US3196614A

US3196614A - Ignition device for combustion equipment

Info

Publication number: US3196614A
Application number: US206003A
Authority: US
Inventors: Toone Brian; Barham Allan Michael
Original assignee: Rolls Royce PLC
Current assignee: Rolls Royce PLC
Priority date: 1961-07-11
Filing date: 1962-06-28
Publication date: 1965-07-27
Anticipated expiration: 1982-07-27
Also published as: DE1426292B1; GB944202A

Description

July 27, 1965 a. TOONE ETAL IGNITION DEVICE FOR COMBUSTION EQUIPMENT 2 Sheets-Sheet 1 Filed June 28, 1962 July 27, 1965 B. TOONE ETAL IGNITION DEVICE FOR- COMBUSTION EQUIPMENT 2 Sheets-Sheet 2 Filed June 28, 1962 United States Patent 3,196,614 IGNITION DEVICE FOR COMBUSTION EQUIPMENT Brian Toone, Littleover, Derby, and Allan Michael Barham, Miclrleover, Derby, England, assignors to Rolls-Royce Limited, Derby, England, a British company Filed June 28, 1962, Ser. No. 206,003 Claims priority, application Great Britain, July 11, 1961, 25,147/61 6 Claims. (Cl. 60-69152) This invention relates to combustion equipment, such for example as is used in gas-turbine engines, of the class in which fuel is burnt in a stream of combustion supporting gas having an elevated temperature and flowing at high velocity.

The invention will be described hereinafter in its application to gas-turbine engines. In such engines when employed for jet propulsion purposes it is often necessary to eflect ignition in the jet pipe for reheat purposes.

According to the present invention, there is provided a' device adapted to promote auto-ignition of fuel injected into the combustion-supporting gas stream, or to improve stability of combustion, or both, which device comprises a mass of refractory material and a foraminate element of platinum, or rhodium, or platinum/rhodium alloy or iridium or other suitable metal having catalytic properties in promotion of combustion, the foraminate element comprising a portion in the form of a spiral roll which has a plurality of spaced convolutions and is located axially in a flow passage extending in the refractory mass between those surfaces thereof which in use face upstream and downstream in the gas stream.

The foraminate element may also include a portion in the form of a disc at the downstream end of the flow passage and may further comprise a portion in the form of a disc at the upstream end of the flow passage.

According to a feature of this invention, in a construction having a disc portion at the downstream end of the flow passage, the disc portion may be formed to a T- shape and the leg of the T-section inserted into a slot or notch in the refractory mass and the spiral roll portion.

In a preferred form, the foraminate element includes a tube which the spiral roll surrounds.

In one construction of device of this invention, the spiral roll of the foraminate element extends between upstream and downstream disc portions and the refractory mass comprises a cylindrical part with the spiral roll in a bore extending through it and with the discs lying against its end surfaces, a cup-shaped refractory casing housing the cylindrical part and having a hole in its base coaxial with the bore of the cylindrical part and a refractory closure plate cemented to the end of the casing remote from its base, the closure plate having a hole in it co-axial with the bore.

In a second construction the foraminate element comprises a tube part and a downstream end disc welded to the tube and having a central hole aligned with the tube bore, the spiral roll surrounding the tube part, and the refractory mass comprises a cup-shaped member housing the tube and spiral roll and having the tube extending through a hole in its base, the discs lying against the external surface of the base, a refractory casing having a recess housing the cup-shaped member, a collar cemented in the open end of the recess to retain the cup-shaped member and foraminate element in position, and a ring of refractory material between the bottom of the recess and the disc, the collar having a hole registering with the tube bore and the casing having a hole extending from the bottom of the recess to the downstream surface of the casing.

3,196,614 Patented July 27, 1965 ice The operational value of a catalytic ignition device is assessed by the ranges over which operating parameters efiecting ignition can be varied whilst obtaining substantially instantaneous ignition, that is ignition within a few seconds of commencing fuel injection e.g. within 5 seconds. An additional characteristic of this device is that if the flame blows off the gutter due to some transient instability, the catalyst causes immediate re-ignition without any mechanical operation being required. One such parameter is the minimum temperature of the gas stream at which ignition can be effected satisfactorily. Another parameter is the minimum value of the fuel/air ratio at which ignition can be effected satisfactorily. Other parameters are the maximum Mach number and the minimum pressure at which satisfactory ignition can be achieved. It is found that with the device of this invention, substantially instantaneous auto-ignition can be achieved over ranges of gas pressure, gas temperature and of fuel/ air ratio which have low minimum values, and at relatively high Mach numbers. 7

