US3209838A - Turbine rotors - Google Patents

Turbine rotors Download PDF

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Publication number
US3209838A
US3209838A US298251A US29825163A US3209838A US 3209838 A US3209838 A US 3209838A US 298251 A US298251 A US 298251A US 29825163 A US29825163 A US 29825163A US 3209838 A US3209838 A US 3209838A
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United States
Prior art keywords
blades
rotor
bracing ring
blade
adjacent
Prior art date
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Expired - Lifetime
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US298251A
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English (en)
Inventor
Frankel Adolf
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Associated Electrical Industries Ltd
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Associated Electrical Industries Ltd
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Publication date
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
    • F01D5/00—Blades; Blade-carrying members; Heating, heat-insulating, cooling or antivibration means on the blades or the members
    • F01D5/12—Blades
    • F01D5/22—Blade-to-blade connections, e.g. for damping vibrations
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F01—MACHINES OR ENGINES IN GENERAL; ENGINE PLANTS IN GENERAL; STEAM ENGINES
    • F01D—NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES
    • F01D5/00—Blades; Blade-carrying members; Heating, heat-insulating, cooling or antivibration means on the blades or the members
    • F01D5/12—Blades
    • F01D5/22—Blade-to-blade connections, e.g. for damping vibrations
    • F01D5/225—Blade-to-blade connections, e.g. for damping vibrations by shrouding

