JP7615741B2 - Combustor for gas turbine engine - Google Patents

Description

The present invention relates to a combustor for a gas turbine engine, and more specifically, to a cooling structure for the combustor.

In the combustor of a gas turbine engine, various fuels can be used, and not only fossil fuels that have been used traditionally, but also substances with low calorific value, such as residue materials (gas, liquid) at the outlet of a chemical reactor, can be used as fuel. With a fuel with low calorific value, it is necessary to increase the equivalence ratio and make the combustion field hot for stable combustion, but when a fuel with high calorific value is used, the temperature of the combustion field in the combustor becomes too high, so the combustor needs to be cooled. For example, Patent Document 1 proposes a configuration for cooling such a combustor, in which at least 50% of the air supplied to the combustor by the compressor is mixed with the fuel to generate a lean air-fuel mixture, the remaining air is used for impingement cooling, and the used impingement cooling air is injected as a radial jet into the post-primary combustion zone through perforations formed in the wall. In addition, in Patent Document 2, the combustor is composed of an outer wall portion in which impingement cooling holes are formed and an inner wall portion in which effusion cooling holes are formed, and an outer opening portion formed in the outer wall portion and an inner opening portion formed in the inner wall portion are connected to form a cylindrical dilution air introduction passage that introduces dilution air into the combustion chamber. A part of the air from the compressor passes through the dilution air introduction passage and is used for fuel combustion, while another part of the air from the compressor passes through the impingement cooling holes in the outer wall portion and collides with the inner wall portion approximately perpendicularly to cool it. Furthermore, the air passes through effusion cooling holes formed in the inner wall portion at an angle to the thickness direction to form an air film on the inner surface of the inner wall portion, preventing the combustion gas generated in the combustion chamber from directly contacting the inner surface of the inner wall portion and suppressing overheating of the inner wall portion.

JP 8-246900 Patent Publication No. 2020-143850

Regarding the above-mentioned configuration for cooling the combustor, when air is used to cool the liner that defines the combustion chamber, if the cooled air is allowed to flow directly into the combustion field, it will lower the equivalence ratio of the mixed gas in the combustor, which is undesirable. In addition, as a structure for cooling the liner that defines the combustion chamber, as in the above-mentioned Patent Documents 1 and 2, a configuration is adopted in which the liner that defines the combustion chamber has a double-wall structure, and the cooling air that flows along the outer surface of the outer liner is made to collide with the inner liner through holes (impingement cooling holes) drilled in the outer liner. In such a configuration, in the flow of cooling air on the outer surface of the outer liner, the cooling effect of the air flow that collides with the inner liner through the downstream holes may be reduced compared to the air flow that collides with the inner liner through the upstream holes. That is, the airflow that passes through the upstream hole flows downstream after colliding with the inner liner, and if the cross-sectional area of the flow passage between the outer liner and the inner liner is approximately the same upstream and downstream, the airflow that collides with the inner liner on the upstream side weakens the momentum of the airflow that collides with the inner liner through the downstream hole. If the cooling effect becomes uneven in this way, it may affect the temperature distribution in the combustion chamber and the durability of the liner (if it remains as it is, the design of the liner may become complicated, such as requiring the heat resistance of the downstream part of the liner to be increased). Therefore, when adopting a configuration in which cooling air is made to collide with the inner liner through the impingement cooling holes of the outer liner as the cooling structure of the liner that defines the combustion chamber, it is advantageous to have a configuration that can suppress the decrease in the cooling effect of the airflow that collides with the inner liner through the downstream hole.

Thus, one object of the present invention is to provide a combustor cooling structure configured to suppress a decrease in the cooling effect of the airflow that impinges on the inner liner through the downstream holes of the outer liner in a gas turbine engine combustor in which the liner defining the combustion chamber is cooled by impinging air through impingement cooling holes in the outer liner.

According to the present invention, the above object is achieved by providing a combustor for a gas turbine engine, comprising:
a cylindrical inner liner defining a combustion field;
a cylindrical outer liner that surrounds the inner liner on the radially outer side of the inner liner and defines an outlet for combustion gas generated in the combustion field;
In the outer liner, holes penetrating from the outer surface to the inner surface are drilled at a plurality of positions along the extending direction of the cylindrical shape, and air flowing along the outer surface of the outer liner passes through the holes and collides with the inner liner to cool the inner liner, and then flows along the outer surface of the inner liner,
This is achieved by a combustor in which the radial spacing between the outer liner and the inner liner or the diameter of the holes drilled in the outer liner is increased along the upstream to downstream side of the air flow flowing on the outer surface of the inner liner.

