Brush-seal designs for elastic fluid turbines

A packing ring for use in forming a seal with a turbine shaft rotatably mounted within the casing of an axial flow elastic fluid turbine, wherein said axial flow elastic fluid turbine includes at least one stage having (i) at least one diaphragm stationarily mounted in said casting and having a plurality of steam directing nozzles, and (ii) a rotor fixedly attached to said turbine shaft and having a plurality of blades bounded by a shroud and disposed adjacent said plurality of steam directing nozzles, said packing ring having a plurality of packing ring segments adapted to be mounted in a groove circumferentially in said diaphragm for forming a seal with said turbine shaft, each said packing ring segment comprising:

• an inner ring portion having a plurality of brush segments mounted within a brush mounting groove formed in said inner ring, each said brush segment having a packet of bristles with said bristles having tip portions trimmed to terminate along a radius of curvature adapted to form a steam seal with said turbine shaft, each said bristle being adapted to be disposed in a plane substantially parallel to the principal plane of said rotor and extending in the direction of rotation of said turbine shaft;
• an outer ring portion adapted to be disposed within said circumferential groove for both axial and radial movement of said segment therein and having a pair of shoulders extending axially in opposite directions adapted for making radial contact respectively with a pair of spaced apart shoulders on said casing and thereby adapted for limiting movement of said segment radially with respect to said shaft;
• a neck portion connected between said inner arcuate portion and said outer ring portion and adapted for extending between said casing shoulders, said neck portion having an axial thickness which is adapted to be less than the distance between said opposing casing shoulders to thereby be adapted to axially locate said seal ring segment against one of said casing shoulders and provide a contact pressure seal at the side of said neck portion which is subject to lower fluid pressure;
• and
• a radial positioning means comprising a spring against said ring segments adapted to forcibly cause said segments to move radially outward away from said shaft, whereas working fluid flowing into the annular space between said casing and said ring segments will urge said segments radially inward towards said shaft, whereby at low speed and small turbine loads the spring forces will predominate, while at high flows and high working fluid pressure the pressure forces will predominate.

An axial flow elastic fluid turbine comprising:

• an outer casting;
• a turbine shaft rotatably supported in said outer casting;
• and
• a plurality of turbine stages installed along said turbine shaft and contained within said outer casting, each said turbine stage including
• a diaphragm stationarily mounted in a recess formed in said turbine casting and having a plurality of steam directing nozzles,
• a rotor fixedly attached to said turbine shaft and having a plurality of blades bounded by a shroud band and being disposed adjacent said plurality of steam directing nozzles, and
• a packing ring consisting of an arrangement of packing ring segments mounted in a circumferentially extending groove formed in said diaphragm and providing a continuously extending seal with said turbine,
• each said packing ring segment including
• a body portion for mounting within said circumferentially formed groove and having a longitudinal extent, a vertical extent, and a horizontal extent, and being particularly adapted for mounting in a portion of said diaphragm, said body portion having a brush mounting groove formed along said vertical extent and extending along said longitudinal extent;
• and
• a plurality of brush segments mounted within said brush mounting groove of said packing ring segment, each said brush segment having a packet of bristles with said bristles having tip portions trimmed to terminate along a radius of curvature adapted to form a steam seal with said turbine shaft, and
• each said bristle being disposed in a plane substantially parallel to the principal plane of said rotor and extending in the direction of rotation of said turbine shafts
• a radial positioning means comprising a spring between adjacent ring segments to forcibly cause said segments to move to a large clearance position, while working fluid flows into to an annular space between said casing and said ring segments urges said segments toward said small clearance position, whereby at low speed and small turbine loads the spring forces will predominate, while at high flows and high working fluid pressure the pressure forces will predominate;
• wherein said brush segment form a continuous seal.

