Patent Application
20090320483
The present application relates generally to gas turbine engines and more particularly relates to a variable orifice plug for use about a flange of a combustor fuel nozzle.
Generally described, a gas turbine ignites a fuel/air mixture in a combustor and generates a combustion gas stream. The gas stream is channeled to a turbine via a hot gas path. Compressed air is channeled to the combustor by a compressor. The combustor generally has a fuel nozzle to facilitate fuel and air delivery to a combustion region. The turbine converts the thermal energy of the combustion gas stream to mechanical energy. The mechanical energy rotates a turbine shaft that may be used to power a generator or other type of load.
Fuel may be provided to the fuel nozzle via a fuel insert body. The fuel insert body may be attached to an end cap and positioned upstream of the fuel nozzle. The fuel insert body may have a number of apertures drilled therein. These apertures may be filled with a plug defining one or more orifices. The orifices may be used to meter the fuel flowing to the nozzle.
One drawback with these inserts is that it is necessary to flow a complete end cap/fuel nozzle assembly to test the flow therethrough so as to create a flow matched set of complete end cap assemblies for a given gas turbine. This testing may take several iterations with different combinations of fuel nozzles mounted to the end caps. Such testing may require a significant amount of time.
In cases where the end caps are not used, holes may be drilled into the bottom of the fuel nozzle. The size of the hole may depend upon the size of the specified fuel nozzle group. As a result, a vender may need to build several differently sized groups of nozzles.
There is thus a desire for a simplified fuel nozzle orifice design. Such a design preferably should be easy to test and should provide versatility in selecting the flow rate therethrough.
The present application thus provides a fuel nozzle for use about an end cap of a combustor. The fuel nozzle may include a flange attached to the end cap, an aperture extending through the flange, a plug positioned in the aperture, and an orifice positioned within the plug.
The present application further provides a combustor for a gas turbine. The combustor may include an end cap, a number of fuel nozzles positioned about the end cap with each of the fuel nozzles including a flange attached to the end cap, and a number of variable orifice plugs positioned with the flange.
The present application further provides a method of operating a combustor. The method includes positioning a number of fuel nozzles about an end cap of the combustor, flowing fuel through the fuel nozzles, and replacing one or more of the fuel nozzles without removing all of the fuel nozzles.
These and other features 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.
Referring now to the drawings, in which like numerals refer to like elements through the several views,
By positioning the orifice plugs 230 directly within the flange 160 of the fuel nozzle 150, more meaningful flow tests may be available. Specifically, the individual fuel nozzles 150 may now be flowed. The individual nozzles 150 may be replaced without having to reflow the entire end cap assembly 110. Moreover, the position and size of the orifice 250 may be modified to suit various fuel operating conditions or scenarios. The volume ratio has been shown to be linked to combustor operational dynamics such that varying the position of the orifice 250 may allow for additional tuning capability. The variable orifice 250 not only offers orifice sizing design tuning but also the location of the orifice 250 within the plug 230 may allow for tuning of the flow chamber volumes both upstream and downstream of the orifice 250.
Moreover, having a number of differently sized nozzles 150 may not be required. Rather, multiple standard apertures 240 may be used with varying designs for the orifice plugs 230 to provide the correct flow. Improved flow control should reduce variation in emissions and combustion dynamics.
It should be apparent that the foregoing relates only to certain embodiments of the present application and that numerous changes and modifications may be 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.
