Open Strut Inner Diffuser Case for Gas Turbine Combustor Thrust Balance
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Solution Overview
Problem
In twin spool gas turbine engines, leakage of high-pressure compressor discharge air through labyrinth seals creates thrust loads on component parts and requires effective cooling, but existing designs lack efficient methods for balancing thrust and cooling air distribution within the combustor section.
Innovation Solution
The introduction of an inner diffuser case with multiple struts, including open struts, that define an annular flow path and communicate secondary flow air across the path to provide a thrust balance and efficient cooling, reducing the axial thrust force on bearing structures by metering the secondary flow air through controlled passages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If high pressure compressor discharge air is bled through labyrinth seal for cooling purposes, then cooling efficiency is improved, but thrust loads on bearing structures increase
Solution Approach 1:
The diffuser case struts are segmented into solid struts and open struts, with the open struts specifically designed to allow secondary flow air passage. This segmentation enables the cooling function to be separated from the structural support function, allowing cooling air to pass through designated open struts without compromising the structural integrity provided by solid struts, thereby reducing thrust loads while maintaining cooling efficiency
Solution Approach 2:
Secondary flow air acts as an intermediary medium that passes through the open struts to provide thrust balance. The controlled passage of this secondary flow through the open struts creates a counteracting force that balances the thrust loads generated by the primary cooling air bleed, thus reducing the net thrust force on bearing structures while maintaining effective cooling
2Force
If secondary flow air is used for thrust balance, then thrust bearing loads are reduced, but cooling air distribution becomes complex
Solution Approach 1:
The strut structure merges multiple functions into a single component: structural support (solid struts), flow passage (open struts), and thrust balance (secondary flow through open struts). By combining these functions into the diffuser case strut assembly, the patent simplifies the overall system architecture while achieving both thrust reduction and effective cooling air distribution without requiring separate complex systems
Solution Approach 2:
The diffuser case struts are designed with multi-functionality, serving simultaneously as structural support elements, flow passage conduits, and thrust balance mechanisms. The open struts specifically provide multiple benefits by allowing secondary flow passage while maintaining structural continuity, thus achieving thrust balance and cooling air distribution through a universal component design
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 enhances thrust balance and cooling efficiency by distributing secondary flow air effectively, reducing the maximum thrust force absorbed by thrust bearings and optimizing pressure distribution within the combustor section, thereby improving the operational stability and efficiency of the gas turbine engine.
Implementation Method 1
multiple of struts extending across the annular flow path wherein at least one of said multiple of struts is an open strut
Implementation Method 2
The diffuser has an expanding cross sectional area in the direction of the airflow to decrease the velocity and increase the static pressure of the air
Implementation Method 3
leakage of high pressure compressor discharge air through a labyrinth seal between a high pressure compressor rear rotor shaft and the diffuser section typically establishes the thrust loads on component parts
Data Source
AI summary
An inner diffuser case for use in a combustor of a gas turbine engine includes a multiple of struts across an annular flow path between an outer shroud and an inner shroud, at least one of the multiple of struts is an open strut.