Some embodiments of this invention will now be described with reference to the accompanying drawings in which:

FIGURE 1 illustrates one form of catalytic device in axial section,

FIGURE 1A is a perspective view of part of the device shown in FIGURE 1,

FIGURE 2 is an exploded view of a second form of device,

FIGURE 3 illustrates in section a third form of catalytic device,

FIGURE 4 illustrates the use of devices according to this invention in gas turbine engine reheat equipment, and

FIGURE 5 is a detail illustration of part of FIG-- URE 4.

- num/rhodium foraminate material at high temperatures.

7 2) and when the catalytic element isin position the portion 12 extends axially through the length of the bore 11 The mass 10 has an axial bore 11 extending through it from one end face to the other.

The device also comprises a catalytic element, conveniently formed from gauze of a 20% Rh/ Pt alloy, and the catalytic element comprises a spiral roll portion 12, a downstream disc portion 13 which covers one end face of the mass 10 and an upstream disc portion 14 which covers the other end face of the mass 10. The spiral portion 12 has a plurality of spaced convolutions (FIGURE and is located therein for instance by a metal pin (not shown) extending transversely across the bore 11 and passing through the convolutions of the spiral roll so pre 1 venting any tendency for the convolutions to telescope In use one or more of these devices are mounted in a stabilising gutter 20, so that the plate 17 projects beyond the convex side of the gutter, which is usually a V-section ring, and the ,base of the casing projects into the concavity of the gutter. The plane of the disc portion 13 may be located at any point inside the convex side of the gutter, upstream of the plane containing the down-stream edges of the gutter.

The gas stream flows from left to right as seen in the drawing and desirably the fuel is injected in the upstream direction into the gas stream at a point which is a selected distance upstream of the gutter; If the fuel injector is too close to the gutter inadequate mixing of the fuel and gas occurs before the mixture reaches the ignition device. Under these conditions rapid lights may not be achieved.

Part of the fuel/air mixture flows through the passage formed by the bore 11 and in so doing flows over the

catalytic element

12, 13, 14 and is ignited. The device is found to have good auto-ignition characteristics.

In experiments, a device according to FIGURES 1 and 2 was constructed and it had the following dimension-s.

The casing 15 had an outside diameter of 1.375 inches, and an inside diameter of 1.00 inch, and the device had an overall length of 1.09 inches.

The spiral roll of the catalytic element had a length of 0.90 inch and a diameter of 0.5 inch, there being six convolutions. The catalytic element was made from Rh/Pt gauze of 0.010 inch thickness, and had a mesh size of 36 meshes/inch.

Theh'ole 14 had a diameter of 0.218 inch and the hole .13 a diameter of 0.25 inch.

The plane of the disc portion 13 stream of the gutter lips.

In a first series of experiments, the fuel injector had an orifice of 0.038 inch in diameter and sprayed upstream and was placed at varying distances between 7 inches and 20 inches upstream of the device, and instantaneous lights were obtained with gas temperatures varying between 350 C. and 600 C., with fuel/ air ratios varying between 0.008 and, 0.035 (the maximum limit obtainable with the fuel pump used) and with gas flows between Mach numbers 0.1 and 0.26. Weak extinction occurred substantially uniformly at a fuel/air ratio of 0.004 and was substantially independent of temperature.

In a secondseries of experiments with the same device, with the injector 14 inches upstream of the device and with gas speeds between Mach numbers 0.25 and 0.5, instantaneous lights were obtained up to about Mach number 0.4. 1

In further experiments, a device was used with the following dimensions altered.

The spiral roll portion was 0.500 inch in diameter and hadeight conv-olutions, the hole 13 was 0.375 inch in diameter, and the hole 14 0.300 inch in diameter.

This device gave instantaneous lights at gas flows of Mach number 0.45 for gas temperatures down to 350 C. and for fuel/ air ratios between 0.005 and 0.03. For gas flows of Machnumber 0.5 instantaneous lights were obtained down to temperatures of 400 C. and effective lights down to 350 C.

