# US 11,028,715 B2 · Reduced leakage air seal > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,028,715 B2 - Document ID: US11028715B2 - Status: Granted - Kind: B2 - Application number: 16/149,499 - Filed: 2018-10-02 - Published: 2020-04-02 - Granted: 2021-06-08 - Earliest claimed: 2018-10-02 - Assignees: Rolls-Royce North American Technologies Inc. - Applicants: Rolls-Royce North American Technologies Inc. - Inventors: Douglas David Dierksmeier - Web page: https://patentgrep.com/patent/US11028715B2 ## CPC - F01D 11/025: {Seal clearance control; Floating assembly; Adaptation means to differential thermal dilatations} - F01D 9/04: forming ring or sector - F05D 2220/321: for a special turbine stage - F05D 2220/323: for aircraft propulsion, e.g. jet engines - F05D 2240/10: Stators - F05D 2240/11: Shroud seal segments - F05D 2240/55: Seals - F05D 2300/50212: dissimilar - F01D: NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES (machines or engines for liquids F03; non-positive displacement pumps F04D) - F05D: INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS ## Abstract An air seal for a jet turbine engine with an upper stator, lower stator and finned turbine disk. The thermal expansion of the stators may be regulated by a control ring, which has a lower rate of thermal expansion that the stators, to prevent rubbing between the stator and fins. ## Claims ### Claim 1 A reduced leakage seal for a gas turbine, comprising: a control ring having a radially outward facing control surface and a radially inward facing control surface, the control ring having a thermal expansion time constant; the control ring coaxial with an axis; an outer ring having a radially inward facing outer stator; the outer ring having a radially inward contact surface cooperating with the radially outward facing control surface limiting a radially inward position of the outer ring with respect to the control ring; the outer ring having a second thermal expansion time constant; an inner ring having a radially outward facing inner stator, the inner ring having a radially outward contact surface cooperating with the radially inward facing control surface limiting a radially outward position of the inner ring with respect to the control ring; the inner ring having a third thermal expansion time constant; a plurality of alignment restraints, the plurality of alignment restraints restricting axial translation of the control ring, the outer ring, and the inner ring with respect to one another; and a rotating structure comprising an axially extending arm comprising a first set of outward facing knives and a second set of inward facing knives, wherein the outward facing knives are axially aligned and opposing the outer stator and the inward facing knives are axially aligned and opposing the inner stator, and wherein the axially extending arm at least in part separates a first volume and a second volume; wherein the thermal expansion time constant of the control ring is greater than the second thermal expansion time constant of the outer ring. ### Claim 2 (depends on 1) The seal of claim 1, wherein the first volume contains hot combustion gases. ### Claim 3 (depends on 1) The seal of claim 1, wherein the thermal expansion time constant of the control ring is greater than or equal a thermal expansion time constant of the rotating structure. ### Claim 4 (depends on 1) The seal of claim 1, wherein the outer ring comprises a first radially extending flange, the first radially extending flange in contact with at least one of the plurality of alignment restraints. ### Claim 5 (depends on 1) The seal of claim 1, wherein the inner ring comprises a second radially extending flange, the second radially extending flange in contact with at least another of the plurality of alignment restraints. ### Claim 6 (depends on 1) The seal of claim 1, wherein each of the control ring, the outer ring, and the inner ring are in contact with each of the others. ### Claim 7 (depends on 1) The seal of claim 1, wherein the plurality of alignment restrains are selected from the group consisting of pins, brackets and clips. ### Claim 8 (depends on 7) The seal of claim 7, wherein the pins comprise shoulder bolts. ### Claim 9 A gas turbine engine comprising: a rotor disk; a hot zone containing combustion gases; a cool zone containing cooling air, and a labyrinth seal separating the combustions gases from the cooling air in the cool zone; the labyrinth seal comprising: a control ring having a radially outward facing control surface and a radially inward facing control surface, wherein the control ring is coaxial with an axis, wherein the control ring has a first thermal expansion time constant; an outer ring comprising a radially inward facing outer stator, wherein the outer ring has a radially inward contact surface cooperating with the radially outward facing control surface limiting a radially inward position of the outer ring with respect to the control ring; the outer ring