US3738770A

US3738770A - Turbines

Info

Publication number: US3738770A
Application number: US00152557A
Authority: US
Inventors: J Bolter
Original assignee: Reyrolle Parsons Ltd
Current assignee: Rolls Royce Power Engineering PLC
Priority date: 1970-06-15
Filing date: 1971-06-14
Publication date: 1973-06-12
Anticipated expiration: 1990-06-12
Also published as: GB1338259A; CA944571A

Abstract

A vapor turbine arrangement comprising a turbine having a plurality of bladed rotor wheels and provided with means for extracting liquid entrained within the vapor passing through the main vapor flow path of the turbine, which means are positioned to extract the liquid at a stage of the vapor expansion within the turbine upstream of a final bladed rotor wheel at the low pressure end of the turbine and which extract a portion of the vapor together with the liquid, the arrangement further having means for the return of the vapor to the main vapor flow path of the turbine, subsequent to separation of the vapor and liquid, at a stage of the vapor expansion within the turbine where the pressure of the vapor is only slightly lower than the pressure at which it was extracted, the vapor being returned to up-stream of at least one bladed rotor wheel of the turbine.

Description

United States Patent [191 Bolter TURBINES [75] Inventor: John Reginald Bolter, Durham,

England [73] Assignee: Reyrolle Parsons Limited, Durham,

England [22] Filed: June 14, 1971 [21] Appl. No.: 152,557

[30] Foreign Application Priority Data June .15, 1970 Great Britain 28,905/70 [52] US. Cl 415/121 A, 415/101, 415/168 [51] Int. Cl. F0ld 25/32, F01d 3/02 [58] Field of Search 415/121 A, 168, DIG. 1,

[56] References Cited UNITED STATES PATENTS 2,181,752 11/1939 Warren 415/168 3,066,912 12/1962 Scheper, Jr. 415/121 A FOREIGN PATENTS OR APPLICATIONS 993,476 5/1965 Great Britain 415/168 June 12, 1973 1,115,125 12/1955 France ..415/168 Primary Examiner-Henry Raduazo Attorney-Holman & Stern 57 ABSTRACT A vapor turbine arrangement comprising a turbine having a plurality of bladed rotor wheels and provided with means for extracting liquid entrained within the vapor passing through the main vapor flow path of the turbine, which means are positioned to extract the liquid .at a stage of the vapor expansion within the turbine upstream of a final bladed rotor wheel at the low pressure end of the turbine and which extract a portion of the vapor together with the liquid, the arrangement further having means for thereturn of the vapor to the main vapor flow path of the turbine, subsequent to separation of the vapor and liquid, at a stage of the vapor expansion within the turbine where the pressure of the vapor is only slightly lower than the pressure at which it was extracted, the vapor being returned to up-stream of at least one bladed rotor wheel of the turbine.

6 Claims, 2 Drawing Figures PAIENIEBJUNI 2m 7 3,738,770

SHEEI 1 0f 2 lb I7 I8 I9 OZI Z2 23 I 28 INVENTOR JOHN REGINALD BOLTER PAIENI Emummn 5738370 SHEEI 2 0F 2 INVENTOR JOHN REGINALD BOLTER 1 TURBINES This invention relates to vapor turbines and is particularly concerned with such turbines designed to operate under conditions where both vapor and liquid are present in the turbine.

PRIOR TECHNIQUES It is common practice in the steam turbine art to provide means for removal of water from such turbines, both to reducethermodynamic losses and to reduce damage to the turbine due to the presence of water.

In axial-flow steam turbines the extraction means are generally provided at the wall of an annular chamber surrounding a rotor blade ring, and it is known, furthermore, that extraction of steam in addition to water in such an arrangement assists in'the removal of water, the degree to which it does so varyingconsiderably with the design of the extraction means. In known arrangements, therefore, water extraction means are arranged to coincide with bled steam extraction areas, or belts as they are often referred to, the extracted water and steam passing to a feed water heater or some other apparatus in which its thermodynamic potential can be utilized. In such arrangements the pressure of steam at the bled steam extraction belt is sufficiently low that the steam and water can be passed directly to, for example, a feed water heater. Bled steam extraction arrangements have consequently been applied only in intermediate and low pressure turbines and towards the final, lower pressure, blading stages-in high pressure turbines.

