Patent Application
20130036743
The subject matter disclosed herein relates to the art of turbomachines and, more particularly, to a combustor assembly for a turbomachine.
In general, gas turbomachines combust a fuel/air mixture that releases heat energy to form a high temperature gas stream. The high temperature gas stream is channeled to a turbine portion via a hot gas path. The turbine portion converts thermal energy from the high temperature gas stream to mechanical energy that rotates a turbine shaft. The turbine portion may be used in a variety of applications, such as for providing power to a pump or an electrical generator.
In a gas turbomachine, engine efficiency increases as combustion gas stream temperatures increase. Unfortunately, higher gas stream temperatures produce higher levels of nitrogen oxide (NOx), an emission that is subject to both federal and state regulation. Therefore, there exists a careful balancing act between operating gas turbines in an efficient range, while also ensuring that the output of NOx remains below mandated levels. One method of achieving low NOx levels is to ensure good mixing of fuel and air prior to combustion. Another method of achieving low NOx levels is to employ higher reactivity fuels that produce fewer emissions when combusted at lower flame temperatures.
According to one aspect of the invention, a combustor assembly includes a combustor body having a combustion chamber, and a nozzle support mounted to the combustor body. The nozzle support includes a central opening, and a plurality of openings extending about the central opening. A central flame tolerant nozzle assembly is positioned within the central opening, and a plurality of micro-mixer nozzle assemblies are mounted in respective ones of the plurality of openings about the central flame tolerant nozzle assembly. Each of the central flame tolerant nozzle assembly and the plurality of micro-mixer nozzle assemblies are configured and disposed to deliver an air-fuel mixture into the combustion chamber.
According to another aspect of the invention, turbomachine includes a compressor portion, a turbine portion operatively connected to the compressor portion, and a combustor assembly fluidly connected to the compressor portion and the turbine portion. The combustor assembly includes a combustor body having a combustion chamber, and a nozzle support mounted to the combustor body. The nozzle support includes a central opening, and a plurality of openings extending about the central opening. A central flame tolerant nozzle assembly is positioned within the central opening, and a plurality of micro-mixer nozzle assemblies are mounted in respective ones of the plurality of openings about the central flame tolerant nozzle assembly. Each of the central flame tolerant nozzle assembly and the plurality of micro-mixer nozzle assemblies are configured and disposed to deliver an air-fuel mixture into the combustion chamber.
According to yet another aspect of the invention, a method of combusting an air-fuel mixture in a turbomachine combustor assembly includes passing a first amount of air and a first amount of fuel to a central flame tolerant nozzle assembly, mixing the first amount of air and the first amount of fuel in the central flame tolerant nozzle assembly to form a first air-fuel mixture and discharging the first air-fuel mixture into a combustion chamber. The method also includes passing a second amount of air and a second amount of fuel to a plurality of micro-mixer assemblies arrayed about the central flame tolerant nozzle, mixing the second amount of air and the second amount of fuel within each of a plurality of tubes in the micro-mixer assemblies to form a plurality of second air-fuel mixtures, discharging the plurality of second air-fuel mixtures into the combustion chamber, and combusting the first air-fuel mixture and the plurality of second air-fuel mixtures in the combustion chamber.
These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings.
The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:
The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.
With initial reference to
Combustor assembly 8 includes a combustor body 30 and a combustor liner 36. As shown, combustor liner 36 is positioned radially inward from combustor body 30 so as to define a combustion chamber 38. Combustor liner 36 and combustor body 30 collectively define an annular combustion chamber cooling passage 39. A transition piece 45 connects combustor assembly 8 to turbine portion 6. Transition piece 45 channels combustion gases generated in combustion chamber 38 downstream towards a first stage (not separately labeled) of turbine portion 6. Transition piece 45 includes an inner wall 48 and an outer wall 49 that define an annular passage 54 defined between inner wall 48 and outer wall 49. Inner wall 48 defines a guide cavity 56 that extends between combustion chamber 38 and turbine portion 6. The above described structure has been provided for the sake of completeness, and to enable a better understanding of the exemplary embodiments which are directed to a nozzle assembly 60 arranged within combustor assembly 8.
As best shown in
Referring to
Central, flame tolerant nozzle 80 is also shown to include a plurality of swirler vanes 115 that extend between center body 92 and inner surface 105 of burner tube 104. Swirler vanes 115 are fluidly connected to fuel passage 96 through a plurality of openings 117 formed in inner body member 94. Swirler vane 115 include fuel injection ports 118 that guide fuel from fuel passage 96 into fuel-air mixing passage 112 as will be discussed more fully below. Central, flame tolerant nozzle 80 also includes cooling passages 110 that facilitate the creation of a coolant film on burner tube 104 providing protection from hot combustion gases. The number, size, and angle of cooling passages 110, or the distance between the rows of cooling passages 110 may vary so as to achieve a desired wall temperature during flame holding events.
