Patent Application
20100242487
The subject matter disclosed herein relates to the art of turbomachines and, more particularly, to a turbomachine including a thermally decoupled can-annular transition piece.
In general, gas turbine engines 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 via a hot gas path. The turbine converts thermal energy from the high temperature gas stream to mechanical energy that rotates a turbine shaft. The turbine may be used in a variety of applications, such as for providing power to a pump or an electrical generator.
Many gas turbines include an annular combustor within which are formed the combustion gases that create the high temperature gas stream. Other turbomachines employ a plurality of combustors arranged in a can-annular array. In such a turbomachine, the combustion gases are formed in each of the plurality of combustors and delivered to the turbine through a transition piece. In addition to providing a passage to the turbine, the transition piece provides an additional opportunity to enhance combustion. Certain turbomachines employ a series of dilution passages arranged in the transition piece. A portion of compressor air is passed along the transition piece, through the dilution passages, and into the combustion airstream. This portion of the compressor air, or dilution gases, is employed to enhance a profile/pattern factor of the combustion gases.
According to one aspect of the invention, a turbomachine includes a plurality of injection nozzles arranged in a can-annular array and a transition piece including at least one wall that defines a combustion flow passage. A dilution orifice is formed in the at least one wall of the transition piece. The dilution orifice guides dilution gases to the combustion flow passage. A heat shield member is mounted to the at least one wall of the transition piece in the combustion flow passage. The heat shield member includes a body having a first surface and an opposing second surface through which extends a dilution passage. The dilution passage is off-set from the dilution orifice. The heat shield member is spaced from the at least one wall of the transition piece defining a flow region between the at least one wall and the second surface.
According to another aspect of the invention, a method of thermally decoupling a transition piece from combustion gases in a turbomachine includes creating cooling gases in a compressor portion of the turbomachine, generating combustion gases in a plurality of combustion chambers arranged in a can-annular array, guiding the combustion gases into a flow cavity of the turbomachine. The flow cavity fluidly connects the can-annular array of combustion chambers with a first stage of a turbine. The method further includes shielding an internal surface of the transition piece from the combustion gases with at least one heat shield member. The at least one heat shield member is spaced from the internal surface of the transition piece to form a flow cavity. The cooling airflow is passed through at least one dilution orifice formed in the transition piece. The dilution orifice is fluidly connected to the flow cavity. Finally, the method includes guiding the cooling airflow through at least one dilution passage formed in the at least one heat shield member. The at least one dilution passage is off-set from the at least one dilution orifice so as create an effusion airflow that passes over a surface of the at least one heat shield member to thermally decouple the inner wall of the transition piece from the combustion gases.
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 reference to
As best shown in
Combustor 6 is coupled to turbomachine 2 through a transition piece 55. Transition piece 55 channels combustion gases from combustion chamber 48 downstream towards a first stage turbine nozzle 62. Towards that end, transition piece 55 includes an inner wall 64 and an outer wall or impingement sleeve 65. Outer wall 65 includes a plurality of openings 66 that lead to an annular flow passage 68 defined between inner wall 64 and outer wall 65. With this arrangement, outer wall 65 controls cooling air flow (and heat exchange) via a pressure differential within annular flow passage 68. Similarly, inner wall 64 includes a plurality of dilution orifices 67 that lead from annular flow passage 68 into a combustion flow passage 72 that extends between combustion chamber 48 and turbine 10. Flow passage 72 includes a compound curvature that is constructed to deliver the combustion gases to first turbine stage 62 in a manner that will be described more fully below.
During operation, air flows through compressor 4, is compressed, and passed to combustor 6 and, more specifically, to injection nozzles 37-39. At the same time, fuel is passed to injection nozzles 37-39 to mix with the compressed air to form a combustible mixture that passes from can-annular array 40 to combustion chamber 48 and ignited to form combustion gases. The combustion gases are then channeled to turbine 10 via transition piece 55. Thermal energy from the combustion gases is converted to mechanical rotational energy that is employed to drive compressor/turbine shaft 12.