Definitions

  • a large steam turbine includes two or more cylinders in each of which the turbine rotor is provided with circumferential series of rotor blades, each series comprising a stage of the turbine. It is important that the steam passing between the blades of a rotor stage shall not escape about the periphery of blades of the stage, and a shroud ring is therefore normally fitted to limit the steam flow to the spaces between the blades.
  • a sectionalized frusto-conical shroud ring is used, each section being joined to a group of blades, say seven in number, and there being a clearance between the butting ends of adjacent sections to permit thermal expansion. These shroud ring sections also serve to brace the blades, so reducing vibration of the blades and the danger of blade failure due to such vibration.
  • the normal frusto-conical type of shroud suffers, particularly when applied to stages having blades with a very large outside diameter running at a high peripheral speed, as in the last stages of the low pressure cylinder, from the disadvantage that the effective attachment of the shroud sections to the blades by the conventional rivetting over of projections on the blades becomes diificult as result of the large centrifugal forces due to the high peripheral speeds, and from the disadvantage that the bending stresses in the shroud material become very large due to the effect of centrifugal force combined with the increasing span which has to be bridged between adjoining blades.
  • Each section of shroud ring keeps the blade tip pitch of the blades which it serves at a substantially constant value, so that the outermost blades of the group of blades must deflect circumferentially. The deflections are progressively larger for the blades towards each end of the group.
  • An object of the present invention is the provision of an improved turbine rotor provided with blade bracing means in which the disadvantages discussed above are at least mitigated.
  • a turbine rotor includes at least one circle of rotor blades which are joined by bracing ring sections each extending between and attached to two adjacent blades and each curved, as viewed in a direction parallel to the rotor axis, outwardly beyond the circle including the parts of the sections which lie 3,209,838 Patented Oct. 5, 1965 "ice adjacent the points of attachment of the sectidns to the blades.
  • FIGURE 1 is'a sectional side elevation of one bladed wheel or disc mounted on the rotor of a steam turbine;
  • FIGURE 2 is a view taken in a direction parallel to the rotor axis of FIGURE 1, and shows a small part only of the periphery of the bladed wheel or disc;
  • FIGURE 3 illustrates a second embodiment of the invention and is a sectional drawing taken on a plane normal to the direction of steam flow between two adjacent blades of a turbine wheel or disc;
  • FIGURE 4 illustrates an alternative embodiment of the invention and corresponds to FIGURE 2;
  • FIGURE 5 is a view in the radially inwards direction of the construction shown in FIGURE 3.
  • the turbine rotor shaft 1 has secured to it a large number of bladed wheels or discs, of which one wheel 3 is shown.
  • Wheel 3 con sists of a hub portion 3H and a thinner disc portion 3D the periphery of which is machined to accommodate in known manner the shaped root portions of blades 5.
  • the tip of each blade is thickened at 5A and on each axially extending side is formed with an axially extending undercut groove 53.
  • a shroud ring section 7 is fitted, comprising a central portion 7A which is curved, as viewed in a direction parallel to the rotor axis, outwardly beyond the circle R including the points of attachment of the ring sections 7.
  • the ends 7B of the sections 7 are enlarged and are complementary to the grooves 5B, so that the section 7 can be slid into place in the grooves and is then effective to locate each blade tip relative to the adjacent blade tip in a circumferential direction.
  • the curvature of the portion 7A is that of a catenary, and the design of the section 7 will be clearer after a consideration of the improved manner in which this shroud ring section operates.
  • the centrifugal force effect will cause a percentage elongation of the blade pitch, e, which can be computed by well established methods from the calculated stress distribution in the turbine disc and the turbine blades. Also, since the material of the shroud ring section is subjected to centrifugal force, a radially directed outward force will be produced on each particle of the section 7. As a result, if one considers any intermediate part of the section 7, it is clear that that intermediate part will be put in a state of tension by the centrifugal force, and will be caused to elongate.
  • the total elongation produced in the shroud ring section by the centrifugal force should correspond to the elongation of the blade tip pitch by the centrifugal force acting on the blades and turbine disc, although in practice a close approximation can produce much of the advantages of the present invention.
  • the tensile stress f which is required in the catenary to obtain the percentage elongation of e in the turbine blade pitch, at the diameter at which the shroud is attached, is given y where E is the modulus of elasticity of the shroud material.
  • A is the cross-section of the catenary, and this must have a radial component W/ 2 where W is the total centrifugal pull on the shroud. This condition must be met if a geometry free of bending stress is to be produced as desired. It follows that in s a- P where a is the angle between the chord and the tangent to the catenary at the point of attachment. The shape of the catenary is defined by conventional mathematical methods by this angle and theknown pitch between the points of attachment.
  • FIGURE 2 shows one way in which this pull can be transmitted to the blade tips.
  • a supporting band can be provided consisting of sections formed similar to the shroud sections described above.
  • FIGURE 3 illustrates banding sections 27 each having a curved portion 27A and radial end parts 27E which are secured by rivets 29 to the blades at a point intermediate their length.
  • the curvature of the portions 27A is decided in the manner described above by the elongation of the pitch distance of the blades 5 at the points of attachment of the sections 27 to the blades.
  • the method of attachment of the sections 27 to the blades shown in FIGURE 3 can be used also for the attachment of peripheral shroud sections to the blade tips.
  • each banding section 37 includes a curved portion 37A and radial end parts 37E which are secured by rivets 39 extending through the blades 5 adjacent their radially outer ends to the adjacent banding sections.
  • the rivets 39 extend perpendicularly to the blade section, so that they take the tension force of the shroud partly in tension and partly in shear, but mainly in shear.
  • FIGURE 5 the complete shroud ring assembly is made up of two rings lying side-by-side, as indicated by ring A and ring B in FIGURE 5.
  • a shroud of rhomboidal shape (as seen in radial view, e.g. as in FIGURE 5) is subject to some shear stresses.
  • the shear stresses increase as the rhombus departs more and more from the rectangular shape, and as its width increases.
  • the inclination of the short faces of the rhombus is determined by the geometry of the blades it is intended to use, and therefore the shear stresses are suitably limited by splitting the shroud ring assembly as shown in rings A and B.
  • the shroud ring assembly can be split into several rings lying side-by-side.
  • a turbine rotor comprising at least one rotor disc; a circumferential row of rotor blades on the disc; socket means formed at the tip of each rotor blade; bracing ring sections joining adjacent blades in the circumferential row adjacent the tip of said blade; each bracing riing section extending between two adjacent blades in the row; each bracing ring section having enlarged portions at each end thereof, said portions being secured in said socket means for attaching said bracing ring section to the rotor blades; and each bracing ring section including a curved part, curved, as viewed in a direction parallel to the rotor axis, so that a central region of the curved part is at a greater radius than two flanking regions of the curved part which are respectively adjacent to the two blades; the curved part being curved to a catenary curve having its ends inclined at an angle satisfying the equation where a is the angle between the chord joining the two points of attachment and the tangent to the catenary at each of these
  • a rotor according to claim 1 in which a plurality of bracing ring sections are spaced inwardly of said first mentioned bracing ring sections and are connected between adjacent rotor blades by pin-like members which extend perpendicularly through the blade between the two sections and transmit tension forces from one ring section to the other.
  • a rotor according to claim 2 in which the first mentioned bracing ring sections are substantially rhomboidal as viewed in a radial direction, and the first mentioned bracing ring sections and the second mentioned bracing ring sections are arranged in a plurality of concentric circles, lying side by side.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Turbine Rotor Nozzle Sealing (AREA)
US298251A 1962-08-22 1963-07-29 Turbine rotors Expired - Lifetime US3209838A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB32285/62A GB987016A (en) 1962-08-22 1962-08-22 Improvements in turbine rotors