In further experiments, the disc portion 13 was made from 0.020 inch thick gauze and good auto-ignition was obtained with added strength of the portion 13. i

The form of device shown in FIGURE 2 is similar to that in FIGURES 1 and 1A and like parts are indicated by like references. 7

Instead of a plane disc portion 13, the downstream portion 113 is folded to a T shape, the limbs 113a of the fold being welded together, and a diametral slot 114 is provided .in the mass 10 and the spiral roll portion 12 to receive the told. This device is intended to was 0.25 inch upstrengthen the disc at high temperature without reducing the gas iflow through the catalyst. To prevent the catalytic roll from pressing on the downstream plate, a locating pin, shown at 115 is used. I

This arrangement gives added strength to the downstream portion 113 so increasing the operational life of the device.

In an experiment, a device of this construction having the modified-dimensions above set forth was subjected i to an endurance test comprising lighting tests at 400 C. and Mach number 0.4 and fuel/air ratios of 0.015, a continuous run of twenty minutes with reheat at a fuel/ air ratio of 0.025, and a continuous run at 750 C. without reheat. This cycle was repeatedand after 10 hours no vital damage to the catalytic element, was found.

In another test simulating normal and reheat operation, no deterioration of the catalytic element was observed afer 60 hours normal operation and 6 hours reheat operation.

In the construction shown inFIGURE 3, the device comprises a foraminate catalytic element which consists of a central tube 20 of expanded catalytic metal, for example 0.020 inch thick expanded rhodium/platinum alloy containing 20 rhodium, a downstream end disc 21 of like material, the disc being welded to the end of the central tube 20 and having a central hole 21a aligned with the bore of the tube 20, and surrounding the tube 20 a spiral roll 22 of a similar catalytic metal, which is say 0.010 inch thick the convolutions of the roll being spaced apart. The catalytic element also has an upstream gauze disc 27. The disc may be folded to a T-shape, the leg 27a of the T being inserted in a transverse slot in the tube 20 and the oonvolutions of the roll 22. The disc 27 conducts heat from the catalytic zone to the relatively cool gases entering the flow pas sage, and the folded arrangement when use-d increases both the mechanical strength and the rate of heat transfer to the relatively cool gases.

The catalytic element is housed in a flow passage extending in a refractory mass which comprises a cupshaped alumina member 23 receiving the roll 22 and main portion of the tube 20, the member 23 having a hole in its base 23a through which the tube 20 extends, the disc 21 lying against the external surface of the base 23a. The members 23 is received. in a recess 24a extending inthe direction of gas flow from the upstream face of a refractory casing 24, there being a hole 24b, extending from the bottom of the recess to the downstream face of the casing 24, the hole 24b being of larger diameter than the hole 21a. A ring of alumina 25 separates the disc 21 from the base of the casing 24. A collar 26 of alumina is cemented into the open end of the recess 24a to retain the member 23 and the catalytic element in position, the collar 26 having a central hole 26a of the same diameter as the bore of the tube 20.

In an experiment, a device of this construction had the following dimensions. The casing 24 had an outside diameter of 1.375 and an inside diameter of 1.00, and the device had an overall length of 1.09. The spiral roll of the cataytic element had a length of 0.9" and a diameter of 0.5", there being 4 convolutions. The catalytic element was made from 20% Rh/Pt gauze of 0.010" thickness. The mesh size was 36 per inch.

The centre tube had a diameter of /4" and was made from 20% Rh/Pt gauze of 0.020" thickness. The mesh size was about 36 per inch.

The collar 26 was made from 20% Rh/Pt material in 0.020" thickness. The hole 26a had a diameter of 3 and a downstream hole 26b had a diameter of 0.375.

The fuel injector had an orifice of 0.038 in diameter, and sprayed upstream at a distance of 14" upstream of the device.

Instantaneous lights were obtained with gas temperatures between 350 C. and 600 C. with fuel/air ratios varying between 0.008 and 0.035, and with gas flows between Mach numbers of 0.1 and 0.5.

A number of devices of this type have also been located in an engine reheat gutter and gave satisfactory lights down to 400 C. (lower limits at which tests were carried out).

In a further device, a marked increase in mechanical reliability was achieved by a number of modifications to the catalytic element shown in FIGURE 3. The tube 20 was increased to 0.375 diameter and was made from 0.030" thick mesh in 20% Rh/Pt with meshes/inch. The plate 21 was made in solid Rh/Pt alloy and was welded to the tube. To restore the catalyst zone to its original volume the internal bore of cup 23 was increased to diameter. The quantity of platinum/rhodrum alloy in the catalytic spiral 22 was unchanged.

