# US 10,371,099 B2 · Spark plug and associated propellant ignition system > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,371,099 B2 - Document ID: US10371099B2 - Status: Granted - Kind: B2 - Application number: 15/091,192 - Filed: 2016-04-05 - Published: 2017-10-05 - Granted: 2019-08-06 - Earliest claimed: 2016-04-05 - Assignees: The Boeing Company - Applicants: The Boeing Company - Inventors: Leora Peltz; William Gregory Peterson; Robert V. Frampton - Web page: https://patentgrep.com/patent/US10371099B2 ## CPC - F02K 9/95: characterised by starting or ignition means or arrangements (safety devices F02K9/38) - F02C 7/264: Ignition - F02C 7/266: Electric (sparking plugs H01T) - F02K 9/94: Re-ignitable or restartable rocket- engine plants; Intermittently operated rocket-engine plants - H01T 13/20: characterised by features of the electrodes or insulation - H01T 13/22: having two or more electrodes embedded in insulation (sparking plugs having two or more spark gaps H01T13/46) - H01T 13/34: characterised by the mounting of electrodes in insulation, e.g. by embedding - H01T 13/38: Selection of materials for insulation - H01T 13/41: with interference suppressing or shielding means - H01T 13/54: having electrodes arranged in a partly-enclosed ignition chamber - H01T 13/08: Mounting, fixing or sealing of sparking plugs, e.g. in combustion chamber - F02K: JET-PROPULSION PLANTS (features of jet-propulsion plants common to gas-turbine plants, air intakes or fuel supply control of air-breathing jet-propulsion plants F02C7/00, F02C9/00) - F02C: GAS-TURBINE PLANTS; AIR INTAKES FOR JET-PROPULSION PLANTS; CONTROLLING FUEL SUPPLY IN AIR-BREATHING JET-PROPULSION PLANTS (construction of turbines F01D; jet-propulsion plants F02K; construction of compressors or fans F04; generating combustion products of high pressure or high velocity F23R; using gas turbines in compression refrigeration plants F25B11/00) - H01T: SPARK GAPS; OVERVOLTAGE ARRESTERS USING SPARK GAPS; SPARKING PLUGS; CORONA DEVICES; GENERATING IONS TO BE INTRODUCED INTO NON-ENCLOSED GASES (overvoltage protection circuits H02H) ## Abstract A spark plug having an insulating body defining a longitudinal axis and including a base portion and an obstruction portion, a first electrode including a proximal portion, a sheathed portion and a distal portion, the sheathed portion of the first electrode extending through the base portion of the insulating body, and a second electrode including a proximal portion, a sheathed portion and a distal portion, the sheathed portion of the second electrode extending through the base portion and the obstruction portion of the insulating body, wherein the obstruction portion axially extends beyond the distal portion of the first electrode. ## Claims ### Claim 1 A spark plug comprising: an insulating body defining a longitudinal axis and comprising a base portion and an obstruction portion; a first electrode comprising a proximal portion, a distal portion and a sheathed portion between said proximal portion and said distal portion, said sheathed portion of said first electrode extending through said base portion of said insulating body; and a second electrode comprising a proximal portion, a distal portion and a sheathed portion between said proximal portion and said distal portion, said sheathed portion of said second electrode extending through said base portion and said obstruction portion of said insulating body, said first electrode and said second electrode being spaced apart to define a gap therebetween, wherein said obstruction portion axially extends beyond said distal portion of said first electrode, wherein said obstruction portion is positioned in flow alignment with said gap with respect to a flow path of a rocket propellant to sustain a flame proximate said gap, and wherein said obstruction portion is positioned downstream of said gap with respect to said flow path of said rocket propellant. ### Claim 2 (depends on 1) The spark plug of claim 1 wherein said insulating body is monolithic. ### Claim 3 (depends on 1) The spark plug of claim 1 wherein said insulating body comprises an electrical insulator material. ### Claim 4 (depends on 3) The spark plug of claim 3 wherein said electrical insulator material comprises a ceramic material. ### Claim 5 (depends on 1) The spark plug of claim 1 further comprising a threaded collar connected to said base portion of said insulating body. ### Claim 6 (depends on 1) The spark plug of claim 1 wherein said obstruction portion has a first length along said longitudinal axis, wherein said gap is defined between said distal portion of said first electrode and said distal portion of said second electrode, said gap having a second length along said longitudinal axis, and wherein said second length is greater than said first length. ### Claim 7 (depends on 6) The spark plug of claim 6 wherein said first length is at least 20 percent of said second length. ### Claim 8 (depends on 1) The spark plug of claim 1 wherein said second electrode comprises a bend such that a distal-most tip of said second electrode is substantially axially aligned with a distal-most tip of said first electrode. ### Claim 9 (depends on 1) The spark plug of claim 1 wherein said obstruction portion comprises a circular cross-sectional shape. ### Claim 10 (depends on 1) The spark plug of claim 1 wherein said obstruction portion comprises an obround or elliptical cross-sectional shape. ### Claim 11 A rocket propellant ignition system comprising: a combustion chamber defining a longitudinal axis; a rocket propellant flowing through said combustion chamber in a flow path; and a spark plug extending into said combustion chamber, said spark plug comprising: an insulating body comprising a base portion and an obstruction portion; a first electrode extending through said base portion of said insulating body, wherein said first electrode comprises a distal-most tip; and a second electrode extending through said base portion and said obstruction portion of said insulating body, said second electrode being spaced apart from said first electrode to define a gap therebetween, wherein said obstruction portion axially extends beyond said distal-most tip, wherein said obstruction portion is in flow alignment with said gap with respect to said flow path of said rocket propellant, and wherein said obstruction portion is positioned downstream of said gap with respect to said flow path of said rocket propellant. ### Claim 12 (depends on 11) The rocket propellant ignition system of claim 11 wherein said combustion chamber is cylindrical. ### Claim 13 (depends on 11) The rocket propellant ignition system of claim 11 wherein said rocket propellant comprises a fuel component and an oxidizer component. ### Claim 14 (depends on 11) The rocket propellant ignition system of claim 11 wherein said rocket propellant has a flame speed, and wherein a superficial velocity of said rocket propellant is greater than said flame speed. ### Claim 15 (depends on 11) The rocket propellant ignition system of claim 11 wherein said insulating body is monolithic. ### Claim 16 (depends on 11) The rocket propellant ignition system of claim 11 wherein said obstruction portion comprises a circular cross-sectional shape. ### Claim 17 (depends on 11) A vehicle comprising said rocket propellant ignition system of claim 11. ### Claim 18 (depends on 17) The vehicle of claim 17 being a rocket. ### Claim 19 A method for igniting a flowing rocket propellant comprising the steps of: flowing a rocket propellant in a flow path through a gap formed between a first electrode and a second electrode, wherein said first electrode passes through a base portion of an insulating body, wherein said first electrode comprises a distal-most tip, wherein said second electrode passes through an obstruction portion of said insulating body and said base portion of said insulating body, wherein said obstruction portion axially extends beyond said distal-most tip, wherein said obstruction portion is positioned in flow alignment with said gap with respect to said flow path of said rocket propellant to obstruct said flow path of said rocket propellant; applying a voltage across said first electrode and said second electrode to generate a spark in said gap to ignite the flowing propellant; and sustaining a flame in said obstructed flow path after said spark ceases to exist. ### Claim 20 (depends on 19) The method of claim 19 wherein said rocket propellant has a flame speed, and wherein a superficial velocity of said rocket propellant is greater than said flame speed.