US2959006A - Semi-vaporisation burner - Google Patents

Description

Nov. 8, 1960 F. G. M. FERRl SEMI-VAPORISATION BURNER 3 Sheets-Sheet 1 Filed Jan. 28, 1958 I Nov. 8, 1960 F. e. M. FERRIE 6 SEMI-VAPORISATION BURNER Filed Jan. 28. 1958 3 Sheets-Sheet 2 Nov. 8, 1960 F. G. M. FERRl 2,959,006

SEMI-VAPORISATION BURNER F'iled Jan. 28, 1958 3 Sheets-Sheet 3 Zh enfif 4/ Ji 1%; M M fia, MIMV United States Patent SEMI-VAPORISATION BURNER Franck Guillaume Michel Ferric, Cachan, France, as-

signor to Societe Nationale dEtude et de Construction de Moteurs dAviation, a company of France Filed Jan. 28, 1958, Ser. No. 711,581

Claims priority, application France Feb. 1, 1957 Claims. (Cl. 60-3957) For improving the combustion in the chambers of jet propulsion units, notably for high-altitude and high-speed flight, it is necessary to provide a mixture of air and fuel which is as homogeneous as possible and to have a very stable pilot flame, in contact with which the ignition of the air-fuel mixture is maintained.

The vaporisation of the fuel is very favourable, but it. cannot be fully effected by reason of the excessive rates. of flow which would necessitate prohibitive vaporisation surfaces and a too considerable weight.

Consequently, the present invention has for its object to provide a burner device operating both with atomisation and vaporisation of the fuel. The said device comprises tubes, the Walls of which are adjacent to a flame zone, so that they are highly heated, and through which the mixture of air and fuel to be vaporised flows. These tubes finally conduct the said mixture into contact with a pilot flame maintained on the downstream side of a screen, which protects it from the incident flow.

Such a device, which is particularly applicable to annular combustion chambers, may be constructed in the form of a profiled'b'ody situated at the inlet to the combustion chamber, which serves as a screen for the pilot flame, and on which tubes of appropriate cross-section and shape are fixed in radial planes with a chosen spaced relationship, so as to obtain a good distribution of the air and to promote the exchanges of fresh air and gas on the downstream side of the burner.

The description which follows with reference to the accompanying drawings, which are given by way of nonlimitative example, will enable the manner in which the invention can be carried into effect to be readily understood, the features appearing both from the drawings and from the text naturally forming part of the said invention.

Figure 1 is an axial sectional view of a first constructional form of a burner according to the invention for an annular combustion chamber.

Figure 2 is a view in the direction of the arrow X of Figure l, in which, however, the injectors 6 have been omitted for the sake of clarity.

Figure 3 is an axial sectional view of another constructional form of the burner.

Figure 4 shows a further modified form.

In the construction according to Figures 1 and 2, the burner disposed at the inlet to the annular chamber 1 (of which the axis is situated at the point at which the radial planes aa and b-b bounding Figure 1 meet) consists of a deflector ring 2 of V-shaped cross-section, of which the wider portion is directed downstream. Tubes 3 backwardly curved in such manner that their ends bear against the flanks of the section iron of the ring 2 are disposed in radial planes of the combustion chamber. The radial portion of each of these tubes is formed with holes 4, which may open in the upstream and downstream directions as in Figure 1 or may also open in the upstream direction or laterally, or may be quincuncially formed, depending upon the result aimed at, without departing from the scope of the invention.

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The ring 2 is formed on the upstream side with holes 5, through which there passes a portion of the mixture of air and fuel, obtained by atomisation of the fuel on the upstream side of the burner through the orifices 7 in the injectors 6. When the combustion chamber is ignited, this carburetted mixture is ignited on the upstream side of the ring 2 with the aid of a sparking plug or glow plug or any other device, and burns within the space 10 between the tubes 3. The flame thus obtained constitutes the pilot flame protected from the general flow by the screen formed by the deflector ring 2.

A portion of the fuel atomised by the injectors 7, 8, 9 penetrates into the tubes 3, which are also entered by the air coming from the compressor, along the path indicated by the arrows.

The carburetted mixture flowing within the tubes 3 heated by the pilot flame is vaporised in contact with the hot walls of these tubes, passes through the holes 4, is ignited in contact with the pilot flame and burns with a very short flame, the vaporising tubes 3 performing the function of flame stabilisers. It will be seen that the burner comprises in principle two successive flame traps. The first consists of the deflector ring 2 and the second is a grid formed by the vaporisation tubes in themselves. It should be noted that the carburetted mixture introduced into each tube at 3 and 11 forms two opposed fluxes in the radial portion 12 of the tubes, whereby there is produced within this portion an intense turbulent movement favourable to a good heat exchange with the walls of the tubes.

