Abstract:
A combustor may include an interior flow path therethrough, a number of fuel nozzles in communication with the interior flow path, and an inlet guide vane system positioned about the interior flow path to create a swirled flow therein. The inlet guide vane system may include a number of windows positioned circumferentially around the fuel nozzles. The inlet guide vane system may also include a number of inlet guide vanes positioned circumferentially around the fuel nozzles and adjacent to the windows to create a swirled flow within the interior flow path.

Description:
FEDERAL RESEARCH STATEMENT 
     This invention was made with government support under Contract No. DE-FC26-05NT42643, awarded by the U.S. Department of Energy (“DOE”). The United States has certain rights in this invention. 
    
    
     TECHNICAL FIELD 
     The present application relates generally to gas turbine engines and more particularly relates to the use of radial inlet guide vanes or swirlers in a combustor so as to provide a more even airflow distribution to the combustor nozzles. 
     BACKGROUND OF THE INVENTION 
     In a gas turbine, operational efficiency increases as the temperature of the combustion gas stream increases. Higher gas stream temperatures, however, may produce higher levels of nitrogen oxide (NO x ), an emission that is subject to both federal and state regulation in the U.S. and subject to similar regulations abroad. A balancing act thus exists between operating the gas turbine in an efficient temperature range while also ensuring that the output of NO x  and other types of emissions remain below the mandated levels. 
     Recent combustion concepts involve the use of a number of nozzles with many small passages in the combustor as opposed to several nozzles with larger passages. These nozzles with small passages offer fast fuel/air mixing in a short flow residence time. The nozzles also provide strong wall heat transfer in combination with effective cooling using fuel and/or air. Thus, these small nozzles or other types of combustion nozzles may have the capability to reduce emissions and also to permit the use of highly reactive types of syngas and other fuels, especially high hydrogen fuels. The design of the nozzles, however, may need to utilize more of the combustor cap space so as to distribute the air properly among the numerous small nozzles. 
     To minimize the emissions and the potential for flashback, it may be desirable to have as uniform an airflow distribution across the nozzles as possible. Current combustor designs may have nozzle to nozzle or even passage to passage airflow variations therein. The outer most nozzles or tubes may receive less airflow due to a local flow separation as the air approaches the nozzles. Such separation may impact nozzle operability as the nozzles with less airflow may suffer flame holding or flashback. Separation also may impact combustion generated emissions, such as Nitrogen Oxides (NOx) and Carbon Monoxide (CO). The extent of the uneven airflow distribution also may change with load or the total air mass flow rate. In the case of a combustor with a short liner or no liner, the cap surface may be curved so as to let the nozzles flow slightly inward. Such a design, however, may need more air near the outer diameter region then currently may be provided. 
     There is thus a desire to provide a more uniform airflow distribution about the combustor and the combustor cap. Preferably such a uniform airflow should provide both reduced emissions as well as improving the overall performance of the gas turbine engine, particularly with the use of highly reactive syngas, hydrogen fuels, and similar types of fuels. 
     SUMMARY OF THE INVENTION 
     The present application thus provides a combustor. The combustor may include an interior flow path therethrough, a number of nozzles in communication with the interior flow path, and an inlet guide vane system positioned about the interior flow path to create a swirled flow therein. 
     The present application further provides a combustor. The combustor may include an interior flow path therethrough, a premixed direct injection nozzle in communication with the interior flow path, and a number of inlet guide vanes positioned about the interior flow path to create a swirling flow therein. 
     The present application further provides a combustor. The combustor may include an interior flow path therethrough, a cap member, a number of nozzles positioned within the cap member and in communication with the interior flow path, and a number of inlet guide vanes positioned about the interior flow path. The inlet guide vanes may extend from a lower portion of a flow passage to create a partly swirling flow and may terminate about a window of the flow passage so as to create a partly non-swirling flow such that an overall swirling flow may have a substantially even distribution across the nozzles. 
     These and other features and improvements of the present application will become apparent to one of ordinary skill in the art upon review of the following detailed description when taken in conjunction with the several drawings and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side cross-sectional view of a gas turbine engine that may be used with the combustor as is described herein. 
         FIG. 2  is a side cross-sectional view of a combustor can with a number of bundled multi-tube injection nozzles of the gas turbine engine of  FIG. 1 . 
         FIG. 3  is a side cross-sectional view of a combustor with an inlet guide vane system as is described herein. 
         FIG. 4  is a side cross-sectional view of the combustor with the inlet guide vane system of  FIG. 3 . 
         FIG. 5  is a plan view of the combustor with the inlet guide vane system of  FIG. 3 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to the drawings, in which like numbers refer to like elements throughout the several views,  FIG. 1  shows a side cross-sectional view of a gas turbine engine  10 . As is known, the gas turbine engine  10  may include a compressor  12  to compress an incoming flow of air. The compressor  12  delivers the compressed flow of air to a combustor  14 . The combustor  14  mixes the compressed flow of air with a compressed flow of fuel and ignites the mixture. (Although only a single combustor  14  is shown, the gas turbine engine  10  may include any number of combustors  14 .) The hot combustion gases are in turn delivered to a turbine  16 . The hot combustion gases drive the turbine  16  so as to produce mechanical work. The mechanical work produced in the turbine  16  drives the compressor  12  and an external load such as an electrical generator and the like. 
