US3752597A - Flow path deflector for axial flow reversing gas turbine - Google Patents

Abstract

A reversing gas turbine with two coaxial rows of oppositely curved rotor blade portions and having two rows of separately adjustable stator blades controlling flow of motive fluid alternately to the forward or reversing rotor blades. A flow path deflector at the outlet of the reversing blades seals the outlet therefrom when the rotor turns in the forward direction, and is pivotable to deflect reversing fluid flow into the exhaust path when the turbine reverses.

Description

United States Patent [191 Heinold' et a1.

[4 Aug. 14, 1973 [5 1 now PATH DEFLECTOR FOR AXIAL FLOW REVERSING GAS TURBINE [75] Inventors: George H. Heinold, Scotia; Thomas R. Huber, Mechanicville, both of N .Y.

[73] Assignee: General Electric Company,

Schenectady, N.Y.

[22] Filed: Dec. 16, 1971 [21] Appl. No.: 208,840

[52] US. Cl 415/152, (SO/39.42, 415/79, 415/154 [51] Int. Cl. F0ld 17/14, F02c 3/00 [58] Field of Search 60/3925, 39.42, 60/39.l7; 415/79, 152, 149, 23, 145, 153, 154

[56] Relerenees Cited UNITED STATES PATENTS 3,286,983 11/1966 Scheper, Jr ..415/79 10/1969 Moellmann 415/23 2/1972 Shipley et a]. 415/145 Primary Examiner-Henry F. Raduazo Attorney-William C. Crutcher et a].

g 57 ABSTRACT A reversing gas turbine with two coaxial rows of oppositely curved rotor blade portions and having two rows of separately adjustable stator blades controlling flow of motive fluid alternately to the forward or reversing rotor blades. A flow path deflector at the outlet of the reversing blades seals the outlet therefrom when the rotor turns in the forward direction, and is pivotable to deflect reversing fluid flow into the exhaust path when the turbine reverses.

4 Claims, 4 Drawing Figures Patented Aug. 14, 1973 I 3 Sheets-Sheet 2 Patanted Aug. 14, 1973 3,752,597

3 Sheets-Sheet 3 FLOW PATH DEFLECTOR FOR AXIAL FLOW REVERSING GAS TURBINE BACKGROUND OF THE INVENTION This invention was made under contract with the United States Government under Contract -35510 with the United States Maritime Administration of the Department of Commerce. The U.S. Government is licensed in accordance with the terms of the aforesaid contract and has reserved the rights set forth in Sections 1 (f) and l (g) of the Oct. 10, 1963 Presidential Statement of Government Patent Policy.

The invention relates to an axial flow, two-shaft gas turbine, wherein the load turbine shaft is reversible. More particularly the invention relates to a flow path deflector for controlling the motive fluid in a reversing gas turbine.

It is desirable in some instances to provide an elastic fluid turbine with additional means to reverse the direction of rotation of the output shaft, such as in marine propulsion units where astern operation is necessary. Although gas turbines have been used in a few marine propulsion systems, one of the major problems has been that of providing suitable and economical astern operation. There have been several suggestions for reversing the propeller shaft without reversing the gas turbine shaft. U.S. Pat. No. 2,912,824 issued to F.H. Van Nest et al. on Nov. 17, 1959, discloses a marine gas turbine powerplant, wherein astern power is provided by a reversible pitch propeller. Other means for obtaining reverse power have included suggestions for fluid or friction clutches with reverse gear or sugges tions for intermediate electric drives.