The injectors may operate with double flow, the nozzles 8 and 9, for example, providing the main flow, while the nozzles 7 provide the basic and starting flow. Owing to this arrangement, it is possible by appropriately choosing the positioning of the nozzles, to admit into the tubes only the quantity of fuel which is capable of being completely vaporised. Although the design of this burner provides a very large vaporisation surface with minimum Weight, the quantity of fuel which can be vaporised is limited. Consequently, the flow of fuel through the tubes (which varies with the positioning of the nozzles) must be adjusted to correspond to the maximum vapour production.

The fuel atomised at 8 and 9 has the whole length of the chamber in which to burn and its passage through the zone heated by the flame (which is maintained by the nozzles 7 and by the mixture vaporised in the tubes 3) permits the vaporisation of the fuel droplets not burnt in the first part of their travel.

In the modification of Figure 3, straight tubes 14 and 15 are welded in opposite pairs to the deflector ring 13 of V-shaped cross-section (which have any alternative aerodynamic form). A bank of fuel injector orifices 18 feeds the pilot flame on the downstream side of the screen formed by the ring 13. The said flame meets the tubes 14 and 15.

A portion of the carburetted mixture obtained by atomisation of fuel by the sets of injector orifices 17 on the upstream side of the ring 13 penetrates into the said tubes, in which it vaporises before being directed by the deflectors 16 welded to the tubes towards the center of the burner, where this mixture is ignited in contact with the pilot flame.

The modified form of Figure 4 is derived from the constructional form of Figure 1, and comprises two additional annular deflectors 19 designed for a better trapping of the flame in the primary zone. These defletcors are formed with holes 20, through which the fuel mixed with the air can feed the trailing zone formed on the downstream side of these deflectors. The more effectively protected flame passes between the tubes (as indicated by the arrows in the figure) and a more intense heating of the said tubes and consequently a greater quantity of vapour are thus obtained. In addition, the fuel leaving the nozzles 9 and 8 is better canalised towards the tubes, the coefficient of filling of which is improved and can be more readily adjusted. A number of interconnecting tubes 22 may be provided at intervals along the periphery of the ring to facilitate the passage of the flame from the central deflector 2 to the deflectors 19. These tubes also promote the ignition of the burner as a whole.

The said burner devices, which have been described as applied to annular combustion chambers, may be adapted for tubular chambers with a number of modifications.

These burners have the following advantages:

Good distribution of the return zones and of the direct air inlets arranged in successive sets;

Large heat exchange surface permitting a high fuel vapour production capacity.

Good cooling (by circulation of cold gas and vaporisation) of the material of which the burner is constructed, which has greater resistance although situated in the hottest part of the chamber.

Increase in the period for which the mixture to be' vaporised remains in the tubes.

The'combustion can take place in such manner that the atomised fuel, which requires a larger combustion space, burns before the chamber, while the vaporised fuel.

burns at the rear of the chamber, which is favourable to the output and assists in shortening the flame.

Readier combustion at low pressures, that is to say, athigh altitude.

What is claimed is:

1. In an annular combustion chamber bounded bytwo coaxial walls and supplied with a high-velocity gaseous flow, a burner device comprising a plurality of arcuately spaced tubular systems extending in radial planes between said coaxial walls and at a distance therefrom, each tubular system being located entirely on one side of the axis of said annular combustion chamber and comprising two radially spaced tubular sections having front inlets facing upstream to collect fractions of said flow and rear means for diverting the collected fractions in a radial direction, the tubular section farther from said axis diverting the collected fraction towards said axis and the tubular section closer to said axis diverting the collected fraction away from said axis, whereby the two collected fractions impinge on each other about half-way between said diverting means and engage a central portion of the flow between said tubular sections, first means for injecting fuel upstream of said front inlets of said tubular sections so that said tubular sections collect fuel as well as fractions of the high velocity gaseous fiow, second means for injecting fuel into said central portion, and means for holding a flame therein.

2. Burner device as claimed in claim 1, wherein the diverting means consists of oppositely directed bends at the rearmost part of the tubular sections of each system.

3. Burner device as claimed in claim 2, comprising a radial ported duct interconnecting the oppositely directed ends of the tubular sections of each system.

4. Burner device as claimed in claim 3, wherein the ports in the duct point in directions radiating from the axis of said duct.

5. Burner device as claimed in claim 1, wherein the flame holding means comprise two coaxial, oppositely inclined, frusto-conical plates bounding a central annular divergent space, and wherein the tubular systems are supported by said plates, the tubular sections" of said systems being fast with said plates and located on the outer side thereof. with respect to said central space.

References Cited in the file of this patent UNITED STATES PATENTS 2,548,087 Williams Apr. 10,1951 2,612,023 Morrison Sept. 30, 1952 2,635,426 Meschino Apr. 21, 1953 2,830,439 Johnson et al. Apr. 15, 1958

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