Sequential Combustor Cooling Gas Dilution
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Solution Overview
Problem
Gas turbines face challenges in maintaining low emissions and operational flexibility due to variations in operating conditions, particularly at part load and transient operations, where existing combustion systems struggle to achieve homogeneous temperature profiles and efficient fuel mixing, leading to increased NOx, CO, and unburned hydrocarbons emissions.
Innovation Solution
A sequential combustor arrangement with a dilution gas admixer and closed loop cooling system is introduced, where compressed cooling gas is used to cool the first combustor products before admixing them with the second combustor, creating a homogeneous temperature profile and optimizing fuel and oxygen distribution, thereby reducing emissions and improving efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the first combustor operates at high temperature to improve power output, then power output is improved, but emissions (NOx, CO, unburned hydrocarbons) increase and operational flexibility decreases
Solution Approach 1:
The combustion process is divided into two sequential stages: a first combustor for high-temperature power generation and a second combustor for low-emission finishing combustion. This segmentation allows each combustor to operate in its optimal temperature range, with the first combustor producing high power and the second combustor ensuring complete combustion at lower temperatures to reduce emissions of NOx, CO, and unburned hydrocarbons.
Solution Approach 2:
A dilution gas admixer is introduced as an intermediary component between the first and second combustors. It mixes cooling gas (taken from the turbine cooling system) with the hot exhaust from the first combustor to create a temperature-conditioned inlet for the second combustor. This intermediary enables temperature control and homogeneous mixing, allowing the second combustor to operate efficiently at lower temperatures for reduced emissions.
2Stability of the object's composition
If cooling gas is used to cool the first combustor products, then a homogeneous temperature profile is achieved, but cooling air consumption increases
Solution Approach 1:
The system uses its own turbine cooling gas as the dilution source for the second combustor. The cooling gas that would otherwise be discarded is recaptured and reused as dilution gas, creating a self-service loop. This approach provides the necessary cooling and homogeneous temperature profile while minimizing additional cooling air consumption by utilizing already-cooled gas from the turbine system.
3Object-generated harmful factors
If the second combustor inlet temperature is reduced to lower emissions, then emissions decrease, but fuel mixing and combustion stability become difficult
Solution Approach 1:
The dilution gas admixer performs preliminary cooling and mixing of the first combustor exhaust with cooling gas before the mixture enters the second combustor. This preliminary action creates a homogeneous temperature and composition profile, ensuring stable combustion conditions in the second combustor even at lower inlet temperatures. The pre-mixing process prevents local hot spots and ensures uniform fuel-air distribution, maintaining combustion stability while enabling lower operating temperatures for reduced emissions.
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 solution effectively reduces NOx emissions, enhances power output, and increases gas turbine efficiency by maintaining a stable combustion process across varying operating conditions, while also recuperating heat and conserving cooling air.
Implementation Method 1
a first combustion chamber (101) for burning the first fuel with the combustor inlet gas, a dilution gas admixer (27) for admixing a dilution gas (33) to the first combustor combustion products (35) leaving the first combustion chamber (101)
Implementation Method 2
a dilution gas admixer (27) for admixing a dilution gas (33) to the first combustor combustion products (35) leaving the first combustion chamber (101)
Implementation Method 3
a second burner (103) for admixing a second fuel (29) and a second combustion chamber (102) for burning the second fuel (29) with the mixture of first combustor combustion products (35) and dilution gas (33)
Data Source
AI summary
A gas turbine with a sequential combustor arrangement as disclosed includes a first combustor with a first burner for admitting a first fuel into a combustor inlet gas during operation and a first combustion chamber for burning the first fuel, a dilution gas admixer for admixing a dilution gas to the first combustor combustion products leaving the first combustion chamber, a second burner for admixing a second fuel and a second combustion chamber. To assure a temperature profile after the dilution gas admixer and to increase the gas turbine's power and efficiency a vane and/or blade of the turbine has a closed loop cooling. The outlet of the closed loop cooling is connected to the dilution gas admixer for admixing the heated cooling gas leaving the vane and/or blade into the first combustor combustion products.