     The gas turbine engine  10  may use natural gas, various other types of syngas, and other types of fuels. The gas turbine engine may be a 7F or a 9F heavy duty gas turbine engine offered by General Electric Company of Schenectady, New York. The gas turbine engine  10  may have other configurations and may use other types of components. Other types of gas turbine engines may be used herein. Multiple gas turbine engines  10 , other types of turbines, and other types of power generation equipment may be used herein together. 
       FIG. 2  shows a side cross-sectional view of an example of a combustor  14  that may be used herein. The combustor  14  includes a combustor can  15  that extends from an end cover  18  positioned at a first end thereof to a cap member  20  at the opposite end thereof. The cap member  20  may be spaced from the end cover  18  so as to define an interior flow path  22  for a flow of the compressed air through the combustor can  15 . The cap member  20  may define a premixed direct injection nozzle  23  extending therethrough or other type of fuel nozzle or injector. The premixed direct injection nozzle  23  may include a number of small nozzles  24  in communication with a fuel path  25 . The small nozzles  24  may be positioned at an angle or they may be straight. The fuel path  25  may extend from the end cover  18  to the fuel nozzles  23  to deliver a flow of fuel thereto. The premixed injection nozzle  23  generally provides good fuel air mixing with low combustion generated NO x  and low fuel pressure loss so as to provide high system efficiency. 
     The combustor  14  further includes a combustor liner  26  and a flow sleeve  28  positioned upstream of the combustor can  15 . The combustion liner  26  and the flow sleeve  28  may define an outer flow path  30  therethrough in reverse flow communication with the interior flow path  22 . The outer flow path may provide cooling to the combustion liner  26 . 
     Air from the compressor  12  thus flows through the outer flow path  30  between the combustion liner  26  and the flow sleeve  28  and then reverses into the combustor can  15 . The air then flows through the interior flow path  22  defined between the end cover  18  and the cap member  20 . As the air passes through the premixed direct injection nozzles  23  of the cap member  20 , the air is mixed with a flow of fuel from the fuel path  25  and is ignited within a combustion chamber  32 . The combustor  14  shown herein is by way of example only. Many other types of combustor  14  designs and combustion methods may be used herein. 
     As the airflow approaches the nozzles  23  of the cap member  20  through the interior flow path  22 , there may be a large velocity distribution variance across the cap member  20 . These velocity variances may be particularly an issue given the use of several premixed direct injection nozzles  24 , each with a number of small tubes  24 , as opposed to the use of a few of the known larger nozzles. Such velocity variances may impact on emission levels and other types of combustion dynamics as is described above. These velocity variances may extend from an outer diameter region  34  towards a central region  36  of the cap member  20 . 
       FIGS. 3-5  show a side cross-sectional view of a combustor  100  as may be described herein. The combustor  100  may include a combustor can  110  similar to that described above. Combustor  100  may include an inlet guide vane system  120  positioned therein. The inlet guide vane system  120  acts as a flow conditioner and may be positioned about the outer flow path  30  between the combustion liner  26  and the flow sleeve  28 . The inlet guide vane system  120  may be mounted to the end cover  18  or otherwise positioned. 
     The inlet guide vane system  120  may include a number of guide vanes  130  with each guide vane  130  radially positioned on an axis  140  for rotation therewith. The guide vanes  130  may be positioned about at a lower part  150  of a flow passage  160  through combustion liner  26 . The guide vanes  130  may terminate lengthwise at a window  170  of the flow passage  160  at a top part thereof (close to the end cover  18 ). The area ratio of the lower part  150  of the flow passage  160  with the number of guide vanes  130  to the window  170  of the flow passage  160  without the guide vanes  130  may be varied to achieve the desired air flow distribution among the downstream nozzles. The angle of the guide vanes  130  may be fixed or adjustable. Any number or shape of the guide vanes  130  may be used. The axes  140  may be attached to a drive motor  180  or otherwise powered. 
     In use, an air flow  190  may advance along the outer flow path  30  and may pass through the inlet guide vane system  120  and into the interior flow path  22  towards the small nozzles  23  of the cap member  20 . The guide vanes  130  may induce a certain swirl angle such that a swirling flow  200  may be created with a higher pressure near the outer diameter region  34  of the cap member  20 . The strength of the swirling flow  200  may be controlled by changing the swirl angle and/or the length of the guide vanes  130 . A transfer function thus may be established between the swirl angle of the guide vanes  130  and the airflow rate so as to ensure a substantially even air distribution across cap member  20  and the nozzles  23  at both full load and part load conditions. 
     The length and chord length of the guide vanes  130 , together with the swirl angle, may be optimized so as to give a more uniform air form distribution across the nozzles  24 . Moreover, the inlet guide vanes  130  may create at least a partly swirling flow while the window  170  of the flow passage  160  may create a partly non-swirling flow such that the resultant overall swirling flow  200  may have a more even distribution across the nozzles  24 . 
     The inlet guide vane system  120  thus provides a low pressure loss and variable swirl conditioner so as to provide a uniform airflow distribution among the nozzles  24  at all load conditions. The inlet guide vane system  120  provides such uniform air distribution even in the context of the use of a short liner  26  with high hydrogen fuel combustion. 
     It should be apparent that the foregoing relates only to certain embodiments of the present application and that numerous changes and modifications may be made herein by one of ordinary skill in the art without departing from the general spirit and scope of the invention as defined by the following claims and the equivalents thereof.