US2704435A - Fuel burning means for a gaseous-fluid propulsion jet - Google Patents

Description

March 22, 1955 5 ALLEN 7 2,704,435

FUEL BURNING MEANS FOR A GASEOUS-FLUID PROPULSION JET Filed May 2, 1,951

l4 l6 l2 l2 l4 I6 7 2| FIGI FIGZ m/mv'roe gummy ALLEN United States Patent FUEL BURNING MEANS FOR A GASEOUS-FLUID PROPULSION JET Sidney Allen, Coventry, England, assignor to Armstrong Siddeley Motors Limited, Coventry, England Application May 2, 1951, Serial No. 224,098

Claims priority, application Great Britain July 17, 1950 2 Claims. (Cl. 6035.6)

This invention relates to a fuel-burning means, for a gaseous-fluid propulsion jet, of the kind having a flame stabilizing device arranged to provide a flame such as will ensure the combustion of fuelparticularly for after burning in, or re-heating, the oxygen-containing exhaust gas of a gas turbine engine for the propulsion of an aircraft, though the invention can also be applied to the burning of fuel in a ram-jet.

The importance of a flame stabilizing device, for reheat fuel, arises from the fact that the exhaust gases of a gas turbine engine may have a speed in the exhaust pipe of the order of 500 feet per second. The same difficulty arises, in general, as regards the burning of fuel in a ram-jet.

One satisfactory form of flame stabilizing device is disclosed in the specification of co-pending patent application cl1 Io. 186,251, filed September 22, 1950, now abanone The main object of the present invention is to ensure satisfactory control of the combustion of re-heat" fuel, and, furthermore, that the high temperatures generated in the jet pipe (as a result of re-heating) will not damage the adjacent part of the jet pipe or air frame.

According to the invention, a fuel-burning means, for a gaseous-fluid propulsion jet, includes a flame stabilizing device which is disposed relatively to a casing, within and spaced annularly from the wall of the jet pipe, so as to be, in end elevation, within the cross-sectional area of the casing, and means for supplying fuel to an appropriate part of the casing to ensure proper combustion of the fuel.

In the accompanying diagrammatic drawing:

Figure 1 is a line diagram of the tail end of the turbine of a gas turbine engine, and of the upstream end of the exhaust or jet pipe thereof incorporating one form of fuel-burning means according to the invention;

Figure 2 is a line diagram of the upstream end of a p'pe for a propulstion jet incorporating another form of fuel-burning means; and

Figure 3 is a sectional elevation of a preferred form of fuel-burning means in a jet pipe of a gas turbine engine, Figure 4 being a sectional view from the right of Figure 3.

In all the figures the reference numeral 11 is applied to the flame stabilizing device, and 12 to a pipe by means of which a pilot supply of fuel can be delivered thereto. It will be observed that the stabilizing device includes a frusto-conical casing with its smaller end upstream.

Likewise, in all the figures, the reference numeral 14 denotes the casing which, according to the invention, is associated with the flame stabilizing device, the upstream end of the casing 14 having an annular manifold 15 round it from which fuel is sprayed into the interior of the easing 14, the fuel being delivered to the manifold 15 by a supply pipe 16. The manifold 15 need not, of course, be exactly at the upstream end of the casing 14, and it may be disposed at any radial position in the annular space between the casing and the stabilizing device. The reference numeral 18 is applied to the wall of the exhaust or jet pipe.

Figure 1 indicates at 20 the tail end of the turbine carrying a row of blades 21, and abutting the tail end of the turbine is the usual inner exhaust cone 22 forming with the outer exhaust cone 23 the usual exhaust diffuser passage leading to the upstream end of the jet pipe 18.

It will be observed that, in Figure 1, the casing 14 is disposed so as to be entirely upstream of the stabilizmg device 11. In the alternative construction of Figure 2,

2,704,435 Patented Mar. 22, 1955 "ice the casing 14 is disposed so as to be entirely downstream of the stabilizing device 11, the casing 14 being disposed relatively to the stabilizing device so that the flame from the latter will enter the casing 14. In the preferred arrangement of Figures 3 and 4, the casing 14 is disposed actually to encircle the stabilizing-device 11, their upstream ends being substantially co-planar.

The stabilizing device shown in Figures 3 and 4 has a centrally-disposed baffle 25 at its upstream end joined to the smaller end of the casing by fixed, swirl-introducing vanes 26-as disclosed in the specification aforesaid. The pilot supply of fuel from the pipe 12 is delivered through nozzle openings 27, on opposite sides of the pipe, into and against the direction of the swirl of the exhaust gases in the stabilizing device. The latter is shown as being supported from the casing 14 by angularly-spaced, streamlined struts 28, and the casing 14 is shown as being supported from the jet pipe wall by means of angularlydisposed, streamlined struts 29.

