US 3645095 A
The disclosure illustrates an improved annular combustor having directional air inlets near the head end of the combustor tending to establish a vortex flow of combustion gases adjacent the combustor fuel nozzles. A series of jets downstream of the fuel nozzles reinforce the vortex flow of gases and deflects it into a horseshoe shape having legs generally parallel to the axis of the annular combustor. Cancelling jets downstream of the deflecting jets terminate the vortex flow and dilute it.
Description (OCR text may contain errors)
United States Patent Melconian Feb. 29, 1972 154] ANNULAR COMBUSTOR  lnventor: Jerry O. Melconian, Stratford, Conn.
 Assignee: Avco Corporation, Stratford, Conn.
 Filed: Nov. 25, 1970 21 Appl; No.: 92,808
 US. Cl ..60/39.36, 60/3965, 431/352 [51 Int. Cl. ..F02c 3/24  Field oiSearch ..60/39.36, 39.65;43l/352  References Cited UNITED STATES PATENTS Ellis ..60/39.65 Poyser Saintsbury ..60/39.65 Pierce ..60/39.36
Primary Examiner-Douglas Hart Attorney-Charles M. Hogan 57] ABSTRACT The disclosure illustrates an improved annular combustor having directional air inlets near the head end of the combustor tending to establish a vortex flow of combustion gases adjacent the combustor fuel nozzles. A series of jets downstream of the fuel nozzles reinforce the vortex flow of gases and deflects it into a horseshoe shape having legs generally parallel to the axis of the annular combustor. Cancelling jets downstream of the deflecting jets terminate the vortex flow and dilute it.
9 Claims, 4 Drawing Figures l l l I I I l 1 l 1 I l l I I l i I i r 'l n I 6 I I I ,1 i l I t I 'l I l l l INVENTOR. JERRY O. MELCONIAN ATTORNEYS.
ANNULAR COMBUSTOR The present invention relates to combustors for gas turbine engines and more specifically to annular combustors.
Fresentday annular combustors achieve a high level of efficiency and compactness withmaximum energy release. One of the reasons for this is that they incorporate air flow designs which establish vortex flows adjacent the combustor fuel nozzles. Generally this promotes recirculation of hot air adjacent the fuel nozzle to insure that combustion is maintained for widely varying flow rates and fuel/air ratios.
With this type of arrangement the size of the annular combustor is greatly decreased. However, since the combustion region is in an annulus, it requires a large number of fuel nozzles which accurately meter fuel flow to provide a uniform distribution of the hot gases throughout the circumference of the annulus. This'fact has limited the application of the annular combustor to small, economical gas turbine engines because the fuel nozzles for this purpose are extremely expensive. The large number required, even for a small combustor, makes an engine prohibitively expensive.
Accordingly, it is an object of the present invention to provide a highly efficient annular combustor while at the same time substantially reducing the number of 'fuel nozzles required for its efficient operation.
The above ends are achieved by a means formed in the walls of an annular combustor to direct pressurized air in a vortex flow closely adjacent a nozzle located in the upstream end of the combustor. A means downstream of the vortex flow means reinforces the vortex flow and deflects it into two spaced downstream legs of vortex flow on either side of each of the nozzles. The axis of rotation of the vortex flow in the legs is generally parallel to the axis of the annular chamber.
The above and other related objects and features of the present invention will be apparent from a reading of the description of the disclosure shown in the accompanying drawing and the novelty thereof pointed out in theappended claims.
In the drawing:
FIG. 1 is a fragmentary, longitudinal sectional view of a gas turbine engine which incorporatesan annular combustor embodying the present invention;
FIG. 2 is a view taken on'line 2-2 of FIG. 1 and-showing the annular combustor of FIG. 1 in an unwrapped condition;
FIG. 3 is a view taken on line 3-3 of FIG. 1;
FIG.;4 is'an illustration of a combustor incorporating an alternate embodiment of thepresent invention.
Referring particularly to FIG. 1, there is shown an outer housing'l0 for a gas turbine engine, only a portion of which is shown, and a diffuser duct 12 cooperating with the outer housing to provide an annular peripheral flow path for pressurized air from a compressor (not shown). The airthat passes from the diffuser duct 12 enters a chamber 14 formed by the housing 10 and a coaxial turbine outlet duct 16.
