Combustion chamber fluid inlet construction

Jan. 29, 1963 l. _w. shutts 3,075,352

COMBUSTION CHAMBER FLUID INLET CONSTRUCTION

Filed Nov. 28, 1958 2 Sheets-Sheet 1

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ΑΤΈΟΕΜΕΈ

Jan. 29, 1963 _L_ _w shutts 3,075,352

COMBUSTION CHAMBER FLUID INLET CONSTRUCTION

Filed Nov. 28, 1958 ₂ Sheets-Sheet 2

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ATTO/WEY

United States Patent Office „ 3,075352

Patented Jan. 29, 1963

3,075,352

COMBUSTION CHAMBER FLUID INLET CONSTRUCTION

Leroy W, Shutts, Indianapolis, Ind., assignor to General Motors Corporation, Detroit, Mich., a corporation of Delaware

Filed Nov. 28,1958, Ser. No. 776,928 5 Claims. (Cl. 60—39.65)

This invention relates to a combustion apparatus.

More specifically, this invention relates to the particular construction of a combustion chamber in a gas turbine engine, the construction being such as to reduce the time necessary to provide a combustible mixture of fuel and air therein, thereby moving the flame front closer to the forward section of the combustion chamber and permitting the use of a shorter combustion can. This therefore reduces the cost of the engine, the weight, and drag, therefore improving the engine.

This invention provides the dome of the combustion can with a stepped cone construction, the overall contour of the stepped cone approximately paralleling the fuel spray cone path. Additionally, the steps of the cone are provided with air inlets at right angles to each other so that small local air jets or vortices are provided to rapidly mix the air and fuel vapor thereby quickly producing a combustible mixture therein.

Therefore, an object of this invention is to provide a combustion can construction such that the proper fuelair mixture is obtained as quickly as possible, therefore . moving the flame front as close as possible to the forward end of the combustion can, permitting a reduction in length of the can.

A further object of the invention is to provide better mixing of the air with the fuel discharged into a combus- ; tion can from the fuel nozzle by providing a multiplicity of air jets producing minute individual vortices quickly intermixing the fuel vapor with the air.

It is a still further object of this invention to provide a combustion can dome structure such that the primary 40 air intermixing with the fuel spray is evenly intermixed by providing air introduction means presenting the air to the primary inlets free from the effects of ram air velocity.

Other features, advantages and objects will become apparent by reference to the detailed description of the 45 invention and to the drawings wherein there is shown the preferred embodiments of this invention.

In the drawings:

FIGURE 1 is a side elevational view of a gas turbine engine embodying this invention with parts broken away 50 and sectioned,

FIGURE 2 is a cross-sectional view through the combustion section on a plane indicated by the lines 2__2 of FIGURE 1,

FIGURE 3 is an enlarged longitudinal cross-section 55 view of the dome on a plane indicated by the lines 3—3 of FIGURE 2,

FIGURE 4 is an end view with parts broken away of the dome of FIGURE 3 on a plane indicated by the lines 4—4 of FIGURE 3.

Reierring now to the drawings and more particularly to FIGURES 1 and 2, there is shown therein schematically a portion of a gas turbine engine 10 having a compressor section 12 of the axial flow type, a diffuser section 14, a combustion section 16 and a turbine section 18 (only partially shown). The combustion section consists of a cannular chamber 20 having an outer wall defined by the engine casing 22 and an inner wall defined by the shroud 24. Positioned within and axially spaced circumferentially around the combustion chamber are a number of combustion cans 26 having the usual igniter plugs 28 inserted therein, the cans being connected to each other by crossover tubes 30 for the propagation of the flame therebetween. As is conventional, only one or two of the igniter plugs 28 need be “live,” the remaining plugs being “dummy” plugs.

The combustion can is generally of a cylindrical shape as shown, with a convergent transition section 32 at one end cooperating with the turbine inlet vanes of the turbine section 18, and a dome end 34 connected to and supported by a fuel nozzle 36 having a connection 38 to a fuel supply line adjacent the diffuser section 14. The cans are generally constructed of overlapping annular sections 40 with spacer members 42 therebetween for air cooling purposes, sections 40 and members 42 being welded together at their corrugated edges (not shown). Dilution air holes 44 and reinforcing members 46 are also provided. The construction of the cans as so far described is known and the details thereof are immaterial to. the present invention, and therefore no further details will be described. The construction of the dome 34 in a manner to permit entry of primary air therethrough to intermix with the fuel spray, which is the subject of this invention, will now be described.