In a simple construction according to the invention, only a single casing 14 (and associated flame stabilizing device) would be used, the casing 14 being cylindrical and of a size (as regards cross-section area) determined by the percentage of exhaust re-heating it is desired to obtain. That is to say, the size of the casing 14 is chosen such that the amount of oxygen-containing gases passing through it will be sufficient to elfect complete burning of the re-heat fuel, the remainder of the exhaust gases passing externally of the casing 14. These exterior gases will not, of course, have their temperatures raised to any dangerous extent, and, in consequence, the jet pipe is protected in the region of the casing 14 where the reheating is being effected.

In the case which the re-heating is mainly effected in the casing 14 (Figures 2 and 3, particularly), some of the re-heat fuel may be directed onto the interior walls of the casing 14 to promote the cooling thereof, and the lower temperature of the non re-heated exhaust gases outside the casing will also have a cooling effect on the smg. It should be understood that in those cases in which flaming gases pass from the outlet end of the casing 14 (Figures 2 and 3), these gases will fan out and, in so doing, will mix with the exhaust gases which have passed externally of the casing. It is desirable that a substantially uniform temperature should be obtained across the whole area of the exhaust nozzle 30 (Figure 3) at the outlet end of the jet pipe.

In cases in which it is desired that a higher mean temperature of the exhaust gases should be obtained, use can be made of two or more casings, as shown at 14a, 14b in Figures 3 and 4, to provide effective control of the combustion. Thus, in one alternative arrangement to that described above, a second casing 14a, of larger diameter than the first 14, is arranged downstream, and preferably to overlap the outlet end, of the first casing 14, and is provided, preferably at its upstream end, with its own supply of re-heat fuel, by way of the manifold 15a. If maximum re-heat is required (i. e., where the excess oxygen in the exhaust gases is to be used as completely as possible), it may be necessary to employ a series of such casings and fuel supplies, as indicated by the third casing 14b and manifold 15b, the upstream end of each preferably overlapping the downstream end of the previous one as shown. Fuel supplies for the second and third manifolds are respectively indicated at 16a, 16b, and supporting struts for the casings 14a, 14b, at 29a, 29b: but, as previously stated, the manifolds 15a, 15b need not be exactly at the upstream ends of the casings 14a, 14b, or of the actual diameters of these casings.

What I claim as my invention and desire to secure by Letters Patent of the United States is:

1. A fuel-burning means, for a gaseous fluid propulsion jet, including a jet pipe through which hot jet gases pass, an open-ended casing within and spaced annularly from said jet pipe, a flame stabilizing device disposed relatively to said casing so as to be, in end elevation, within the cross-sectional area of said casing and comprising a hollow diffuser member round and through which the hot jet gases pass and within which is to be burnt a pilot supply of fuel to produce a stable flame issuing at the downstream end, means for supplying fuel to an appropriate part of said casing to ensure proper combustion of the fuel, a second casing, of larger diameter than the first casing, within and spaced annularly from said jet pipe and disposed to be mainly downstream of said first casing, and means for supplying fuel to an appropriate part of said second casing to ensure proper combustion of this fuel.

2. A fuel-burning device for a gaseous fluid propulsion jet engine comprising a jet pipe adapted to have oxygen bearing exhaust gases from the engine flow therethrough, a casing within and spaced annularly from said jet pipe and disposed in the path of at least some of the exhaust gases passing through said jet pipe so that some of said gases will pass through the easing, a flame stabilizing diffuser member of substantially frusto-conical shape disposed relatively to said casing so as to be, in end elevation, within the crosssectional area of said casing and disposed in the path of at least some of the exhaust gases passing through the casing so that some of said gases will pass through said diffuser member, said ditfuser member having its smaller end disposed upstream, pilot fuel supply means for said diffuser member near the smaller end of the diffuser member, said pilot fuel being vaporized by said exhaust gases passing through said diffuser member, means for igniting said pilot supply, means for supplying fuel to an appropriate part of said casing to ensure proper combustion of the fuel, a second casmg of larger diameter than the first casing disposed within and spaced annularly from said jet pipe with its major portion downstream of said first casing, and means for supplying fuel to an appropriate part of said second casing to ensure proper combustion of this fuel, said second casing adapted to receive re-heated exhaust gases from said first casing and to receive some of the exhaust gases passing through said jet pipe.

References Cited in the file of this patent UNITED STATES PATENTS 2,417,445 Pinkel Mar. 18, 1947 2,517,015 Mock et al. Aug. 1, 1950 2,518,000 Goddard Aug. 8, 1950 2,520,388 Earl Aug. 29, 1950 2,545,495 Sforzini Mar. 20, 1951 2,548,087 Williams Apr. 10, 1951 2,560,207 Berggren et al. July 10, 1951 2,592,110 Berggren et al. Apr. 8, 1952

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