Positioned in the pressure chamber 14 is an annular combustor generally referred to by reference character 18. Combustor 18 comprises inner and outer walls 20; 22, respectively, which are secured to an upstream closed end 24 having a series of circumferentially spaced fuel nozzles 36(only one is shown). The inner and outer walls 20, 22 join outer and inner turbine inlet ducts 26,28 by a sliding thermal expansion joint toform an open downstream outlet- 30. A turbine inlet nozzle assembly 32 is secured to the downstream end of turbine inlet ducts 26 and 28. A bladed rotatable turbine wheel34 is positioned downstream of nozzle32. Turbine wheel34 may be one of a series of turbine wheels positioned along dashed line 35 that are rotated by passage of hot gases from the turbine nozzle 32. However, only turbine wheel 34 is shown to simplify the description of the invention.
In operation of the engine, pressurized air in chamber 14 enters the interior of combustor l8'through openings to be described in detail later and fuel is injected into the combustor 18 by fuel nozzles 36. The fuel is mixed' with air and themixture ignited by suitable means to provide a hot propulsive gas stream. The hot gas stream flows to the downstream outlet 30 and is discharged from turbine inlet nozzle assembly 32 across bladed turbine wheel 34. The rotating output of turbine wheel 34 is generally used to drive a bladed compressor which supplies pressurized air for the combustor 18. Downstream of turbine wheel 34 the hot gases may pass through successive power turbine stages driving. an output shaft or may be discharged through a nozzle to provide a reaction propulsion for the engine.
In accordance with the present invention the combustor l8 incorporates flow-directing features to be described below.
The upstream closed end 24 of the combustor 18 joins the outer'wall 22 at a series of corrugations 38. The net effect of this is to form a plurality of inlet ducts 40 (see particularly FIG. 3) that admit pressurized air and direct it in an upstream direction, as shown by the arrows in FIG. 1, representing the flow of the air into the combustor. The upstream closed end 24 joins the inner wall 20 along a series of corrugations 42. This junction forms a series of inlet ducts 44 (see FIG. 3) which direct air into combustor 18 in a downstream direction as shown in FIG. 1. Directly downstream of the nozzles 36 are a series of flow-deflecting inlet ducts 46 and 48.
As is apparent from FIGS. 1 and 2, these ducts are positioned so that the airflow'entering the interior of the combustor 18 through ducts 46 and 48 has sufficient strength to reinforce and establish a strong vortex flow immediately adjacent the nozzles 36. This vortex flow in the vicinity of the nozzles 36 has an axis of rotation which extends circumferentially relative to the annular combustor 18. Because the flow in the combustor 18 is toward the outlet 30, the vortex flows established adjacent each nozzle 36 is deflected into two downstream legs L] and L These legs extend toward the outlet 30 and their axis of rotation is generally parallel to the axis of the annular combustor 18. To cancel the vortex flow in legs L and- L a series of cancelling jets are provided through openings 50, 52. These jets are positioned to oppose the direction of rotation of the vortex flow, as shown particularly in FIGS. 2 and 3. Once the vortex flow in legs L and L has been cancelled, suitable diluting .air is provided through openings 54 to cool the mixture for discharge from outlet30.
Although it is not described herein, to enable a clearer understanding of the present invention suitable air inlets can be provided to film cool the'inner' and-outer walls 20, 22, as is apparent to those skilled in the art.
During operation ofv the engine the air flow described above causes a strong vortex flow immediately adjacentthe nozzles 36. This flow recirculates and maintains the hot downstream gases adjacent the nozzle to stabilize and maintain combustion. However,- the deflecting jets from ducts'46, 48 split the flow from: each nozzle to immediately distribute the combustion gases over a relatively .wide spacing. The result is two discrete legs which uniformly pass toward the outlet 30. It can be seen that what has been accomplished with this arrangement is that the combustion gases from each nozzle have been split and discharged over a wide circumferential distance in the combustor 18. The net effect of this distributionis to provide the equivalent of a combustor utilizing twice the number of nozzles astheconstruction shown above. Thisis illustrated inFIG. 2 where a series of center lines, designated N, are placed in line with the axis of the legs of vortex flow. It can be seen that-the resultant distribution of the combustor described above can only be accomplishedin prior art designs by utilizing twice the'number of nozzles. It isapparent that this construction,'while;retaining excellent distribution, enables a substantial reduction in the cost of an annular combustor, thereby permitting it to be used in relatively economical arrangements.
