressure section; The radial impulse turbine stage is of the all-round feed type;
a rotor, a bucket surrounding and opening at the periphery of the rotor, a device for mounting the rotor so as to rotate about an axis coincident with the axis of the turbine stage, and a bucket for directing work fluid to the bucket. a device for introducing the work fluid into the bucket, the device having an annular array of convergent work fluid distribution nozzles for discharging the work fluid into the bucket; and a device for introducing the work fluid into the bucket. has vanes that alternately define the profile of the nozzle, the vanes extending from a first position corresponding to the exit from each nozzle to a second position corresponding to the trailing edge of an adjacent nozzle.
having a surface facing the axis of the turbine stage that is continuously curved up to a position, the wedge angle of these vanes being up to 3° at the edge of the vane corresponding to the outlet of said nozzle; a discharge plenum downstream of the rotor; a bucket formed in the rotor is configured to discharge the work fluid into the discharge plenum after the work fluid has passed through the single bucket. A double pressure turbine. 2. The double pressure turbine of claim 1, wherein the nozzle surface of the radial impulse turbine stage is curved and has a radius approximately equal to the radius of the circumferential edge of the radial impulse turbine.