Angled Annular Walls for Gas Turbine Diffuser Flow Control
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Solution Overview
Problem
When turbine and diffuser systems are integrated, they often do not function optimally due to independently designed components, leading to suboptimal performance, with issues in total pressure and swirl profiles at the diffuser inlet and potential separation problems downstream.
Innovation Solution
The integration of a turbine and axial-radial diffuser system with specifically angled inner and outer annular walls across various sections, creating desirable total pressure and swirl profiles and preventing separation by varying wall angles to match energy-rich and energy-poor flow conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If turbine and diffuser are independently designed for optimal performance, then each component achieves its design optimum, but the integrated system performs suboptimally due to mismatched total pressure and swirl profiles
Solution Approach 1:
The diffuser wall angles are varied locally along the axial direction to match the changing flow conditions. The first diffuser section has a first wall angle optimized for energy-rich flow from the turbine, while the second diffuser section has a second wall angle optimized for energy-poor flow, creating local optimization throughout the diffuser length
Solution Approach 2:
The diffuser design transitions dynamically to adapt to changing flow conditions. By having different wall angles in different sections, the diffuser can accommodate the transition from high-energy flow near the turbine to lower-energy flow downstream, maintaining optimal performance across varying operating conditions
2Ease of manufacture
If constant wall angles are used in the diffuser, then manufacturing is simplified, but flow separation occurs downstream due to mismatched flow energy conditions
Solution Approach 1:
The diffuser is segmented into multiple sections along the axial direction, with each section having its own optimized wall angle. This segmentation allows each portion to handle specific flow energy conditions appropriately, preventing flow separation while maintaining manufacturability through modular design
3Stress or pressure
If the diffuser is designed for high pressure recovery, then total pressure profiles improve, but swirl control becomes insufficient leading to separation
Solution Approach 1:
Different sections of the diffuser have different wall angles optimized for their specific functions. The first section prioritizes pressure recovery with steeper walls, while the second section prioritizes swirl control and flow attachment with gentler walls, achieving both objectives simultaneously
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 improves diffuser performance by enhancing pressure recovery and preventing separation, as demonstrated by improved normalized pressure total absolute (PTA) and swirl profiles, and increased pressure recovery coefficient (Cp) values.
Implementation Method 1
The first inner annular wall is angled with respect to the axis of rotation at a first inner angle average, the first outer annular wall is angled with respect to the axis of rotation at a first outer angle average along the last stage airfoil section
Implementation Method 2
The diffuser section receives the exhaust fluids from the turbine, and gradually increases the pressure and reduces the velocity of the exhaust fluids
Data Source
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AI summary
A gas turbine (10) includes a turbine (16) and an axial-radial diffuser (18). The turbine includes a last stage airfoil section (28) having a first inner annular wall (58), a plurality of airfoils (100), a tip shroud including a first outer annular wall (102), and a stationary shroud (52) including a second outer annular wall (70). The first inner and the first and second outer annular walls are angled at a first inner and a first and second outer angle average (α3, θ3, θ4), respectively. The axial-radial diffuser includes third inner and outer annular walls (62, 74), wherein the third inner and outer annular walls (62, 74) are angled at a third inner and outer angle average (α5, θ5), respectively. The first outer angle average is greater than the third (θ3>θ5), the first inner angle average is greater than the third (α3>α5), and the third outer angle average is greater than the second (θ5>θ4).