More specifically, turbine 10 drives compressor 4 via compressor/turbine shaft 12 (shown in
In order to protect inner wall 64 from the effects of the hot combustion gases, transition piece 55 includes a plurality of heat shield members 80-85. As each heat shield member 80-85 includes similar structure, a detailed description will follow with reference to
As stated above, heat shield member 80 is mounted to yet spaced from inner wall 64 of transition piece 55. Towards that end, transition piece 55 includes a plurality of mounting members, two of which are indicated at 104 and 105 that project outward from inner wall 64. In the exemplary embodiment shown, mounting members 104 and 105 take the form of hook members 108 and 109. Each hook member 108, 109 includes a corresponding first end section 111 and 112 as well, that extend to a second end section 114 and 115. Correspondingly, heat shield member 80 includes a plurality of mounting elements, two of which are indicated at 120 and 121, that project outward from second surface 94.
In the exemplary embodiment shown, mounting elements 120 and 121 take the form of hook elements 124 and 125. Each hook element 124, 125 includes a corresponding first end 126 and 127 that extends to a respective second end 130 and 131 prior to terminating in a hook (not separately labeled). Hook elements 124 and 125 engage with hook members 108 and 109 to mount heat sealed member 80 to transition piece 55 so as to define flow passage 100. With this arrangement, cooling air flowing through combustor flow passage 72 passes through dilution orifice 67 into flow region 100 to form dilution air. The dilution air passes along flow region 100 and through dilution passage 96 into combustor flow passage 72. Accordingly, heat shield member provides a thermal barrier to inner wall 64 of transition piece 55. The thermal barrier affords a level of protection to various portions of inner wall 64. For example, by decoupling inner wall 64 from the combustion gases in flow passage 72, cracking of inner wall 64, particularly in areas around dilution orifices 67, is mitigated. More specifically, hot gases ingested into a vena contracta formed with the dilution air mixes with the combustion gases leads to cracking of the inner wall 64 in areas adjacent dilution orifices 67. By providing an off set between dilution orifice 67 and dilution passage 96 ingestion of the hot gases is eliminated such that heat shield member 80 prolongs an overall operation lie of transition piece 55.
Reference will now be made to
Reference will now be made to
In further accordance with the exemplary embodiment shown, heat shield member 170 is mounted to, yet spaced from inner wall 64 of transition piece 55 so as to define flow passage 100. More specifically, inner wall 64 includes a mounting member 209 shown in the form of an opening 211. Outer wall 65 also includes an opening (not separately labeled) that is in alignment with opening 211. Heat shield member 170 includes a mounting element 215 shown in the form of a projection or stud 218 that extends from second surface 173. Stud 218 is configured to extend through opening 211 so as to secure heat shield member 170 to transition piece 55. More specifically, stud 218 includes a first end portion 226 that extends to a second end portion 227 and includes a threaded section 233 that is configured to receive a fastener 238. Fastener 238, shown in the form of a nut having a plurality of internal threads (not shown) configured to engage with threaded section 233, is secured to stud 218 thereby mounting heat shield member 170 to transition piece 55. A second fastener 240 can be employed to provide a desired spacing from inner wall 64 so as to ensure alignment between adjacent heat shield members and provide uniformity to flow passage 100.
At this point, it should be understood that the heat shield member is constructed in accordance with the exemplary embodiment to provide structure to reduce heat exposure to inner wall 64 of transition piece 55. As noted above, by decoupling inner wall 64 from the combustion gases in flow passage 72, cracking of inner wall 64, particularly in areas around dilution orifices 67 is mitigated. More specifically, hot gases ingested into a vena contracta formed with the dilution air mixes with the combustion gases leads to cracking of the inner wall 64 in areas adjacent dilution orifices 67. By providing an off set between dilution orifice 67 and dilution passage 96 ingestion of the hot gases is eliminated such that heat shield member 80 prolongs an overall operation life of transition piece 55. That is, by providing a sacrificial component within transition piece 55, the heat shield members enhance serviceability and maintenance while extending an overall service life of turbomachine 2.
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.