In an experiment with this device, the fuel injector had an injection hole 0.038" in diameter and was located 14 upstream of the catalyst. Instantaneous lights were obtained with gas flows between Mach numbers 0.1 and 0.5 and with gas temperatures above 340 C. and with fuel/air ratios between .005 and 0.03.

The device has good auto-ignition and combustion stabilising characteristics and is robust giving a good operational life.

In yet another construction, suitable for multigutter stabilisers of gas turbine reheat systems, two or more catalytic elements as above described are located in bores in a rectangular refractory mass. Such a device is found to have good auto-ignition characteristics.

Instead of mounting the ignition devices as above described in the stabilising gutter, for instance as shown in FIGURE 1, one or more of such devices may be mounted in bores in a radially-extending strut jointing two concentrically-arranged gutters, or in a plurality of such struts.

Such an arrangement is shown in FIGURES 4 and 5 which illustrates reheat equipment in the jet pipe of a gas turbine engine. The reheat equipment comprises a spider support 31 mounted in the jet pipe 30, annular reheat fuel manifolds 32 feeding fuel to injectors 33 the manifolds being supported by struts 34 mounted on the spider 31, and a flame stabiliser comprising an outer annular gutter 35 supported by struts 36 from the spider 31 and an inner annular gutter 37 which is connected to the gutter 35 by angularly spaced V-section sheet metal struts 38. The struts 38 each house one or more catalytic elements as above described. For instance in FIGURE 4, each strut 38 houses two catalytic devices 39, such as are shown in FIGURE 3, and in FIGURE 5 a strut 38 is shown housing a single catalytic device 40 having two radially spaced flow passage 4012 each housing a catalytic element. Clearly the base of the strut 38 has holes 38a in it registering with the inlet ends of the flow passages of the catalytic device, or devices. The catalytic devices are retained in position by indenting the sides of the strut 38 into grooves 40a in the casing of the catalytic element 40 and by angle-section metal strips 42 and top and bottom retaining plate 43 which are welded on to the strut.

We claim:

1. A prime mover ignition device adapted to promote auto-ignition of fuel injected into a combustion supporting gas stream, or to promote combustion stability, or both, comprising a mass of refractory material and a foraminate element of platinum, or rhodium, or iridium, or alloys of these, or other suitable metal having catalytic properties in promotion of combustion, the foraminate element comprising a portion in the form of spiral roll which has a plurality of spaced convolutions and is located axially in a flow passage, extending in the refractory mass between those surfaces thereof which in use face upstream and downstream in the gas stream and a portion in the form of a disc at the downstream end of the flow passage, the disc portion at the downstream end being formed to a T-shaped and the leg of the T-section being inserted into a slot or notch in the refractory mass and the spiral roll portion.

2. A prime mover ignition device adapted to promote auto-ignition of fuel injected into a combustion supporting gas stream, or to promote combustion stability, or both, comprising a mass of refractory material and a foraminate element of platinum, or rhodium, or iridium, or alloys of these, or other suitable metal having catalytic properties in promotion of combustion, the foraminate element comprising a portion in the form of spiral roll which has a plurality of spaced convolutions and is located axially in a flow passage, extending in the refractory mass between those surfaces thereof which in use face upstream and downstream in the gas stream, a tube which the spiral roll surrounds, and an upstream plate which is folded to a T-shape to increase mechanical strength and also to increase the amount of heat transferred to the incoming gas mixture.

3. A prime mover ignition device adapted to promote auto-ignition of fuel injected into a combustion supporting gas stream, or to promote combustion stability, or both, comprising a mass of refractory material and a foraminate element of platinum, or rhodium, or iridium, or alloys of these, or other suitable metal having catalytic properties in promotion of combustion, the foraminate element comprising a portion in the form of spiral roll which has a plurality of spaced convolutions and is located axially in a flow passage, extending in the refractory mass between those surfaces thereof which in use face upstream and downstream in the gas stream, the spiral roll of the foraminate element extending between upstream and downstream disc portions, the refractory mass comprising a cylindrical part with the spiral roll in a bore extending through it and with the discs lying against its end surfaces, a cup-shaped refractory casing housing the cylindrical part and having a hole in its base co-axial with the bore of the cylindrical part and a refractory closure plate cemented to the end of the casing remote from its base, the closure plate having a hole in it co-axial with the bore, the downstream disc being folded to a T-shape, the limbs of the fold being welded together and being inserted in a diametral slot in the cylindrical part and the spiral roll.

