Leaf Seal for Turbine Transition Duct Thermal Expansion
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Solution Overview
Problem
The connection between combustor ducts and turbine sections in turbine systems experiences undesirable shifts due to thermal expansion, leading to gaps and leakage, as the ducts are offset from the longitudinal axis, causing mixing of cooling air and hot gas.
Innovation Solution
The implementation of leaf seals at the interface between the transition ducts and the turbine section, which accommodate thermal growth by allowing movement along or about various axes, ensuring a consistent seal despite offsetting of the ducts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ducts are offset from the longitudinal axis to shift hot gas flow radially or tangentially, then the efficiency and power output of the turbine system increase, but thermal expansion causes undesirable shifts in the ducts leading to gaps and leakage between the ducts and turbine sections
Solution Approach 1:
The seal interface is designed to be dynamic rather than rigid, allowing the duct to move relative to the turbine section during thermal expansion. The seal maintains contact between the duct outlet and turbine section throughout the range of motion, preventing gaps while accommodating the offset configuration that improves power output.
Solution Approach 2:
The seal geometry is designed to change its effective sealing parameters as the duct expands thermally. The curved or angled seal surface allows the contact point to migrate along the seal interface, maintaining sealing effectiveness despite changes in duct position and orientation caused by thermal growth.
2Loss of energy
If ducts are offset from the longitudinal axis, then first stage nozzles can be eliminated reducing pressure drops, but thermal expansion causes unexpected gaps that allow mixing of cooling air and hot gas
Solution Approach 1:
The seal interface is designed to be dynamic rather than rigid, allowing the duct to move relative to the turbine section during thermal expansion. The seal maintains contact between the duct outlet and turbine section throughout the range of motion, preventing gaps while accommodating the offset configuration that improves power output.
Solution Approach 2:
The design accepts thermal expansion as an inevitable harmful effect, but converts it into a beneficial dynamic sealing mechanism where the seal geometry is specifically designed to maintain contact during expansion, turning the potential harm of movement into a reliable sealing solution.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The leaf seals effectively prevent gaps and leakage by accommodating thermal expansion, maintaining a sealed interface between the transition ducts and the turbine section, even with longitudinal, radial, and tangential offsets, thus enhancing the system's efficiency and power output.
Implementation Method 1
thermal expansion of the ducts can cause undesirable shifts in the ducts along or about various axes
Data Source
Figure 1~2
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AI summary
A turbine system includes a transition duct (50) which includes an inlet (52), an outlet (54), and a passage (56) extending between the inlet and the outlet and defining a longitudinal axis, a radial axis, and a tangential axis. The outlet of the transition duct is offset from the inlet along the longitudinal axis and the tangential axis. The transition duct further includes an interface member (142) for interfacing with a turbine section. The turbine system further includes a leaf seal (140) contacting the interface member to provide a seal between the interface member and the turbine section.