Patent Application
20110314827
The present disclosure relates generally to gas turbine systems, and more particularly to fuel nozzle assemblies in gas turbine systems.
Gas turbine systems are widely utilized in fields such as power generation. A conventional gas turbine system includes a compressor, a combustor, and a turbine. In a typical gas turbine system, compressed air is provided from the compressor to the combustor. The air entering the combustor is mixed with fuel and combusted, Hot gases of combustion flow from the combustor to the turbine to drive the gas turbine system and generate power.
Natural gas is typically utilized as a primary fuel for a gas turbine system. The natural gas is mixed with air in a fuel nozzle assembly in or adjacent to the combustor to provide a lean, pre-mixed air/fuel mixture for combustion. Gas turbine systems typically also require a secondary fuel that allows the system to continue to run when the primary fuel is not available. The secondary fuel is typically a liquid fuel, such as oil.
Typical prior art solutions for providing secondary fuel in a fuel nozzle assembly supply the secondary fuel as a fuel stream sprayed directly into or adjacent to an ignition source. This fuel stream is a relatively rich fuel mixture, as opposed to the relatively lean pre-mixed air/ fuel mixture obtained when using the primary fuel. Consequently, the temperature of the combusted secondary fuel mixture and the resulting rate of NOx formation are typically undesirably high. To lower the temperature and NOx level, water and compressed atomizing air are typically supplied and mixed with the secondary fuel as the fuel is sprayed into the ignition source. However, this system is relatively inefficient, wasteful, and expensive. For example, independent systems must be utilized to supply the water and to supply and compress the atomizing air.
Further, as the secondary fuel is supplied and flowed through the fuel nozzle assembly, it may cause coking. Coking is the oxidative pyrolysis or destructive distillation of fuel molecules into smaller organic compounds, and further into solid carbon particles, at high temperatures. Coking thus causes the deposition of solid carbon particles onto various surfaces of the fuel nozzle assembly, leading to the disruption of flow in the fuel nozzle assembly.
Thus, an apparatus for pre-mixing a secondary fuel in a fuel nozzle assembly would be desired in the art. Additionally, an apparatus for supplying a secondary fuel in a fuel nozzle assembly that reduces the associated expenses and increases the associated efficiency would be advantageous. Further, an apparatus for supplying a secondary fuel in a fuel nozzle assembly that prevents or reduces coking in the fuel nozzle assembly would be desired.
Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.
In one embodiment, an insert for pre-mixing a secondary fuel in a pre-mixing annulus of a fuel nozzle assembly is disclosed. The insert includes a cartridge extending through at least a portion of the fuel nozzle assembly and configured to flow the secondary fuel therethrough. The insert further includes an adapter coupled to the cartridge, the adapter defining a fuel plenum and at least one radially extending injection bore. The at least one injection bore is configured to accept at least a portion of the secondary fuel from the cartridge and inject the secondary fuel into the pre-mixing annulus.
In another embodiment, a fuel nozzle assembly for pre-mixing a secondary fuel is disclosed. The fuel nozzle assembly includes an outer burner tube and an inner burner tube defining a pre-mixing annulus therebetween, the inner burner tube further defining an inner annulus. The fuel nozzle assembly further includes an insert, the insert including a cartridge extending through at least a portion of the fuel nozzle assembly and configured to flow the secondary fuel therethrough, and an adapter coupled to the cartridge and the inner burner tube, the adapter defining a fuel plenum and at least one radially extending injection bore. The injection bore is configured to accept at least a portion of the secondary fuel from the cartridge and inject the secondary fuel into the pre-mixing annulus.
These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.
A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures, in which:
Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.
Referring to
Still referring to
During operation, pressurized air exiting the compressor section 12 flows into each combustor 16 through a flow sleeve 30 of a combustion chamber 32 and an impingent sleeve 34 of the transition piece 22, where it is swirled and mixed with fuel injected into each fuel nozzle assembly 28. The air/fuel mixture exiting each fuel nozzle assembly 28 flows into the combustion chamber 32, where it is combusted. The hot gases of combustion then flow through a transition piece 22 to the turbine section 18 in order to drive the system 10 and generate power. It should be readily appreciated, however, that a combustor 16 need not be configured as described above and illustrated herein and may generally have any configuration that permits pressurized air to be mixed with fuel, combusted and transferred to a turbine section 18 of the system 10.
