US 3750392 A
A spark igniter for gas turbine engines, having passage means for positioning a small quantity of liquid fuel directly in the path of the spark, which fuel is vaporized, ignited, and expelled as a jet of flame into the combustion chamber to ignite the main fuel flow.
Claims available in
Description (OCR text may contain errors)
[ Aug. 7, 1973 United States Patent 1 Zoll 2,574,495 11/1951 Parker...................,.. .....60/39.82P 3,057,159 10/1962 Benedict....................l....60/39.82S
1 N M r we vr. B Dm NC m 0 m1 H m mm R EA NE m p. mm 4 M MW  Assignee: Curtiss-Wright Corporation, FOREIGN PATENTS OR APPLICATIONS Wood-Ridge, NJ.
Dec. 22, 1971 1,018,963 2/1966 Great Britain.....;.......,.... 60/3982 S 765,175 1/1957 Great Britain.....,....,..,.... 60/39 82 S  Filed:
Appl' 210975 Primary Examiner-Clarence R. Gordon Assistant Examiner-Warren Olsen P6 2 7 c E2 0 1 S 2 3 9 3 0 6  US. Cl. AttorneyRaymond P. Wallace et al.  Int.
h c r a e ABSTRACT  References Cited UNITED STATES PATENTS A spark igniter for gas turbine engines, having passage L m a u t e m m mu." 1 a" e aB bug-1 aOOm RCLS 983 4565 9999 1111 ///l 250 l 1 6 29 8480 2 4 2 2 9582 5687 1 2232 60/39 82 S 60/3982 S 60/3982 P 60/3982 S 4 Claims, 2 Drawing Figures 7 4 ZT I L Z 2 & -X\ E j 1 /z T x 1 x /w /w /H .Lr 0 \l n 2 .x XXX K a m 1 H /////1 U I 1 HIGH ENERGY IGNITION DEVICE BACKGROUND OF THE INVENTION This invention pertains to gas turbine engines, and more particularly to a means of lighting off a gas turbine engine from rest state. Successful and reliable ignition of a gas turbine, particularly in the cold state, requires a high energy ignition system to assure that sufficient heat is released to ignite a self-propagating flame front, since fuel vaporization in the cold engine is relatively low. High energy electrical ignition systems as commonly used for this purpose range from 4 to 20 joules of stored electrical energy, and more particularly toward the higher end of that range; Such a system is necessarily complex and expensive.
SUMMARY OF THE INVENTION The present invention provides a high energy ignition device requiring only 0.5 to 2 joules of stored electrical energy, the remainder of the igniting energy being supplied by positioning a very small quantity of liquid fuel between the electrodes directly in the path of the spark. The spark generated by the power supply of relatively low energy vaporizes the fuel and ignites it, producing a sudden expansion of flaming gas which is propelled as a ball of flame from the igniter into the main fuel and air mixture. The power supply of the ignition device is pulsed at about one to times per second, preferably about three times. However, since it operates for only a few seconds until a self-propagating flame front is established in the combustor, after which the priming fuel is shut off, the fuel consumed by the igniter is negligible. It would amount to about half a pound of fuel for a full hour of operation.
It is therefore an object of this invention to provide a reliable ignition device with low electrical power requirement.
It is another object to provide an ignition device in which the electrical energy is supplemented by primary fuel in the path of the spark.
The foregoing objects and advantages and other ancillary thereto will be understood on reading the following specification in connection with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional elevation of the igniter of the invention, mounted in a combustion chamber; and
FIG. 2 is a cross-section taken on line 2-2 of FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 shows a fragment of the wall 11 of a turbine combustion chamber, with an igniter 12 mounted thereon and projecting into the combustion zone. A head member 13 has a mounting flange 14 which is secured to the exterior of the combustor wall 11 by screws as shown, or by other convenient means. The combustor wall is provided with an aperture 16, through which a tubular well 17 borne by the head member 13 extends into the combustion zone.
A tubular insulator 18, formed of fused aluminum oxide or other suitable high temperature insulating material, is positioned in the well 17 and seated against the inner end wall thereof, the insulator also extending through the head 13. The insulator may be retained by any convenient means. In the example shown, the outer end of the aperture through the head is threaded, and an annular gland l9 surrounding the insulator is screwed into the thread, seating against a shoulder 21 of the insulator to hold it firmly in place. An electrode 22 is coaxially disposed in the inner diameter of the tubular insulator, maintained in position by a gastight packing 23 surrounding the electrode within the insulator tube.
