Staged Tangential Nozzles for Can-Annular Combustor Emissions
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Solution Overview
Problem
Gas turbine combustors face challenges in minimizing pollutant emissions, particularly NOx and CO production, due to high peak flame temperatures and oxygen concentrations, which are not adequately addressed by existing designs.
Innovation Solution
A novel can-annular combustor design with staged fuel and air nozzles that create enhanced mixing of combustion reactants, reducing oxygen concentration and peak flame temperatures, and utilizing compressor discharge air to burn CO before entering the turbine, along with tangentially firing fuel and air nozzles to enhance ignition and reduce emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If traditional fuel-air nozzles are used in can-annular combustors, then the combustion process can be maintained, but high peak flame temperatures and oxygen concentrations result in high pollutant emissions (NOx and CO)
Solution Approach 1:
The combustor is divided into multiple zones with different functions: a central recirculation zone, an intermediate mixing zone, and an outer combustion zone. Fuel and air are introduced at different locations and stages, creating distinct regions with different oxygen concentrations and temperature profiles that reduce peak flame temperatures and pollutant formation
Solution Approach 2:
Different regions of the combustor are designed with different local characteristics: the central region has high fuel concentration for combustion, while the outer regions have higher air concentration for mixing and cooling. This spatial variation in composition creates lower peak temperatures and reduced NOx emissions in critical zones
2Productivity
If fuel and air are mixed thoroughly before combustion, then combustion efficiency is improved, but high oxygen concentration leads to increased NOx production
Solution Approach 1:
Air is introduced into the combustor before fuel in certain zones, creating pre-mixed regions that promote efficient combustion. However, the staged introduction and spatial distribution ensure that not all regions have high oxygen-fuel mixing simultaneously, reducing peak temperatures and NOx formation while maintaining overall combustion efficiency
Solution Approach 2:
The combustion process is extended from a single-plane mixing approach to a three-dimensional staged mixing process. Fuel and air are introduced at different axial and radial positions, creating a multi-dimensional mixing pattern that achieves efficient combustion while distributing oxygen concentration to reduce NOx production
3Stability of the object's composition
If compressor discharge air is introduced closer to the fuel nozzles, then mixing is enhanced, but the CO burnout is insufficient
Solution Approach 1:
The air introduction system is segmented into multiple stages: initial air introduction for mixing near the fuel nozzles, and subsequent air introduction further downstream for CO burnout. This staged air supply ensures both good mixing and complete combustion of CO before gases exit the combustor
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 design significantly reduces pollutant emissions, minimizing the need for emission control devices and environmental impact by optimizing combustion conditions, including lower NOx production and complete CO combustion.
Implementation Method 1
The original feature of the invention is that the fuel and air nozzles are placed in such a way as to create an environment with enhanced mixing of combustion reactants and products
Implementation Method 2
A fuel air nozzle can take on different configurations such as single to multiple annular inlets with swirling vanes on each one
Implementation Method 3
the introduction of compressor discharge air downstream of the combustion region allows for any CO produced during combustion to be burned/consumed before entering the first stage turbine
Implementation Method 4
the tangentially firing fuel and fuel-air nozzles directs any initial flame fronts to the adjacent burner nozzles in each can, greatly enhancing the ignition process of the combustor
Implementation Method 5
A typical method for cooling the combustor is effusion cooling, implemented by surrounding the combustion liner with an additional, offset liner, which between the two, compressor discharge air passes through and enters the hot gas flow path through dilution holes and cooling passages
Implementation Method 6
This technique removes heat from the component as well as forms a thin boundary layer film of cool air between the liner and the combusting gases
Data Source
AI summary
A combustion device used in gas turbine engines to produce propulsion or rotate a shaft for power generation includes a can-annular combustor with a system of fuel and air inlet passages and nozzles that results in an optimal combustion environment of fuel and air. Fuel, air and/or fuel-air inlets are placed at various longitudinal locations and circumferentially distributed, and direct the flow tangentially or nearly tangent to the can liner. The combustion device provides an optimal mixing of fuel and air, creates an environment for combustion that reduces pollutant emissions, reduces the need for costly pollution control devices, enhances ignition and flame stability, reduces piloting issues, and improves vibration reduction.