If steam were to be taken from the turbine'at some point of high pressure in the expansion relative to the turbine exhaust pressure, for passage to some apparatus at a lower pressure, such as a feed water heater, or for water extraction purposes, or for both purposes, it would have to be throttled resulting in-a loss of efficiency in the steam cycle which could outweigh the advantage gained by removal of water from the turbine. High pressure turbines using superheated steam at high pressures and temperatures donot present any problems as regards water extraction since the steam is in a dry condition throughout its expansion within the turbine. In certain types of power plant'however, for instance a water cooled nuclear reactorplant, turbines may be required to operate with saturated steam at relatively low pressure compared with that of superheated steam for high pressure turbines operating with dry steam, but at a sufficient pressure, nevertheless, to

' cause bled steam extraction from the higher pressure blading stages to lower pressure apparatus to be aninefficient process.

SUMMARY OF THE INVENTION The invention consists in a vapor turbine arrangement comprising a turbine having a plurality of bladed rotor wheels and provided with means for extracting liquid entrained within the vapor passing through the main vapor flow path of the turbine, which means are positioned to extract the liquid at a stage of the vapor expansion within the turbine upstream of a final bladed rotor wheel at the low pressure end of the turbine and which extract a portion of the vapor together with the liquid, the arrangement further providing for the return of the vapor to the main vapor flow path of the turbine, subsequent to separation of the-vapor and liquid, at a stage of the vapor expansion within the turbine where the pressure of the vapor is only slightly lower than the pressure at which it was extracted, the vapor being returned up-stream of at least one bladed rotor wheel of the turbine.

Turbine arrangements in accordance with the invention may make use of any vapor/liquid separation equipment in which loss of pressure in the vapor in passing through the equipment is small, for example centrifugal separators of the type described in our (copending British Patent application No. 40050/68 now Patent No. 1,283,355). The invention is particularly useful in steam turbines where the efficiency of the water extraction system employed is improved by the extraction of steam also, as is the case with the afore mentioned co-pending application in which a slotted circumferentially extending drainage area is employed; and as is also the case with water extraction systems in corporated within a turbine casing of the type disclosed in (our co-pending British Patent application N o. 39987/68 now Patent No. 1,283,044).

While the invention may be applied in single flow turslightly lower are simply achieved.

Accordingly, the invention further consists in a vapor turbine arrangement in accordancewith the first of the preceding three paragraphs, in which the turbine is of the multi-flow type having at least two main flow paths for motive fluid through the turbine, liquid and vapor being extracted from a first main vapor flow path of the turbine and the vapor being returned to a second main vapor flow path of the turbine, subsequent to separation of the vapor and liquid, at a stage of the vapor expansion within the second main vapor flow path where the pressure of the vapor is only slightly lower than the pressure at which it was extracted from the first main vapor flow path.

The invention further consists in a vapor turbine arrangement in accordance with the preceding paragraph in which one or more extractions of liquid and vapor and return of vapor per main vapor flow path are made.

The invention also consists in a vapor turbine arrangement in accordance with either of the preceding two paragraphs in which vapor/liquid separation is effected within the turbine casing.

The invention also consists in a vapor turbine arrangement in accordance with any of the preceding three paragraphs in which the blade paths of the first rangement in accordance with the preceding paragraph I in which blades of at least a portion of the blade path in the first main vaporflow path are made to differ in length from the blades in a corresponding section of the f blade path in the second main vapor flow path.

The invention also consists in a vapor turbine ar-' rangement in accordance with the first of the preceding two paragraphs in which the blade openings of at least" a portion of the blade path in the first main vapor flow path are made to differ in width from the blade open- BRIEF DESCRIPTION THE DRAWINGS FIG. 1 shows a cross-section through a double-flow steam turbine in accordance with the preferred form of the invention; and

FIG. 2 shows a simplified side-elevation of the turbine shown in FIG. 1.

DETAILED DESCRIPTION OF THE DRAWINGS Referring first to FIG. 1, the turbine shown comprises a rotor l and a stator made up of an outer casing 2 and inner sections 3a-3e.

The rotor is provided with ten blade wheels to each side of the center line X-X of the turbine, blade wheels 4-13 lying in a first main flow path for steam entering centrally at annular chamber 14 and exhausting at left-hand chamber 15, while blade wheels 16-25 lie in the second main flow path for steam which also enters at chamber 14 but exhausts at right-hand chamber 26. Each rotor blade wheel is immediately preceded in the steam flow path by a stator blade wheel, as shown, the stator blade wheels being carried by sections 3a-3e.

The turbine shown is intended for use with steam which is substantially wet after the fourth rotor blade wheel in each flow is reached, that is to say at the points indicated by

reference numerals

27 and 28 in FIG. 1, and may, for example, be a high pressure turbine powered by steam from a water cooled nuclear reactor.

In accordance with the present invention, water and steam are extracted from the region of point 27 following the fourth rotor blade stage in the left-hand flow, preferably by way of louvred extraction belts in accordance with out afore-mentioned British Patent No. 1,283,044 the mixture entering an annular chamber 29.

