COMBUSTOR FOR GAS TURBINE ENGINE

Description

TECHNICAL FIELD

The present invention relates to a combustor for a gas turbine engine.

BACKGROUND ART

As a combustor for generating combustion gas in a gas turbine engine, an annular combustor is known in the art that includes a liner (housing) defining a doughnut or torus-shaped combustion chamber therein centered around a central axis, and a plurality of fuel injection nozzles is attached to an axial end of the liner to inject fuel mixed with air into the combustion chamber. See JP2017-150796A (U.S. Pat. No. 10,317,085B2), for instance.

In such a combustor, cooling air holes are provided through the wall of the liner, and the cooling air ejected from the cooling air holes into the combustion chamber flows along the wall surface of the liner on the combustion chamber side, thereby cooling the liner appropriately.

In order to effectively cool the liner by the cooling air ejected from the cooling air holes into the combustion chamber, it is preferable that the cooling air flows in a layer along the wall surface of the liner on the side of the combustion chamber.

For this purpose, the air flow along the inner surface of the liner is desired to be a laminar flow free from turbulence as much as possible. To achieve this goal, it is advantageous to direct the air flow along the inner surface of the liner and reduce the flow velocity of the cooling air as much as possible. If the cross-sectional area of each cooling air hole is progressively increased in the direction of the air flow, the flow velocity of the cooling air can be reduced without creating turbulence.

However, in order to effectively decelerate the cooling air within the cooling air holes provided in the liner, it is necessary to increase the passage length of the cooling air holes. Increasing the passage length of the cooling air holes requires the wall thickness of the liner to be increased, and this necessitates an increase in the weight of the combustor, and causes an undesired increase in the weight of the gas turbine engine.

SUMMARY OF THE INVENTION

In view of such a problem of the prior art, a primary object of the present invention is to provide a combustor for a gas turbine engine that can effectively decelerate the velocity of the cooling air (cooling air flow) that flows through the cooling air holes and favorably cool the wall of the combustor while avoiding an increase in the weight of the combustor.

To achieve such an object, an aspect of the present invention provides a combustor (18) for a gas turbine engine (10) that is placed in a compressed air chamber (44) of the gas turbine engine to generate combustion gas, the combustor being provided with a liner (100) that defines a combustion chamber (46) therein around a prescribed central axis, the liner comprising: a thick wall portion (130) provided in a part of a wall of the liner, the thick wall portion having a small axial length and extending circumferentially around the central axis; an air guide portion (132) that extends from the thick wall portion along the wall of the liner so as to define a gap (134) jointly with the inner surface of the wall of the liner; a plurality of first cooling air holes (128) passed through the wall and opening to the gap; and a plurality of second cooling air holes (136) passed through the thick wall portion.

According to this aspect, owing to the presence of the thick wall portion, the passage length of the second cooling air holes can be increased so that the cooling air ejected from the second cooling air holes into the combustion chamber is effectively decelerated without increasing the weight of the combustor or causing a turbulence to the air flow. At the same time, the air guide portion increases the effective length of the first cooling air holes and favorably guides the air flow so that the cooling air is effectively decelerated and guided along the inner surface of the wall of the combustor without causing a turbulence to the air flow.

In the above aspect, preferably, the liner includes an end wall (102) substantially orthogonal to the central axis and a peripheral wall (104, 106) extending along the central axis and connected to the end wall via a first end part (104A, 106A) of the peripheral wall which is curved so as to join a main part of the peripheral wall with the end wall, the thick wall portion is provided in a junction portion (126) between the first end part of the peripheral wall and the end wall, and the air guide portion extends from the thick wall portion radially outward substantially in parallel with the end wall.

Alternatively, the liner includes an end wall (102) substantially orthogonal to the central axis and a peripheral wall (104, 106) extending along the central axis and connected to the end wall via a first end part (104A, 106A) of the peripheral wall which is curved so as to join a main part of the peripheral wall with the end wall, the thick wall portion is provided in a junction portion (126′) between the first end part of the peripheral wall and a main part of the peripheral wall, and the air guide portion extends from the thick wall portion substantially in parallel with the peripheral wall away from the end wall.