Referring to
In exemplary embodiments, when the primary fuel is not available for use with the system 10 and fuel nozzle assemblies 28 of the present disclosure or when otherwise desired, a secondary fuel 70 may be flowed through the fuel nozzle assemblies 28, mixed with air 42, and combusted. The secondary fuel 70 may, in exemplary embodiments, be a liquid fuel, such as oil or an oil mixture. However, it should be understood that the secondary fuel of the present disclosure may be any suitable fuel for use in a fuel nozzle assembly 28.
An insert 100 may thus be provided in the fuel nozzle assembly 28 for flowing the secondary fuel 70 therethrough. The insert 100 of the present disclosure may advantageously allow pre-mixing of the secondary fuel 70 with air 42 in the pre-mixing annulus 60 of the fuel nozzle assembly 28, such that the air/fuel mixture provided to and combusted in the combustion chamber 36 is a relatively lean mixture. Additionally, the air/fuel mixture may beneficially be atomized in the pre-mixing annulus 60. Further, the insert 100 of the present disclosure may prevent or reduce coking in the fuel nozzle assembly 28, as discussed below.
As shown in
The adapter 104 may be coupled to the cartridge 102 and disposed in the fuel nozzle assembly 28. Further, the adapter 104 may be coupled to the inner burner tube 64. For example, the adapter 104 in certain embodiments may be joined, such as through welding, or may be fastened, such as through a suitable mechanical fastening device or sealing device, to the inner burner tube 64, and may be retrofitted to existing inner burner tubes 64 if desired. Alternatively, the adapter 104 may be an integral component of the inner burner tube 64. Further, the adapter 104 may be positioned in the fuel nozzle 28 such that the inner annulus 106 is divided into an upstream inner annulus 108 and a downstream inner annulus 110.
The cartridge 102 may, as shown in
The adapter 104, one embodiment of which is shown in
The cartridge 102 of the present disclosure may define a passage or a plurality of passages. The passages may be configured to flow the secondary fuel 70 or another fluid therethrough. In exemplary embodiments, as shown in
As shown in
The cartridge 102 may further define a diffusion passage 122, as shown in
The cartridge 102 may further define a coolant inlet passage 124 and a coolant outlet passage 126, as shown in
It should be understood that the flow of secondary fuel 70, coolant 130 or any other fluid through the various passages of the cartridge 102 may be controlled and regulated manually or by utilizing a suitable control system.
In exemplary embodiments, the adapter 104 of the present disclosure may define at least one longitudinally extending bypass passage 132, or a plurality of longitudinally extending bypass passages 132. The bypass passages 132 may be configured to flow air 42 or coolant 130 through the adapter 104. For example, as discussed above, the adapter 104 may be coupled to the inner burner tube 64, and may divide the inner annulus 106 into an upstream inner annulus 108 and a downstream inner annulus 110. The bypass passages 132 may be in fluid communication with the inner annulus 106. For example, the bypass passages 132 may be in fluid communication with both the upstream inner annulus 108 and the downstream inner annulus 110. Thus, air 42 or coolant 130 flowing through the passage 46 into the annulus 106, such as into the upstream inner annulus 108, may flow through the bypass passages 132 and into the downstream inner annulus 110. The air 42 or coolant 130 flowing through the bypass passages 132 may cool the adapter 104, and may further prevent or reduce coking by providing a flow to loosen and remove existing coking and prevent the deposition of coking.
In exemplary embodiments, the inner burner tube 64 may define at least one radially extending coolant bore 134, or a plurality of radially extending coolant bores 134. The coolant bores 134 may be provided in the inner burner tube 64 adjacent the downstream inner annulus 110, At least a portion of the air 42 or coolant 130 provided to the downstream inner annulus 110 may thus be flowed through coolant bores 134 and into the pre-mixing annulus 60. The coolant bores 134 may be sized, shaped, and arranged such that the air 42 or coolant 130 flowing through the coolant bores 134 provides film cooling to the inner burner tube 64, cooling the inner burner tube 64, and further preventing or reducing coking on the outer surface of the burner tube 64 by providing a film to loosen and remove existing coking and prevent the deposition of coking.
The insert 100 of the present disclosure advantageously provides pre-mixing of secondary fuel 70 in fuel nozzle assemblies 28 of gas turbines 10. Further, the insert 100 reduces the expenses and increases the efficiency associated with providing the secondary fuel. For example, the insert 100 does not require the use of water to cool the combusted secondary fuel 70, and further does not require an independent compressed atomizing air source. Additionally, the insert 100 provides various air and coolant flows throughout the fuel nozzle assembly 28 to prevent or reduce coking in the fuel nozzle assembly 28 due to the use of the secondary fuel 70.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims.