The mixture is next led by way of an external pipe 30, as shown in FIG. 2, to a steam/water separator 31, which may be of the centrifugal type as disclosed in our afore-mentioned British Patent No. 1,283,355, after which the dried steam passes by way of pipe 32 to an annular chamber 33 in the right-hand stator casing. The steam is then led into the righthand flow in the region of point 28 so that it may do useful work in the fifth and successive blade wheels of the right-hand side of the turbine.

The blade paths of blade wheels 4-7 in the left-hand flow and blade wheels 16-19 in the right-hand flow are designed so that the pressure at point 28 is slightly less, of the order of less, say, than the pressure at point 27, and this small difference in pressure is sufficient to cause the steam to flow through

pipes

30 and 32 and separator 31. The pressure difference may be achieved by making the blades of corresponding blade wheels in the two flows of different lengths, or by variations in the openings of the blades of the corresponding wheels.

Further drying of the steam may be achieved by repeating the process described at a later stage of the steam expansion. As shown in the figures, steam and water may be removed from the right-hand flow at annular chamber 34, dried in a separator 35, and returned to the left-hand flow by way of annular chamber 36.

In the form of the invention shown, a baffle 37 serves to separate steam at different pressures in the chambers 29 and 33. In alternative forms of the invention not shown, the steam/water separator apparatus may be included within the stator outer casing 2 in which case the baffle 37 may be omitted. The combined annular chamber so formed may be fitted with baffles to promote separation of the water and steam and the water then allowed to drain from the chamber. Whichever system of steam/water separation is used, the water extracted would normally be fed to a feed heater or other apparatus by way of control orifices and a flashbox.

While the form of the invention shown incorporates two extractions and returns per flow, there may be any number of such drying arrangements incorporated in a single turbine, the number being limited in practice by the space available for conduction of the flows and economic considerations.

While turbine arrangements according to the invention are particularly useful for axial-flow steam turbines operating with steam which is wet or becomes wet within a high pressure cylinder, the invention is not restricted to such operation but may be used in vapor turbines driven by fluids other than steam and where the effective vapor flow is other than axial.

I claim:

1. A vapor turbine arrangement comprising a turbine having a plurality of bladed rotor wheels and provided with means for extracting liquid entrained within the vapor passing through the main vapor flow path of the turbine, which means are positioned to extract the liquid at a stage of the vapor expansion within the turbine upstream of a final bladed rotor wheel at the low pressure end of the turbine and which extract a portion of the vapor together with the liquid, the arrangement further having means for the return of the vapor to the main vapor flow path of the turbine, subsequent to separation of the vapor and liquid, at a stage of the vapor expansion within the turbine where the pressure of the vapor is only slightly lower than the pressure at which it was extracted, the vapor being returned up-stream of at least one bladed rotor wheel of the turbine, the turbine being of the multi-flow type having at least two main flow paths for motive fluid through the turbine, liquid and vapor being extracted from a first main vapor flow path of the turbine and the vapor being returned to a second main vapor flow path of the turbine, subsequent to separation of the vapor and liquid, at a stage of the vapor expansion within the second main vapor flow path where the pressure of the vapor is only slightly lower than the pressure at which it was extracted from the first main vapor flow path.

2. The vapor turbine arrangements as claimed in claim 1, in which more than one extraction of liquid and vapor and more than one return of vapor per main vapor flow path are made.

3. The vapor turbine arrangement as claimed in claim 1, in which vapor/liquid separation is effected within the turbine casing.

4. The vapor turbine arrangement as claimed in claim 1, in which the blade paths of the first and second main flow paths are designed to introduce the required difference in pressure of the vapor in the turbine between an extraction point in the first main flow path and a corresponding return point in the second main flow path.

5. The vapor turbine arrangement as claimed in claim 4, in which blades of at least a portion of the blade path in the first main vapor flow path are made to differ in 3 ,73 8 ,770 5 6 length from the blades in a corresponding section of the made to differ in width from the blade openings in corblade path in the main vapor w responding sections of the blade path in the second 6. The vapor turbine arrangement as claimed 1n claim 4, in which the blade openings of at least a portion of main vapor flow path the blade path in the first main vapor flow path are 5

Claims

5. The vapor turbine arrangement as claimed in claim 4, in which blades of at least a portion of the blade path in the first main vapor flow path are made to differ in length from the blades in a corresponding section of the blade path in the second main vapor flow path.

6. The vapor turbine arrangement as claimed in claim 4, in which the blade openings of at least a portion of the blade path in the first main vapor flow path are made to differ in width from the blade openings in corresponding sections of the blade path in the second main vapor flow path.