The outer diameter of insulator 18 is slightly less than the inner diameter of well 17, so that an annular channel 24 exists between the two parts. Head 13 is provided with a connection 26 which may be either a nipple or a tapped thread, as shown, for attaching a fuel line. A passage 27 communicates between the connection 26 and the annular channel 24, whereby the channel may receive a supply of fuel from a tank (not shown).
The inner end portion of the insulator 18 has its inner diameter expanded in a funnel-shaped portion 28 for a short distance approximately equal to the length of the spark path, and the flat end face of the insulator, which is seated on the inner end wall 15 of well 17, is provided with a plurality of shallow diametral slots thereacross which communicate between the funnel portion 28 and the annular channel 24, permitting flow of fuel to the funnel portion. If desired the wall of the insulator may have holes drilled through it a little above the end, instead of slots, so that the fuel is delivered to some portion of the funnel wall. The end wall 15 of well 17 has a coaxial aperture 31 therein of approximately the same diameter as the larger end of funnel portion 28. The central electrode 22 extends only as far inward as the smaller end of the funnel portion, and the spark gap is between the inner end 32 of the electrode and the edge of aperture 31.
In operation, when it is desired to light off the engine a valve (not shown) is opened between the fuel supply and the fuel connection 26 in the igniter device. Very little pressure is needed to feed the fuel, one or two pounds above atmospheric being sufficient. In many cases the position of the fuel tank at a normal distance above the igniter will provide sufflcient pressure. Fuel travels through passage 27 into the annular channel 24, and thence through passages 29 to the inner surface of funnel 28. To some extent the fuel will creep upward on the inner diameter of the funnel if slots rather than holes are used; at most only a few drops are required at the point of arc. The power supply, containing capacitor-stored electrical energy of 0.5 to 2 joules, is activated, and the arc strikes along the inner wall of the funnel, vaporizing and igniting any fuel present. The flaming gases are propelled by the force of their own expansion out of the funnel as a ball of flame into the fuel-air mixture of the combustor. The igniter may continue to operate for a few seconds, pulsing at a rate of about three times per second, but only a very short period of operation is required to reliably ignite the combustor with a self-propagating flame front, after which the power supply of the igniter is switched off and the fuel valve to the igniter is closed.
The angle of the funnel 28 should not be too great, in order that the flame ball will be readily self-propelled therefrom. The included angle of the funnel may be from about 15 to about 40, with an angle of about 30 having been found satisfactory.
What is claimed is:
1. In a gas turbine engine having a combustion chamher and a fuel supply and means for delivering a fuel-air mixture to the combustion chamber, an igniting device wherein the improvement comprises:
a. a head member mounted on the combustion chamher and having a fuel connection to receive fuel from the fuel supply and bearing a tubular well extending into the combustion chamber, the well having an apertured inner end wall;
b a tubular insulator positioned within the well and having an electrode disposed therein, the insulator defining a spark path between the electrode and the inner end of the well;
c. the tubular insulator having a smaller outer diameter than the inner diameter of the well and defining an annular channel therewith, the head member having passage means communicating between the fuel connection and the annular channel, and the inner end of the insulator having passage means therein communicating between the annular channel and the spark path to deliver fuel thereto;
d. the inner end face of the insulator being seated against the apertured inner end wall of the well, the inner diameter of the insulator at its inner end being funnel shaped with the larger diameter of the funnel adjacent to the end wall of the well, the aperture in the end wall of the well being approximately the same diameter as the large end of the funnel; and
e. an electrical power supply connected to the electrode to initiate an arc across the spark path to vaporize and ignite the fuel in the spark path, the ignited fuel being propelled as a flame into the main fuel-air mixture.
2. The combination recited in claim 1, wherein the funnel portion of the insulator has an included angle from about 15 to about 40, the electrode extends inwardly into the insulator to a position approximately even with the smaller diameter of the funnel portion, and the spark path is along the funnel wall between the electrode and the edge of the aperture through the inner end wall of the well.
3. The combination recited in claim 2, wherein the funnel portion of the insulator has an included angle of approximately 30.
4. The combination recited in claim 3, wherein the electrode has connected thereto an electrical power supply capable of delivering about 0.5 to 2 joules of stored electrical energy.