GB2079926A - Combustor Assembly - Google Patents

Abstract

A gas turbine engine combustor 10 has mixing slots 46 formed in a circumferential wall 20 of the combustor so that the slots are inclined to the longitudinal axis of flow 50 through the combustor and wherein the slots on opposite sides of the circumferential wall are crossed with respect to one another to increase combustor turbulence and mixing vortices while eliminating the penetration of inlet air flow through the slots to opposing walls of the combustor to retain the action of momentum ratio of the inlet air jet momentum to main stream gas momentum on mixing of the combustion components. <IMAGE>

Description

SPECIFICATION Combustor Assembly This invention relates to gas turbine engines and more particularly to air-mixing holes in a gas turbine combustor for supplying combustion air to the combustion process so as to mix recirculating combustion products within the combustion zone.

Various proposals have been suggested to produce a flow field in a lean combustion zone of a turbine combustor which has thermodynamic and aerodynamic flows conductive to stable combustion during a combustion process.

Examples of such arrangements include provision of a plurality of round holes or inclined slots formed in a combustor wall for directing air from a pressurized air supply plenum radially inwardly into longitudinal flow through the combustor so as to improve mixing within the reaction and dilution zones of a combustor. Such arrangements are suitable for their intended purpose, they are configured so that flow from one segment of the wall will tend to penetrate to an opposing wall surface of the combustor. This will produce an interaction effect between the combustor wall and the inlet air flow to reduce the influence of its momentum on the mixing process within the combustor; or, interact in the center of the combustor with other jets forming a core of air which minimizes mixing capability.

A combustor assembly according to the present invention includes the combination of liner wall means separating a source of air supply from a combustion zone having a main gas flow stream therethrough, said liner wall means including first and second portions on opposite sides of said combustion zone, a first plurality of slots in the first portion at spaced points therealong, each of said first plurality of slots having a planar projection of the major axis thereof inclined with respect to the main gas flow stream in the plane of projection to produce an air inlet flow into the combustion zone for aerodynamically swirling the inlet flow with respect to the main gas flow stream, a second plurality of slots located at spaced points on said second portion of said liner means, each of said second plurality of slots having a planar projection of the major axis thereof inclined with respect to the main gas flow stream in the plane of projection for directing air inlet flow into the opposite side of said combustion zone as an air swirl with respect to said axially directed main gas flow stream, and each one of said second plurality of slots being located substantially diametrically opposite one of said first plurality of slots and having the major axis thereof intersecting the major axis of theopposed slot to produce opposed inlet air flows into said combustion zone for increasing turbulence and mixing vortices within said axially directed main gas flow stream, said inlet air flow through said opposed slots interacting to prevent full penetration of inlet air flow from either of said first or second slots fully across said combustion zone into contact with said liner wall means thereby to prevent collision of the inlet air flow with the opposing portions of said liner wall means so as to reduce the influence of flow wall contact momentum changes on the flow mixing patterns produced by said inclined slots with respect to the main gas flow stream during operation of the combustor.

The invention and how it may be performed are hereinafter particularly described with reference to the accompanying drawings, wherein a preferred embodiment of the present invention is clearly shown, and in which: Figure 1 is a longitudinal sectional view of a combustor for a gas turbine engine including the improved mixing slot configuration of the present invention; Figure 2 is a vertical sectional view taken along the line 2-2 of Figure 1; Figure 3 is a fragmentary, elevational view of the inner surface of the combustor viewed from line 3-3 in Figure 2 looking in the direction of the arrows; Figure 4 is a fragmentary sectional view of an annular combustor assembly including the inclined slot configuration of the present invention; Figure 5 is a fragmentary, developed elevational view of the slot configuration in the embodiment of Figure 4; and Figure 6 is a graph of overall mixing quality versus momentum ratio of inlet air velocity to combustion hot gas velocity for various dilution air hole shapes to direct dilution air into a combustion process for mixing with combustion products having a main stream flow directed longitudinally of the combustion zone.

Referring now to the drawing, in Figure 1 a gas turbine engine combustor 10 is illustrated located within an engine casing 12 that defines an inlet air plenum 14 into which compressed air is directed to supply combustion air for the combustor 10. The combustor 10 is representative of combustors for gas turbine engines that can be improved by use of the present invention. Combustor 10 is a can type combustor including a dome 1 6 having an annular connector ring 18 on the outer periphery thereof that is secured to one end of an annular combustor liner wall 20. The liner wall 20 is connected to a transition member 22 for directing combustion products from the combustor 10 to a turbine nozzle ring 24 from whence combustion products flow to power a gas turbine wheel (not shown).In the illustrated arrangement, fuel supply for the combustor 10 is supplied from an airblast nozzle 26 having an annular outer wall 28 thereof secured in an opening 30 of the dome 1 6. The air blast nozzle 26 includes a fitting 32 sealingly fitted within a bore 34 through the engine casing 12. It, in turn, is held in place by a lock nut 36 from whence a connector tube 38 extends outboard of the casing 1 2. A ring of swirler vanes 40 is located in the air blast nozzle 26 to produce a recirculation pattern 42 in a combustion zone 44 to mix the air and fuel so as to enhance the combustion process in the zone 44.The primary aerodynamic phenomena in such gas turbine engines is mixing in the combustion zone produced by recirculation of air and fuel therein or by the penetration of cool dilution air flow jets into the main stream of hot gas which flows longitudinally of the combustion zone 44. In accordance with the present invention, the rate of mixing produced by jets of dilution air is increased in order to reduce the length of the combustor without adversely affecting efficient burning of the air/fuel mixture therein. Moreover, the increased rate of mixing that is obtained by the present invention will extend combustor and turbine durability by producing more uniform profiles of combustion products at the transition member 22 and provide more air for cooling due to increased mixing efficiency.