Referring now more in detail to FIGURES 3 and 4 showing detailed cross-sectional and end views of the subject combustion can, it will be seen that the combustion can dome 34 has a flat or blunt nose dome 48 closing the upstream end of the combustion can. Centrally thereof at the axis of the can is an annular aperture or opening 50 for the insertion therein of the fuel nozzle 36 inserted into the dome of the combustion can for supporting the can. The can is provided with a boss 54 inserted through the longitudinal wall of the can as shown for receiving therein a conventional igniter plug 56 fixed to the engine casing 22 and extending towards the center of the can as shown. Fixedly secured to the after part of the can is the stepped cone dome 58 forming the subject of this invention. The stepped cone constitutes an inner annular wall of the combustion can and its general overall outline substantially parallels the conventional cone-shaped fuel spray pattern imposed on the fuel by the fuel nozzle 36 to fill as much of the diameter of the dome as possible. The stepped cone 58 has a wavy or zigzag outline or periphery as shown comprising a single piece of sheet metal corrugated or bent i in steps to comprise a number of axially extending portions 60 alternated with radially extending portions 62, the finished cone appearing as a stepped shape. As shown, each of the axial portions 66' is provided with a number of circumferentially spaced holes or apertures 64 through which the air is admitted with a jet effect producing small scale turbulent areas on the aft side of the cone. The radial portions 62 are likewise provided with a number of circumferentially and equally spaced apertures or openings 66 for the admission of gas therethrough. The particular number and size of the apertures at each step ye chosen so as to produce the greatest number of vortices possible to produce the maximum mixing of the fuel and air, the size of the apertures increasing with an increase in the radial distance from the axis because of the need for a greater volume of air to properly mix with the greater volume of fuel spray. The number of radial and axial apertures at each step of the dome are equal, while the number of apertures at different steps, is different. It is to be noted by reference to the drawings that the axial and radial apertures 64 and 66 at each step of the dome are offset laterally or staggered circumferentially with respect to each other so that the radial and axial jets of air will pass or cross over each other to set up a swirling action between the two to produce a great number of small vortices completely filling the areas immediately adjacent the fuel spray cone with small side turbulences so that better and quicker mixing of the fuel with the air is accomplished.

3,075,352 having a plurality of openings therein for the admission of gas therethrough directly into said chamber, an inner annular corrugated wall secured to portions or the end and longitudinal walls of said member, the overall shape of said inner wall substantially paralleling’ the cone-shape of said fuel spray, said inner wall comprising ,a plurality of annular axially and radially extending portions axially alternated with each other and joined at their adjacent edges, each of said adjacent portions having a plurality of circumferentially spaced apertures therein, each of the axially adjacent apertures being substantially at right angles to the other for the admission of gas therethrough in a plurality of spaced jet paths in different planes, the spacing of said paths imparting a swirling motion to said gas adjacent each of said apertures, tne admission of gas through the apertures in said outer wall distributing said gas evenly to the apertures in said inner wall, the admission of gas through the apertures in said inner wall providing efficient atomization of the fuel 20 spray therein by the creation of local vortices adjacent said apertures due to said swirl, the apertures in the radial portions of said inner wall being offset circumferentially in a staggered manner with respect to the apertures m the adjacent axial portions of said inner wall to impart said 25 swirling motion to the gas admitted therethrough by the passage of one gas jet over another.

2. A combustion chamber for burning fuel therein having a perforated fuel and gas inlet wall portion, means projecting fuel through said wall portion in a spray pat30 tern generally parallel to the overall shape of said wall portion and spaced from the wall portion, said wall portion comprising a plurality of successively arranged strips of substantially equal width at an angle to each other and joined at their adjacent edges to provide a step-like 35 corrugated aspect having substantially equally proportioned corrugations, each of said strips having a row of perforations for the admission of gas therethrough in jet streams directly into said chamber and at substantially equal angles to the line of projection of said fuel, the ⁴⁰ perforations of adjacent strips being misaligned with respect to each other so that the jets of gas at angles to each other pass each other without direct impingement thereby setting up local turbulences in the area of mixture of the fuel and gas promoting intimate mixture of the fuel and gas.

