US2929210A - Pulsating ignition torch means - Google Patents

Description

.March 22, 1960 L. D. HOWES 2,929,210

PULSATING IGNITION TORCH MEANS Filed Dec. 27, 1957 I 714445;.- ME I- INVENTOR. LESL/E a. HOWES,

I Afro/n 2,929,210 'ri inst nct: ic'riirioii reta n MEANS nears n, none, rhoeaix aae; negate to The Garrett Corporation; Los AngelesgCalifi; a corporation of California I xp neaaan necenaba 21, a seria 1%. been '6 (Ziaiitis. (c1. so-sits The present invention relates -to a pulsating ignition torch means, and mere particularly to a pulsating ignition torch means for use in igniting fuel mixtures in combustiof chambers such as those employed in gas turbine en s- V Fuel mixtures, when moving at high velocities, in a flame tube, are sometimes Idiflicult to ignite, and this .difiiculty is particularly noticeable when an attempt is inside to ignite fuel mixtures which are under adverse conditions such vas low temperatures and/or low ambient pressures encountered at high altitudes. Pulsating ignition torches of the prior arthave been utilized toproject high velocity flames through fuel mixtures moving rapidly through flame tubes of vgas turbine engines, and it has been found that such pulsating ignition torches overcome most conditions which adversely affect ignition of fuel mixtures in various fuel combustion devices. I I

It is known that equipment to be installed, in aircraft must be compact, light in weight, and readily serviceable.

Accordingly, it is an object of the invention to provide a novel pulsating ignition torch device which is particularly constructed and adapted for installation on airborne equipment such as gas turbines and combustion starting systems used to crank aircraft engines.

Another object of .the invention is to provide a pulsating ignition torch means having a hollow screw-threaded fixture which is adapted to connect the present torch means to a combustion chamber, and, concurrently, to serve as a conductor of air to support combustion in the torclr means. j

Another object of the invention is to provide a pulsating ignition torch means which is readily and easily connected to or disconnected from a combustion chamber wallliniember; whereby the torch means may be readily serviced or replaced. I I I I Another object of the invention is to provide a pulsating ignition torch means having an integral torch tube which isreadily' removable from a combustion chamber flame tube,- whereby removal of the flame tube from the: combustion chamber cap is facilitated.

Further objects and advantages of the present inventionmay be apparent from the following specification, appended claims, and-accompanying drawings, in which:

Figure 1 is a sectional view of a pulsating ignition torchmeans shown in connection with a fragmentary portionof a combustion chamber device; and

'Fig. 2 is a sectional view taken on the plane indicated by the line 2+2 of Fig. 1.

,As shown in Fig. 1-,' the pulsating ignition torch means of the present invention is mounted on a combustion chamber cap member 12. This cap member is a hollow cylindrical structure which is generally concentric with a flame' tube- 14 disposed therein: The adjacent walls ofthe cap andthe tube 14 are spaced apart to permit openings 16 in the wall thereof. Concentrically of the United States Patent ire 2,929,210 Patented Mar. 22, 1950 2 flame tube and atone end thereof is a conventional fuel nozzle 18 which directs a spray of fuel droplets in a diverging pattern into the flame tube 14. Generally, the flow of fuel'mixtur'es through the tube 14 is at high velocity, thereby creating a ,difficult ignition problem.

The present ignition tor'ch .means 10 is provided with a hollow cylindrical housing 20 having a' closed Wall 22 on one end adjacent the combustion chamber cap 12. This wall 22 is provided with a central opening 24 which is closely fitted .over a boss 26 fixed in any suitable manner to the cap12. I

The boss 26 is provided with an internally threaded bore 28 which, is engaged by external threads on a hollow cylindricalqbolt 30 disposed concentrically in the cylindrical housing. member 20.

The bolt extends through an opening 32 in a wall member 34 and is provided with a head 36 which engages the outer side thereof. This wall member 34 is removably disp'osedto close the end of the housing 20 opposite the wall 22 thereof. The bolt 30 is provided with airtoutlet openings 38 adjacent to the wall member 34.

These openings 38 communicate with a central bore 40 in the bolt '30, and threadedly secured in the end of the bore 40 is a member 42 having a restricted orifice which communicates with the space, between adjacent walls of the cap 12 and flame tube 14. The orifice 42 permits a predetermined amount of air to flow through the bore 40 and openings 38 into the interior of the housing 20. Fluid pressure between the walls of the cap 12 and the flame tube 14 ,is slightly higher than that within the flame tube 14,, due to a slight pressure drop across the side Wall of the flame tube caused by a restriction' of flow through the openings 16 therein.