In either case, the part of the liner adjacent to the first end part of the peripheral wall can be favorably cooled.

In the above aspect, preferably, the combustor consists of an annular combustor including an annular end wall substantially orthogonal to the central axis and having an outer peripheral edge and an inner peripheral edge, an outer peripheral wall extending along the central axis and connected to the outer peripheral edge of the end wall via a first end part thereof which is curved so as to join a main part of the outer peripheral wall with the end wall, and an inner peripheral wall extending along the central axis and connected to the inner peripheral edge of the end wall via a first end part thereof which is curved so as to join a main part of the inner peripheral wall with the end wall, the thick wall portion is provided in each of junction portions (126, 126′) between the first end part of the outer peripheral wall and the end wall and between the first end part of the inner peripheral wall and the end wall, and the air guide portion extends from each of the thick wall portions radially away from the end wall.

Thereby, the present invention can be favorably applied to the annular type combustor.

In the above aspect, preferably, the second cooling air holes are inclined in a circumferential direction, and the second cooling air holes of one of the junction portions are inclined in a different circumferential direction from the second cooling air holes of the other junction portions.

According to this aspect, in the case of an annular combustor, the passage length of the second cooling air holes is increased, allowing the downstream portion of each second cooling air hole to be extended without increasing the weight of the combustor for the given wall thickness thereof so that the cooling air ejected from the second cooling air holes into the combustion chamber is even more effectively decelerated.

In the above aspect, preferably, the thick wall portion and the air guide portion define inner surfaces which face the combustion chamber and are substantially planar and continuous to each other.

Thereby, the cooling air is caused to flow closely along the inner surface of the wall of the combustor in a layer.

In the above aspect, preferably, the thick wall portion defines a substantially smooth outer profile and an inwardly bulging inner profile.

Alternatively, the thick wall portion may define an outwardly bulging outer profile and a substantially smooth inner profile.

In either case, a smooth flow of the cooling air along the inner surface of the wall of the combustor can be accomplished.

In the above aspect, preferably, the second cooling air holes include a part (136B) that is flared from a side of the cooling air chamber to a side of the combustion chamber.

According to this aspect, the flow of the cooling air is effectively decelerated by the flared portion so that the wall of the combustor can be favorably cooled.

In the above aspect, preferably, the second cooling air holes each include an upstream portion (136A) having a substantially constant inner diameter, and a downstream portion (136B) that is flared from a side of the cooling air chamber to a side of the combustion chamber.

According to this aspect, since the cooling air ejected from the second cooling air hole into the combustion chamber is effectively slowed down, the cooling air flowing along the wall surface of the combustion chamber is less likely to separate from the wall surface so that the liner is effectively cooled.

In the above aspect, preferably, the downstream portion of each second cooling air hole has a cross-sectional shape that is elongated in a radial direction.

According to this aspect, the cooling air flowing along the wall surface of the combustion chamber is less likely to separate from the wall surface so that the liner is effectively cooled.

In the above aspect, preferably, the second cooling air holes are inclined in a circumferential direction.

According to this aspect, the passage length of the second cooling air holes is increased, allowing the downstream portion of each second cooling air hole to be extended without increasing the weight of the combustor for the given wall thickness thereof so that the cooling air ejected from the second cooling air holes into the combustion chamber is even more effectively decelerated.

The present invention thus provides a combustor for a gas turbine engine that can effectively decelerate the velocity of the cooling air (cooling air flow) that flows through the cooling air holes and favorably cool the wall of the combustor while avoiding an increase in the weight of the combustor.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic diagram of a gas turbine engine fitted with a combustor according to an embodiment of the present invention;

FIG. 2 is a perspective view of the combustor partly in section;

FIG. 3 is a fragmentary sectional perspective view of a part of the combustor;

FIG. 4 is a fragmentary perspective view of a part of the combustor partly in section;

FIG. 5 is an enlarged sectional view of an essential part of the combustor;

FIG. 6 is a view similar to FIG. 5 according to another embodiment of the present invention; and

FIG. 7 is a view similar to FIG. 2 showing a combustor according to yet another embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

FIG. 1 is a sectional view of a gas turbine engine system 10 for electric power generation fitted with a combustor according to an embodiment of the present invention. As shown in FIG. 1, the gas turbine engine system 10 comprises a radial compressor 14 and a radial turbine 16 which are disposed coaxial to each other and connected to each other via a rotatable shaft 12. The rotatable shaft 12 is further connected to the input shaft of an electric generator 20.