The improved mixing, more particularly, is produced by dilution air flow from the inlet air plenum 14 into the combustion zone 44 through a plurality of specially configured, circumferentially spaced dilution air flow slots 46.

Each of the slots 46 has a planar projection of the major axis 48 thereof which is inclined, preferably at an angle of 450, with respect to the longitudinally directed main gas stream 50 of combustion gas flow through the combustion zone 44.

As can be best seen in Figure 3, each of the slots 46 has a substantial length along its major axis 48 and is of reduced width to produce an inlet jet stream into the combustion zone 44 that will increase the rate of mixing within the zone 44. The inclination will produce the aerodynamic swirling of the main gas stream and will also increase the rate of mixing of the combustion products. Furthermore, each of the slots 46 is located circumferentially around the liner wall 20 as shown in Figure 2 in a manner so that there is a diametrically opposed pair of slots.As shown in Figure 3, each of these diametrically located pairs of slots 46 is arranged in a crossed configuration so that diametrically opposing ones of the circumferentially spaced slots will produce an interactive crossing of the radially inwardly directed dilution air jet flows therethrough which will prevent penetration of the entire dilution air jets from each of the opposed slots 46 to the opposite wall surface of the liner wall 20. The cross configuration of the major axes 48 as shown in Figure 3 thereby will prevent penetration of the dilution air jets to an opposing wall segment of the liner wall and a collision between such a jet and the opposing wall. Since there is no abrupt momentum change in the energy of the air jet, the slot configuration will maintain the influence of dilution air jet flow momentum into the main stream on mixing.

Otherwise, a collision of the jet stream with the opposing wall will remove energy from the dilution air inlet flow and will reduce the effectiveness of the influence of momentum on the mixing process.

The aforedescribed embodiment of Figures 1 through 3 thus can be summarized as showing circumferentially arranged, inclined, uniformly spaced dilution air flow slots that are crossed with respect to one another when looking at a pair of slots located at diametrically located points on the can configured liner wall 20.

The embodiment of Figures 4 and 5 shows a combustor 52 having walls including an outer annular liner 54 and an inner annular liner 56 joined by a ring formed end wall 58 having an outside periphery 60 and an inside periphery 62 thereof joined to an outer connector ring 64 and an inner connector ring 66, respectively. Rings 64, 66 connect to the upstream ends of the outer and inner annular liners 54, 56, respectively.

Circumferentially spaced fuel nozzles 68 are supported in end wall 58 and supply fuel into a primary reaction zone 70 of the combustor 52.

The outer liner 54 and inner liner 56 have downstream axial segments 54a, 56a that define an annular dilution zone 72. The liner is broken as shown in Figure 4 to emphasize the separation of downstream segments of the inner and outer annular liners 54, 56 which define dilution zone 72 upstream of a reverse flow transition outlet path 73 that leads to a downstream turbine wheel 75.

In the illustrated arrangement, the outer annular liner segment 54a includes a plurality of uniformly spaced, circumferentially located dilution air flow slots 76 for directing coolant into the dilution zone 72. The inner annular liner 56 includes a plurality of uniformly circumferentially spaced slots 78 therein which are located radially opposite the slots 76 and arranged in a crossed relationship with respect thereto as shown in Figures 4 and 5. The major axis of each of the slots 76, 78 are inclined with respect to the direction of longitudinal flow of the mainstream of hot gas through the annular combustion chamber.

The slots 76, 78 each have relatively elongated dimensions on their major axis and are relatively thin to direct a jet of dilution air flow into the annular combustion chamber at the annular dilution zones 72 so as to aerodynamically swirl the main stream gas flow thus increasing the rate of mixing. This is highly desirable because of the high ratio of dilution air jet momentum to main stream momentum as is typically found in such a reverse flow annular combustor dilution zone 72.

