US3542501A

US3542501A - Igniters for gas turbine engines

Info

Publication number: US3542501A
Application number: US750287A
Authority: US
Inventors: Cyril Charles Jones; William Roger Vanryne
Original assignee: Rotax Ltd
Current assignee: Lucas Support Services Ltd
Priority date: 1967-08-04
Filing date: 1968-08-05
Publication date: 1970-11-24
Anticipated expiration: 1987-11-24
Also published as: GB1226336A; FR1578322A; DE1751825A1

Description

United States Patent [72] Inventors Cyril Charles Jones Stanmore; William Roger Vanryne, Bourne End, England [2i] Appl. No. 750,287

[22] Filed Aug. 5,1968

[45] Patented Nov. 24, 1970 [73] Assignee Rotax Limited London, England a British company [32] Priority Aug. 4, 1967 [33] Great Britain [54] IGNITERS FOR GAS TURBINE ENGINES 7 Claims, 3 Drawing Figs.

US. Cl 431/258 F23q 7/06 43 H258, 196

[56] References Cited UNITED STATES PATENTS 3,242,967 3/1966 Schmitt 43 H258 3,307,610 3/1967 Sunday 431/258 Primary Examiner-Edward G. Favors Arlorney- Holman, Glascock, Downing & Seebold ABSTRACT: An igniter for igniting air/fuel mixtures in combustion chambers and comprising a sleeve member in which is mounted a target against which a jet of fuel impinges thereby to atomize the fuel, the atomized fuel being mixed with an annular air stream flowing in the same direction as the jet of fuel and the air/fuel mixture being ignited by an electric heating element disposed internally of the airstream and upstream of the target plate.

Patented Nov. 24, 1970 3,542,501

Sheet 2 of 2 M Maw 46 ATTORNEY IGNITERS FOR GAS TURBINE ENGINES This invention relates to igniters for igniting air/fuel mixtures in combination chambers and has for its object to provide such an igniter in a simple and convenient form.

An igniter in accordance with the invention comprises in combination, an orifice through which liquidfuel can be directed under pressure. a target upon which the jet of fuel leaving the orifice impinges, the target being shaped so as to atomize and direct the fuel radially relativethe the jet, means for producing an axially moving annular airstream into which the atomized fuel is directed. and means for igniting the air/fuel mixture to produce a flame which can be used to cause ignition ofthe air/fuel mixture in the combustion chamber.

In the accompanying drawings:

FIG. 1 is a sectional side elevation of one example of an igniter in accordance with the invention;

FIG. 2 shows a modification of part of the igniter of HO. 1;

and

FIG. 3 shows how the igniter is mounted in the combustion chamber ofa gas turbine engine.

As shown in FIG. 1 of the drawings the igniter comprises a cylindrical body part having a stepped external periphery. The narrower portion of the body part is provided adjacent the steps with a screw thread whereby it can be engaged within a threaded mounting boss and when so mounted the narrower end of the body part projects into the combustion charriber in which it is desired to ignite an air/fuel mixture. As shown in FIG. 3, the mounting boss 11 is carried by an external casing 12 of the combustion chamber whose wall is indicated at 13.

Formed in the body part 10 is a stepped bore 14 the wider portion of which lies within the wider portion ofthe body part. The narrower portion of the bore terminates in a restricted outlet 15 and through which the flame leaving the igniter enters the combustion chamber. Furthermore, formed in the narrow portion of the body part intermediate the screw threaded portion and the end thereof is a ring of air inlet apertures 16 which extends into the narrower portion of the bore 14-.

Extending with in the narrower portion of the bore 14 is a sleeve member 17 having an outwardly directed flange 18 which is disposed within the wider portion of the bore. The sleeve member extends to a point adjacent the outlet 15 and its outer periphery is less than that of the narrower portion of the bore thereby defining an annular chamber 19 to which air is supplied through the apertures 16. The end of the chamber 19 adjacent the narrower end of the bore is closed by an inter nal flange formed on the wall of the bore 14 and this acts to locate the sleeve member within the narrower portion of the bore. The diameter of the flange 18 is the same as that of the wider portion of the bore so that the sleeve member is located at both ends.

Formed in the wall of the sleeve member is a first row of apertures 20 these being positioned near the flange l8 and a second row of apertures 2i which are positioned substantially midway between the ends of the sleeve member. The apertures 20 are larger in size than the apertures 21.

