# US 2019/0376402 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 2019/0376402 A1 - Document ID: US20190376402A1 - Status: Published application - Kind: A1 - Application number: 16/146,508 - Filed: 2018-09-28 - 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/US20190376402A1 ## 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. The seal has a ring annularly and continuously extending about a central axis. A runner that is configured for rotation about the central axis and rotatable relative to the ring. The runner has a face facing a face of the ring. The face of the ring is spaced apart from the face of the runner by a gap. Surface discontinuities are circumferentially distributed around the central axis. The surface discontinuities are located at specific locations and distributed in specific ways. 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 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 at least in part 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 and equally distanced from one another along a circumferential direction relative to the central axis, the surface discontinuities located at least at one of the runner face and a face of the housing, the face of the housing facing the runner, the surface discontinuities located downstream of the ring relative to a flow of fluid circulating within the gap. ### Claim 2 (depends on 1) The controlled gap seal of claim 1, wherein the surface discontinuities are tabs extending from the at least one of the runner face of the runner and the face of the housing. ### Claim 3 (depends on 2) The controlled gap seal of claim 2, wherein each of the tabs has a cylindrical shape. ### Claim 4 (depends on 1) The controlled gap seal of claim 1, wherein the surface discontinuities are grooves defined at the at least one of the runner face and the face of the housing. ### Claim 5 (depends on 4) The controlled gap seal of claim 4, wherein a cross-section of each of the grooves taken about a plane normal to the central axis is square. ### Claim 6 (depends on 1) The controlled gap seal of claim 1, wherein the surface discontinuities are located at both of the runner face and the face of the housing. ### Claim 7 (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 8 (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 9 (depends on 1) The controlled gap seal of claim 1, wherein the surface discontinuities are located solely on the face of the housing. ### Claim 10 A controlled gap seal for a gas turbine engine, comprising: a ring 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 at least in part 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 and equally distanced from one another along a circumferential direction relative to the central axis, the surface discontinuities located at the runner face, the surface discontinuities located upstream of the ring relative to a flow of fluid circulating within the gap. ### Claim 11 (depends on 10) The controlled gap seal of claim 10, wherein the surface discontinuities are tabs extending away from the runner face. ### Claim 12 (depends on 11) The controlled gap seal of claim 11, wherein each of the tabs has a cylindrical shape. ### Claim 13 (depends on 10) The controlled gap seal of claim 10, wherein the surface discontinuities are grooves defined at the runner face. ### Claim 14 (depends on 13) The controlled gap seal of claim 13, wherein a cross-section of each of the grooves taken about a plane normal to the central axis is square. ### Claim 15 (depends on 10) The controlled gap seal 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 16 (depends on 10) The controlled gap seal 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 17 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 runner and a ring, the ring in sealing engagement with a housing 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 and equally distanced from one another along a circumferential direction relative to the central axis, the surface discontinuities located either upstream of the gap and on the runner or located downstream of the gap and on at least one of the runner and the housing of the controlled gap seal. ### Claim 18 (depends on 17) The method of claim 17, wherein circulating the flow between the surface discontinuities includes imparting a circumferential component to a flow direction of the flow. ### Claim 19 (depends on 18) The method of claim 18, wherein imparting the circumferential component includes imparting the circumferential component in a direction opposite a direction of rotation of the runner. ### Claim 20 (depends on 17) The method of claim 17, wherein circulating the flow between the surface discontinuities includes circulating the flow within grooves.