JPH0682003B2 - Combustor liner cooling system - Google Patents

Description

Description: BACKGROUND OF THE INVENTION The present invention relates to an apparatus for cooling a gas turbine engine, and specifically a combustor liner of a gas turbine engine.

In a gas turbine engine, energy is provided by burning fuel in a combustor or combustion chamber.
Fuel is supplied through a fuel nozzle at one end of the combustor, mixed with air and burned. The combustor liner is heated by radiation from the burning fuel flame and by the transmission of combustion gases as they flow along the liner. A relatively cool air flow is usually provided along the outside of the combustor to avoid excessive liner temperatures. In addition, holes or other passages are provided in the combustor liner to allow some of the cooling air flowing through the outside of the combustor to flow as a film along the inside of the combustor liner, allowing cooling to be provided inside and outside the combustor liner. Perform from both.

One means of cooling the inner surface of the combustor liner is about 20
The provision of a very large number of very small holes perforated in the wall of the combustor at an angle of °, the air diverted from outside the combustor passing through these holes being directed along the inner surface of the liner. . These holes are laser drilled and are only about 0.02 inches in diameter. A large number of such very small holes are used to generate a proper and uniform cooling air to the liner inner surface. About 40,000 such holes are drilled in a particular gas turbine engine. The large number of closely spaced holes across the combustor wall allow the cooling air to flow as a film over substantially the entire inner surface of the liner to achieve very effective cooling.

However, there is one significant problem with this solution for combustor liner cooling. Due to the extremely small size of the holes, dust particles in the cooling air block a significant number of holes, reducing the cooling air flow through the holes and causing inadequate and non-uniform cooling of the combustor liner inner surface.

The present invention has significantly improved this problem. Before the dirt particles reach these small pores, a configuration is provided to remove from the air substantially all dirt particles large enough to have a reasonable chance of plugging these small pores. That is, according to the present invention, the likelihood of blocking the holes and preventing the passage of cooling air to the inner surface of the combustor liner is significantly reduced and more effective cooling of this inner surface has been achieved.

Accordingly, it is an object of the present invention to remove dust particles from the cooling air supplied to the inner surface of a combustor liner such that these particles block the very small holes provided in the liner wall for passage of the cooling air. Is to prevent that.

SUMMARY OF THE INVENTION In practicing the present invention, in one form thereof, a shield is disposed in a spaced relationship from an outer surface of the combustor liner and extends over a plurality of very small holes formed in the combustor liner. It prevents the air from flowing directly into the holes. In addition, the shield has a space between the shield and the combustor liner to receive backflowing air. A portion of the air flowing along the outer surface of the combustor liner is deflected back into the passage formed between the shield and the combustor liner. A relatively small number of substantially larger holes are provided in the combustor liner at the points of air reversal and dust particles in the air flow through these larger holes due to the centrifugal forces acting on them. Try to. Second
Larger holes in the group are provided in the combustor liner at approximately the front end of the space between the shield and the combustor liner. The air has to undergo a second reversal as it flows into the very small holes in the combustor liner, and almost any particles that may remain will leave the second group of larger holes during this reversal of the air flow. Shed through. Thus, the air that reaches the tiny holes in the combustor liner and is directed to the inner surface of the combustor liner for cooling is substantially free of dust particles, minimizing the possibility of plugging these tiny holes.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1, a portion of a gas turbine engine combustor, generally indicated at 10, is illustrated. The combustion chamber is of the annular type, which includes an outer wall 12 and an inner wall 14 with an annular space therebetween. A combustor 16 is provided inside the annular space. Combustor 16 includes an outer liner 18 and an inner liner 19. A plurality of fuel nozzles, one of which is designated by 20, is provided at one end of the combustor and supplies combustion fuel into the combustor. Combustion air is supplied along passage 22. A portion of this air flows through the openings 24 surrounding each fuel nozzle into the interior of the combustor where it mixes with the fuel and burns there. In a typical gas turbine engine, openings 24 are provided in the vortex generator, which imparts a swirling motion to the air to achieve thorough mixing with the fuel. However, since these details are not part of the present invention,
It is omitted in the figure.

A part of the air flowing along the inlet passage 22 is indicated by an arrow in FIG.
Passes around the outside of the combustor 16, as shown at 26. The inner surfaces of the combustor liners 18, 19 are heated by radiation from the burning flame of the fuel in the combustor and by transfer by the flow of combustion products along the walls of the combustor. Air flowing through the combustor along passageway 26 helps prevent the combustor liners 18, 19 from reaching excessively high temperatures. However,
It has been found desirable to have a separate flow of air to cool the inner surface of the combustor liner in order to maintain it within acceptable limits. To that end, holes 28 are provided in the combustor liners 18, 19 so that some of the air traveling along the passages 26 is substantially flowed through these holes as a film along the inner surface of the combustor liner.

