Air Inlet Arrangement For Gas Turbine Engine Combustion Chamber

Abstract

A combustion chamber to gas turbine engines equipped with a flame tube provided with air inlet openings for combustion and mixing air; further air inlet openings are provided in the flame tube at the level of the combustion chamber end wall, through which small quantities of air are adapted to be blown radially inwardly toward the discharge point of the fuel injection nozzle. This invention relates to a combustion chamber for gas turbine engines, whose flame tube contains air inlet openings for the supply of combustion and mixing air. As a rule, the ratio of the cross-sectional areas of the primary and secondary air inlet openings is so chosen that the fuel-air mixture in the combustion zone of the combustion chamber is approximately stoichiometric. It is well known, however, that in this case frequently zones of a richer fuel-air mixture occur so that combustion in these zones is only incomplete, with resulting deposits of carbon black on the end wall of the combustion chamber and/or pollution of the exhaust gases. This is particularly true for combustion chambers incorporating a flameholder, since in the same there is little or no air introduced into the spraying zones of the fuel injector. Among the known measures that have been employed to avoid such carbon deposits are an increase in the proportion of primary air and the use of additional small air inlet ports in the susceptible, endangered zones. Both of these measures, however, can be used only to a limited extent because an increased proportion of primary air will result in a poor LEAN extinction limit and also because the use of too large and/or too many air inlet ports has been known to disturb the reduced pressure zone behind the flameholder. The purpose of this invention is, therefore, to eliminate the above-mentioned drawbacks of the known types of combustion chambers and to provide a combustion chamber which offers, in addition to a high degree of combustion at partial load and a good LEAN extinction limit, a combustion which produces neither carbon deposits nor a pollution of the exhaust gases. It is proposed according to the invention for this purpose, to provide air inlet openings in the flameholder arranged at the level of the combustion chamber end wall, which will blow small quantities of air radially into the flame tube in the direction of the discharge tip of the fuel injector nozzle. According to a further feature of the invention, the flame tube may be equipped with tubes and/or ribs arranged coaxially to the air inlet openings in the flame tube. The air flowing inward at a high velocity will have the following effect: 1. The excess fuel existing directly adjacent to the end wall of the combustion chamber will be removed; 2. A zone of high turbulence will be created adjacent to the combustion chamber end wall, which will have a favorable effect on the combustion process; and 3. Any carbon black particles which may still be produced will be prevented from depositing.

Description

These and other objects, features and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawing which shows, for purposes of illustration only, two embodiments in accordance with the present invention, and wherein:

FIG. 1 is a longitudinal sectional view of a reverse flow combustion chamber incorporating a flameholder;

FIG. 2 is a cross-section taken along line A - B of FIG. 1, and

FIG. 3 is a modified embodiment for the cross-section taken along line A - B of FIG. 1.

Referring now to the drawing wherein like reference numerals are used throughout the various views, and more particularly to FIG. 1, this figure illustrates the invention in connection with a reverse flow combustion chamber whose outer casing terminates at the right-hand portion of the drawing, in a flameholder 2 with the fuel injection nozzle 3 installed in its center. The outer casing 1 houses coaxially to its longitudinal axis 4 the flame tube 5 which terminates, in the right-hand portion of the drawing, between the outer casing 1 and the flameholder 2, in a rim-like or bulge-like deflector 6 which produces a favorable flow reversing section 7 for the primary air duct. Secondary air is supplied through air inlet ports 8 of circular area.

The primary air enters through the primary air reversing duct 7 in the direction of arrow E (downstream direction with respect to the flow of combustion chamber products) between the flameholder 2 and the flame tube 5 into the primary zone 9 of the combustion chamber, producing the reverse flow zone 10 in which the fuel 11 injected by the fuel injector nozzle 3 is combusted.

Air flows radially inwardly through the air inlet openings 12 proposed by the invention, in the direction of arrows F (upstream direction with respect to the combustion chamber flow) towards the discharge tip of the fuel injector nozzle 3, i.e., toward the point of fuel discharge. The air inlet openings 12 are arranged at the level of the conically flaring rear wall 15 of the combustion chamber formed by flameholder 2. Any deflection of the airstreams from the direction of arrows F under the influence of the primary air inlet stream in the direction of arrow E will be prevented by tubes 13 (FIGS. 1 and 2) and/or ribs 14 (FIG. 3) suitably welded into the flame tube 5.

The tubes 13 and the ribs 14 further assist the directional flow of the air towards the discharge tip of the fuel injector nozzle 3 by their radially inward arrangement inclined in the direction of the fuel injector nozzle 3. The invention can also be applied to annular combustion chambers as well as to combustion chambers having an annular outer casing housing several individual combustion chambers.

