Spiral Diffuser Gas Turbine Exhaust Orthogonal Flow
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Solution Overview
Problem
Conventional gas turbine exhaust systems experience pressure losses and flow disturbances due to the placement of hot struts in the flow path, which leads to inefficiencies, thermal concerns, and maintenance challenges, particularly with the aft rotor bearing, and require costly materials and complex designs to mitigate swirl and thermal issues.
Innovation Solution
The implementation of a spiral-shaped diffuser system with a central transition portion and a spiral portion that redirects the hot exhaust gas flow orthogonally, eliminating the need for struts in the flow path and allowing for efficient pressure recovery without swirl removal, positioning the aft rotor bearing and support structures outside the flow path for reduced heat exposure and improved accessibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If hot struts are placed in the flow path to support the diffuser, then structural support is provided, but pressure losses and flow disturbances increase
Solution Approach 1:
The patent removes the hot struts from the flow path entirely. The diffuser is supported by cold struts positioned outside the flow path, eliminating the need for hot struts that caused pressure losses and flow disturbances. This extraction of the problematic component resolves the contradiction between providing structural support and minimizing energy losses.
Solution Approach 2:
The patent introduces cold struts as an intermediary support structure positioned outside the flow path. These cold struts provide the necessary structural support for the diffuser without interfering with the gas flow, thus mediating between the need for structural integrity and the requirement to minimize flow disturbances.
2Force
If hot struts are positioned in the flow path, then rotor load is transferred to ground, but thermal concerns require cooling air and shielding
Solution Approach 1:
The patent extracts the hot struts from the flow path and replaces them with cold struts positioned outside the flow path. This eliminates the thermal exposure of load-bearing components, removing the need for cooling air and shielding while maintaining the rotor load transfer function.
Solution Approach 2:
The patent repositions the support struts from within the flow path to outside the flow path, effectively moving them to another spatial dimension. This dimensional change allows the struts to perform their load transfer function without being exposed to high temperatures in the flow path.
3Stability of the object's composition
If long diffuser is used to remove flow components, then uniform flow into HRSG is achieved, but vibration and cost increase
Solution Approach 1:
The patent employs a spiral-shaped diffuser instead of a long straight diffuser. The spiral curvature efficiently removes swirl and flow components while minimizing the diffuser length, thereby reducing vibration and material costs while achieving uniform flow into the HRSG.
Solution Approach 2:
The spiral diffuser uses curved geometry to gradually redirect and stabilize the flow, eliminating the need for a long straight diffuser section. This curved design reduces vibration and material requirements while effectively achieving uniform flow distribution into the HRSG.
4Stability of the object's composition
If swirl is reduced at base load, then exhaust gas uniformity is improved, but swirl returns at part load causing inefficiencies
Solution Approach 1:
The spiral diffuser design efficiently manages swirl across all operating conditions. The spiral geometry naturally handles the swirl generated at part load conditions while maintaining uniform flow, eliminating the need for separate swirl control mechanisms and maintaining efficiency across the full operating range.
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 design enhances operational efficiency, reduces maintenance costs, and improves the performance of gas turbine engines by minimizing flow interference, cooling requirements, and maintaining high swirl levels, leading to increased efficiency and reduced system losses.
Implementation Method 1
a spiral-shaped diffuser section having a central transition portion and a spiral portion
Implementation Method 2
a helical flow section extending outward from the central portion to provide a helical section of the flow path
Implementation Method 3
to recover the pressure of the hot exhaust gas exiting the turbine blade section
Data Source
AI summary
A power generation system (10). Stationary and rotatable blades (34, 37) are positioned about a rotor (8) to receive exhaust gas (46) from a combustor (6) and to impart an axial velocity component. A section of ductwork (48) is positioned to receive the exhaust gas and has a central transition portion (80t) into which the rotor extends. A spiral portion (80s) of the ductwork comprises a helically shaped flow section (80) extending outwardly from the central portion to provide a helical section of the flow path to carry the exhaust gas away from the central portion. A portion of the flow path along the helically shaped flow section may have an area in cross section which increases as a function of position along the flow path. The spiral portion is positioned to redirect the exhaust in a direction orthogonal to the rotor.