The gas turbine engine system 10 is provided with a front end plate 22, a front housing 24, an intermediate housing 23 and a rear housing 28 connected to one another in this order. The electric generator 20 is connected to the electric generator 20 at the front end plate 22.

The radial compressor 14 is provided with a compressor liner 32 attached to the front housing 24 to define a compressor chamber 30, a diffuser 34 attached to the front housing via a diffuser fixing member 36, and an air intake guide member 38 attached to the front end plate 22 so as to define an annular air intake 40 in cooperation with the compressor liner 32. A compressor rotor 42 attached to the rotatable shaft 12 is rotatably positioned in the compressor chamber 30. The compressor rotor 42 is rotated by the rotatable shaft 12 which is the output shaft of the radial turbine 16 as will be discussed hereinafter.

The radial compressor 14 draws air (outside air) from the air intake 40, compresses and pressurizes the air by the rotation of the compressor rotor 42, and forwards the compressed and pressurized air (compressed air) into the diffuser 34.

The rear housing 28 includes a part that defines a compressed air chamber 44 into which compressed air is introduced from the diffuser 34. The compressed air chamber 44 has an annular cross-sectional shape about the central axis of the rotatable shaft 12. A combustor 18 is provided in the compressed air chamber 44. The combustor 18 defines a combustion chamber 46 which has an annular cross-sectional shape about the central axis of the rotatable shaft 12. A plurality of fuel injection nozzles 48 is provided in the combustor 18. The fuel injection nozzles 48 inject fuel into the combustion chamber 46.

The combustors 18 are provided inside the rear housing 28 around the central axis of the rotatable shaft 12. The rear housing 28 includes a part that defines a compressed air chamber 44 into which compressed air is introduced from the diffuser 34. Each combustor 18 defines a combustion chamber 46. A plurality of fuel injection nozzles 48 is attached to the combustor 18 to inject fuel into the combustion chamber 46. In the combustion chamber 46, a mixture of the fuel injected into the combustion chamber 46 by the fuel injection nozzles 48 and the compressed air from the radial compressor 14 is combusted to generate high-temperature combustion gas (compressed fluid). A turbine nozzle 50 is provided at the gas outlet of the combustor 18.

The radial turbine 16 is provided with a turbine chamber 52 that is defined by an inner part of the rear housing 28 and communicates with the gas outlet of the combustor 18. The turbine chamber 52 is separated from the compressor chamber 30 by a partition member 54. The side of the turbine chamber 52 remote from the partition member 54 along the central axis is defined by a shroud 56. A radial turbine impeller 58 that is integrally formed with the rotatable shaft 12 is rotatably positioned in the turbine chamber 52.

The turbine nozzle 50 is annular in shape and surrounds the radial turbine impeller 58, and forwards combustion gas radially inward and circumferentially toward the radial turbine impeller 58. The combustion gas ejected from the turbine nozzle 50 rotationally drives the radial turbine impeller 58. The combustion gas that has rotationally driven the radial turbine impeller 58 is expelled to the atmosphere from an exhaust gas passage 60 defined by a cylindrical member connected to the rear end of the rear housing 28.

The rotatable shaft 12 is connected to a rotor shaft 62 of the generator 20. Thus, the rotatable shaft 12 of the radial turbine 16 drives the generator 20 to generate electric power.

The details of the combustor 18 will be described in the following with reference to FIGS. 1 to 5.