Located within the sleeve member 17 at a position adjacent but on the same side of the row of apertures 21 as the row of apertures 20 is a target 22. The target 22 is mounted by means of a stout wire support 23 and is of generally conical form with its base surface substantially flat and normal to the longitudinal axis of the igniter. The base surface defines a target surface as will be described. The sleeve member together with its associated flange is formed from metal and extending into the sleeve member is an annular heating element support 24 hav-,

ing a flange positioned within the wider portion of the bore 14. The support 24 is provided with a lining 24a formed from a ceramic material and its annular end surface is of concave form and supports a coiled electric heating element 25. The outer diameter of the support 24 is slightly smaller than the internal diameter of the sleeve member 17 so that an annular clearanceis provided communicating with the apertures 20. The connections for the heating element are led through elongated passages respectively formed in the lining 2.4a and are connected respectively to the body part and an electrical connecter as will bedescribed.

The electrical connecter comprises an annular ring 26 formed from metal and which is provided with an integral tag 27 which extends through an aperture formed in a first heatresistant insulating washer 28 which is positioned intermediate the flange of the support 24 and a pressure pad 29 slidable in the wider portion of the bore 14. Also provided are a pair of thinner heat-resistant insulating washers 30 which are positioned on opposite sides of the ring 26 and which are mounted within the washer '28. Trapped between the pressure pad 2? and the adjacent washer 30 is one of the connections of the heating element and the other connection is trapped between the ring 26 and the other washer. The pressure pad 29 is formed from metal and is held in position by an externally threaded nut 31 which is engaged with a complementarily threaded portion of the wider portion of the bore M.

Formed integrally with the pressure pad 29 is a stem 32 which at its free end is formed as a fuel inlet. The stem is hollow and is provided with a stepped bore 33. Adjacent the step in the bore is an orifice plate 34 in which is formed a centrally disposed orifice and upstream of the orifice plate is a filter pad 35 the pad being secured to a retaining nut 36 which acts to retain the orifice plate in position.

In use, liquid fuel under pressure is supplied to the inlet and ajet offuel emerges from the orifice of the orifice plate 34 and strikes the target 22. Upon striking the plate the fuel is atomized and directed radially and is mixed with air leaving the annular clearance between the support 24 and the sleeve member 17. This air entering through apertures 20. Some droplets of fuel impinge upon the heating element and are ig' nited thereby and a flame emerges from the outlet 15 which is used to ignite the air/fuel mixture in the combustion chamber. The air entering through the apertures 21 acts to stabilize the flame.

In the alternative arrangement of HG. 2 the apertures 21 are omitted but the flame is stabilized by rods 40 extending inwardly from the sleeve member 17, and positioned downstream of the target face.

In order to prevent blow back of fuel a nonreturn valve 41 may be provided upstream of the fuel inlet and if desired and depending upon the nature of the fuel, a fuel preheater 42 may be provided upstream of the valve 41. Reference numeral 43 indicates a pump for supplying fuel under pressure and reference numeral 44 a source of electric supply for the heat ing element 25v ln order to prevent a stagnant zone occuring within the bore in the lining 24a three equiangularly spaced passages 50 (only one of which is shown) are provided. These extend within the support 24 and air from the apertures 20 flows therethrough to provide a low rate of flow of air along the bore in the lining 24a.

We claim:

1. An igniter for igniting an air/fuel mixture in a combustion chamber and comprising a sleeve member, a support within the sleeve member, a target mounted upon said support, an annular heating element support extending into the sleeve member and defining an annular clearance therewith, an orifice through which liquid fuel can be directed under pressure onto said target, said target being shaped so as to atomize the fuel and direct the fuel radially relative to the jet. means for causing air to flow through said clearance to produce an annular airstream into which the atomized fuel is directed, a heating element mounted at the end of said heating element support adjacent the target, said heating element when energized igniting the air/fuel mixture produced by the target to produce a flame which extends from the sleeve member and which can be used to ignite an air/fuel mixture contained in the combustion chamber, a first series of apertures formed in the sleeve member and through which air enters said annular clearance, and means adjacent the target for stabilizing the flame produced by the burning of the air/fuel mixture produced by the target.

2. An igniter as claimed in claim 4 in which the means for stabilizing the flame comprises a second series of apertures formed in the sleeve member and through which air can enter the interior ofthe sleeve member to produce an air stream adjacent the target.

3. An igniter as claimed in claim 1 in which the means for body part is of stepped form, the narrower portion ofthe bore accommodating said sleeve member and said support. and the wider portion of the bore accommodating mounting flanges for the sleeve member and support, a pressure pad acting to retain the flanges within th wider portion of the bore, and a stem formed integrally with the pressure pad. said stem being of hollow form and defining a fuel inlet at its end remote from the pad, the pressure pad being retained relative to the body part by a nut engaged within the wider end thereof.

6. An igniter as claimed in claim 5 in which the orifice is formed in an orifice plate mounted within said stem.

7. An igniter as claimed in claim 5 in which the end of the ,body part remote from the fuel inlet defines a restricted outlet