Secondary Flow Oil Separator Baffle for Gear Windage Loss
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Solution Overview
Problem
In gas turbine engines, the circulation of air carrying oil around gears leads to parasitic losses, excess heating, and reduced efficiency due to oil entering the gear mesh, causing increased engine oil gulp and reduced scavenge system efficiency.
Innovation Solution
A baffle assembly with upstream and downstream portions is used to manage air and oil flow, guiding secondary flow circulations and preventing oil from impinging on the gear by forming flow channels that direct air radially outward and inward, thereby reducing oil impingement and windage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If oil is distributed into the transmission and gear compartments to provide cooling and lubricating functionality, then the lubrication and cooling of gears is improved, but parasitic losses and excess heating occur due to oil impinging on the gear and entering the gear mesh
Solution Approach 1:
The baffle is divided into an upstream portion and a downstream portion, each with separate flow channels. The upstream portion handles flow from one side of the gear while the downstream portion handles flow from the opposite side, allowing independent optimization of oil control in different regions of the gear compartment.
Solution Approach 2:
The baffle assembly acts as an intermediary structure between the oil distribution system and the gear. It intercepts and redirects the air-oil secondary flow before the oil can impinge on the gear or enter the gear mesh, thereby preventing parasitic losses while maintaining the beneficial cooling and lubrication effects.
2Temperature
If air circulates around the rotating gear to replace radially outward moving air, then cooling airflow is maintained, but oil is carried along with the air flow causing increased oil aeration and reduced scavenge system efficiency
Solution Approach 1:
The baffle provides different flow management characteristics at different locations. The upstream and downstream portions create localized flow control zones that redirect air and oil separately, allowing the cooling function to be maintained in one area while oil separation occurs in another area.
Solution Approach 2:
The baffle extracts oil from the air-oil mixture in the secondary flow. By providing flow channels that allow oil to separate and drain away from the main air circulation path, the oil is removed from the cooling airflow, preventing oil aeration while maintaining the cooling function.
3Device complexity
If a single baffle structure is used to manage air and oil flow, then device complexity is reduced, but the ability to effectively guide both upstream and downstream secondary flow circulations is limited
Solution Approach 1:
The baffle is segmented into upstream and downstream portions with distinct flow channels optimized for each direction of secondary flow. This segmentation allows each portion to effectively manage its specific flow pattern, improving overall flow management efficiency while maintaining a relatively simple integrated structure.
Solution Approach 2:
The baffle assembly performs multiple functions within a single integrated structure: it guides upstream secondary flow, guides downstream secondary flow, separates oil from air, and maintains cooling airflow. This multi-functionality achieves high flow management efficiency without requiring multiple separate components.
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 baffle assembly reduces heat generation, improves oil scavenging, and enhances engine efficiency by minimizing oil-related losses and improving thrust specific fuel consumption.
Implementation Method 1
As the air moves radially outward, other air is drawn to an ID portion of the gear to replace the radially outward moving air. This motion creates a secondary flow circulation such that air from the rim of the gear is drawn back into the ID of the gear where the air then repeats the cycle.
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
An assembly (70) for a compartment (50B) of a gas turbine engine (10) that includes a housing (72), a gear (74), and a baffle (86, 86A) disposed about the gear (74). The baffle (86, 86A) includes an upstream portion (88) and a downstream portion (98). The upstream portion (88) includes an upstream inner wall (92) and an upstream outer wall (90) separated from the gear (74). The upstream inner wall (92) is positioned between the upstream outer wall (90) and the gear (74). An upstream flow channel (96) is formed between the upstream inner wall (92) and the upstream outer wall (90). The downstream portion (98) of the baffle (86, 86A) includes a downstream inner wall (102) and a downstream outer wall (100) separated from the gear (74). The downstream inner wall (102) is positioned between the downstream outer wall (100) and the gear (74). A downstream flow channel (104) is formed between the downstream outer wall (100) and the downstream inner wall (102).