It has been suggested in marine propulsion systems for steam turbines that two concentric rows of blades on a a single wheel, one of the rows having reversed curvature, can beemployed to obtain forward or reverse rotation of the turbine'wheel. However, selective admission of motive fluid to the desired row is easily accomplished under steam turbine practice by means of opening external valves to admit steam through fixed nozzle partitions in a nozzle box." This type of control of the motive fluid is unsuitable for a gas turbine since the combustion products cannot simply be bottled up" in the manner that steam can. Accordingly, the adjustment of motive fluid power and flow through turbine buckets in conventional axial flow gas turbines is either accomplished by controlling addition of fuel (in a single shaft gas turbine), or by adjusting the ratio of pressure drops across two independent turbine stages (in a two-shaft gas turbine) as disclosed in the aforementioned Van Nest patent. A suitable variable area adjustable nozzle to accomplish divison of power between stages in a two-shaft gas turbine is disclosed in U.S. Pat. No. 2,919,890 issued to A.N. Smith et al. on Jan. 5, 1960.

One of the problems encountered when turbine buckets are provided with two concentric rings of blades with opposite curvatures is that of the large rotation losses which prevail in the set of blades which are rotating backwards. These rotation losses can amount to a substantial portion of the total power produced by the blades rotating in the forward direction. Although operating considerations will often tolerate relatively large losses when the turbine is operated in reverse (since this takes place a relatively small percentage of the time), these rotation losses must be held to an absolute minimum when the turbine is operating in the forward or most efficient mode.

Prior constructions have suggested closing off entry of motive fluid at the inlet to the reversing bucket row.

One such arrangement is disclosed in U.S. Pat. No. 3,286,982, issued Nov. 22, 1966 to G.W. Scheper, Jr., and assigned to the present assignee. However, calculations show that losses in some cases might amount to 10 to 15 percent of the total power, due to leakage and rotation losses from the reversing portion of the turbine blades.

An improved construction for minimizing the aforesaid losses is disclosed in U.S. Pat. No. 3,286,983, issued Nov. 22, 1966 to G.W. Scheper, Jr., and assigned to the present assignee, which provided adjustable guide vanes at the outlet of the reversing blade row to effect a smooth enclosure for reducing losses due to backward rotation of the blade portions. U.S. Pat. No. 3,286,983 is incorporated herein by reference. The construction shown in the aforesaid patent requires two separate exhaust paths for the motive fluid when in the forward and reversing modes. This construction has several disadvantages such as assembly problems, structural stability and possible vibration of the exhaust diffuser middle wall and requires a larger exhaust hood.

The present invention involves the use of pivotable flow deflecting elements and although such elements have been suggested in the prior artsuch as U.S. Pat. No. 3,472,487 to Moellmann, they have been generally used to divert fluid into alternate outlets.

Accordingly, one object of the present invention is to provide an improved construction for a reversing gas turbine which requires only a single exhaust flow path.

Another object of the invention is to provide an improved and less expensive construction for reducing rotational pumping losses and leakage through the reversing blades when not in use.

Another object of the invention is to provide improved efficiency in the forward mode of a reversing gas turbine.

Still another object of the invention is to provide an improved construction over that shown in U.S. Pat. No. 3,286,983.

SUMMARY OF THE INVENTION Briefly stated, the invention comprises a plurality of movable deflector elements at the outlet of the revers' ing blade portions which in one position form a circumfei'ential wall blocking the outlet from the reversing blade sections, and in another position deflect motive fluid from the reversing sections into a common exhaust flow path.

DRAWING Other objects and advantages of the inventions will becomeapparent from the followingdescription, taken in connection with the accompanying drawing, in which:

FIG. 1 is a simplified schematic elevation view, taken in section, of a portion of the gas turbine nozzle and bucket assembly,

FIG. 2 is an enlarged cross-sectional view showing the flow deflector in the reversing position,

FIG. 3 is a perspective view of a pair of deflector elements, and I FIG. 4 is a sectional view taken along lines IV-IV of FIG. 3.

Referring now to FIG. 1 of the drawing, a portion of the turbine casing 1 supports annular flow guiding duct walls 2, 3. Walls 2, 3 conduct hot motive fluid from a compressor turbine" wheel 4 on one shaft to a load turbine wheel 5 on another separate shaft by way of an adjustable nozzle assembly shown generally as 6.

