The present invention relates to combustors that may be used in combustion turbines. More specifically, the present invention relates to a nozzle system for injecting fuel into a combustor.
Gas turbines play a predominant role in a number of applications, namely in aircraft propulsion, marine, propulsion, power generation and driving processes, such as pumps and compressors. Typically, a gas turbine includes a compressor, a combustor and a turbine. In operation, air is fed into the system where it is compressed by a compressor and a portion of the air further mixed with fuel. The compressed air and fuel mixture are then burned to cause an expansion, which is responsible for driving the turbine.
In an effort to reduce emissions, combustors have been designed to premix fuel and air prior to ignition. Premixed fuel and air burn at a lower temperature than the stoichiometric combustion, which occurs during traditional diffusion combustion. As a result, premixed combustion results in lower NOx emissions.
A typical combustor includes a plurality of primary fuel nozzles that surround a central secondary nozzle. Traditional secondary nozzles may include passageways for diffusion fuel and premix fuel all within the same elongated tubular structure. This type of nozzle often includes a complex structure of passageways contained within a single tubular shell. The passageways for creating the diffusion flame extend through the length of the nozzle. Premix fuel is dispensed upstream of the diffusion tip in order to allow fuel to mix with compressed air flowing through the combustor prior to reaching the flame zone, which is located downstream of the nozzle. As a result, passageways for premix fuel are typically shorter than passageways for diffusion fuel.
Additionally, premix fuel may be mixed with air upstream of the diffusion tip and, more importantly, radially outward of the secondary nozzle structure. In this type of secondary nozzle, premix fuel is carried along only a portion of the nozzle length until it is passed radially outward from the nozzle body to a premix injector tip. At the injector tip, the premix fuel is dispensed into the air flow path. As the fuel and air continue to travel downstream along the remainder of the secondary nozzle length, they become mixed, allowing for more efficient combustion within the flame zone, downstream of the nozzle tip.
While compressed air is hot, fuel is typically cool in comparison. The temperature differentials flowing through the different passageways in the secondary nozzle may result in different levels of thermal expansion of the materials used to construct the nozzle. It is contemplated that it would be beneficial to simplify the secondary nozzles to reduce the high stresses on the nozzle structures resulting from their internal complexity, extreme operating conditions and thermal expansion differentials.
Provided is a secondary nozzle for inclusion within a combustor for a combustion turbine. The secondary nozzle comprises a flange and an elongated nozzle body extending from the flange. At least one premix fuel injector is spaced radially from the nozzle body and extends axially from the flange, generally parallel to the nozzle body.
The secondary nozzle comprises a fuel source, a flange and a first nozzle tube extending axially from the flange. At least one second nozzle tube is spaced radially outward from the first nozzle tube and has a proximal end fixed to the flange. The second nozzle tube is fluidly connected to the fuel source. The second nozzle tube has a distal end, axially spaced from the proximal end of the second nozzle and having at least one aperture therein. A passageway extends between the proximal end of the second nozzle tube and the distal end of the second nozzle tube, said passageway fluidly connects the fuel source and the at least one aperture.
Described herein is an exemplary combustor for use in a combustion turbine. The combustor of the type illustrated is one of a plurality of combustors, typically positioned after the compressor stage within the combustion turbine.
Referring now to the figures and initially to
Inlet air for combustion (as well as cooling) is pressurized by the turbine compressor (not shown) and then directed into the combustor 10 via the combustor flow sleeve 12 and a transition duct (not shown). Air flow into the combustor 10 is used for both combustion and to cool the combustor 10. The air flows in the direction “A” between the combustor flow sleeve 12 and the combustor wall 13. Generally, the airflow illustrated is referred to as reverse flow because the direction “A” is in an upstream direction to the normal flow of air through the turbine and the combustion chambers.
The combustor 10 includes a primary combustion chamber 42 and a secondary combustion chamber 44, located downstream of the primary combustion chamber 42. A venturi throat region 46 is located between the primary and secondary combustion chambers 42, 44. As shown in
Referring now to
Air swirlers may be provided in connection with the primary nozzles 16 to facilitate mixing of combustion air with fuel to provide an ignitable mixture of fuel and air. As mentioned above, combustion air is derived from the compressor and routed in the direction “A,” between the combustor flow sleeve 12 and the combustor wall 13. Upon reaching the rear wall assembly 14, the pressurized air flows radially inward between the combustor wall 13 and the rear wall 14 into the primary combustion chamber 42. Additionally, the combustor wall 13 may be provided with slots or louvers (not shown) in both the primary and secondary combustion chambers 42, 44 for cooling purposes. The slots or louvers may also provide dilution air into the combustor 10 to moderate flame temperature within the primary or secondary combustion chambers 42, 44.