The interaction of the opposed, circumferentially inclined slots 76, 78 produced by the crossed configuration shown in Figure 5, creates an interaction against complete cross flow so that dilution air jets from either of the inner or outer slots 76, 78 will not penetrate to collide on the opposing wall of either the outer or inner annular liners 54, 56 nor interact as a solid core between the walls. Accordingly, the arrangement retains the desirability of a high momentum ratio between the momentum of the dilution air flow jet momentum to the lesser momentum of the main stream flow so as to retain high levels of mixing of the combustion process in the dilution zone 70.

Figure 6 shows a graph of mixing quality versus momentum ratio. Curve 80 shows such a relationship for eight round holes spaced around the circumference of a can liner; curve 82 is the relationship of mixing quality to momentum ratio for eight axial slots formed in the circumference on a can liner. Curve 84 is a like curve for the inventive slots arranged at 450 to the axis of the main flow and wherein the slots are located diametrically opposite one another in a crossed relationship to retain the momentum ratio by preventing collision and penetration of the higher momentum dilution air jets against wall segments to the combustor liner. The decreasing magnitude of overall mixing quality of greater momentum ratios implies increased mixing uniformity for a given amount of dilution air flow through the improved cross slot configuration of the present invention.

The ordinate in each of the curves 80, 82 84 represents an overall mixing quality with respect to the jet/hot gas equilibrium temperature through the following equation: TTEQ dA T9TEQ where T is the measured mixed gas temperature; TEQ is a calculated equilibrium temperature and Tg is the hot gas temperature. Improvement in mixing is noted by reduction in the magnitude of s. These figures illustrate the jet mixing phenomena when total mixer effective area is constant and momentum ratio is varied.

A combustor assembly according to the present invention provides a means of improving primary aerodynamic processes within the combustion zone of a gas turbine engine combustor by inclusion of means for mixing an inlet air jet with air and fuel by the provision of cool dilution air jets that are aligned in cross opposition to one another to increase the rate of mixing between the air and fuel of a combustion zone thereby to enable the overall-length of the combustors to be shortened and to extend durability of combustor and turbine components by having more uniform profiles of combustion products at the outlet transition of a combustor.

Claims (5)

Claims

1. A combustor assembly including the combination of liner wall means separating a source of air supply from a combustion zone having a main gas flow stream therethrough, said liner wall means including first and second portions on opposite sides of said combustion zone, a first plurality of slots in the first portion at spaced points therealong, each of said first plurality of slots having a planar projection of the major axis thereof inclined with respect to the main gas flow stream in the plane of projection to produce an air inlet flow into the combustion zone for aerodynamically swirling the inlet flow with respect to the main gas flow stream, a second plurality of slots located at spaced points on said second portion of said liner means, each of said second plurality of slots having a planar projection of the major axis thereof inclined with respect to the main gas flow stream in the plane of projection for directing air inlet flow into the opposite side of said combustion zone as an air swirl with respect to said axially directed main gas flow stream, and each one of said second plurality of slots being located substantially diametrically opposite one of said first plurality of slots and having the major axis thereof intersecting the major axis of the opposed slot to produce opposed inlet air flows into said combustion zone for increasing turbulence and mixing vortices within said axially directed main gas flow stream, said inlet air flow through said opposed slots interacting to prevent full penetration of inlet air flow from either of said first or second slots fully across said combustion zone into contact with said liner wall means thereby to prevent collision of the inlet air flow with the opposing portions of said liner wall means so as to reduce the influence of flow wall contact momentum changes on the flow mixing patterns produced by said inclined slots with respect to the main gas flow stream during operation of the combustor.

2. A combustor assembly, according to claim 1, in which the combination comprises a cylindrical liner separating the source of air supply from a cylindrical combustion zone having the main gas flow stream therethrough, said cylindrical liner including, as said first and second plurality of slots, a plurality of slots formed therein at uniformly, circumferentially spaced points therearound, each of said slots having a planar projection of the major axis thereof inclined with respect to said main gas flow stream in the plane of projection to produce said air inlet flow into the combustion zone, and opposed pairs of said slots being located substantially diametrically opposite each other and having the major axes thereof intersecting to produce said opposed crossed inlet air flows into said combustion zone.

3. A combustor assembly according to claim 1, in which the combination comprises an outer annular liner and an inner annular liner, means jointed to said inner and outer liner forming an annular combustion zone, said source of air supply separated by said inner and outer liner from said annular combustion zone, means producing said main gas flow stream through said annular combustion zone, means forming said first plurality of slots in said outer annular liner at uniformly spaced points, and means forming said second plurality of slots in the inner annular liner at uniformly circumferentially spaced points, each one of said second plurality slots being located substantially diametrically opposite of one of said first plurality of slots and having the major axis thereof intersecting the major axis of the opposed slot to produce opposed crossed inlet air flows into said annular combustion zone.

4. A combustor assembly substantially as hereinbefore particularly described and as shown in Figures 1 to 3 of the accompanying drawings.

5. A combustor assembly substantially as hereinbefore particularly described and as shown in Figures 4 and 5 of the accompanying drawings.