3. A combustion chamber for burning fuel therein having a perforated fuel and gas inlet wall portion, means projecting fuel through said wall portion in a spray pattern generally parallel to the overall shape of the wall 50 portion and spaced therefrom, said wall portion comprising a plurality of successively arranged strips approximately at right angles to each other and joined at their adjacent edges to provide a step-like corrugated aspect, each of said strips having a row of perforations for the 53 admission of gas therethrough in jet streams at right angles to each other and directly into said chamber and proximate to said fuel at substantially equal angles to the peripheral line defining said fuel spray pattern, the perforations of adjacent strips being staggered lengthwise of the 60 strips so that the jets of gas at right angles to each other pass each other without direct impingement thereby setting up local turbulences in the area of mixture of the fuel and gas promoting intimate mixture between the fuel and gas.

4. A combustion chamber having a perforated pyramidal-shaped gas and fuel inlet wall portion, said wall portion consisting of a tier of cylindrical strips of substantially equal axial width with successive strips having diameters increased by substantially equal increments, each ⁷⁰ of said strips having a row of gas jet orifices therein, said strips being joined at adjacent edges by an annular radially extending strip of substantially uniform width secured thereto having a similar row of gas jet orifices, the mutu₇₅ ally adjacent strips together providing orifices at right

A number of circumferentially spaced baffle members 68 are secured to the inner dome wall 53 as shown in FIGURE 4 to act as gas or air deflectors imparting a swirl to the air to cause the air to continually wash the inside surface of the can immediately adjacent the baffles thereby cooling the can at this portion. Because of the apertured stepped cone construction producing a quicker combustible mixture of the fuel and air, the flame front, which in previous combustion can constructions held a position at about the baffle plates, now moves : forward closer to the dome wall.

The compressor discharge air as delivered to the diffuser section 14 is introduced to the stepped cone dome wall through the blunt end 4§ of the combustion can by way of a number of spaced apertures or holes 70. The primary purpose of these holes 7® is for distributing the air therethrough into contact with the inner stepped cone dome 58 so that the air entering through the apertures 64 and 66 in the dome will have a more uniform pressure and be free from the impact pressure’and other uneven velocity effects of the ram air. The air entering through the openings 70 thus fills the chamber 72, which in effect is a plenum chamber, and is evenly distributed over the entire outer surface of the stepped dome 58.

The operation of the gas flow through the combustion can is therefore as follows. The air discharged from the compressor outlet 74 is delivered to the combustion can dome 34 with great ram velocity and enters through holes 70 in the combustion can dome end 48 to fill the chamber 72. Chamber 72 causes the air to be evenly distributed to the apertures 64 and 66, that is, tne air entering through the holes 70 breaks up the mass of ram air so that these and other effects are not relayed into the apertures 64 and 66. The compressor discharge air therefore enters the holes 64 and 65 creating a great number of small local vortices or turbulences adjacent each , of the holes, the staggering of the axial and radial holes of each step imparting the swirl to the jets of air by the one crossing over the other. At the same time, the fuel is being fed through the fuel nozzle 36 and sprayed into the combustion can in substantially a cone shape path, the path approximately paralleling the overall average periphery of the inner wall or dome 58. The individual turbulent air swirls created on the downstream δία^ of the holes 64 and 66 therefore strike the fuel spray im- , mediately mixing therewith to quickly produce a combustible mixture which can be immediately ignited to cause the flame front 78 to hola as close as possible to the front of the combustion can. By movement of the flame front closer to the combustion can, the length of the combustion can can be decreased thereby decreasing the weight, cost and drag of the engine.

Therefore, it will be seen that this invention provides a combustion can construction that reduces ffie time necessary to provide the proper fuel-air mixture for combustion while increasing the efficiency and reducing the overall length of the combustion can. While the combustion can dome has been shown in these figures in its preferred form, it will be clear to those skilled in the art that many modifications can be made therefrom without departing from the scope of the invention.