A torch tube 44 establishes communication between the interiors of the flame tube 14 and the housing 20,

thereby causing fluid pressure in the housing to substantially equal that inside thefla'me tube 14., Thus, pressure'in the housing 20 will also be slightly lower than that in the space between adjacent walls of the cap 12 and flame tube 14. The air will thereby be caused to flow from said space into the housing 20 through the bore 40in the'bolt 30. I j II I I The torch tube 44 is fixed to the end wall 22 of the housing ,20 and projects through openings 46 and 48 in the ,cap 12 and flame tube 14, respectively. I \I Projecting into the housing 20 is a spark plug 50. It is threaded into a boss 52 fixed to the cylindrical hous ing member 20 by welding or otherwise, as desired. Also projecting into the housing 20 is a fuelnozzle 54 which is secured to a boss 56 wel'ded or otherwise secured to thetcylindrical housing 20. I V

The fuel nozzle 54 is a conventional spray nozzle which is supplied with liquid fuel under pressure, and, when the present torch means is operating, this nozzle 54 directs a continuous spray of atomized fuel into the housing 20 for mixture with air entering the housing via the openings 38, .bore 40, orifice 42, from the space between adjacent walls of the cap 12 and tube 14'. I It, will be seen that thebolt 30 provides a fixture for holding the torch means 10 of the present invention on a combustion chamber device and concurrently serves as an air supply, conduit to furnishcombustion air to the interior of the torch housing. When the head 56 of this bolt 30 is engaged by awrench, the threaded portion of the bolt may be tightenedin the. internal threads 28 of the boss 26",. thereby forcing wall member 34 into intimately engaged relation vvith pne endI of the housing'20 .andforcing' the end wall 22 t o b ear securely against a plate 58 fixed to, t he outer side of. the c ap IZ and surrounding the boss 26. This-plate 5$ is provided with anopening 69 through which th e torchtube 44 extends, and from which it is readily removable.

When the bolt 30 is rotated to disengage the threads 28, the bolt and wall member 34 may be removed from the housing 20, or the entire assembly may be removed from the cap 12 by retracting the torch means in a direction axially of the bolt 30, so that the torch tube 44 is removed from the openings 46 and 48 in the walls of the cap 12 and flame tube 14. i

In operation, a combustion device including the cap 12, tube 14, and fuel nozzle 18 operate to produce gas for various uses; for example, to drive a .gas turbine. In such uses, the air flowing through the tube 14 moves at high velocity due to a substantially high pressure ratio of the air delivered thereto via the space between adjacent walls of the cap 12 and tube 14.

The nozzle 18 directs a diverging pattern of fuel spray which mixes with air entering the flame tube 14 via the openings 16. Due to the high velocity of the fuel mixture in the tube 14, ignition thereof by a conventional spark plug is diflicult because the thermal capacity of the plug is not sufficient to cause flame propagation in the fuel mixture. While a spark plug may ignite a small portion of the mixture, the flame resulting therefrom blows out due to the high velocity of the fuel mixture in the tube. The foregoing difficulties are alleviated by operation of a pulsating ignition torch means according to the present invention.

This torch means causes pulsating flames which travel at very high velocity laterally through the fuel mixture in the flame tube. The pulsating flames are created in the present torch means under conditions wherein air flow and fuel mixture velocities are low.

These low velocities are readily attained by passing the air through the restricted orifice and then through one or more larger openings 38 into the housing 20, as hereinbefore described. Thus, the flow velocities of the fuel mixture in the torch are much lower than those in the flame tube, thereby permitting the torch fuel mixture to be ignited by a spark plug.

There is a distinct advantage in generating pulsating flames rather than a continuous flame. since a continuous flame at low velocity, if issued into the high velocity stream of fuel and air in the flame tube 14, will be blown downstream therein and will not penetrate laterally through the high velocity fuel mixture. By contrast, pulsating flames, being generated by explosive action in the torch housing, issue from the torch at very high velocity and travel completely across the interior of the flame tube 14. Further, these flames carry heated particles of fuel which are readily combinable with additional air existing in the flame tube, thereby propagating mass combustion therein.

Pulsating flames are created by the torch means of the present invention in a manner substantially as follows: The ratio of fuel oil to air, which is admitted into the torch housing 20, is preferably about 1:1 by weight, as compared to a stoichiometric mixture which may be maintained at a ratio of 1:15 fuel oil and air by weight. Therefore, it will be seen that the fuel and air mixture utilized by the present ignition torch means is overrich. In other words, there is an excess of fuel for the amount of oxygen contained in the air. This overrich fuel mixture is obtained by continuous operation of the fuel nozzle 54, while the orifice 42 admits a restricted flow of air into the bore 40 and through the openings 38 into the housing 20 following each intermittent combustion period when pressure in the housing 20 is low. v

It will be understood that each pulsating explosion in the torch housing causes an increase of fluid pressure therein which momentarily exceeds that of air passing into the housing via the openings 38. This intermittently interrupts the supply of air to the torch. Such a mode of operation augments pulsating combustion and is usually characteristic thereof.

During operation of the torch means, the spark plug 50 is continuously energized, and periodically suflicient air accumulates in the housing 20 to thereby intermittently provide combustible mixtures which reach the electrodes of the spark plug 50. A combustible mixture may not extend throughout the entire area internally of the housing 20, since the housing will contain an overrich fuel mixture.