In the above configuration, the "gas turbine engine" may be any type of gas turbine engine configured to rotate and drive a turbine with high-temperature, high-pressure gas obtained by burning fuel and compressed air in a combustor, obtain rotational force, and drive a compressor that compresses air to be supplied to the combustor. The "cylindrical inner liner" and the "cylindrical outer liner" may be formed of heat-resistant materials commonly used in this field. The "outer surface" and "inner surface" of the outer liner are the radially outer surface and the radially inner surface of the cylindrical outer liner. The fuel fed to the combustion field defined by the inner liner may be a fuel commonly used as a fuel for gas turbine engines, and may be a gaseous fuel such as city gas or a liquid fuel such as kerosene, but is not limited to these, and may be a flammable material such as a residue material at the outlet of a chemical reactor or liquid ammonia. The compressed air is supplied to the combustion field in an arbitrary manner by the compressor compressing and sending out the air taken in from the atmosphere, and in the combustion field, air and fuel flow in from one end side, i.e., the upstream end side, of the inner liner, and are combusted to become combustion gas, which flows out to the other end side, the downstream end side, of the inner liner, generating thermal energy. The outer liner is connected to the inner liner at its upstream end, and is arranged to be spaced from the inner liner along the downstream side from there, so that an air flow passage is formed between the outer liner and the inner liner. A part of the compressed air may be branched and circulated on the outer surface of the outer liner for cooling the combustor, and the air flowing on the outer surface of the outer liner passes through holes that function as impingement cooling holes drilled in the outer liner as described above, collides with the inner liner, and then flows through the air flow passage between the outer liner and the inner liner. As described above, the outer liner has multiple holes drilled along the extension direction of its cylindrical shape. Furthermore, the outer liner may extend to cover the downstream end of the inner liner, and the air flow that flows through the flow passage between the outer liner and the inner liner may be configured to merge with the fluid (combustion gas) from the inner liner downstream of the downstream end of the inner liner.

As already mentioned, in the above combustor configuration, air flowing along the outer surface of the outer liner passes through the holes in the outer liner, collides with the inner liner to cool the inner liner, and then flows along the outer surface of the inner liner. In particular, in the configuration of the present invention, the radial spacing between the outer liner and the inner liner or the hole diameter of the holes drilled in the outer liner is increased from the upstream to downstream side of the air flow flowing on the outer surface of the inner liner, thereby making it possible to suppress a decrease in the cooling effect of the air flow passing through the downstream holes in the outer liner and colliding with the inner liner. That is, as already mentioned, in a configuration in which the airflow from the impingement cooling holes in the outer liner collides with the inner liner to cool it, the amount of cooling of the airflow is determined by the pressure difference between the outer surface of the outer liner and the inner surface of the outer liner (the outer surface of the inner liner), and since the air cooled upstream flows toward the downstream end of the inner liner, if the distance between the outer liner and the inner liner remains almost unchanged downstream, the pressure difference on the downstream side will be smaller than that on the upstream side, and further, the airflow flowing from the upstream of the inner liner shifts the flow velocity vector from the radial direction of the double liner to the downstream side (in the combustor axial direction), making it difficult for the airflow from the downstream hole to reach the outer surface of the inner liner. In contrast, if the radial distance between the outer liner and the inner liner is increased from the upstream to downstream of the air flow flowing on the outer surface of the inner liner as in the configuration of the present invention described above, the radial cross-sectional area between the double liners on the downstream side increases, and the pressure between the double liners decreases, ensuring the differential pressure that determines the amount of cooling of the air flow. Also, since the flow rate of the cooled air from the upstream between the double liners slows, the air flow from the downstream hole is more likely to reach the outer surface of the inner liner, and the decrease in cooling effect is suppressed. Similarly, if the hole diameter of the hole drilled in the outer liner is increased from the upstream to downstream of the air flow flowing on the outer surface of the inner liner, the air flow from the downstream hole increases, and the air flow from the downstream hole is more likely to reach the outer surface of the inner liner, and the decrease in cooling effect is suppressed.

In the above configuration, the outer liner and the inner liner are formed separately and, as described above, may be connected at their upstream ends and fastened using fasteners such as pins or bolts. Fastening with pins or bolts may be at least two locations, and preferably three or more locations. Because the liner has a split structure, it is possible to replace each part, and the material life can be utilized more effectively than when the outer liner and the inner liner are formed as a single unit.

In addition, in the above configuration, the airflow that collides with the outer surface of the inner liner and flows along the outer surface of the inner liner may be able to merge with the fluid (combustion gas) from the inner liner downstream of the downstream end of the inner liner, as described above, and the airflow may be used as secondary combustion air or dilution air. Furthermore, a portion of the airflow may be used as film cooling air that protects the inner surface of the outer liner from high-temperature burnt gas by flowing directly along the inner surface of the outer liner.

