Sequential combustor arrangement with a mixer

Abstract

A sequential combustor arrangement and method are disclosed which can include a first burner, a first combustion chamber, a mixer for admixing a dilution gas to the hot gases leaving the first combustion chamber during operation, a second burner, and a second combustion chamber arranged sequentially in a fluid flow connection. The mixer can include at least one injection opening in the mixer wall for admixing the dilution gas to cool the hot flue gases leaving the first combustion chamber. Further, the mixer can include a damper with a damper volume and a neck connecting the damper volume to the mixer, for modulating and damping pressure pulsations inside the mixer.

Claims

1. A sequential combustor arrangement comprising: a first burner, a first combustion chamber, a mixer for admixing a dilution gas to hotter gases leaving the first combustion chamber during operation, a second burner, and a second combustion chamber arranged sequentially in a fluid flow connection, wherein the mixer is configured to guide combustion gases in a hot gas flow path extending between the first combustion chamber and the second burner, wherein the mixer includes at least one injection opening for admixing the dilution gas to cool hot flue gases leaving the first combustion chamber, and a damper for damping pressure pulsations inside the mixer having a damper wall which encloses a damper volume and a neck connecting the damper volume to the mixer; an opening of the neck that opens to the hot gas flow path being spaced apart from the at least one injection opening such that a flow rate of the dilution gas passable into the mixer via the at least one injection opening is constant over time so that hot gas of the hot gas flow path is cooled to a predetermined temperature profile; and a dilution gas feed connected to the at least one injection opening, wherein a ratio of a pressure loss coefficient of the dilution gas feed to a pressure loss coefficient of the at least one injection opening is smaller than a ratio of a pressure loss coefficient of a purge gas feed that is fed to the damper volume to a pressure loss coefficient of the neck.

2. The sequential combustion arrangement according to claim 1, wherein one of: a distance in flow direction of the hot gas along the hot gas flow path between the at least one injection opening and the opening of the neck to the hot gas flow path in a mixer wall of the mixer is less than three times a hydraulic diameter of the mixer at the opening of the neck; and a distance between the at least one injection opening and the opening of the neck to the hot gas flow path in the mixer wall is less than the hydraulic diameter of the mixer at the opening of the neck.

3. The sequential combustion arrangement according to claim 2, wherein the mixer wall of the mixer is enclosed by the damper wall forming a cooling duct for cooling the inlet section of the mixer between the upstream end of the mixer and a first injection opening of the at least one injection opening for admixing the dilution gas.

4. The sequential combustion arrangement of claim 2, wherein the distance between the at least one injection opening and the opening of the neck to the hot gas flow path in the mixer wall is less than the hydraulic diameter of the mixer at the opening of the neck.

5. The sequential combustion arrangement according to claim 3, wherein the neck extends from the damper wall through the cooling duct to the mixer wall.

6. The sequential combustion arrangement according to claim 5, wherein a duct wall at least partly encloses the mixer wall delimiting a connecting duct for feeding dilution gas to the at least one injection opening.

7. The sequential combustion arrangement according to claim 5, wherein the at least one injection opening comprises a plurality of injection openings and wherein the neck opens to the hot gas flow path between the injection openings or upstream of the injection openings in a hot gas flow direction.

8. The sequential combustion arrangement according to claim 1, wherein the purge gas feed is positioned to supply the purge gas feed as cooling air to the damper volume.

9. The sequential combustion arrangement according to claim 1, wherein the neck has a neck wall defining a neck volume inside the neck wall, wherein the neck is associated with the damper volume for fluid communication between the damper volume and the hot gas flow path in the mixer, and wherein the damper includes a gap between the neck wall and the damper wall.

10. The sequential combustion arrangement according to claim 1, wherein the neck has a neck wall defining a neck volume inside the neck wall, wherein the neck is associated with the damper volume for fluid communication between the damper volume and the hot gas flow path in the mixer, and wherein the combustor arrangement includes a gap between the neck wall and the damper wall to avoid stresses at an interface between a wall of the mixer and the neck wall.

11. The sequential combustion arrangement according to claim 1, wherein a flow capacity of a dilution gas flow path from a compressor plenum to the hot gas flow path in the mixer is at least two times larger than a flow capacity of a purge air flow path from the compressor plenum to the hot gas flow path in the mixer.

12. A gas turbine engine with at least one compressor, a combustor, and at least one turbine, wherein the gas turbine engine comprises: a sequential combustor arrangement according to claim 1.