A packing ring segment for use in forming a labyrinth seal with a turbine shaft rotatably mounted within the casing of an axial flow elastic fluid turbine, wherein said axial flow elastic fluid turbine includes at least one stage having (i) at least one diaphragm stationarily mounted in said casting and having a plurality of steam directing nozzles, and (ii) a rotor fixedly attached to said turbine shaft for rotation about an axis of rotation and having a plurality of blades bounded by a shroud band disposed within a principal plane of said rotor and adjacent said plurality of steam directing nozzles, said packing ring segment comprising:

• a body portion for mounting within a portion of said diaphragm and having a longitudinal extent, a vertical extent, and a horizontal extent, and being particularly adapted for mounting in a portion of said diaphragm, said body portion having a groove formed along said vertical extent and extending along said longitudinal extent, said body portion having a bore in a side edge surface for accepting a spring spanning said bore and an adjacent packing ring segment according to this claim;
• and
• a plurality of brush segments mounted within said groove of said packing ring segment, each said brush segment having a packet of bristles with said bristles having tip portions trimmed to terminate along a radius of curvature continuously extending along the longitudinal extent of said body portion effective to form a labyrinth seal when a turbine shaft is positioned along said tip portions of said bristles, and
• each said bristle being disposed at an acute angle with respect to said radius of curvature.

A moveable brush sealing system for inhibiting the flow of a wording fluid between a rotating shaft and a stationary casing comprising:

• a stationary casing having a circumferential seal ring groove formed therein, said seal ring groove having an opening into a clearance area surrounding said shaft;
• at least one segmented retractable seal ring including a plurality of seal segments, each of said seal ring segments including:
• (i) an outer member mounted within and supported by said seal ring groove, (i) an inner member mounted within said clearance area, said inner member including an outer surface facing said casing and an inner arcuate surface facing said rotating shaft, and (iii) a neck member extending through said opening in said seal ring groove and connecting said inner and outer members;
• a spring biased against said seal ring segment to move said seal ring segment to a large diameter position in which said seal member has a large clearance with respect to said rotating shaft;
• aperatures through the casing or through at least one of said segments to permit the free flow of working fluid into the seal ring groove to move the segment to a small diameter position in which the seal member has a small clearance with respect to the shaft;
• and
• a seal member attached to the inner arcuate surface of said inner member of said seal segment, said seal member including a brush seal having an array of bristles that extend generally radially inwardly toward said rotating shaft.

A seal for use in an elastic fluid turbine to minimize leakage of the working fluid between rotating and stationary components including:

• a segmented seal ring supported by and at least partially contained in an annular seal ring groove formed in the stationary component to permit motion of said seal ring between a larger diameter position and a smaller diameter position corresponding respectively to the large and small clearance position of said seal ring with respect to the rotating component, said seal ring groove being partially defined by a pair of opposing, spaced apart shoulders disposed axially on said stationary component which form an opening of said groove extending radially into the clearance area between said stationary and said rotating components;
• each segment of said seal ring including (i) an outer ring portion disposed within said seal ring groove for both axial and radial movement therein, (ii) an inner ring portion disposed in said clearance area which includes (a) an inner arcuate portion having a sealing member which includes a number of teeth extending therefrom in the direction of said rotating component and (iii) a neck portion connecting said inner ring portion and said outer ring portion and extending between said opposing, spaced apart shoulders on said stationary component, said neck portion having an axial thickness which is less than the distance between said opposing, spaced apart shoulders to permit said seal ring segment to move axially against one of said shoulders to provide a contact pressure seal at the side of said neck portion which is subject to lower turbine fluid pressure;
• a compressed spring biased against said ring segments to forcibly cause said segments to move radially outwardly to said larger diameter large clearance position at shut off and under low turbine loads;
• at least one opening formed in said stationary portion or in at least one of said segments to allow said working fluid to flow into the annular space between said casing and said ring segments to urge said segments radially inwardly toward said smaller diameter small clearance position as turbine load increases;
• and
• wherein said sealing member further includes at least one brush element, said brush element including a circumferentially arranged row of bristles that extend from said inner arcuate portion of said inner ring portion toward said rotating component.

A packing ring for sealing a shaft in a steam turbine, the packing ring disposed in a groove of a diaphragm in a casing of the steam turbine, comprising:

• a. a plurality of ring segments, ring segment having an inner face adapted to form a steam seal with the shaft, and having a brush mounted on said inner face, having bristles adapted to form a steam seal with the shaft;
• b. at least one spring, for biasing one or more of said ring segments radially away from the shaft;
• and
• c. a steam biasing means, for biasing said ring segments radially toward the shaft upon a sufficient build up of steam pressure within the turbine, whereby the force of said spring will predominate during low speeds and turbine loads, and whereby the force of said steam biasing means will predominate during high speeds and turbine loads.