Thus, according to the present invention, in a cooling structure for a combustor of a gas turbine engine, in which cooling air is impinged on the inner liner through the impingement cooling holes of the outer liner, by increasing the radial distance between the outer liner and the inner liner or the hole diameter of the hole drilled in the outer liner along the upstream to downstream side of the air flow flowing on the outer surface of the inner liner, the decrease in the cooling effect of the air flow from the impingement cooling holes on the downstream side of the outer liner is suppressed. This effect is expected to facilitate the adjustment of the temperature distribution in the combustion field and the design for the durability of the liner. In addition, in the above-mentioned double liner structure of the present invention, since the cooling air does not flow directly into the combustion field, it is possible to maintain a stable combustion state in the combustion field. The configuration of the present invention may be advantageously used in combustors of various gas turbine engines.

Other objects and advantages of the present invention will become apparent from the following description of preferred embodiments of the present invention.

FIG. 1(A) is a schematic cross-sectional view of one embodiment of a combustor of a gas turbine engine according to the present embodiment, as viewed from the lateral direction, and FIG. 1(B) is an enlarged view of a portion marked (B) in FIG. 1(A). FIG. 2(A) is a schematic cross-sectional view of another embodiment of a combustor of a gas turbine engine according to the present embodiment, as viewed from the lateral direction, and FIG. 2(B) is an enlarged view of a portion marked (B) in FIG. 2(A). FIG. 3(A) is a schematic cross-sectional view of another aspect of a combustor of a gas turbine engine according to this embodiment, as viewed from the side, and FIG. 3(B) is an enlarged view of a portion marked (B) in FIG. 3(A).

Reference Signs List 1: Combustor 2: Inner liner 2a: Inner liner upstream end 2b: Inner liner downstream end 3: Outer liner 3a: Outer liner upstream end 3b: Outer liner downstream end 3p: Impingement cooling hole 4: Fuel nozzle 5: Combustor outlet 6: Cooling air flow passage 7: Fixing pin BP: Combustion field FL: Fuel Ar, ar: Cooling air flow

Referring to Fig. 1(A) showing a schematic configuration of a combustor , a combustor 1 of a gas turbine engine of the present embodiment may be applied to any type of gas turbine engine. In this configuration, the combustor 1 has a cylindrical inner liner 2 that defines a combustion field BP, a cylindrical outer liner 3 that surrounds the inner liner 2 from the radial (radial) outside, and a fuel nozzle 4 that injects fuel FL into the combustion field BP. In the combustion field BP, compressed air delivered from a compressor (not shown) and fuel from the fuel nozzle 4 are mixed and combusted, and the combustion gas flows out from an outlet 5 defined by the outer liner 3 downstream of the combustion field BP and is sent to a turbine (not shown). The inner liner 2 and the outer liner 3 may be formed of a heat-resistant material commonly used in this field, and are typically cylindrical, but may be cylindrical in other shapes (elliptical cylinder, square cylinder). As shown in the figure, the inner liner 2 and the outer liner 3 are connected at their respective upstream ends 2a, 3a to form a double liner structure that defines an annular space 6 (cooling air flow passage) through which air can flow between them. In addition, as shown in Fig. 1(B), the outer liner 3 is drilled with a plurality of impingement cooling holes 3p that penetrate from its outer surface to its inner surface along its upstream end 3a side to its downstream end 3b side. A part of the compressed air Ar flows on the outer surface of the outer liner 3, and the air flow ar flows from the impingement cooling holes 3p to the inner surface side of the outer liner 3 and collides with the outer surface of the inner liner 2 to cool the inner liner 2.

As described above, the combustion field BP is formed in a double liner structure, and the air cooling the inner liner 2 does not flow directly into the combustion field BP, so that the equivalence ratio of the combustion field is prevented from fluctuating due to the cooling air, and it is possible to maintain a stable combustion state of the combustion field. The air flow that collides with the outer surface of the inner liner 2 and cools the inner liner 2 may flow through the cooling air flow passage 6 toward the downstream end 2b of the inner liner 2 and merge with the combustion gas flowing out downstream of the combustion field BP, and this air flow may be used as secondary combustion air or dilution air. Furthermore, a part of this air flow may flow in a layer along the inner surface of the outer liner 3 toward the downstream end 3b of the outer liner 3, forming a film-like air layer that protects the inner surface of the outer liner from the high-temperature burnt gas.

In the above configuration, the inner liner 2 and the outer liner 3 may be formed separately, and may be connected at the upstream ends 2a, 3a by fastening the fixing pin 7 as shown in FIG. 1(B). The fastening points of the fixing pin 7 may be provided at least in two places, preferably three or more places, along the circumferential direction of the upstream ends 2a, 3a. Since the inner liner 2 and the outer liner 3 are separable, they can be replaced separately, and the material life can be utilized more effectively than when the outer liner 3 and the inner liner 2 are formed integrally.

