Parallel Cooling Concept for Gas Turbine Transition Piece
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Solution Overview
Problem
Existing gas turbine combustor cooling systems face increased pressure drop and leakage issues due to higher engine gas temperatures, leading to reduced cycle efficiency and higher emissions, with prior solutions either increasing complexity or introducing leakage into the combustion system.
Innovation Solution
A parallel cooling concept is introduced, utilizing a transition piece assembly with a second air inlet system that feeds both upstream and downstream portions of the convective cooling channel, reducing overall pressure drop and leakage by optimizing air flow and mixing, and allowing for a manufacturing-friendly design using existing techniques like welding and metal sheet forming.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If higher engine gas temperatures are used to increase power output, then power output is improved, but cooling bleed requirements increase resulting in reduced cycle efficiency and increased emission levels
Solution Approach 1:
The cooling system is divided into two independent parallel paths: a first cooling path with impingement cooling for the transition piece, and a second cooling path with convective cooling for the sequential liner. This segmentation allows each path to be optimized independently, reducing total cooling flow requirements while maintaining component temperature control at higher engine gas temperatures.
Solution Approach 2:
A bypass system acts as an intermediary element that redirects a portion of the cooling air flow from the sequential liner cooling path back to the combustion plenum. This intermediary mechanism recovers cooling air that would otherwise be wasted, reducing the net cooling bleed requirement and improving cycle efficiency while enabling higher engine gas temperatures.
2Reliability
If traditional series cooling arrangements are used, then cooling coverage is improved, but pressure drop increases
Solution Approach 1:
The cooling system is segmented into parallel paths rather than series arrangement. The first cooling path handles transition piece cooling with impingement cooling, while the second cooling path handles sequential liner cooling with convective cooling. This parallel segmentation eliminates the additive pressure drop effect of series arrangements, reducing total pressure drop while maintaining comprehensive cooling coverage.
Solution Approach 2:
Instead of the conventional series arrangement where cooling air flows sequentially through multiple components, the invention inverts the arrangement by using parallel paths where cooling air is divided and flows simultaneously through different cooling zones. This inversion fundamentally changes the pressure drop characteristics from additive to approximately equal to the highest individual path pressure drop.
3Stress or pressure
If effusion cooling techniques are used to lower pressure drop, then pressure drop is reduced, but leakage into the combustion system increases resulting in higher emissions
Solution Approach 1:
The bypass system serves as an intermediary that captures cooling air from the sequential liner cooling path and redirects it to the combustion plenum. This intermediary mechanism prevents cooling air leakage into the combustion system, thereby reducing emissions while maintaining low pressure drop characteristics of the parallel cooling arrangement.
Solution Approach 2:
The invention converts the potential harm of cooling air leakage into a benefit by using the bypass system to redirect this cooling air back to where it is needed in the combustion plenum. This transforms what would be a harmful leakage into a useful contribution to combustion air supply, reducing emissions while maintaining efficient cooling.
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
This approach significantly reduces the needed pressure drop by half compared to prior art, achieving efficient cooling with lower leakage penalties and simpler manufacturing processes, thereby improving cycle efficiency and reducing emissions.
Implementation Method 1
Cooling medium through the cooling apertures (201) enters the plenum (203) created between external and internal liners (101, 102) and a cooling medium flows along at least the first section (200) of the transition piece assembly (100)
Implementation Method 2
the flow sleeve assures that the convection cooling air is directed as desired along the transition piece from the turbine end to the combustor liner end, over the dimpled surface, increasing the heat transfer coefficients and reducing the temperature of the transition piece
Data Source
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AI summary
The invention relates to a transition piece assembly (100) for a gas turbine. The transition piece has one end adapted for connection to a gas combustor (500) and an opposite end adapted for connection to a first turbine stage (600). Said transition piece has at least one external liner (101) and at least one internal liner (102); the internal liner forms the hot gas flow channel (103). A first section (200) of the transition piece assembly upstream of a first turbine stage (600) has a plurality of cooling apertures (201) in the external liner. Cooling medium (202) through the cooling apertures (201) enters a plenum (203) created between the external and internal liners (101, 102) and the cooling medium flows along at least the first section (200) of the transition piece assembly. At least one second section (300) of the transition piece assembly upstream of the first section (200) with respect to the hot gas flow (104) has at least one additional air inlet system (301). The additional air inlet system (301) of the second section (300) is designed in the manner that the cooling medium (302) is discharged into at least one air plenum (303) created between external and internal liners in two different directions.