13. A method of operation of a gas turbine comprising the sequential combustor arrangement of claim 1, the method comprising: operating the mixer for admixing the dilution gas to hot gases leaving the first combustion chamber during operation, wherein the opening of the neck to the hot gas flow path is spaced apart from the at least one injection opening such that a distance in flow direction of the hot gas flow path between the at least one injection opening and the opening of the neck is one of: (i) less than three times a hydraulic diameter of the hot gas flow path at the opening of the neck, and (ii) is less than a hydraulic diameter of the mixer at the opening of the neck; feeding the dilution gas into the mixer via the at least one injection opening such that a flow rate of the dilution gas passed into the mixer via the at least one injection opening is constant over time so that hot gas of the hot gas flow path is cooled to a predetermined temperature profile; and affecting pulsation in the mixer via the damper such that a node of a pulsation wave of the pulsation is positioned adjacent the at least one injection opening by the opening of the neck of the damper, the pulsation in the mixer occurring during operation of the sequential combustor arrangement.

14. The method of operation of a gas turbine according to claim 13, wherein an average velocity of the dilution gas in the at least one injection opening is at least twice as high as a time averaged flow velocity in the neck.

15. The method of operation of a gas turbine according to claim 13, comprising: feeding a purge gas of the purge gas feed to the damper, wherein a pressure drop over the purge gas feed connected to the neck is at least twice as large as a pressure drop over the neck.

16. A method of operation of a gas turbine comprising the sequential combustor arrangement of claim 1, the method comprising: operating the mixer for admixing the dilution gas to hot gases leaving the first combustion chamber; using the damper for damping pressure pulsations inside the mixer during the operating of the mixer, such that a distance in flow direction of the hot gas flow path between the at least one injection opening and the opening of the neck facilitates formation of a node of a pulsation wave of a pulsation generated in the mixer during the operating of the mixer; and feeding the dilution gas into the mixer via the at least one injection opening and performing the using of the damper so that the node of the pulsation wave is shifted toward the at least one injection opening and also has a reduced amplitude.

17. The method of claim 16, wherein the distance that spaces apart the opening of the neck from the at least one injection opening of the mixer is one of: (i) less than three times a hydraulic diameter of the hot gas flow path at the opening of the neck, (ii) is less than a hydraulic diameter of the mixer at the opening of the neck, and (iii) is less than one sixth a wave length of the pulsation wave in the mixer.

18. The method of claim 16, wherein there is a gap defined between a wall of the mixer and a wall of the neck to avoid stresses at an interface between the wall of the mixer and the neck.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) The disclosure, its nature as well as its advantages, shall be described in more detail below with the aid of the accompanying figures. Referring to the figures:

(2) FIG. 1 shows a generic gas turbine with a sequential combustion arrangement with a damped mixer for admixing dilution gas;

(3) FIG. 2 shows a sequential combustor arrangement with a mixer with an injection openings and a damper;

(4) FIG. 3 shows an example of the mixer with a connecting duct for feeding dilution gas through an injection tube into the hot gas flow downstream of a damper neck in more detail;

(5) FIG. 4 shows another example of the mixer with a connecting duct for feeding dilution gas through an injection nozzle into the hot gas flow downstream of a damper neck in more detail;

(6) FIG. 5 shows a close up of the cross section of an example for the damper connection to the mixer wall;

(7) FIG. 6 shows a close up of the cross section of another example for the damper connection to the mixer wall;

(8) FIG. 7 shows a mixer indicating the location of a pulsation wave without damping and of the pulsation wave after shifting and dampening.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

(9) FIG. 1 shows a gas turbine 100 with a sequential combustor arrangement 104 according to the disclosure. It comprises a compressor 103, a sequential combustor arrangement 104, and a turbine 105. The sequential combustor arrangement 104 comprises a first burner 112, a first combustion chamber 101, and a mixer 117 for admixing a dilution gas to the hot gases leaving the first combustion chamber 101 during operation (see FIG. 2). Downstream of the mixer 117 the sequential combustor arrangement 104 further comprises a second burner 113, and a second combustion chamber 102. The first burner 112, first combustion chamber 101, mixer 117, second burner 113 and second combustion chamber 102 are arranged sequentially in a fluid flow connection. Fuel can be introduced into the first burner 112 via a first fuel injection 123, mixed with compressed air 108 which is compressed in the compressor 103, and combusted in the first combustion chamber 101. Dilution gas which is supplied from a compressor plenum 133 via a dilution gas feed 122 is admixed in the subsequent mixer 117. Additional fuel can be introduced into the second burner via a second fuel injection 124, mixed with hot gases leaving the mixer 117, and combusted in the second combustion chamber 102. The hot gases leaving the second combustion chamber 102 are expanded in the subsequent turbine 105, performing work. The turbine 105 and compressor 103 are arranged on a shaft 106.

(10) The remaining heat of the exhaust gas 107 leaving the turbine 105 can be further used in a heat recovery steam generator or boiler (not shown) for steam generation.

(11) In the example shown here compressor exit gas is admixed as dilution gas. Typically compressor exit gas is compressed ambient air. For gas turbines with flue gas recirculation (not shown) the compressor exit gas is a mixture of ambient air and recirculated flue gas. Air is used as representing any gas comprising oxygen.

(12) Typically, the gas turbine system includes a generator (not shown) which is coupled to a shaft 106 of the gas turbine 100.

