Transition piece having cooling rings

A transition piece having a first end configured to be coupled to a turbine and a second end disposed opposite to the first end and configured to be coupled to a combustor, the transition piece comprising:

• an inner transition piece providing a gas channel, the inner transition piece including
• an inner surface facing the gas channel, and
• an outer surface disposed opposite to the inner surface so as to face an outside of the inner transition piece, the outside of the inner transition piece configured to receive a flow of cooling air in an axial direction of the transition piece, the cooling air flowing over the transition piece from the first end to the second end;
• a plurality of cooling rings disposed on the outer surface of the inner transition piece and separated from each other in the axial direction, each cooling ring of the plurality of cooling rings including a three-sided structure configured with the outer surface to form a continuous cavity having an annular shape surrounding the inner transition piece, the three-sided structure including two axially facing sides respectively connected to the outer surface of the inner transition piece, and an outwardly disposed side connecting the two axially facing sides, the two axially facing sides substantially parallel to each other such that each of the two axially facing sides is substantially perpendicular to the outer surface of the inner transition piece, the outwardly disposed side facing the outside of the inner transition piece in a radial direction and receiving the flow of cooling air in the axial direction of the transition piece;
• a plurality of cooling rings disposed on the outer surface of the inner transition piece and separated from each other in the axial direction, each cooling ring of the plurality of cooling rings including a three-sided structure configured with the outer surface to form a continuous cavity having an annular shape surrounding the inner transition piece, the three-sided structure including the flow of cooling air in the axial direction of the transition piece;
• a plurality of film holes formed through the inner transition piece and configured to enable the continuous cavity of each of the plurality of cooling rings to communicate with the gas channel;
• and
• a plurality of impingement holes formed through the outwardly disposed side of the cooling ring and configured to enable the continuous cavity of each of the plurality of cooling rings to communicate with the outside of the inner transition piece,
• wherein the outwardly disposed side of each cooling ring of the plurality of cooling rings receives a portion of a downstream flow of the cooling air from the first end to the second end, the downstream flow of the cooling air flowing in the axial direction and passing over the outwardly disposed side of each cooling ring of the plurality of cooling rings,
• wherein the plurality of film holes are configured to enable the continuous cavity to communicate with the gas channel and the plurality of impingement holes are configured to enable the continuous cavity to communicate with the outside of the inner transition piece, such that the portion of the downstream flow of the cooling air flows from the outside of the inner transition piece to the gas channel through a series arrangement of the plurality of impingement holes, the continuous cavity, and the plurality of film holes,
• wherein the cooling air having passed through the plurality of impingement holes but not having passed through the plurality of film holes passes through the continuous cavity by passing between the two axially facing sides of the three-sided structure and by not passing through either of the two axially facing sides of the three-sided structure,
• wherein the plurality of cooling rings include a first cooling ring and a second cooling ring that are spaced apart from each other by a streamwise distance (L2) between a trailing side of the first cooling ring and a trailing side of the second cooling ring,
• wherein the plurality of film holes include a first plurality of cooling ring holes arranged to correspond to the first cooling ring and a second plurality of cooling ring holes arranged to correspond to the second cooling ring, the first plurality of cooling ring holes having an effective cooling distance (L1) with respect to the second plurality of cooling ring holes, and
• wherein the streamwise distance is substantially equal to the effective cooling distance.