Recirculating Nozzle for Gas Turbine Combustion Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current combustion systems in gas turbine engines face instability and emission challenges at lean fuel-to-air ratios, leading to increased NOX, CO, and UHC levels, with traditional methods failing to provide stable combustion and efficient emissions reduction without complex auxiliary systems.
Innovation Solution
A recirculation product injection nozzle system that creates inner and outer recirculation zones through radial swirlers, recirculating combustion products to mix with compressor discharge air and fuel, promoting distributed combustion with high turbulence and oxidizer temperatures, thereby stabilizing the combustion process and reducing emissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If lean direct injection and premixing techniques are used to reduce NOX emissions, then fuel-to-air ratio can be reduced, but combustion instabilities increase and engine operating envelope is limited
Solution Approach 1:
The combustion process is segmented into multiple zones with different fuel-air mixing characteristics. The nozzle creates distinct recirculation zones that provide localized high-temperature environments while maintaining overall lean combustion conditions, allowing NOX reduction without sacrificing combustion stability.
Solution Approach 2:
Fuel is injected into pre-formed recirculation zones that are created by the swirler geometry before the actual combustion occurs. This preliminary arrangement of fuel and air in controlled recirculation zones ensures stable combustion initiation and propagation, preventing instabilities that would otherwise occur with direct lean injection.
2Object-generated harmful factors
If combustion residence time is shortened to reduce NOX emissions, then flow path length is reduced, but higher frequency instabilities occur that are more damaging to engine components
Solution Approach 1:
The patent introduces spatial recirculation zones that extend the effective combustion residence time in a different spatial dimension. By creating toroidal recirculation flows that loop back through the combustion zone, the system achieves extended residence time for NOX reduction without increasing the linear flow path length, thereby avoiding higher frequency instabilities.
3Reliability
If distributed combustion with high turbulence is used to achieve stable lean combustion, then oxidizer temperature must be very high, but this requires complex heat exchangers or recirculation ducts that are heavy and space-consuming
Solution Approach 1:
The recirculation function is merged directly into the fuel injection nozzle structure. The swirler geometry and recirculation zones are integrated into the nozzle body, eliminating the need for separate external recirculation ducts and heat exchangers. This integration achieves high-temperature oxidizer conditions while maintaining a compact, lightweight design.
Solution Approach 2:
The nozzle design creates self-sustaining recirculation zones that automatically maintain high oxidizer temperatures through the geometry-driven flow patterns. The recirculation is self-generated by the swirler outlet configuration and does not require external heating systems or complex thermal management equipment.
4Reliability
If conventional recirculation ducts are used to provide high oxidizer temperatures for distributed combustion, then combustion stability is achieved, but the system becomes heavier and occupies more space
Solution Approach 1:
The recirculation function is extracted from the external ducting system and relocated to the nozzle structure itself. By embedding the recirculation zones within the nozzle body and using the fuel injection geometry to create the recirculation flows, the patent eliminates heavy external recirculation ducts while maintaining combustion 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 system achieves stable, low-emission combustion with reduced NOX, CO, and UHC levels, maintaining high efficiency and reducing thermo-acoustic instabilities, while eliminating hot spots and ensuring homogeneous temperature distribution across the combustor.
Implementation Method 1
An outer air swirler is mounted to the nozzle housing and is configured to impart swirl to a flow of compressor discharge air from upstream of the inlet end passing through the outer air swirler with sufficient swirl strength to recirculate combustion products from downstream of the outlet end into an outer recirculation zone
Implementation Method 2
Distributed combustion has been successfully demonstrated in industrial furnaces. The technique involves using a very lean mixture wherein high temperature oxidizer reacts with fuel at very high levels of turbulence in a distributed reaction zone.
Implementation Method 3
An outer fuel injector is mounted proximate to the outer air swirler and is configured and adapted to inject a spray of fuel into the outer recirculation zone
Data Source
AI summary
Combustion systems and the related methods operate to supply a stream of combustion products to a turbine in a gas turbine engine by forming an outer recirculation zone of recirculating combustion products within a combustor and by forming an inner recirculation zone inboard of the outer recirculation zone. The inner and outer recirculation zones are formed by imparting swirl to compressor discharge air passing through an outer air swirler and an inner air swirler radially inboard of the outer air swirler. Fuel is injected from an outer fuel injector into the outer recirculation zone, and fuel is also injected from an inner fuel injector into the inner recirculation zone.