(13) FIG. 2 shows an exemplary embodiment of a mixer 117 as an enlarged section of the FIG. 1. In this example compressed gas from the compressor plenum 133 (see FIG. 1, compressed gas 108 downstream of compressor 103) is supplied via a dilution gas feed 122 (only shown in FIG. 1) and is guided along the combustor liner in a connection duct 111 as dilution gas 110. From the connection duct 111 the dilution gas 110 is injected into the mixer 117 via an injection tube 115. For cooling the mixer wall 119 and for feeding the injection tubes 115 with dilution gas 110 a duct wall 121 is arranged parallel to the mixer wall 119.

(14) A damper is arranged near the dilution gas injection openings 115, 115a, which are in this example shown as injection tubes 115. The damper comprises a damper wall 126 which defines a damper volume 118 and a damper neck 116. The neck 116 is associated with the damper volume 118 for fluid communication between the damper volume 118 and the hot gas flow 109.

(15) The mixer can for example have an annular cross section, rectangular or trapezoidal cross section or circular. For the example of a cylindrical mixer 117 with a circular cross section the diameter is equal to the hydraulic diameter D.

(16) FIG. 3 shows the dilution gas injection and damper of region III, IV from FIG. 2 in more detail. Upstream (in hotgas flow direction) the side wall 119 of the mixer 117 is enclosed by a damper wall 126 forming an annular cooling duct 125 for cooling the inlet section of the mixer 117. The damper volume 118 is thus separated from the hot gas flow 109. Purge air is feed to the damper via a purge gas feed 114 into the damper volume 118 and purges the neck 116. The neck 116 is offset by a distance to dilution injection x. The Distance to dilution injection x shall be kept small relative to the diameter of the mixer to enable the damper to shift a node of the pulsation towards the exit opening of the injection tube 115.

(17) FIG. 4 is based on FIG. 3. Instead of injection tube 115 an injection nozzle 115 is shown in FIG. 4.

(18) FIG. 5 shows an example of the neck 116 which connects the damper volume 118 to the hot gas flow 109. The neck wall 127 defines a neck volume. In this example the neck 116 is attached to the mixer wall 119 and extends through the cooling duct 125 towards the damper volume 118. In addition the damper comprises a gap 129 between the neck wall 127 and the damper wall 126. Optionally, a flange 130 is provided at the opening of the damper wall 126 to delineate the gap 129. A cylindrical neck 116 is indicated by the neck axis 128. In this case an annular gap 129 encircles the neck wall 127. The gap can be purged by cooling air 125.

(19) FIG. 6 is based on FIG. 5. In this example the neck wall 127 is attached to the damper wall 126 and a gap 129 is provided between the neck wall 127 and the mixer wall 119. A flange 130 is provided at the opening of the mixer wall 119 to delineate the gap 129. The gap can be purged by cooling air 125.

(20) In FIG. 7 the position of a pulsation wave 131 in the hot gas flow 109 in a mixer 117 is indicated relative to the position of an injection opening 115 and a neck 116. The dotted line indicates an initial pulsation wave 131 without a damper volume 118. The solid line indicates a shifted pulsation wave 132. The shifted pulsation wave 132 is displaced by a shift of pulsation wave node s due to the effect of the damper. Due to the damping effect the amplitude of the shifted pulsation wave 132 is reduced relative to the initial pulsation wave 131. The resulting pulsations at the injection opening 115 are for example one order of magnitude smaller than without the damper.

(21) All the explained advantages are not limited just to the specified combinations but can also be used in other combinations or alone without departing from the scope of the disclosure. Other possibilities are optionally conceivable, for example, for deactivating individual burners or groups of burners to modify the pulsation behavior of the combustor arrangement. Further, the dilution gas can be re-cooled in a cooling air cooler before admixing in the mixer. Further two or more dampers can be arranged near the injection openings 115, 115a. The dampers can be designed to dampen and shift one pulsation frequency or different dampers of a plurality of dampers can be designed to dampen and shift different pulsation frequencies.

LIST OF DESIGNATIONS

(22) 100 Gas Turbine 101 First Combustor 102 Second Combustor 103 Compressor 104 Sequential combustor arrangement 105 Turbine 106 Shaft 107 Exhaust Gas 108 Compressed Air 109 Hot gas flow 110 Dilution gas 111 Connecting Duct 112 First burner 113 Second burner 114 Purge gas feed 115 Injection tube 115a Injection nozzle 116 Neck 117 Mixer 118 Damper Volume 119 Mixer wall 120 Cooling gas 121 Duct wall 122 Dilution gas feed 123 First fuel injection 124 Second fuel injection 125 Cooling duct 126 Damper wall 127 Neck wall 128 Neck axis 129 Gap 130 Flange 131 Pulsation wave 132 Shifted pulsation wave 133 Compressor plenum s shift of pulsation wave node x Distance to dilution injection D Hydraulic diameter of mixer