Patent Application
20140000269
The invention relates generally to combustors, and more specifically, to a combustion nozzle for injecting an air-fuel mixture into a combustion zone within a combustor.
A combustor is a component or area of an engine where combustion takes place. In a gas turbine engine, for example, a compressor feeds high pressure air to the combustor or combustion chamber. The combustor then heats the air along with a fuel at a constant pressure. After combustion, the generated exhaust gases are fed from the combustor to the turbine via the nozzle guide vanes. Such an engine employed in a gas turbine plant or a combined cycle plant, for example, is operated to achieve higher operational efficiency under higher temperature and higher pressure conditions, and tends to increase emissions (for example, CO, NOx) in an exhaust gas stream. Although various factors for generation of emissions are known, the dominant one is flame temperature in a combustor.
CO emissions in gas turbines are an important parameter for machines which are required to operate away from baseload (maximum capacity) conditions. Increased CO emission is associated with the typically lower pressures/temperatures associated with part load operation of the machine. Such conditions are characterized by inadequate consumption of CO produced in the flame front.
In accordance with one exemplary embodiment of the present invention, a combustion nozzle is disclosed. The combustion nozzle includes a mixing section and an exit section. The mixing section includes an air inlet, and a fuel inlet. The exit section includes a plurality of jets formed in a predefined pattern on an exit surface. A ratio of a core area of the plurality of jets to an exit surface area is greater than 0.25.
In accordance with another exemplary embodiment of the present invention, a gas turbine is disclosed. The gas turbine includes an air compressor, a combustor coupled to the compressor, and a turbine coupled to the combustor. The combustor includes a casing, and an exemplary combustion nozzle disposed upstream of a combustion zone within the casing.
In accordance with another exemplary embodiment of the present invention, a method includes mixing air and a fuel within a mixing section of an exemplary combustion nozzle to generate an air-fuel mixture. The method further includes injecting the air-fuel mixture via an exit section of the exemplary combustion nozzle to a combustion zone disposed downstream of the exemplary combustion nozzle.
In accordance with another exemplary embodiment of the present invention, a method for forming an exemplary combustion nozzle is disclosed.
These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
In accordance with the embodiments of the present invention, a combustion nozzle is disclosed. The exemplary combustion nozzle includes a mixing section having an air inlet, and a fuel inlet. The nozzle further includes an exit section having a plurality of jets formed in a predefined pattern on an exit surface. A ratio of a core area of the plurality of jets to a nozzle exit total surface area is greater than 0.25. In accordance with a specific embodiment of the prevent invention, a gas turbine having the exemplary combustion nozzle is disclosed. In accordance with certain other embodiments, a method associated with the combustion nozzle is disclosed. At part-load conditions, the intra-jet recirculation zones generated by the exemplary combustion nozzles are sufficiently large to consume the carbon monoxide (CO) produced at the flame front of the combustor.
Turning now to drawings and referring first to
The combustor 12 includes a combustion nozzle for receiving compressed air 11 and the fuel stream, mix the air 11 and the fuel stream to generate an air-fuel mixture, and inject the air-fuel mixture to a combustion zone. The combustion nozzle is explained in greater detail with reference to subsequent figures.
Referring to
A combustion nozzle 28 is disposed within the combustion chamber 24. The exemplary combustion nozzle 28 includes a mixing section 30 and an exit section 32. The combustor 12 further includes a fuel plenum 34 for supplying a fuel to the combustion chamber 24. The fuel enters the combustion nozzle 28 via one or more fuel inlet holes 36 provided in the mixing section 30. The mixing section 30 also has an air inlet 38 for receiving the air stream 11 from the compressor.
In certain embodiments, the fuel may include hydrocarbons, natural gas, or high hydrogen gas, or hydrogen, or biogas, or carbon monoxide, or syngas, or inert gas, or water vapor, or oxidizers along with predetermined amount of diluents. Diluents may include nitrogen, carbon dioxide, water, steam, or the like.
The mixing section 30 of the combustion nozzle 28 is configured to mix air 11 and the fuel and generate an air-fuel mixture. The exit section 32 is configured to receive the air-fuel mixture and inject the air-fuel mixture to a combustion zone 40 of the combustion chamber 24. The exit section 32 is configured to generate turbulent flow of the air-fuel mixture in the combustion zone 40 of the combustor 12. The exit section 32 includes a plurality of jets formed in a predefined pattern on an exit surface 42. The exit surface 42 with the plurality of jets is explained in greater detail with reference to subsequent figures.
Referring to
In accordance with the embodiments of the present invention, a ratio of a core area of the plurality of jets to an exit surface area is greater than 0.25. In one embodiment of the exit section having a desired jet distribution, the ratio of the core area of the plurality of jets 44 to the exit surface area is in the range of 0.25 to 0.4. In another embodiment of the exit section having an alternate desired jet distribution, the ratio of the core area of the plurality of jets 44 to the exit surface area is in the range of 0.4 to 0.5. In yet another embodiment of the exit section having an alternate desired jet distribution, the ratio of the core area of the plurality of jets 44 to the exit surface area is greater than 0.5. It should be noted herein that although a circular nozzle is shown, it should not be construed as limiting the scope of the invention. Aspects of the present invention are also applicable to non-circular nozzles.
In some embodiments of the exit section having a desired jet distribution, a ratio of a diameter of the core area of the plurality of jets 44 to an exit surface diameter is in the range of 0.5 to 0.63. In certain other embodiments of the exit section having an alternate desired jet distribution, a ratio of a diameter of the core area of the plurality of jets to an exit surface diameter is greater than 0.63.
As discussed previously, CO emission in gas turbines is an important parameter for machines which are required to operate away from baseload (maximum capacity) conditions. Increased CO emission is associated with the typically lower pressures/temperatures associated with part load operation of the machine. At such conditions, the intra-jet recirculation zones generated by conventional combustion nozzles based on arrays of jet phase are not sufficiently large to consume the CO produced at the flame front of the combustor.
It should be noted herein that “bluff area” on the exit surface of the exit section of the nozzle leads to generation of CO. In accordance with the embodiments of the present invention, distributed jets with minimal “bluff areas” on the exit surface of the section of the nozzle enable generation of intra-jet recirculation zones sufficiently large to consume the CO produced at the flame front of the combustor. In other words, the plurality of jets 44 are spaced in such a way so as to occupy “a large area” of the exit surface 42.
Referring to
In one embodiment of the exit section 32 having a desired jet spacing, a ratio of the spacing “s” between two mutually adjacent jets among the plurality of jets to the jet diameter “d” is in a range of 1.5 to 1.9. In another embodiment of the exit section 32 having an alternate desired jet spacing, a ratio of the spacing “s” between two mutually adjacent jets among the plurality of jets 44 to the jet diameter “d” is in a range of 1.9 to 2.5. In yet another embodiment of the exit section 32 having an alternate desired jet spacing, a ratio of the spacing “s” between two mutually adjacent jets among the plurality of jets to the jet diameter “d” is greater than 2.5.
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In accordance with the embodiments discussed above, achieving low CO emissions from a gas turbine is driven by optimal spacing between the jets of the nozzle. The optimal spacing between the jets increase the size of the recirculation zones between the jets to consume the CO produced in the flame front. Embodiments of the present invention disclose distributed jets with minimal bluff areas on the exit surface of the nozzle. The lower CO emissions enable part-load operation of the gas turbine.
While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.