Although not material to the present invention, turbine wheel 4 drives a suitable multi-stage axial flow compressor furnishing air to the combustion chamber where fuel is burned. Turbine wheel 4 provides no useful power but when acting in conjunction with its compressor and combustion chamber, serves as a hot gas generator or source of motive fluid. Other suitable sources of hot motive combustion fluid can be provided by the use of converted aircraft jet engines suitably arranged to discharge into duct walls 2, 3.

The turbine wheel 5 provides useful power through an output load shaft 7 which may be directly coupled to a ship's propeller with gears. Disposed about the periphery of wheel 5 in suitable dovetail slots, indicated at 8, are a number of radially directed bucket members 9. The radially outer portion of bucket member 9 comprises a blade portion 9a shaped to provide forward rotation of the turbine wheel 5 in the usual manner. The radially inner portion is a blade portion 9b with reverse curvature to provide astern' operation or reverse rotation of wheel 5. Blade portions 9 1, 9b are separated by an intermediate platform portion 90 which extends circumferentially to abut similar platforms on other bucket members 9 and to thereby provide a circumferential flow separating wall.

On the downstream end of turbine wheel 5, a curved outer annular wall 10 and an inner annular wall 11 provide a common exhaust duct 12 for gas from either the inner or outer ring of bucket members 9. a flow deflector 13 is positioned at the inner wall of exhaust duct 12. Supporting struts 14 extend across duct 12.

Referring more particularly now to the variable nozzle assembly 6, this consists of an outer circumferential row of radially directed and movable nozzle partitions or vanes 15 arranged to direct motive fluid into the outer ring of turbine blade portions 9a. Radially inward from and concentric with partitions 15 is an inner circumferential row of radially directed and movable nozzle partitions or vanes 16.

The radially innermost boundary for the motive fluid is provided by means of an annular member 17 having an outer surface 17a which is a portion of a sphere and having an inner flange 17b arranged to slide within a groove in a suitable stationary wall 18 for thermal expansion and contraction.

Radially separating the nozzle partitions 15 and 16 is an intermediate annular member 19 with spherical surfaces on its upper and lower sides at 190 and 19b, respectively. Member 19 has a suitable sealing lip 20 cooperating with the platforms 9c of the bucket wheel. It is provided with a suitable extension 21 extending upstream into the annular duct defined between walls 2, 3 to divide the flow. Member 19 and extension 21 are supported by means of struts 22 extending through the walls of casing 1. Struts 22 are provided with streamlining heat shields 23.

The outer boundary surface for motive fluid is provided by means of an outer annular member 24 with an inner spherical surface 24a. The center of curvature for all of the spherical surfaces 17a, 19a, 19b. and 17a is located on the turbine shaft axis so that the partitions may pivot about a radial axis without binding the stationary structure or each other. The annular members 17, 19, or 24 may be full rings or may be suitably constructed in segmented fashion by means well known in the art to provide for thermal expansion and contraction.

Attached to the radially outer part of each of the outer partitions 15 is a radially extending operating stem 25. Stem 25 is hollow and is mounted for rotation within a a bushing 26. In a similar manner, attached to the radially outer end of each of the inner partitions 16 is a radially extending operation stem 27. This extends outward through a radial hole 15a inside'each of the outer partitions 15 and through the hollow stem 25. Operating levers 28, 29 are attached to stems 25, 27, respectively.

In this manner, outer nozzle partitions 15 can be pivoted about a radial axis with levers 28 to vary the effective flow area of the outer gas path independently of nozzle partitions 16 which can be pivoted by levers 29 to vary the effective flow area of the inner gas path. Inner and outer nozzle actuating ring members 30 and 31 are attached by pins to each of the inner and outer sets of circumferentially spaced operating levers 28, 29 so that the entire ring of inner partitions 16 can be actuated in unison independently of the entire ring of outer partitions 15. The spherical surface portions 17a, 19a, 19b, 24a enable independent rotation of the partitions while maintaining sealing engagement of the respective partitions with the boundary walls.