With this arrangement, fuel enters fuel passage 96 and flows toward end wall 98. The fuel then enters annular reverse flow channel 97 and flows upstream into a cooling chamber 100. The fuel flows around divider 99 and into outlet chamber 101 and into swirler vanes 115. In accordance with one aspect of the exemplary embodiment, divider 99 takes the form of a metal wall that restricts fuel flow direction into outlet chamber 101 thereby cooling internal surfaces of swirler vanes 115. Cooling chamber 100 and outlet chamber 101 may take on a variety of shapes including non-linear shapes such as, a zigzag coolant flow passage, a U-shaped coolant flow passage, a serpentine coolant flow passage, or a winding coolant flow passage. In addition to flow into swirler vanes 115, a portion of the fuel may also flow directly from the cooling chamber 100 to the outlet chamber 101 through by-pass openings 125 provided in the divider 99.
In accordance with an aspect of the exemplary embodiment, by-pass openings 125 may allow, for example, approximately 1-50%, 5-40%, or 10-20%, of the total fuel flow flowing across divider 99 to flow directly between cooling chamber 100 and outlet chamber 101. Utilization of the by-pass openings 103 may allow for adjustments to any fuel system pressure drops that may occur, adjustments for conductive heat transfer coefficients, or adjustments to fuel distribution to fuel injection ports 118. By-pass openings 125 may also improve fuel distribution into and through fuel injection ports 118. Additionally, by-pass openings 125 may reduce a pressure drop from cooling chamber 100 to the outlet chamber 101 thereby facilitating fuel passage through fuel injection ports 118. Furthermore, by-pass openings 103 may also allow for tailored flow through the fuel injection ports 118 to alter an amount of swirl imparted to the fuel flow prior to introduction into fuel-air mixing passage 112 via injection ports 118. In addition to discharging fuel, swirler vanes 115 impart a swirler to air flow passing through fuel-air mixing passage 112 to improve the fuel-air mixing. Accordingly, central, flame tolerant nozzle 80 takes the form of a pre-mixed swirling nozzle or swozzle. Moreover, the particular arrangement of bypass openings 103 provides fuel and cooling control that enables flame tolerant nozzle 80 to withstand flame holding and or flame ingestion events associated with burning higher reactivity fuels.
Reference will now be made to
The particular location of fuel inlet 149 establishes a desired air-fuel mixture. For example, arranging fuel inlet 149 adjacent to second surface 66 of cap member 64 provides a short mixing interval so as to establish lean, direct injection of fuel and air into combustion chamber 38. Arranging fuel inlet 149 centrally between first end section 133 and second end section 134 of main body section 131 establishes a partially pre-mixed injection of fuel and air into combustion chamber 38, and positioning fuel inlet 149 adjacent to first end section 133 establishes a more fully pre-mixed injection of fuel and air into combustion chamber 38. The length of tubes 138 and placement of fuel openings will be based on desired operating characteristics. Additionally, micro-mixer assembly 84 could have more than one fuel plenum with multiple fuel openings at different axial locations along the plurality of mini-tubes 138. With this arrangement, each micro-mixer assembly 84-89 may be constructed similarly or, provided in one of a plurality of configurations, e.g. lean direct injection, partially pre-mixed lean direct injection and fully pre-mixed lean direct injection, to control combustion within a particular combustor. The particular arrangement of mini-tubes 138 within micro-mixer nozzle assembly 84 facilitates the use of higher reactivity fuels. That is, the particular geometry of mini-tubes 138 inhibits injection of flame or flame holding within micro mixer nozzle assembly 84. In addition, the particular size, pattern and arrangement of mini-tubes may vary. Thus, higher reactivity fuels can be employed in combustor assembly 8.
The use of the central flame tolerant nozzle in combination with the micro mixer nozzle assemblies provides for flexibility of fuel choice. More specifically, the cooling features incorporated into the central flame tolerant nozzle, including for example, the fuel cooled center body, the center body tip, the swirler vanes, and the air cooled burner tube, enable the nozzle to withstand prolonged flame holding events. During such a flame holding event, the cooling features protect the nozzle from any hardware damage and allow time for detection and correction measures that blow the flame out of the pre-mixer and reestablish pre-mixed flame under normal mode operation. Thus, the combustor assembly may combust higher reactivity fuels such as full syngas as well as natural gas, high hydrogen gas and the like without suffering nozzle damage. The use of higher reactivity fuels leads to lower emissions, in particular NOx emissions that may increase an over all operational envelope of the turbomachine.
While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.