Referring now to
Fuel for the primary nozzles 16 is supplied by a primary fuel source 20 and is directed through the rear wall 14. Secondary transfer and premix fuel sources 24, 25 are provided through the flange 22 to the secondary nozzle 18. Although not shown here, the secondary nozzle 18 may also have a diffusion circuit or pilot circuit for injecting fuel into the combustor 10.
The secondary nozzle 18 comprises a nozzle body 30 and at least one premix fuel injector 32. The secondary nozzle 18 is located within the centerbody 38 and is surrounded by the liner 40, as shown in
The premix fuel injectors 32 are shown aligned directly between the primary nozzles 16 and the nozzle body 30 to facilitate airflow through the centerbody 38 and around the nozzle body 30. In such an arrangement, the second ends 36 of the premix fuel injectors 32 are disposed proximate the primary nozzles 16. Air flow “A” into the combustor 10 travels radially inward from outside of the combustor wall 13. A portion of this air travels downstream, into and through the primary combustion chamber 42. Another portion of the air, by way of example 5 to 20% of the total air flow through the combustor, travels radially inward past the primary nozzles 16 and the primary combustion chamber 42 into the centerbody 38 before travelling downstream through the centerbody. The direction of this second portion of airflow along the flange 22 and rear wall 14 is denoted by the letter “B” in
Referring now to
The transfer fuel passages 64 are fluidly connected to the transfer manifold 51, which is fed by the transfer fuel source 24. The transfer fuel passages 64 include a longitudinal tube 66 and at least one radial passageway 68. The passageway 68 is directed radially outward from the tube 66 and is aligned with an aperture 71 in the wall of the nozzle body 30. The passageway 68 jets the fuel through the opening 71 to the outside of the sleeve 52 to mix with the air flowing along the wall 52. A second opening 70 is shown upstream of opening 71 and provides an inlet for air into the portion of the cavity 31 surrounding the central tube positioned within the nozzle body 30. A portion of the air moving past the opening 70 is directed into the cavity 31 to cool the nozzle body 30. The air in the cavity 31 is exhausted from the openings 58 on the end 54 of the nozzle. The central tube feeds fuel to the nozzle end 54 for supporting a flame in the secondary combustion chamber 44. (See
The outer sleeve portion 52 of the nozzle body 30 extends from the flange 22 to a distal tip 54. The tip 54 of the nozzle body 30 has at least one aperture 58 for allowing the passage of pressurized air from inside of the passageway 31 that surrounds the central tube portion.
As mentioned above, fuel is supplied to the secondary nozzle 18 through the transfer fuel source 24 and the premix fuel source 25. As seen best in
The premix fuel injectors 32 extend distally from the flange 22 having a length that is less than that of the nozzle body 30. A distal end 60 of the premix fuel injectors 32 includes premix apertures 62 for dispensing fuel into the area of the centerbody 38 outside of the nozzle body 30. The premix fuel is mixed with air flowing within the liner 40. When the mixture reaches the secondary combustion chamber 44, the mixture is optimized for efficient combustion in the secondary combustion chamber 44 (see
Unlike typical secondary nozzles, where diffusion and premix fuel is discharged through a single structure extending from a flange, use of a stand alone premix fuel injector 32 allows for a simplification of the nozzle body 30. The injectors 32 shown allow for less internal passageways inside the nozzle body 30 than the typical nozzles. This simplification reduces the stress on the secondary nozzle 18 that may arise from heat differentials within the nozzle structures 18, 32 due to the variation in temperature of the fuel and the pressurized air. Additionally, the contemplated design is easier to maintain and allows for a degree of modularity not possible with traditional secondary nozzles.
In addition to the structures shown, the premix fuel injectors 32 may have a dispensing ring fluidly connected to one or more sets of the premix apertures 62. Other dispenser tip structures may also be used with the premix fuel injectors 32 of the type particularly shown.
Referring now to
In
Referring now to
A variety of modifications to the embodiments described will be apparent to those skilled in the art from the disclosure provided herein. Thus, the invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof and, accordingly, reference should be made to the appended claims, rather than to the foregoing specification, as indicating the scope of the invention.
This application is a continuation of U.S. application Ser. No. 12/365,539, filed Feb. 4, 2009.
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Child | 12535262 | US |