Flow deflector 13, which is the object of the present invention, is shown in FIG. 1 in a position for forward rotation of the load turbine shaft 7. A circumferential array of delfectors 13 is provided, each arranged to pivot radially inward about a pin 35 upon movement of an actuating rod 36. Any suitable arrangement may be used for moving actuating rods 36 such as a common member to which all rods are attached, or by means of separate pneumatic or hydraulic actuators such as indicated at 37. Deflectors 13 pivot into an L-shaped nesting ring 38 which may be integral or in sections, and which has sealing lips 39 forming close clearances with the rotating trubine wheel 8.

Referring now to FIG. 2 of the drawing, an enlarged view shows the details of the flow deflector 13 which is pivoted into position for reversing operation. The deflector 13 has an arcuate flow guiding sidewall 40 and a blocking sidewall 41. The sidewalls are approximately at right angles to one another and are connected by a web 42. Pivoting about pin 35 is accomplished by a pin 43 on the end of actuating rod 36 sliding in a curved slot 44 in the web 42. A number of equivalent devices for pivoting the flow deflector are well known to those skilled in the art. For example, a single master actuat ing ring may be used to pivot all of the flow deflecting elements by means of linkages attached from the ring to each element.

Sealing strips 45, 46 extending from the walls 40, 41 on one side of each deflector complete the assembly. When the deflector is in an elevated position as indicated by the phantom lines 47, the sealing strips 45 are active to seal the spaces between flow guiding walls 40 while the sealing strips 46 serve to accomplish a seal between the blocking wall portions of the deflector.

Referring now to FIG. 3 of the drawing, a perspective view is shown of a deflector element 13 and its position with respect to an adjacent deflector element 13. The sealing strips 45, 46 are attached to and project from one side of the flow guiding wall portion 40 and blocking wall portion 41, respectively. Flow guiding walls 40, 40 have arcuately curved surfaces so that, together with strips 45, 45', they together make up a circumferential flow guiding surface when the deflectors are in the raised position or a conical surface when the flow guiders are in a depressed position. The blocking wall portions 41, 41' are flat circular sectors which, together with strips 46, 46' make up a circular radial blocking wall at the rotor blade outlets when in the raised position.

Although the strips 45, 46 are shown in FIGS. 3 and 4 as being separate members welded to the undersides of walls 40, 41, they may also be formed as an integral part of the walls if deflectors 13 are cast.

Sealing strip 45 requires radial clearance as the flow deflectors 13 pivot. This is necessary since deflectors 13, 13' converge toward one another both radially and circumferentially when moving from the outer to the inner position.

FIG. 4 shows the position of the flow guiding walls 40 when in the raised or outer position. A slight clearance gap 48 is provided by means of a slight kink 49 in sealing strip 45'. Due to the different rates of closure, gap 48 closes and wall 40 overlaps sealing strip 45 as illustrated by the phantom lines 50 illustrating the lowered position OPERATION OF THE INVENTION Referring to FIG. 1 of the drawing, normal forward rotation of the wheel 8 is accomplished by pivoting the inner nozzle partitions 16 to a closed position and placing deflectors 13 in the raised position. Control of turbine load is accomplished by manipulating the position of the outer nozzle partitions 15. The deflector forms close clearances with the platform 9c on the bucket wheel and its blocking wall 41 reduces rotational losses in the blade portions 9b, while its flow guiding wall 40 forms a part of the exhaust duct for the flow of motive fluid from blades 9a.