One such device for effectively cooling the inner surface of the liner is shown in FIGS. 2 and 3 in an enlarged and somewhat exaggerated manner. This device, having the configuration shown in these figures, includes a large number of very small holes 28 drilled in the combustor liner. These holes are drilled using a laser device and are formed at an angle of about 20 ° with respect to the inner surface of the combustor liner 18, and the air exhausted from these holes runs along the inner surface of the combustor liner 18. Most of it is cast as a film to make its cooling effective. In one particular embodiment of a gas turbine engine, the total number of holes 28 provided in the combustor of the combustion chamber is 20,000 and each hole is approximately
It has a diameter of 0.02 inches. Due to the large number of very small holes, the device distributes the cooling air effectively and evenly over the entire surface of the combustor. The use of very small holes is effective in achieving uniform cooling, but on the other hand involves the problem that the holes are prone to being blocked by dirt particles in the air flowing along the passages 22. This is particularly problematic when an aircraft equipped with a gas turbine engine operates in a dusty atmosphere, such as during gliding and takeoff. According to the invention, a device has been provided which ensures that the possibility of plugging these very large numbers of holes is substantially eliminated.

Referring to FIGS. 1 and 2, the liner 18 is formed with a radially extending outer wall portion 30. A shield or blocking member 32 is mounted on the combustor at wall portion 30. The shield is of L-shaped cross section and includes a first leg 34 which is secured in a suitable manner to the combustor wall portion 30 for mounting the shield 32 in proper relationship with the combustor liner. The shield is a long second secondary that extends rearward away from the combustor liner and is generally parallel to it.
Includes legs. The legs 36 are positioned so as to be interposed between the air flow along the passage 26 and the plurality of holes 28 formed in the combustor liner. As best seen in FIG. 2, the rear end of leg 36 has a hole 28 formed in the combustor liner.
Just beyond the last one, preventing the flow of air in passageway 26 directly into and through hole 28.

On the opposite side of the rear end of leg 36, a passage is provided for air to flow into the space between shield 32 and the outer surface of liner 18. Although this description refers to airflow to liner 18, as the description progresses a similar flow of air
It will be clear that this will happen for 19. An unnecessary duplicate explanation is omitted.

As shown in FIG. 2, the space 38 for the air flow is shielded.
It is provided between the rear end of 32 and a flange 40 supporting the liner 18. Combustor 16 compared to the pressure in passage 26 outside the combustor
Due to the low pressure within, some of the air flowing along passage 26 is deflected through space 38 and in the opposite direction through space 42 between shield 32 and the outer surface of the combustor liner, as indicated by arrow 44. Be washed away. The space 38 constitutes the inlet for the flow of air along the passage as described below. The rear ends of the legs 36 of the shield 32 are curved, as indicated at 46, to facilitate guiding air flowing through the inlet 38 and into the backflow passage. Shield 32 to further aid air flow to the backflow passage
A flow guide 48 having a portion generally parallel to the curved end 46 of the shield 32 is mounted on the combustor liner approximately midway between the curved end 46 of the shield 32 and the flange 40. Flow guide 48 has inlet 38
Is divided into two sections, one for passing a portion of the air along the passage indicated by arrow 44, and the other for passing another portion of the air along the second passage 50. belongs to.

A plurality of holes 52 are provided in the combustor liner between the flow guide 48 and the flange 40 for penetrating the combustor liner to remove dust particles from the air which block those with holes 28. These holes are much larger than holes 28, and dust particles large enough to block holes 28 are removed from the air stream flowing into space 42 along passages 44 and are free to pass through holes 52.
In one particular embodiment of the invention, the holes 28 are 0.02 inches in diameter, while these holes are about 0.05 inches. There are fewer holes 52 than holes 28. In one particular embodiment of the invention, there are between about 400 and 500 such combustion chamber holes 52 for about 20,000 holes 28 of the liner 18.

As best shown in FIG. 2, some of this deflected air enters space 42 and is formed by space 42 between shield 32 and combustor liner 18, as indicated by arrow 44. Reverse the flow path. The second portion of this deflected air is directed in the direction of arrow 50 into flow space 52 in space 54 between the end of guide 48 and flange 40. Due to the centrifugal forces acting on the deflected airflow during this reversal of the airflow, heavier dust particles therein flow along the outer passageway 50 and thus toward the holes 52. These dust particles are thus removed from the part of the deflected air flowing in the direction of the arrow 44 which flows back through the space 44. That is, the number of dust particles in the air stream flowing into the passageway 44 is substantially reduced, and the air that subsequently flows through the holes 28 has few such dust particles, and such particles may block the holes 28. Sex is minimal.

