# US 2019/0376401 A1 · Controlled gap seal with surface discontinuities > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0376401 A1 - Document ID: US20190376401A1 - Status: Published application - Kind: A1 - Application number: 16/204,367 - Filed: 2018-11-29 - Published: 2019-12-12 - Earliest claimed: 2018-06-08 - Assignees: Pratt & Whitney Canada Corp. - Applicants: Pratt & Whitney Canada Corp. - Inventors: Ignatius THERATIL; Aldo ABATE - Web page: https://patentgrep.com/patent/US20190376401A1 ## CPC - F16J 15/441: {with floating ring} - F01D 11/003: {by packing rings; Mechanical seals} - F01D 11/025: {Seal clearance control; Floating assembly; Adaptation means to differential thermal dilatations} - F16J 15/44: Free-space packings - F01D 11/06: Control thereof - F05D 2220/32: in gas turbines - F05D 2240/50: Bearings - F05D 2240/55: Seals - F05D 2260/98: Lubrication - F16J 15/445: {with means for adjusting the clearance} - F16J: PISTONS {(specially adapted for dampers F16F9/32)}; CYLINDERS; SEALINGS - 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 There is disclosed a controlled gap seal for a gas turbine engine including a ring configured to be in a sealing engagement with a housing and a runner configured for rotation relative to the ring about the central axis. The runner has a runner face facing a ring face of the ring. The ring face is spaced apart from the runner face by a gap. A plurality of surface discontinuities are circumferentially distributed around the central axis on the runner face and/or the ring face. The plurality of surface discontinuities are spaced relative to one another such that a first set of adjacent surface discontinuities are circumferentially spaced from each other at a different distance than a second set of adjacent surface discontinuities. A method of using the controlled gap seal is disclosed. ## Claims ### Claim 1 A controlled gap seal for a gas turbine engine, comprising: a ring configured to be in a sealing engagement with a housing, the ring annularly and continuously extending about a central axis; a runner configured for rotation relative to the ring about the central axis, the runner having a runner face facing a ring face of the ring, the ring face spaced apart from the runner face by a gap; and a plurality of surface discontinuities circumferentially distributed around the central axis on the runner face and/or the ring face, the plurality of surface discontinuities spaced relative to one another such that a first set of adjacent surface discontinuities are circumferentially spaced from each other at a different distance than a second set of adjacent surface discontinuities. ### Claim 2 (depends on 1) The controlled gap seal of claim 1, wherein the surface discontinuities are tabs extending from the runner face and/or the ring face. ### Claim 3 (depends on 2) The controlled gap seal of claim 2, wherein the tabs have a cylindrical shape. ### Claim 4 (depends on 1) The controlled gap seal of claim 1, wherein the surface discontinuities are grooves. ### Claim 5 (depends on 4) The controlled gap seal of claim 4, wherein the grooves have a square cross-section. ### Claim 6 (depends on 1) The controlled gap seal of claim 1, wherein the surface discontinuities are located on both of the runner face and the ring face. ### Claim 7 (depends on 1) The controlled gap seal of claim 1, wherein the controlled gap seal includes the housing, the surface discontinuities being located on a face of the housing that is oriented toward the runner. ### Claim 8 (depends on 1) The controlled gap seal of claim 1, wherein for each two adjacent ones of the surface discontinuities, a channel is defined therebetween, the channel extending in both an axial direction relative to the central axis and the circumferential direction. ### Claim 9 (depends on 1) The controlled gap seal of claim 1, wherein a height of the surface discontinuities along a radial direction relative to the central axis is less than that of the gap. ### Claim 10 A gas turbine engine, comprising: a controlled gap seal located between a housing and a shaft of the gas turbine engine, the shaft rotating about a central axis of the gas turbine engine, the controlled gap seal including: a ring in a sealing engagement with the housing, the ring annularly and continuously extending about the central axis; a runner secured to the shaft and rotatable relative to the ring, the runner having a runner face facing a ring face of the ring, the ring face spaced apart from the runner face by a gap; and a plurality of surface discontinuities circumferentially distributed around the central axis located on the runner face, a face of the ring that faces the runner, and/or a face of the housing facing the runner, a distance taken between a first set of two adjacent ones of the surface discontinuities being different than that between a second set of two adjacent ones of the surface discontinuities. ### Claim 11 (depends on 10) The gas turbine engine of claim 10, wherein the surface discontinuities are tabs extending from the runner face, the face of the housing, and/or the face of the ring. ### Claim 12 (depends on 11) The gas turbine engine of claim 11, wherein the tabs have a cylindrical shape. ### Claim 13 (depends on 10) The gas turbine engine of claim 10, wherein the surface discontinuities are grooves. ### Claim 14 (depends on 13) The gas turbine engine of claim 13, wherein the grooves have a square cross-section. ### Claim 15 (depends on 10) The gas turbine engine of claim 10, wherein the surface discontinuities are located on both of the runner face of the runner and the face of the ring. ### Claim 16 (depends on 10) The gas turbine engine of claim 10, wherein the surface discontinuities are located on both of the face of the housing and the runner face. ### Claim 17 (depends on 10) The gas turbine engine of claim 10, wherein for each two adjacent ones of the surface discontinuities, a channel is defined therebetween, the channel extending in both an axial direction relative to the central axis and the circumferential direction. ### Claim 18 (depends on 10) The gas turbine engine of claim 10, wherein a height of the surface discontinuities along a radial direction relative to the central axis is less than that of the gap. ### Claim 19 A method of operating a controlled gap seal, comprising: imparting a pressure differential between a cavity and an environment outside the cavity; fluidly connecting the cavity to the environment via a gap of the controlled gap seal, the gap located between a rotating component and a static component of the controlled gap seal; and disrupting a flow circulating within the gap by circulating the flow between surface discontinuities circumferentially distributed around a central axis of the controlled gap seal, the surface discontinuities located on the rotating component and/or the static component, a first set of adjacent surface discontinuities are circumferentially spaced from each other at a different distance than a second set of adjacent surface discontinuities. ### Claim 20 (depends on 19) The method of claim 19, wherein circulating the flow between the surface discontinuities includes imparting a circumferential component to a flow direction of the flow.