FIG. 4 illustrates an alternate embodiment of the present invention as applied to thick annular combustors for relatively large engines. A combustor, generally indicated by reference character 60, comprises inner and outer walls 62 and 64, respectively. An upstream closed end 66 joins the inner and outer walls 62, 64 at a series of corrugations 68, 70, respecnnimz an! a tively. The corrugations cooperate to form a series of inlets which direct air in a downstream direction. A series of holes 72, 74 for deflecting jets are positioned downstream of each one of a series of fuel nozzles 76.
in operation, the flow of air past the corrugations 68, 70 tends to form a vortex flow. This vortex flow is greatly reinforced by the air jets from the openings 72, 74. In addition, the air jets deflect the resultant vortex flow into circumferentially spaced axially directed legs. The result of this is that the fuel flow from the nozzle 76 is distributed into upper and lower vortex flows immediately adjacent it and the flow in the vortex flows is further split to distribute it circumferentially around the annulus of the combustor 60.
For an equivalent annular combustor having a relatively thick annulus, the above arrangement enables a reduction in the number of nozzles required to produce uniform distribution of the combustion gases. In addition, the efficient burning and mixing of the nozzles enables a greatly reduced length for the combustor which in turn enables a substantial reduction in the length of the engine.
It is noted that this embodiment is particularly suited for straight through axial flow gas turbines since the corrugations 70 and 68 both face in the direction of flow from an upstream located compressor. This arrangement, however, may be incorporated in a reverse flow engine such as the one described in FIG. 1 by incorporating a turning duct adjacent the corrugations 70 to turn the flow 180 for entry into the combustor,
While the combustor design of FIGS. 1-3 has been described in connection with an engine of the reverse flow type, it is apparent that the combustor could be used in engines of the straight flow type by using suitable turning ducts without departing from the spirit and scope of the present invention.
Having described the invention, what is claimed as novel and desired to be secured by Letters Patent of the United States is:
1. In a combustor comprising an annular walled chamber immersed in pressurized air and having an upstream closed end and a plurality of circumferentially spaced nozzles injecting fuel in an axial direction from the upstream end for combustion with pressurized air in said chamber and a downstream lower pressure open end for discharging combustion gases therefrom, the improvement comprising:
means formed in the walls of said annular chamber for directing pressurized air in a vortex flow closely adjacent said nozzles and having the axis of rotation of the vortex flow extending circumferentially relative to said annular chamber; and
means downstream of said vortex flow means for reinforcing and deflecting said vortex flow into two spaced downstream legs of vortex flow on either side of each of said nozzles and having the axes of rotation of the vortex flows in said legs generally parallel to the axis of said annular chamber,
whereby the number of fuel nozzles for said combustor is substantially reduced.
2. Apparatus as in claim 1 wherein said vortex deflecting means comprises means defining at least one opening in the wall of said annular chamber downstream of each nozzle for directing a jet of air of sufficient strength toward the interior of said annular chamber to reinforce and deflect said circumferentially directed vortex flow into said downstream legs.
3. Apparatus as in claim 2 wherein said deflecting means comprises:
means defining a forwardly positioned opening and means defining a plurality of smaller downstream openings adjacent said forwardly positioned opening.
4. Apparatus as in claim 1 wherein said vortex flow means comprises:
means for forming a series of openings around the circumference of one wall of said annular chamber for directing pressurized air into the interior of said chamber in an up stream direction; means for forming a series of openings on the opposite wall of said annular chamber for directing pressurized air into said annular chamber in a downstream direction whereby vortex flow is established.
5. Apparatus as in claim 1 further comprising means downstream of said deflecting means for defining air jets positioned to cancel out the vortex flow in said legs.
6. Apparatus as in claim 5 wherein said deflecting means comprises means for forming at least one opening positioned downstream of said nozzle for directing a-flow of pressurized air in a jet toward the interior of said annular chamber with sufficient strength to reinforce the vortex flow and deflect it into said two spaced downstream legs.
7. Apparatus as in claim 6 wherein:
said vortex flow means comprises means for forming a series of openings around the circumference of one wall of said annular chamber for directing pressurized air into the interior of said annular chamber in an upstream direction and means for forming a series of openings on the opposite wall of said annular chamber for directing air in a downstream direction whereby said vortex flow is established.
8. Apparatus as in claim 7 wherein said deflecting means comprises:
means defining a forwardly positioned opening and means defining a plurality of smaller downstream openings adjacent said forwardly positioned opening.
9. Apparatus as in claim 1 wherein said chamber is relatively thick and wherein:
said vortex flow means is positioned on opposite walls of said chamber for establishing two stacked vortex flows adjacent each of said nozzles;
said deflecting means is positioned on opposite walls of said chamber for reinforcing each of said vortex flows and deflecting them into two spaced downstream legs of vortex flows, each having their axis of rotation generally parallel to the axis of said annular combustor.