To further remove any dust particles that may remain, the present invention provides a second reversal of the air flow and further includes a plurality of larger holes beyond the point of reversal, if desired. As shown in FIG. 2, the holes 28 slope rearwardly, where air flowing in opposite directions along the passage 42 through the space 42 must undergo a second reversal in order to pass through the holes 28. The legs 34 of the shield 32 help to carry out this second reversal by blocking further air flow along the first backflow path at the front end of the space 42. A plurality of second oversized holes 56 are provided in the combustor liner adjacent the legs 34 of the shield 36 to remove any remaining dust particles in the air flowing through the space 42. As with the first inversion of air, the air is
A second reversal, which occurs in space 42 when directed through, causes the relatively heavy debris particles to flow into a relatively large radius passage, indicated by arrow 57, so that the particles cross holes 28 and into holes 56. It further reduces the likelihood of debris remaining in the air flowing through the holes 28.

The air passing through hole 52 is lined in the direction generally indicated by arrow 58.
The combustor liner 18 is open because it flows along the inside surface of the combustor 18.
It is formed with a flange or blocking leg 60 positioned inwardly of and away from 52. A similar flange or blocking leg 62 is provided remote from the opening 58,
Air passing through the openings 58 flows generally along the combustor liner in the direction indicated by arrow 64.

Thus, the present invention provides a device for preventing direct air flow into the very small holes 28, with some of the air flowing through the combustor being reversed in direction before reaching the small holes 28. . Larger holes are provided at the reversal points to pass dust particles that are ejected outwardly toward these larger holes during such reversal of the air flow. In order to remove dust particles more completely and reliably, the second aspect of the air is used in the configuration of the present invention.
Inversion is performed and a second plurality of oversized holes are provided past this second inversion point to remove dust particles that may remain in the air. Thus, the air that finally reaches the small pores is substantially free of dirt particles and the risk of clogging of these small pores with dirt particles is minimized.

[Brief description of drawings]

FIG. 1 is a sectional view of a part of a gas turbine engine showing a combustor cooling device of the present invention. 2 is an enlarged view of a portion of the structure shown in FIG. 1 showing details of the present invention. FIG. 3 is another enlarged view of a portion of the inner surface of the combustor liner showing the small holes used in the combustor liner in an exaggerated form. 10 ... Gas turbine, 12, 14 ... Outer, inner wall, 16 ... Combustor, 18, 19 ... Inner, outer liner, 22, 26 ... Cooling air flow, 28 ... Small hole, 32 ... Shield, 34, 36 ... 1st , 2nd leg, 38 ... Inlet, 40 ... Flange, 44 ... Backflow, 48 ... Flow guide, 50 ... Backflow, 52,56 ... First and second large holes, 64,68 ... Air flow containing dust .

Claims (10)

[Claims] 1. A combustor for a gas turbine engine having a liner positioned to flow cooling air through its outer surface, wherein the combustor comprises: (a) a slope toward a rear portion of the combustor. Flow air along the inner surface of the liner, and (b) prevent direct flow of air to the small holes and backflow air between the outer surface and the small holes. First means on the liner forming a passage; and (c) second means installed behind the first means for deflecting a portion of the air to cause deflected air to flow back into the passage. And (d) a plurality of first oversized holes in the liner at a reversal point of the airflow for passing dirt particles. 2. A shield which is fixed to said outer surface of said liner in front of said small hole and extends parallel to said outer surface to a point behind said small hole to form said passage. A combustor according to claim 1. 3. The combustor according to claim 1, wherein the plurality of small holes are significantly larger in number than the plurality of larger holes. 4. The combustor of claim 1, wherein the small holes have a diameter of about 0.02 inches and the larger holes have a diameter of about 0.05 inches. 5. The first means extends generally parallel to the liner and the first leg secured to the liner in front of the small hole, but behind the last of the small holes, but not the first. Second that extends rearward to the front of the larger hole
A shield having a substantially L-shaped cross section having legs, wherein the first
The legs block the direct flow of air to the small holes and block the backflow of air from further flowing along the passage to cause a second reversal of the air flow to flow through the small holes. The combustor according to claim 1. 6. The rear end of the shield is curved outward to facilitate guiding a backflow of air into the passage.
The described combustor. 7. A curved flow guide having a portion extending generally parallel to said curved portion of said shield, said flow guide secured to said liner at a location remote from said trailing end of said shield. The combustor of claim 5, wherein the combustor forms an inlet with the rear end of the shield that facilitates backflow of air into the passage. 8. The combustor according to claim 7, wherein the larger hole is located in a rear portion of the inlet so that dust particles in the air are directed to the larger hole during inversion of the air. . 9. In addition to the plurality of first oversized holes,
A combustor according to claim 5 including a plurality of second oversized holes proximate said first leg through which dirt particles in the air pass when the direction of the air flow is reversed a second time. 10. A first flange disposed in an air passage through which the combustor liner flows through the plurality of first oversized holes and an air passage through which the combustor liner flows through the plurality of second oversized holes. The combustor of claim 9, further comprising a second flange disposed therein, the first and second flanges deflecting air through the oversized holes to flow along an inner surface of the liner.