4. A prime mover ignition device adapted to promote auto-ignition of fuel injected into a combustion supporting gas stream, or to promote combustion stability, or both, comprising a mass of refractory material and a foraminate element of platinum, or rhodium, or iridium, or alloys of these, or other suitable metal having catalytic properties in promotion of combustion, the foraminate element comprising a portion in the form of spiral roll which has a plurality of spaced convolutions and is located axially in a flow passage, extending in the refractory mass between those surfaces thereof which in use face upstream and downstream in the gas stream, the spiral roll of the foraminate element extending between upstream and downstream disc portions, the refractory mass comprising a cylindrical part with the spiral roll in a bore extending through it and with the discs lying against its end surfaces, a cup-shaped refractory casing housing the cylindrical part and having a hole in its case co-axial with the bore of the cylindrical part and a refractory closure plate cemented to the end of the casing remote from its base, the closure plate having a hole in it coaxial with the bore, and a metal retaining pin extending across the bore of the cylindrical part and through the convolutions of the spiral roll to retain the spiral roll within the bore.

5. A prime mover ignition device adapted to promote auto-ignition of fuel injected into a combustion supporting gas stream, or to promote combustion stability, or both, comprising a mass of refractory material and a foraminate element of platinum, or rhodium, or iridium, or alloys of these, or other suitable metal having catalytic properties in promotion of combustion, the foraminate element comprising a portion in the form of spiral roll which has a plurality of spaced convolutions and is located axially in a flow passage, extending in the refractory mass between those surfaces thereof which in use face upstream and downstream in the gas stream, the foraminate element further comprising an upstream disc, a tube part and a downstream end disc welded to the tube and having a central hole aligned with the tube bore, the

spiral roll surrounding the tube part, and the refractory mass comprising a cup-shaped member housing the tube and spiral roll and having the tube extending through a hole in its base, the downstream end disc lying against the external surface of the base, a refractory casing having a recess housing the cup-shaped member, a collar cemented in the open end of the recess to retain the cupshaped member and foraminate element in position, and a ring of refractory material between the bottom of the recess and the disc, the collar having a hole registering with the tube bore and the casing having a hole extending from the bottom of the recess to the downstream surface of the casing.

6. A device according to claim 5, the upstream disc being folded to a T-shape, the leg of the T being inserted in a transverse slot in the tube and in the convolutions of the spiral roll.

References Cited by the Examiner UNITED STATES PATENTS Williams et a1.

DONLEY J. STOCKING, Primary Examiner. ABRAM BLUM, SAMUEL LEVINE, Examiners.

Claims

1. A PRIME MOVER IGNITION DEVICE ADAPTED TO PROMOTE AUTO-IGNITION OF FUEL INJECTED INTO A COMBUSTION SUPPORTING GAS STREAM, OR TO PROMOTE COMBUSTION STABILITY, OR BOTH, COMPRISING A MASS OF REFRACTORY MATERIAL AND A FORAMINATE ELEMENT OF PLATINUM, OR RHODIUM, OR IRIDIUM, OR ALLOYS OF THESE, OR OTHER SUITABLE METAL HAVING CATALYTIC PROPERTIES IN PROMOTION OF COMBUSTION, THE FORAMINATE ELEMENT COMPRISING A PORTION IN THE FORM OF SPIRAL ROLL WHICH HAS A PLURALITY OF SPACED CONVOLUTIONS AND IS LOCATED AXIALLY IN A FLOW PASSAGE, EXTENDING IN THE REFRACTORY MASS BETWEEN THOSE SURFACES THEREOF WHICH IN USE FACE UPSTREAM AND DOWNSTREAM IN THE GAS STREAM AND A PORTION IN THE FORM OF A DISC AT THE DOWNSTREAM END OF THE FLOW PASSAGE, THE DISC PORTION AT THE DOWNSTERAM END BEING FORMED TOA T-SHAPED AND THE LET OF THE T-SECTION BEING INSERTED INTO A SLOT OR NOTCH IN THE REFRACTORY MASS AND THE SPIRAL ROLL PORTION.