The combustor 18 of the illustrated embodiment consists of an annular combustor, and as shown in FIG. 1, has a liner (housing) 100 disposed approximately concentrically within the annular compressed air chamber 44. As shown in FIG. 2, the liner 100 includes an annular end wall 102 extending substantially orthogonally to the central axis, an outer peripheral wall 104 extending in the axial direction and connected to the outer peripheral edge of the end wall 102 at a first end part 104A thereof, and an inner peripheral wall 106 also extending in the axial direction and connected to the inner peripheral edge of the end wall 102 at a first end part 106A thereof, defining the annular combustion chamber 46 around the central axis.

The liner 100 is manufactured by the AM (Additive Manufacturing) process, in which metal is layered from bottom to top, with the end wall 102 facing downward and the central axis of the liner 100 extending vertically.

The outer surface of the liner 100 is exposed to the flow of compressed air in the compressed air chamber 44 so that the liner 100 is cooled by the compressed air flowing along the outer surface thereof.

A plurality of mounting portions 110 is formed on the end wall 102 at predetermined intervals in the circumferential direction for mounting the corresponding fuel injection nozzles 48 thereto. Each fuel injection nozzle 48 mixes fuel (supplied via a fuel supply passage not shown in the drawings) with the compressed air in the compressed air chamber 44 and injects the resulting mixture into the combustion chamber 46. In the combustion chamber 46, the mixture is combusted, and generates high-temperature combustion gas.

The second ends 104B, 106B of the outer peripheral wall 104 and the inner peripheral wall 106 oppose each other so as to jointly define an annular combustion gas outlet 112 which faces radially inward. The combustion gas outlet 112 communicates with the turbine nozzle 50 (see FIG. 1) of the radial turbine 16 to supply combustion gas to the radial turbine 16.

The combustion gas created in the combustion chamber 46 flows from the side of the end wall 102 to the combustion gas outlet 112 as indicated by letter F in FIG. 2.

Each of the outer peripheral wall 104 and the inner peripheral wall 106 is provided with a plurality of raised wall portions 114 extending in the circumferential direction and spaced at a predetermined interval in the axial direction, and an inclined wall portion 116 connects each pair of adjacent raised wall portions 114. More specifically, as shown in FIG. 3, each inclined wall portion 116 extends circumferentially around the central axis between an outer edge portion 114A (a radially outer edge) of the adjacent raised wall portion 114 on the upstream side with respect to the flow direction F of the combustion gas and an inner edge portion 114B (radially inner edge) of the adjacent raised wall portion 114 on the downstream side with respect to the flow direction F of the combustion gas.

A plurality of cooling air holes 120 is formed through each of the raised wall portions 114 at a predetermined interval in the circumferential direction. A plurality of cooling air holes 108 is formed through the end wall 102. Compressed air from the compressed air chamber 44 is supplied to each of the cooling air holes 108, 120 as cooling air.

The outer peripheral edge of the end wall 102 is smoothly connected to the first end part 104A of the outer peripheral wall 104, and the inner peripheral edge of the end wall 102 is smoothly connected to the first end part 106A of the inner peripheral wall 106. The first end part 104A of the outer peripheral wall 104 and the first end part 106A of the inner peripheral wall 106 are arcuate in shape in longitudinal sectional view, and smoothly connect the end wall 102 which is substantially planar and orthogonal to the central axis to the outer peripheral wall 104 and the inner peripheral wall 106, respectively, which extend along the central axis.

In a junction portion 126 where the first end part 104A of the outer peripheral wall 104 is connected to the outer periphery of the end wall 102, an annular thick wall portion 130 having a small axial length and extending circumferentially is formed in the liner 100. In this embodiment, the thick wall portion 130 bulges inward (or into the combustion chamber 46) whereas the outer surface of the junction portion 126 is smoothly connected to the end wall 102 and the first end part 104A of the outer peripheral wall 104. A similar junction portion 126 is formed between the first end part 106A of the inner peripheral wall 106 and the inner periphery of the end wall 102, and another annular thick wall portion 130 is formed in this junction portion 126 in a similar fashion. Since the two junction portions 126 are similar in structure, only the one on the outer periphery of the end wall 102 will be discussed in the following disclosure to avoid redundancy.