1(B), in the case of a configuration in which the airflow ar from the impingement cooling hole 3p of the outer liner 3 collides with the outer surface of the inner liner 2 and then flows through the cooling air passage 6 toward the downstream end 2b of the inner liner 2, the amount of air is greater on the downstream side than on the upstream side in the cooling air passage 6, so if the cross-sectional area of the cooling air passage 6 does not change much from the upstream side to the downstream side, the pressure inside the cooling air passage 6 becomes higher the further downstream. In this regard, the amount of air flowing from the impingement cooling hole 3p to the outer surface of the inner liner 2 increases as the pressure difference between the outer surface and the inner surface of the outer liner 3 increases, and the cooling effect increases accordingly. However, if the internal pressure of the cooling air passage 6 increases downstream as described above, the pressure difference between the outer surface and the inner surface of the outer liner 3 at the impingement cooling hole 3p decreases downstream, which may result in a decrease in the cooling effect.

In the first aspect of this embodiment, as can be seen from Figs. 1(A) and (B), the diameters of the cylindrical shapes of the outer liner 3 and the inner liner 2 are designed so that the downstream spacing Rd between the outer liner 3 and the inner liner 2 is larger than the upstream spacing Ru. With this configuration, the cross-sectional area of the cooling air flow passage 6 increases from the upstream side to the downstream side, thereby suppressing the increase in the internal pressure of the cooling air flow passage 6 and suppressing the decrease in the differential pressure between the outer surface and the inner surface of the outer liner 3 at the impingement cooling hole 3p, thus suppressing the decrease in the air flow rate from the downstream impingement cooling hole 3p and suppressing the decrease in the cooling effect on the downstream side. The degree to which the downstream spacing Rd is made larger than the upstream spacing Ru can be determined by suitability.

2(A) and (B), in the configuration in which the airflow from the impingement cooling hole 3p of the outer liner 3 collides with the outer surface of the inner liner 2 and then flows through the cooling air flow passage 6 toward the downstream end 2b of the inner liner 2, as another mode for suppressing the decrease in the amount of air from the impingement cooling hole 3p downstream of the cooling air flow passage 6, the impingement cooling holes 3p may be drilled so that the hole diameters δ1 to δ5 of the impingement cooling holes 3p from the upstream side to the downstream side become larger toward the downstream side (i.e., δ1<δ2<δ3<δ4<δ5), as shown in FIG. 2(B). This suppresses the decrease in the airflow rate from the impingement cooling hole 3p downstream, and suppresses the decrease in the cooling effect downstream. The degree to which the downstream hole diameter is made larger than the upstream hole diameter can be determined by suitability. [In the example of FIG. 2, the downstream spacing Rd between the outer liner 3 and the inner liner 2 may be approximately the same as the upstream spacing Ru.]

3(A) and (B), the configurations in the first and second embodiments may be combined. Specifically, as shown in FIG. 3(B), the diameters of the cylindrical shapes of the outer liner 3 and the inner liner 2 are designed so that the downstream interval Rd between the outer liner 3 and the inner liner 2 is larger than the upstream interval Ru, and the impingement cooling holes 3p may be drilled so that the hole diameters δ1 to δ5 of the impingement cooling holes 3p from the upstream side to the downstream side become larger toward the downstream side. With this configuration, it is expected that the decrease in the air flow rate from the downstream impingement cooling holes 3p and the resulting decrease in the cooling effect on the downstream side are more reliably suppressed.

Thus, the configuration of this embodiment is expected to eliminate unevenness in the cooling action from upstream to downstream of the liner (inner liner) that defines the combustion field, and to facilitate designing the durability of the liner according to the temperature distribution of the combustion field.

The above description is given in relation to an embodiment of the present invention, but many modifications and changes are easily possible for those skilled in the art, and it is clear that the present invention is not limited to the embodiment exemplified above, but can be applied to various devices without departing from the concept of the present invention.

Claims (1)

1. A combustor for a gas turbine engine, comprising:
a cylindrical inner liner defining a combustion field;
a cylindrical outer liner that surrounds the inner liner on the radially outer side of the inner liner, is connected to the inner liner on the upstream side of the combustion field, and defines an outlet for combustion gas generated in the combustion field;
the outer liner is perforated at a plurality of positions along the cylindrical extension direction with holes penetrating from the outer surface to the inner surface, and air flowing along the outer surface of the outer liner passes through the holes and collides with the inner liner to cool the inner liner, and then flows along the outer surface of the inner liner to the downstream side of the combustion field and merges with the combustion gas on the downstream side ;
A combustor in which a radial distance between the outer liner and the inner liner increases from the upstream side to the downstream side of the flow of the air flowing on the outer surface of the inner liner.

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