having a second thermal expansion time constant; an inner ring comprising a radially outward facing inner stator, wherein the inner ring has a radially outward contact surface cooperating with the radially inward facing control surface limiting a radially outward position of the inner ring with respect to the control ring, wherein the inner ring has a third thermal expansion time constant; and a plurality of alignment restraints, wherein the plurality of alignment restraints restrict axial translation of the control ring, the outer ring, and the inner ring with respect to each other; and a rotating structure comprising an axially extending arm comprising a first set of outward facing knives and a second set of inward facing knives, wherein the outward facing knives are axially aligned and opposing the outer stator and the inward facing knives are axially aligned and opposing the inner stator, and wherein the axially extending arm at least in part separates a first volume and a second volume; wherein the first thermal expansion time constant of the control ring is greater than the second thermal expansion time constant of the outer ring. ### Claim 10 (depends on 9) The engine of claim 9, wherein the control ring has an axial overlap with the first stator limiting a minimum radial position of the first stator with respect to the control ring. ### Claim 11 (depends on 10) The engine of claim 10, wherein the control ring has a second axial overlap with the second stator limiting a maximum radial position of the second stator with a respect to the control ring. ### Claim 12 (depends on 11) The engine of claim 11, wherein the axial overlap and the second axial overlap comprise a tab extending axially from the control ring. ### Claim 13 (depends on 12) The engine of claim 12, wherein a plurality of pins maintains the control ring, the first stator, and the second stator concentric to a center axis of the turbine engine. ### Claim 14 A method of controlling gaps between knives and stators in a labyrinth seal for a gas turbine engine comprising: providing the labyrinth seal including: a control ring having a radially outward facing control surface and a radially inward facing control surface, wherein the control ring has a first thermal expansion time constant; the control ring coaxial with an axis; an outer ring having a radially inward facing outer stator, wherein the outer ring has a radially inward contact surface cooperating with the radially outward facing control surface limiting a radially inward position of the outer ring with respect to the control ring; the outer ring having a second thermal expansion time constant; an inner ring having a radially outward facing inner stator, the inner ring having a radially outward contact surface cooperating with the radially inward facing control surface limiting a radially outward position of the inner ring with respect to the control ring; the inner ring having a third thermal expansion time constant; a plurality of alignment restraints, the plurality of alignment restraints restricting axial translation of the control ring, the outer ring, and the inner ring with respect to one another; and a rotating structure comprising an axially extending arm comprising a first set of outward facing knives and a second set of inward facing knives, wherein the outward facing knives are axially aligned and opposing the outer stator and the inward facing knives are axially aligned and opposing the inner stator, and wherein the axially extending arm at least in part separates a first volume and a second volume; wherein the thermal expansion time constant of the control ring is greater than the second thermal expansion time constant of the outer ring; varying a radius of the rotating structure associated with the labyrinth as a function of time, temperature and rotational speed of the rotating structure; varying a radius of the control ring as a function of time and temperature; limiting radial contraction of the outer ring as a function of the radius of the control ring during a first engine condition; limiting radial expansion of the inner ring as a function of the radius of the control ring during a second engine condition; wherein a first gap in the labyrinth seal is a function of the radius of the rotating structure and radial expansion of the inner ring during the second engine condition and a second gap of the labyrinth seal is a function of the radius of the rotating structure and the radial contraction of the outer ring during the first engine condition. ### Claim 15 (depends on 14) The method of claim 14, wherein the second engine condition is a transition from idle to steady state cruise. ### Claim 16 (depends on 14) The method of claim 14, wherein the first engine condition is a transition from steady state cruise to idle. ### Claim 17 (depends on 14) The method of claim 14, wherein the first engine condition and second engine condition are a transition from idle to cruise to idle.