From an inner end part of the annular thick wall portion 130, an eave-shaped air guide portion 132 extends radially outward substantially in parallel with the first end part 104A of the outer peripheral wall 104 (or the end wall 102) so that a gap 134 is created between the air guide portion 132 and the opposing part of the first end part 104A of the outer peripheral wall 104. The gap 134 is thus open in the radially outer direction.

A plurality of first cooling air holes 128 is formed through a radially inner part of the thick wall portion 130 and is arranged circumferentially at regular intervals. Each first cooling air hole 128 is passed through the wall of the combustor 18 substantially orthogonally thereto (or substantially along the central axis). Each first cooling air hole 128 has an inlet 128A opening to the combustion chamber 46 and an outlet 128B opening to a radially inner end of the gap 134 (or the end of the gap 134 remote from the open end thereof). In this embodiment the first cooling air holes 128 consist of straight holes having a substantially constant cross section.

The thick wall portion 130 is rounded in shape and the air guide portion 132 extends from the thick wall portion 130 in such a manner that a smooth contour facing the combustion chamber 46 is defined jointly by the thick wall portion 130 and the air guide portion 132.

A plurality of second cooling air holes 136 is formed through the thick wall portion 130 at regular intervals in the circumferential direction. Each second cooling air hole 136 extends linearly and is inclined in the circumferential direction at a specified angle with respect to the axial direction from the inlet end thereof (on the side of the compressed air chamber 44) to the outlet end thereof (on the side of the combustion chamber 46). Each second cooling air hole 136 includes an upstream portion 136A on the side of the compressed air chamber 44 which has a substantially constant inner diameter along the length thereof, and a downstream portion 136B on the side of the combustion chamber 46 consisting of a shaped hole (flared portion) which is flared from the side of the compressed air chamber 44 to the side of the combustion chamber 46. The downstream portion 136B of each second cooling air hole 136 has a cross-sectional shape that is elongated in the circumferential direction.

The second cooling air holes 136 formed at the radially outer peripheral edge of the end wall 102 are generally similar to the second cooling air holes 136 formed at the radially inner peripheral edge of the end wall 102. However, as shown in FIG. 3, the direction of inclination of the second cooling air holes 136 formed at the radially outer peripheral edge of the end wall 102 is opposite from that of the direction of inclination of the second cooling air holes 136 formed at the radially inner peripheral edge of the end wall 102. Therefore, the cooling air ejected from the second cooling air holes 136 formed along the radially outer peripheral edge of the end wall 102 is directed in an opposite direction to the cooling air ejected from the second cooling air holes 136 formed along the radially inner peripheral edge of the end wall 102. This contributes to a favorable flow distribution of the cooling air in the region in and around the end wall 102.

Owing to this structure of each junction portion 126, the compressed air in the compressed air chamber 44 is ejected from the first cooling air holes 128 initially along the central axis and is then guided by the air guide portion 132 into the gap 134 as cooling air. The cooling air ejected into the gap 134 is guided by the air guide portion 132 into a radial flow as the cooling air flows through the gap 134. The cooling air is turned into a laminar flow as it flows through the gap 134 owing to the relatively large length and small width of the gap 134. Thereby, the part of the combustor 18 adjacent to the first end part 104A of the outer peripheral wall 104 can be favorably cooled.

Since the second cooling air holes 136 are formed through the thick wall portion 130, the passage length thereof is extended owing to the increased thickness of the wall of the combustor 18. Thereby, a shaped hole of a desired configuration can be formed without increasing the weight of the combustor 18, and the cooling air ejected from the second cooling air holes 136 into the combustion chamber 46 is favorably decelerated and turned into a laminar flow in a favorable manner. Further, the cooling air flows along the inner surface of the liner 100 in particular the inner surface of the first end part 104A of the outer peripheral wall 104 at angle to the axial direction, the part of the liner 100 adjacent to the first end part 104A of the outer peripheral wall 104 is favorably cooled and optimally protected against the combustion gas.

The thick wall portion 130 is useful not only for increasing the length of the second cooling air holes 136 but also for forming the air guide portion 132 without creating an abrupt protrusion on the inner surface of the liner 100, the overall cooling performance of the combustor 18 can be optimized with a minimum increase in the weight of the combustor 18.