While I have shown and described only two embodiments of the present invention, it is understood that the latter is not limited thereto but is susceptible of numerous changes and modifications as known to those skilled in the art, and I therefore do not wish to be limited to these details as shown and described but intend to cover all such changes and modifications as are encompassed by the scope of the appended claims. It is further noted that the terms upstream and downstream refer to the direction of flow of combustion chamber products in the flame tube, both in the specification and in the claims.

Claims

I claim:

1. A combustion chamber arrangement for a gas turbine engine comprising: a flame tube and an end wall forming a combustion chamber space, fuel injector nozzle means having a fuel discharge point located centrally of said end wall for injecting fuel into said combustion chamber space in a downstream direction, air introducing means for supplying combustion and mixing air to said combustion chamber space, said air introducing means including first air inlet means arranged in the flame tube for introducing air in an upstream direction parallel to and along said end wall toward said discharge point and second air inlet means for introducing air into said combustion chamber space in a downstream direction, said end wall being tapered conically outwardly in the downstream direction from said discharge point to adjacent the first air inlet means, and an outer casing surrounding said flame tube with an annular space between said outer casing and said flame tube for conducting mixing and combustion air to said air introducing means, said second air inlet means being constructed as an annular opening between said end wall and said flame tube, said end wall being formed by an extension of said outer casing.

2. An arrangement according to claim 1, wherein said first air inlet means includes a plurality of cylindrical inlet tubes extending from said annular space across said annular opening inwardly into said combustion chamber space.

3. An arrangement according to claim 1, wherein said first air inlet means includes a plurality of part-cylindrical rib means extending from openings leading from said annular space and across said annular opening.

4. An arrangement according to claim 2, wherein said air introducing means includes third air inlet means for introducing air into said combustion chamber space, said third air inlet means including a plurality of openings in said flame tube means which communicate with said annular space and said combustion chamber space at a position downstream of said first and second air inlet means.

5. An arrangement according to claim 3, wherein said air introducing means includes third air inlet means for introducing air into said combustion chamber space, said third air inlet means including a plurality of openings in said flame tube means which communicate with said annular space and said combustion chamber space at a position downstream of said first and second air inlet means.

6. A combustion chamber arrangement for a gas turbine engine comprising: a flame tube and an end wall forming a combustion chamber space, fuel injector nozzle means having a fuel discharge point located centrally of said end wall for injecting fuel into said combustion chamber space in a downstream direction, said end wall being tapered conically outwardly in the downstream direction from said discharge point to adjacent the downstream end of said end wall, and air introducing means for supplying combustion and mixing air to said combustion chamber space, said air introducing means including first air inlet means arranged in the flame tube for introducing air in an upstream direction parallel to and along said end wall toward said discharge point and second air inlet means for introducing air into said combustion chamber space in a downstream direction, said second air inlet means being formed by an annular opening between said flame tube and said downstream end of said end wall, said first air inlet means including means extending across said annular opening for precluding intermixing of the flow from said first and second air inlet means, whereby flow from said first air inlet means is not interrupted by flow from said second inlet means such that it can effectively remove any excess fuel adjacent said end wall, prevent depositing of carbon black particles on said end wall, and create a zone of high turbulence adjacent said end wall.

7. An arrangement according to claim 6, wherein said means extending across said annular opening includes a plurality of cylindrical inlet tubes extending inwardly into the combustion chamber space through said flame tube means.

8. An arrangement according to claim 7, wherein said inlet tubes are circumferentially spaced from one another around the circumference of said flame tube means.

9. An arrangement according to claim 6, wherein said means extending across said annular opening includes a plurality of part-cylindrical rib means extending inwardly into the combustion chamber space from openings in said flame tube means.

10. An arrangement according to claim 9, wherein said rib means are circumferentially spaced from one another around the circumference of said flame tube means.

11. An arrangement according to claim 6, further comprising an outer casing surrounding said flame tube means with an annular space between said outer casing and said flame tube means for conducting mixing and combustion air to said air introducing means.

12. An arrangement according to claim 10, wherein said means extending across said annular opening includes a plurality of cylindrical inlet tubes extending from said annular space across said annular opening inwardly into said combustion chamber space.

13. An arrangement according to claim 10, wherein said means extending across said annular opening includes a plurality of part-cylindrical rib means extending from openings leading from said annular space and across said annular opening.

14. An arrangement according to claim 11, wherein said air introducing means includes third air inlet means for introducing air into said combustion chamber space, said third air inlet means including a plurality of openings in said flame tube means which communicate with said annular space and said combustion chamber space at a position downstream of said first and second air inlet means.

15. An arrangement according to claim 11, wherein said end wall is formed by an extension of said outer casing.