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  After-burner chamber with secure ignitionUSPTO Application #: 20060292504Title: After-burner chamber with secure ignition Abstract: A turbojet having an after-burner chamber presenting a specific injector opening into the burner ring to provide secure ignition. The after-burner chamber has an annular fuel injection duct, an ignition spark plug, and an ignition injector installed facing the spark plug and connected to specific fuel feed means. (end of abstract) Agent: C. Irvin Mcclelland Oblon, Spivak, Mcclelland, Maier & Neustadt, P.C. - Alexandria, VA, US Inventors: Sebastien Pierre Louis Baboeuf, Sabine Constance Maud Charpenel, Didier Noel Durand, Jacques Andre Michel Roche USPTO Applicaton #: 20060292504 - Class: 431005000 (USPTO) Related Patent Categories: Combustion, Process Of Combustion Or Burner Operation, Burning Waste Gas, E.g., Furnace Gas, Etc. The Patent Description & Claims data below is from USPTO Patent Application 20060292504. Brief Patent Description - Full Patent Description - Patent Application Claims
[0001] The invention relates to an after-burner chamber for a turbojet, and more particularly it relates to an improvement in the ignition system for said after-burner. BACKGROUND OF THE INVENTION [0002] After-burning is used in military aircraft to increase the thrust of the engine quickly, and consequently to increase the speed of the airplane, when flying conditions make that necessary. [0003] U.S. Pat. No. 5,396,761 describes an after-burner chamber having a plurality of burners extending radially, one of which is fitted with an ignition system comprising a spark plug associated with an injector. The injector has orifices facing away from the spark plug, such that ignition is not ensured under all operating conditions of the jet. [0004] U.S. Pat. No. 3,931,707 describes an after-burner chamber fitted with a burner ring having a plurality of nozzles delivering fuel upstream from a ring of stationary vanes where the fuel mixes with air entering the ring via a downstream slot. A spark plug serves to ignite the fuel. However, there is nothing to control vaporization of the fuel to ensure that the mixture will ignite under all flying conditions. OBJECTS AND SUMMARY OF THE INVENTION [0005] The invention applies to a similar type of combustion chamber fitted with an annular burner and a spark plug capable of generating sparks for igniting after-burning. In such a system, the end of the spark plug is placed facing a point on an annular fuel distribution duct. In that type of after-burner, depending on the altitude and the speed of the airplane when after-burning is triggered, the pressure and the temperature at which fuel is injected into the duct can be too low or too variable. It is not possible to act directly on the injection pressure in the annular duct. Consequently, ignition is not certain and sometimes after-burning is not triggered, and that is not necessarily due to the spark plugs operating poorly. The invention serves to solve this problem. [0006] More particularly, the invention provides an after-burner chamber comprising an annular fuel injection duct and an ignition spark plug mounted in the vicinity of said annular duct, wherein an ignition injector is installed facing said spark plug and is connected to specific fuel feed means suitable for delivering said fuel under a controlled pressure independent of the feed conditions to said annular duct. [0007] Thus, the specific ignition injector fed by a fuel source that is different from that which feeds the burner and that is used for spraying fuel for a few seconds in front of the ignition spark plug, guarantees that after-burning will ignite. [0008] Once after-burning has started, the specific feed source for the ignition injector can be switched off until the next time after-burning is to be triggered. The spark plug issues several sparks per second until ignition occurs. The ignition period lasts for a few seconds, e.g. three seconds to ten seconds. [0009] The injector is provided with a special nozzle that vaporizes the jet into particles that are very fine, being smaller than fifty micrometers. [0010] In an embodiment in which the annular duct is mounted in a burner ring, said injector projects inwards from said ring, behind the spark plug. [0011] In an after-burner chamber, it is conventional to distinguish between a hot inner primary stream in which the gas delivered by the turbine flows, and a cooler outer secondary stream that is separated from the primary stream by a shroud. When the burner ring is placed in the hot primary stream, -the injector and the spark plug are housed in a protective sheath fastened to an outer casing, commonly referred to as the heater casing and opening out into said burner ring. The protective sheath isolates the ignition system from said hot primary stream. In addition, the protective sheath advantageously includes ventilation orifices communicating with the cold secondary stream. In this way, cold air flows continuously inside the protective sheath in order to keep the ignition system at an acceptable temperature. BRIEF DESCRIPTION OF THE DRAWINGS [0012] The invention will be better understood and other advantages thereof will appear better in the light of the following description of a turbojet having an after-burner chamber in accordance with the principles of the invention, and given purely by way of example, with reference to the accompanying drawings, in which: [0013] FIG. 1 is a fragmentary half-section of the upstream portion of an after-burner chamber in which the burner ring is placed in the secondary stream; [0014] FIG. 2 is a diagram on a larger scale showing the disposition of the aeromechanical injector and of the ignitor spark plug relative to the burner ring; [0015] FIG. 3 is a perspective view of the burner ring seen looking along arrow 3 in FIG. 2 and showing the connection of the specific injector; [0016] FIG. 4 is a perspective view looking along arrow 4 in FIG. 2 and showing the burner ring and the specific injector; and [0017] FIG. 5 is a section view on a radial plane through the after-burner chamber showing the ignition system of the burner ring when the ring is situated in the relatively hot primary stream. MORE DETAILED DESCRIPTION [0018] With reference to FIGS. 1 to 4, there can be seen a portion of the after-burner chamber 11 of a turbojet 12, situated downstream from the turbine (not shown) on its axis X'X. Conventionally, the casing 14 of the after-burner chamber is connected by bolts to the end of a diffuser casing 16 also referred to as a heater casing. An inner exhaust casing 18 is connected to an exhaust cone 19 extending axially in the central portion of said diffuser casing 16. [0019] In the space defined between said diffuser casing 16 and the casing 18 together with the cone 19, there is a "confluence" shroud 20 which separates and channels the inner primary gas stream F.sub.1 and the outer secondary gas stream F.sub.2. The primary stream F.sub.1 of gas from the turbine is at high temperature while the secondary stream F.sub.2 coming from the compressor is at relatively low temperature and enables the structural elements of the after-burner chamber to be cooled. An inner jacket 22 carried by the casing 14 defines the after-burner chamber downstream from a combustion system 25 essentially comprising a burner ring 26 and radial arms 27 extending from the burner ring towards the inside of the after-burner chamber almost as far as the axis X'X thereof. [0020] Between them, the jacket 22 and the casing 14 define an annular cooling channel 28 extending around the after-burner chamber 11. Continue reading... Full patent description for After-burner chamber with secure ignition Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this After-burner chamber with secure ignition patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like After-burner chamber with secure ignition or other areas of interest. ### Previous Patent Application: Photothermographic material and image forming method Next Patent Application: System for controlling the delivery of a fuel gas to a burner apparatus Industry Class: Combustion ### FreshPatents.com Support Thank you for viewing the After-burner chamber with secure ignition patent info. IP-related news and info Results in 2.10389 seconds Other interesting Feshpatents.com categories: Daimler Chrysler , DirecTV , Exxonmobil Chemical Company , Goodyear , Intel , Kyocera Wireless , |
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