Reversing the gas turbine is accomplished by opening the inner ring of nozzle partitions 16 and closing the outer ring of nozzle partitions 15. At the same time, the flow deflector 13 is moved to its inner position as illustrated byFlG. 2. Flow from the reversing blades 9b is deflected radially outward by walls 40 of the deflectors into the common exhaust duct 12. Control of the reversing load is accomplished by manipulating inner nozzles 16. Slight leakage through the closed nozzle partitions 15 is of little consequence, since reversing is usually carried out for short time periods and efficient operation is not a primary requisite.

By employing the pivotable deflector members, a single exhaust duct 12 can be used which provides many economies in a reversing gas turbine. Structural stability is increased because there is no need for a flow dividing wall in the exhaust path.

While there has been described what is considered at present to be the preferred embodiment of the invention, other modifications will become apparent to those skilled in the art, and it is desired to cover in the appended claims all such modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. A reversible axial flow turbine comprising:

a source of hot motive fluid,

a turbine rotor having inner and outer coaxial rows of rotor blade portions thereon, the inner row comprising blade portions of reversed curvature to those of the outer row for effecting rotation opposite that of the outer row,

inner and outer coaxial rows of adjustable nozzle blades, each of said rows of blades being pivotable as a group from open to closed position for selectively and separately admitting motive fluid to a selected row of rotor blade portions,

an exhaust duct disposed and arranged to receive motive fluid from the outer row of rotor blades,

and r movable flow deflecting means disposed at the outlet of said inner row of rotor blades and adapted and arranged to block motive fluid flow therefrom in a first position and to deflect motive fluid flow therefrom into said exhaust duct in a second position, said flow deflecting means comprising a plurality of arcuate, pivotable elements having cooperating adjacent flow guiding wall portions, each element being pivoted at one end thereof, and the other end being aligned with the inner part of the outer row of rotor blades in said first position and aligned with the inner part of said inner row of rotor blades when in said second position.

2. The combination according to claim 1, wherein said flow deflector elements further include cooperating adjacent blocking wall portions arranged to form a continuous annular wall at the outlet of said inner rotor blade row when the deflector is in said first position.

3. The combination according to claim 1, wherein said adjacent flow guiding wall portions are provided with circumferentially extending strip portions arranged to provide overlapping joints with the adjacent flow guiding walls when the flow deflector elements are pivoted.

4. The combination according to claim 1 including first actuator means for closing said inner group of nozzle blades and second actuator means for moving said flow deflector elements into said first position.

Claims (4)

1. A reversible axial flow turbine comprising: a source of hot motive fluid, a turbine rotor having inner and outer coaxial rows of rotor blade portions thereon, the inner row comprising blade portions of reversed curvature to those of the outer row for effecting rotation opposite that of the outer row, inner and outer coaxial rows of adjustable nozzle blades, each of said rows of blades being pivotable as a group from open to closed position for selectively and separately admitting motive fluid to a selected row of rotor blade portions, an exhaust duct disposed and arranged to receive motive fluid from the outer row of rotor blades, and movable flow deflecting means disposed at the outlet of said inner row of rotor blades and adapted and arranged to block motive fluid flow therefrom in a first position and to deflect motive fluid flow therefrom into said exhaust duct in a second position, said flow deflecting means comprising a plurality of arcuate, pivotable elements having cooperating adjacent flow guiding wall portions, each element being pivoted at one end thereof, and the other end being aligned with the inner part of the outer row of rotor blades in said first position and aligned with the inner part of said inner row of rotor blades when in said second position.

2. The combination according to claim 1, wherein said flow deflector elements further include cooperating adjacent blocking wall portions arranged to form a continuous annular wall at the outlet of said inner rotor blade row when the deflector is in said first position.

3. The combination according to claim 1, wherein said adjacent flow guiding wall portions are provided with circumferentially extending strip portions arranged to provide overlapping joiNts with the adjacent flow guiding walls when the flow deflector elements are pivoted.

4. The combination according to claim 1 including first actuator means for closing said inner group of nozzle blades and second actuator means for moving said flow deflector elements into said first position.

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