Patent Application
20080072602
Embodiments of the present invention solve a cooling problem created by a specific redesign of a combustor for a gas turbine engine. As part of this redesign process, a base of a fuel rocket component of the combustor was widened. In part this design change afforded greater structural stability to support a fuel swirler that was to be attached at its free or distal end. The wider fuel rocket also provided sufficient space for coiling a fuel oil tube to address thermal expansion of that fuel supply tube. Within the bore of the coiling a gas sleeve was provided for provision of a fuel gas to a point downstream, on a flow basis, of most or all of the coiling.
The inventors of the present invention realized, however, that at the base of the fuel rocket there would be a zone having a high thermal gradient given that this is where a cooler support housing joins a substantially hotter fuel rocket structure. Also, a weld along the relatively wider rocket base, which is expected to be weaker than the fuel rocket itself, would not be cooled in a manner that the earlier versions were cooled, e.g., merely by the flow of fuel gas within a narrower fuel rocket. Consequently, the base area and the weld, which attaches the wider rocket base to the combustor support housing, would be subject to higher temperatures that would unacceptably shorten the life of the weld. The inventors conceived of an innovative solution to cool this weld without the use of a separate cooling air flow from fluid compressed by the turbine compressor, and without use of other performance- or efficiency-decreasing approaches. This was achieved by providing active cooling using a portion of the fuel gas flowing into the gas sleeve.
To cool the rocket weld 114 during gas fuel operation, a plurality of impingement holes 128 are provided through the gas sleeve inlet 122. In the embodiment depicted in
Generally it is appreciated that during operation of some embodiments a support housing will have a substantially lower temperature than a base area of a fuel rocket attached to it, where that fuel rocket base area is not provided with active cooling by use of a flow of fuel gas from the fuel system within the fuel rocket. Whereas in embodiments in which the base area is welded to the support housing, given that such welds are less strong than the fuel rocket itself with regard to tolerating thermal stresses, the active cooling described herein, when directed to the base area, is effective to maintain the weld at a cooler temperature, closer to the temperature of the support housing. The active cooling also is effective to move the area of high relative stress, which is due to a large temperature gradient, further from the base, toward the distal end of the fuel rocket, where the fuel rocket structure better tolerates this stress.
Accordingly, embodiments of the invention provide a plurality of impingement holes, or more generally apertures, in a gas sleeve wherein the impingement holes have compound angles effective to actively cool a desired area of surrounding structure, such as a rocket base, with a rotationally swirling flow of cooling fuel gas. For specific embodiments, a desired compound angle to achieve active cooling to a desired area, and simultaneously to provide a desired angle of rotational swirling, may be calculated and drilled or otherwise formed into a gas sleeve by means known to those skilled in the art.
During typical operations, a small portion, less than half, or substantially less than half, of the total supplied fuel gas passes through impingement holes 128 or 228. This portion of gas heats up by cooling the rocket weld 114, and thereby increases the average fuel gas temperature.
The embodiment depicted in
Also, the relative positions of the apertures and the area to be cooled by the portion of fuel gas passing through the apertures is not meant to be limited to the relative positions depicted in
More generally, it is appreciated that a gas sleeve for providing fuel gas to a burner, which may be disposed within a fuel rocket assembly of a gas turbine engine combustor, comprises a plurality of apertures to provide impingement-type cooling of a desired area, structure, or component, such as a critical weld joint, wherein the impingement-type cooling is effective to extend the life of such areas, structures or components.
With regard to the use of the terms “hole” and “aperture,” it is appreciated that a hole is but one type of aperture that may be used in embodiments of the present invention. As used herein, the term aperture is taken to mean any defined opening through a body, including but not limited to a round hole, an elliptical hole, a conical hole, a slit, or otherwise shaped passage through the body for the purpose of directing a fluid to cool a surface of a structure or component.
Embodiments of the present invention include specific individual components, such as a gas sleeve as set forth herein, a fuel rocket assembly or rebuild kit comprising such gas sleeve, a combustor (which may include a plurality of fuel rocket assemblies configured on a support housing), and a gas turbine engine comprising such gas sleeve in each of one or more fuel rocket assemblies in combustors.
Based on the above disclosure and appended figures, it is further appreciated that embodiments of the present invention also pertain to methods for cooling a desired area or structure of a fuel rocket assembly of a gas turbine engine combustor. One such method may be described as follows:
1. forming a plurality of apertures through a gas sleeve to provide impingement cooling, the forming comprising providing a tilt angle of the apertures directed toward an area or a structure in need of impingement cooling;
2. attaching the gas sleeve to a support housing to convey a fuel gas;
3. attaching a fuel rocket onto the support housing to enclose the gas sleeve; and,
4. supplying a flow of the fuel gas through the gas sleeve from the support housing, wherein a portion of the flow passing through the apertures is effective for cooling the desired area or structure of the fuel rocket assembly.
Another related method for cooling a desired area of a fuel rocket assembly of a gas turbine engine combustor may be described as follows: directing a portion of fuel gas to be consumed in the combustor through a plurality of apertures to impinge the area to be cooled by said portion prior to said portion being consumed, wherein the plurality of apertures are formed through a gas sleeve at angles to direct said portion to the area, the gas sleeve attached to the support housing to convey a fuel gas and fitting within the fuel rocket.
In various embodiments, the desired area of the fuel rocket assembly includes a weld attaching the base of the fuel rocket to the support housing. Also, per the above discussion, the forming step noted above may also comprise additionally providing a rotational angle effective to create a rotationally swirling flow of cooling fuel gas from the apertures.
It should be understood that the examples and embodiments described herein are for illustrative purposes only and that various modifications or changes in light thereof will be suggested to persons skilled in the art and are to be included within the spirit and purview of this application and the scope of the appended claims.