When an explosion or intermittent flame is created by ignition of the fuel mixture, it causes a rapid pressure and temperature rise in the housing 20, thereby projecting a high velocity flame outwardly through the torch tube 44 and laterally through a high velocity fuel mixture flowing in the flame tube 14. Each intermittent flame vaporizes excess fuel in the housing 20, whereupon subsequent flow of air through the openings 38 into the housing 20 creates a combustible mixture which is subsequently fired when it reaches electrodes of the spark plug 50.

Various locations of the openings 38 in the bolt 30 have been tried with respect to the disposition of the spark plug 50 and the fuel nozzle 54; however, no particular location of the openings 38 seems to be predominantly critical or advantageous. It is possible that variations in the spacing of the openings 38 relative to the spark plug 50 may have some effect on the pulsating frequency of the torch. However, the openings 38 may be'located at almost any desired position along the bolt 30 without unduly compromising the functioning of the present torch means.

It will be obvious to those skilled in the art that vari 'ous modifications of the present invention may be resorted to in a manner limited only by a just interpretation of the following claims.

I claim:

1. In a pulsating ignition torch means for a combus tion chamber device having a flame tube and a cap surrounding the flame tube, the combination comprising: a torch housing; a hollow fixture member disposed in said housing to secure the latter to said cap, said fixture member having a restricted passage therein which intercommunicates with the interiors of said housing and said cap for conducting air at a fixed rate from the latter into said housing; ignition means projecting into said housing; a fuel nozzle, said nozzle being constructed to deliver an amount of fuel into said housing to create an overrich mixture with air concurrently passing through said restricted passage into said housing; and a torch tube extending from said torch housing to project through said cap and said flame tube for delivering a pulsating flame from said housing into the flame tube of said combustion chamber device.

2. In an ignition torch means for a combustion chamber device having a flame tube and a cap surrounding the flame tube, the combination comprising: a cylindrical torch housing; a tubular member disposed concentrically thereof to secure said housing to said cap and establish communication between the interiors of said housing and said cap to conduct air at a fixed rate from the latter to said housing; ignition means projecting into said housing; a fuel nozzle disposed to deliver fuel into said housing; and a torch tube extending from said torch housing into said cap and said flame tube for delivering a flame from said housing into the flame tube of said combustion chamber device.

3. In a pulsating ignition torch means for a combustion chamber device having a flame tube and a cylindrical cap surrounding the flame tube, the combination comprising: a hollow cylindrical torch housing having a removable wall; a hollow fixture member extending through said wall and connecting it with said housing, said fixture being disposed to secure said housing to said cap and having a passage therein to establish communi' cation between the interiors of said housing and said cap and conduct air at a fixed rate from said cap to .said housing; ignition means projecting into said housing; a

fuel nozzle disposed to deliver fuel into said housing; and a torch tube extending from said torch housing into said cap and said flame tube, said torch tube serving to direct a pulsating flame from said housing into the flame tube of said combustion chamber device.

4. In a pulsating ignition torch means for a combustion chamber device having a flame tube and a concentric cylindrical cap surrounding the flame tube, the combination comprising: a torch housing; a hollow threaded bolt connecting said torch housing to said cap and provided to conduct air at a fixed rate from the interior of said cap into said housing; ignition means projecting into said housing; a fuel nozzle disposed to deliver fuel into said housing; and a torch tube extending from said torch housing into said cap and said flame tube, said torch tube serving to direct a pulsating flame from said housing into the flame tube of said combustion chamber device.

5. In a pulsating ignition torch means for a combustion chamber device having a flame tube and a cylindrical cap surrounding the flame tube, the combination comprising: a torch housing; a boss secured to said cap and having a bore communicating with the interior of said cap, said boss having screw threads thereon; a bolt threadedly engaging said boss and securing said pulsating ignition torch means to said cap, said bolt having a bore communicating with the interior of said housing and the bore in said boss to conduct air at a fixed rate from the interior of said cap into said housing; ignition means projecting into said housing; a fuel nozzle disposed to deliver fuel into said housing; and a torch tube extending from said torch housing into said cap and said flame tube, said torch tube serving to direct a pulsating flame from said housing into the flame tube of said combustion chamber device.

6. In a pulsating ignition torch means for a combustion chamber device having a flame tube and a cylindrical cap surrounding the flame tube, the combination comprising: a boss secured to said cap and having a bore disposed to communicate with the interior of said cap, said boss having screw threads thereon; a torch housing; a bolt threadedly engaging said boss and securing said torch housing to said cap, said bolt having a bore communicating with the interior of said housing and the bore in said boss; a restricted orifice member removably positioned in the bore of said bolt, said orifice being provided to admit air to flow at a fixed rate from the interior of said cap into said housing; ignition means projecting into said housing; a fuel nozzle disposed to deliver fuel into said housing; and a torch tube extending from said torch housing into said cap and 'said flame tube, said torch tube serving to direct a pulsating flame from said housing into the flame tube of said combustion chamber device.

References Cited in the file of this patent FOREIGN PATENTS 616,481 Great Britain Jan. 21, 1949

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