Gas Turbine Combustor Transition Piece Contraction Ratio Optimization
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Solution Overview
Problem
The existing combustor transition piece designs in gas turbines increase cooling air, leading to reduced combined efficiency due to increased heat exchange at the transition piece outlet, which lowers the temperature of exhaust gas and reduces steam generation, thereby decreasing overall efficiency.
Innovation Solution
Optimizing the cross-sectional area change from the transition piece inlet to the outlet by setting the contraction ratio within a specific range (0.79≤Dout/Din≤0.9) to reduce flow velocity and heat exchange, while maintaining a stable and monotonous velocity profile to prevent local increases or decreases, thus improving combined efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the cross-sectional area of the transition piece outlet is increased to slow down the flow velocity of combustion gas, then the heat-transfer coefficient is decreased and the amount of heat exchange is reduced, but the size of the first stage turbine nozzle in the radial direction cannot be increased as it is aerodynamically determined
Solution Approach 1:
The patent optimizes the contraction ratio parameter (Dout/Din) within a specific range (0.79-0.9) to achieve the desired balance between flow velocity reduction and heat exchange minimization, rather than simply increasing the outlet area
2Loss of energy
If the cross-sectional area of the transition piece outlet is increased to reduce flow velocity and heat exchange, then combined efficiency is improved, but the structural constraints in the gas turbine casing prevent the combustor center line from being arranged in parallel with the axial center of the rotor
Solution Approach 1:
The patent addresses the oblique arrangement by optimizing the contraction ratio and controlling the velocity profile characteristics rather than changing the geometric arrangement of the combustor
Solution Approach 2:
Instead of trying to arrange the combustor in parallel with the axial center (ideal configuration), the patent accepts the oblique arrangement and compensates by optimizing the transition piece contraction ratio to achieve the desired flow characteristics
3Loss of energy
If the contraction ratio from transition piece inlet to outlet is increased to reduce heat exchange, then the flow velocity at the wall surface is reduced, but the flow stability may be compromised
Solution Approach 1:
The patent identifies and optimizes the contraction ratio parameter within a specific range (0.79-0.9) that simultaneously achieves flow velocity reduction and maintains flow stability
Solution Approach 2:
The patent uses computational fluid dynamics (CFD) simulation to analyze the velocity profile and provides feedback for optimizing the contraction ratio, ensuring both heat exchange reduction and flow stability
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 optimized shape of the combustor transition piece reduces heat exchange at the outlet, enhancing the combined efficiency by maintaining a stable flow velocity and minimizing the cooling air effect, thereby improving the overall performance of the gas turbine.
Implementation Method 1
the heat quantity to be cooled can be reduced from the beginning, the combined efficiency is improved. If the flow velocity of the combustion gas is slowed by increasing the cross-sectional area of the transition piece outlet, the heat-transfer coefficient is also decreased, thereby reducing the amount of heat exchange.
Data Source
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Figure 3~4
AI summary
Provided is a designing method of a combustor transition piece (22) comprising setting an angle of a center line (s) of a combustor (2) relative to an axial center (R) of a rotor (4) of a gas turbine, setting a contraction ratio from a transition piece inlet (221) in which combustion gas flows to a transition piece outlet (222) from which the combustion gas flows out, forming an inner outline in a radial direction, by extending a straight line in parallel with the center line (s) from an inner end in a radial direction of the transition piece inlet (221) to a downstream side, while maintaining a cross-sectional area of the transition piece inlet (221), extending a straight line in parallel with the axial center (R) from an inner end in a radial direction of the transition piece outlet (222) to an upstream side, and connecting the straight lines by an arc, forming an outer outline in the radial direction by smoothly connecting an outer end in a radial direction on a tubular downstream side where the cross-sectional area of the transition piece inlet (221) is maintained, to an outer end in the radial direction of the transition piece inlet (221), and monotonously reducing a cross-sectional area from the tubular downstream side to the transition piece outlet (222), along the inner outline in the radial direction and the outer outline in the radial direction.