Separate Cooling and Dilution Air Feeding in Gas Turbine Mixers
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Solution Overview
Problem
Conventional gas turbine systems face challenges in achieving operational flexibility and reducing emissions, especially at part load and transient conditions, due to inadequate cooling methods that result in high pressure drops and inefficiencies when using heat exchangers or side-wall injection of cooling media.
Innovation Solution
The solution involves feeding only part of the dilution air and cooling air from the compressor plenum, with the remainder coming from the sequential liner exit, using a mixer with injection pipes to effectively cool the hot gas flow and reduce thermo-acoustic coupling, self-ignition risks, and hot gas ingestion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If heat exchangers are used for cooling the hot gas flow, then cooling efficiency is improved, but pressure drop increases and device complexity increases
Solution Approach 1:
The cooling function is segmented into multiple injection pipes distributed around the mixer perimeter, each injecting cooling air at different locations. This replaces the single heat exchanger approach with distributed injection points, achieving cooling while maintaining flow path simplicity and minimizing pressure drop.
Solution Approach 2:
The cooling function is extracted from the main heat exchanger and implemented through separate injection pipes that introduce cooling air directly into the hot gas flow. This separates the cooling action from the main flow path, allowing independent control and reduced pressure drop across the main system.
2Temperature
If cooling air is injected from side walls to cool the hot gas flow, then cooling is achieved, but thermo-acoustic coupling increases and mixing efficiency decreases
Solution Approach 1:
Cooling air is injected at specific localized positions through injection pipes positioned at the mixer perimeter, rather than uniform side-wall injection. This creates localized cooling zones that reduce thermo-acoustic coupling while maintaining overall cooling effectiveness. The injection points are strategically positioned to optimize mixing and minimize harmful acoustic effects.
3Device complexity
If all dilution air is fed from the compressor plenum, then system simplicity is maintained, but cooling efficiency decreases and hot gas ingestion risk increases
Solution Approach 1:
The dilution air supply is segmented into two sources: compressor plenum and sequential liner exit. This segmentation allows optimization of different air streams for different purposes - compressor plenum for general dilution and sequential liner exit for enhanced cooling - thereby improving cooling efficiency while maintaining reasonable system complexity.
4Stability of the object's composition
If injection pipes are used to admix dilution medium, then mixing efficiency is improved, but device complexity increases
Solution Approach 1:
The injection pipes are designed with adjustable positioning and orientation capabilities, allowing dynamic optimization of injection angles and locations based on operating conditions. This dynamic adaptability enhances mixing efficiency while the modular pipe design keeps the overall structure relatively simple and maintainable.
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 reduces thermo-acoustic coupling, enhances cooling efficiency, lowers risks of self-ignition and hot gas ingestion, and improves mixing, resulting in lower NOx and CO emissions while maintaining operational flexibility.
Implementation Method 1
a mixer for admixing a dilution air to the hot gas flow leaving the combustion chamber... for admixing the dilution medium or air to cool the hot gas flow leaving combustion chamber
Implementation Method 2
The mixer is adapted to guide combustion gases in a hot gas flow path extending between the first combustion chamber and the second burner
Data Source
AI summary
A combustor arrangement of a gas turbine engine or power plant is disclosed, having at least one combustion chamber, at least one mixer arrangement for admixing air or gas to the hot gas flow leaving the combustion chamber. The mixer arrangement is configured to guide combustion gases in a hot gas flow path extending downstream of the combustion chamber, wherein the mixer includes a plurality of injection pipes pointing inwards from the side walls of the mixer arrangement for admixing air portions to cool at least the hot gas flow leaving combustion chamber. The mixer arrangement is applied to at least one volume of dilution air flowing from a first plenum and at least one volume of cooling air flowing from a second plenum.