Steam Injection Manifold Aerodynamic Interference
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Solution Overview
Problem
Gas turbine engines face challenges in reducing NOx emissions due to high combustor flame temperatures, and existing steam injection systems cause aerodynamic interference when located aft and downstream of the diffuser, affecting the flow stream and performance.
Innovation Solution
An annular steam injection manifold with circumferentially evenly distributed, non-uniformly sized steam injection holes is designed, positioned aftwardly and radially inwardly of the diffuser outlet, and an annular baffle with a convex surface that conforms to diffuser flow streamlines is used to minimize aerodynamic interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If steam injection manifold is located aft and downstream of the diffuser, then steam injection can be achieved, but aerodynamic interference with the flow stream of CDP air occurs
Solution Approach 1:
The patent applies local quality by creating a dedicated steam injection zone within the combustion chamber that is spatially separated from the diffuser flow path. The steam injection holes are positioned in the forward end wall of the combustion chamber, injecting steam locally into the combustion zone without interfering with the downstream flow stream from the diffuser. This localized injection approach allows steam to be introduced where needed while avoiding aerodynamic interference with the CDP air flow.
2Quantity of substance
If steam injection manifold is located radially inwardly of the diffuser, then steam injection is possible, but no room is available in engines without radial space
Solution Approach 1:
The patent transitions from a radial injection approach to an axial injection approach. Instead of positioning the steam injection manifold radially inwardly of the diffuser (which requires radial space), the injection holes are positioned in the forward end wall of the combustion chamber, utilizing the axial dimension. This dimensional change allows steam injection in engine configurations where radial space is not available, thereby improving adaptability across different engine designs.
3Object-generated harmful factors
If lean premixed combustion is used, then NOx emissions are reduced, but flame temperatures must be maintained at lower levels
Solution Approach 1:
The patent introduces steam as a third component to change the combustion parameters. By injecting steam into the lean premixed combustion zone, the combustion chemistry is modified to allow for lower flame temperatures while maintaining adequate combustion efficiency. The steam acts as a thermal ballast and diluent, enabling the combustion process to operate at reduced temperatures that limit NOx formation while still achieving complete combustion of the fuel-air mixture.
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 configuration allows for effective steam injection into the combustion chamber with minimal interference, achieving a uniform distribution of steam and reducing NOx emissions while maintaining engine performance.
Implementation Method 1
Steam injection for providing steam to a combustion zone of the combustor has also been developed for achieving low NOx emissions. Steam injection increases the mass flow and therefore increases the power output and steam injection ahead of the combustion reaction zone reduces the amount of oxides of nitrogen generated in the combustion process.
Implementation Method 2
an annular baffle with a convex surface that conforms to diffuser flow streamlines is used to minimize aerodynamic interference
Data Source
AI summary
A gas turbine engine steam injector includes an annular steam injection manifold aftwardly bounded by an aft manifold wall having steam injection holes disposed therethrough and located axially aft and radially inwardly of a diffuser outlet. An outer baffle wall around manifold has a curved convex surface which may generally conform to a streamline emanating from outlet. Holes may be circumferentially evenly distributed and non-uniformly sized around the aft manifold wall. Hollow struts extend between radially outer and inner bands of a diffuser and a steam supply header in steam supply communication with a fluid passage of at least one of the struts having a passage outlet open to steam cavity within cavity casing located inwardly of inner band. Openings are disposed in an aft cavity wall between cavity and the injector. Passages may be in only a non-uniformly distributed portion of the struts adjacent to each other.