Publications (1)

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US3209838A true US3209838A (en) 1965-10-05

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US298251A Expired - Lifetime US3209838A (en) 1962-08-22 1963-07-29 Turbine rotors

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US (1) US3209838A (de)
CH (1) CH404695A (de)
DE (1) DE1426780A1 (de)
GB (1) GB987016A (de)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3733146A (en) * 1971-04-07 1973-05-15 United Aircraft Corp Gas seal rotatable support structure
US4521159A (en) * 1982-06-10 1985-06-04 Rolls-Royce Limited Load distribution member
US4734010A (en) * 1985-05-31 1988-03-29 Bbc Brown, Boveri & Company, Limited Damping element for independent turbomachine blades
US4784571A (en) * 1987-02-09 1988-11-15 Westinghouse Electric Corp. Apparatus and method for reducing blade flop in steam turbine
US20110142654A1 (en) * 2009-12-14 2011-06-16 Marra John J Turbine Blade Damping Device With Controlled Loading
US20110142650A1 (en) * 2009-12-14 2011-06-16 Beeck Alexander R Turbine Blade Damping Device with Controlled Loading
USRE45690E1 (en) 2009-12-14 2015-09-29 Siemens Energy, Inc. Turbine blade damping device with controlled loading

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1499103A (en) * 1922-04-18 1924-06-24 Westinghouse Electric & Mfg Co Turbine blade
GB315722A (de) * 1928-07-16 1930-02-27 The British Thomson-Houston Company Limited
DE563458C (de) * 1929-02-10 1932-11-05 Siemens Schuckertwerke Akt Ges Versteifung von Dampfturbinenschaufeln
US2914299A (en) * 1954-02-05 1959-11-24 Gen Electric Co Ltd Steam turbines

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1499103A (en) * 1922-04-18 1924-06-24 Westinghouse Electric & Mfg Co Turbine blade
GB315722A (de) * 1928-07-16 1930-02-27 The British Thomson-Houston Company Limited
DE563458C (de) * 1929-02-10 1932-11-05 Siemens Schuckertwerke Akt Ges Versteifung von Dampfturbinenschaufeln
US2914299A (en) * 1954-02-05 1959-11-24 Gen Electric Co Ltd Steam turbines

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3733146A (en) * 1971-04-07 1973-05-15 United Aircraft Corp Gas seal rotatable support structure
US4521159A (en) * 1982-06-10 1985-06-04 Rolls-Royce Limited Load distribution member
US4734010A (en) * 1985-05-31 1988-03-29 Bbc Brown, Boveri & Company, Limited Damping element for independent turbomachine blades
US4784571A (en) * 1987-02-09 1988-11-15 Westinghouse Electric Corp. Apparatus and method for reducing blade flop in steam turbine
US20110142654A1 (en) * 2009-12-14 2011-06-16 Marra John J Turbine Blade Damping Device With Controlled Loading
US20110142650A1 (en) * 2009-12-14 2011-06-16 Beeck Alexander R Turbine Blade Damping Device with Controlled Loading
US8540488B2 (en) 2009-12-14 2013-09-24 Siemens Energy, Inc. Turbine blade damping device with controlled loading
US8616848B2 (en) 2009-12-14 2013-12-31 Siemens Energy, Inc. Turbine blade damping device with controlled loading
USRE45690E1 (en) 2009-12-14 2015-09-29 Siemens Energy, Inc. Turbine blade damping device with controlled loading

Also Published As

Publication number Publication date
GB987016A (en) 1965-03-24
DE1426780A1 (de) 1969-05-08
CH404695A (de) 1965-12-31

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