Owing to the presence of the thick wall portion 130, the second cooling air holes 136 can be formed into favorable shaped holes for creating a laminar flow, the liner 100 can be protected from combustion gas without substantially increasing the weight of the combustor 18.

Since the downstream portion 136B of each second cooling air holes 136 is flared or widened toward the combustion chamber 46, the cooling air ejected from the second cooling air holes 136 into the combustion chamber 46 is decelerated and caused to flow along the inner surface of the junction portion 126, instead of peeling away from the inner surface of the junction portion 126. Thereby, the first end part 104A of the outer peripheral wall 104 of the liner 100 is suitably cooled and protected against the heat of the combustion gas.

Since the downstream portion 136B of each second cooling air hole 136 has a cross-sectional shape that is elongated in the circumferential direction, the cooling air flowing along the wall surface of the combustion chamber 46 is less likely to peel off from the wall surface so that the liner 100 is cooled all the more effectively.

The second cooling air holes 136 are inclined in the circumferential direction, and this also contributes to increase the passage length thereof so that the second cooling air holes 136 are each allowed to include a section formed as a shaped hole which is suitable for generating a laminar flow.

Since the direction of inclination of the second cooling air holes 136 formed at the radially outer peripheral edge of the end wall 102 is opposite from that of the direction of inclination of the second cooling air holes 136 formed at the radially inner peripheral edge of the end wall 102 as shown in FIG. 3, the cooling air ejected from the second cooling air holes 136 formed along the radially outer peripheral edge of the end wall 102 is directed in an opposite direction to the cooling air ejected from the second cooling air holes 136 formed along the radially inner peripheral edge of the end wall 102. This contributes to a favorable flow distribution of the cooling air in the region in and around the end wall 102.

In another embodiment of the present invention, the thick wall portion 130 bulges toward the compressed air chamber 44 as shown in FIG. 6. In this case, the thick wall portion 130 bulges outward or toward the compressed air chamber 44 instead of the combustion chamber 46 so that the smoothness of the inner surface of the combustor 18 is improved. As a result, the cooling air is allowed to flow with a minimum flow turbulence along the inner surface of the combustor, and this contributes to a favorable cooling of the liner 100 of the combustor 18.

Thus, whereas the thick wall portion 130 defined a substantially smooth outer profile and an inwardly bulging inner profile in the preceding embodiment, in this embodiment, the thick wall portion 130 defines an outwardly bulging outer profile and a substantially smooth inner profile.

In yet another embodiment of the present invention, as shown in FIG. 7, the thick wall portion 130 is provided in an end part of the outer peripheral wall 104 that extends along the central axis adjacent to the end wall 102. The air guide portion 132 extends from the thick wall portion 130 along the central axis away from the end wall 102. The first cooling air holes 128 extend in the radial direction, and the second cooling air holes 136 extend in the radial direction with a certain circumferential slant so as to increase the length of the second cooling air holes 136. In this case also, the second cooling air holes 136 are formed as shaped holes. Similarly to the previous embodiments, the thick wall portion 130 and the air guide portion 132 are provided also in an end part of the inner peripheral wall 106 that extends along the central axis in a similar fashion.

Although the present invention has been described in terms of preferred embodiments thereof, it is obvious to a person skilled in the art that various alterations and modifications are possible without departing from the scope of the present invention which is set forth in the appended claims.

For instance, in the case where the thick wall portion 130 is provided at each of the outer peripheral part and the inner peripheral part of the end wall, the air guide portions 132 may extend in a radially inward direction and radially outward direction from the respective thick wall portions 130. Similarly, in the case where the thick wall portions are provided at end parts of the outer peripheral wall 104 and inner peripheral wall 106, respectively, that extend along the central axis adjacent to the end wall 102, the air guide portions 132 may extend in a radially inward direction and a radially outward direction from the respective thick wall portions 130.

The combustor 18 is not limited to an annular type but may also be a can type. In addition, the combustor 18 is not limited to a combustor for a gas turbine engine for power generation and can be applied to combustors for various gas turbine engines, such as combustors for gas turbine engines for aircraft.