Oil Drainback Diffuser for Bearing Sump Airflow Control
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Solution Overview
Problem
In gas turbine engine bearing compartments, the introduction of a drain tube under positive pressure leads to significant airflow, which interferes with the scavenge capability of the sump and increases the risk of blockage due to debris, as existing solutions like orifices are prone to blockage and reduce the system's ability to handle debris effectively.
Innovation Solution
A diffuser device is introduced in the drain tube, featuring larger side openings than the end opening, which diffuses the flow and reduces the risk of blockage by maintaining mass flow while minimizing in-line flow velocity, similar to orifices, but without restricting the flow area, thus preventing flooding and debris accumulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a drain tube is introduced under positive pressure to return oil to the bearing compartment, then oil recirculation is achieved, but significant airflow enters the compartment interfering with sump scavenge capability
Solution Approach 1:
A diffuser device is introduced as an intermediary component in the drain tube. This diffuser has multiple openings that distribute the airflow from the drain tube into the bearing compartment, transforming a concentrated high-velocity jet into a dispersed low-velocity flow pattern that minimizes interference with sump scavenge capability while maintaining oil recirculation functionality
2Object-generated harmful factors
If an orifice is used to restrict airflow through the drain tube, then air velocity is reduced, but the system becomes prone to blockage by debris
Solution Approach 1:
The single restricted flow path of an orifice is segmented into multiple parallel flow paths through the diffuser's multiple openings. This segmentation distributes the airflow into several streams, reducing the velocity impact on scavenge capability while maintaining a larger total flow area that is less susceptible to complete blockage by debris. Even if some openings are partially blocked, others remain functional
Solution Approach 2:
The diffuser transforms the concentrated one-dimensional jet flow from the drain tube into a multi-dimensional dispersed flow pattern. By creating multiple openings arranged in different spatial positions and orientations, the airflow is distributed in multiple directions, reducing the linear velocity impact while maintaining effective air flow for pressure balance
3Object-generated harmful factors
If the drain tube end is located low in the compartment strut to prevent back flow, then head height is increased, but debris from the buffer cavity has greater impact on bearing compartment components
Solution Approach 1:
The diffuser acts as an intermediary that intercepts and redistributes the airflow and any entrained debris before they can directly impact bearing compartment components. The multiple openings disperse the flow in a controlled manner, reducing the direct impact velocity and distributing debris impact across multiple locations rather than concentrating it on single 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 diffuser device effectively manages airflow and reduces the risk of blockage, maintaining the scavenge capability of the sump while preventing flooding and ensuring efficient oil recirculation without the risk of orifice blockage, thereby enhancing the overall performance of the oil drainback system.
Implementation Method 1
A diffuser device is introduced in the drain tube, featuring larger side openings than the end opening, which diffuses the flow and reduces the risk of blockage by maintaining mass flow while minimizing in-line flow velocity
Data Source
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AI summary
A diffuser for an oil drainback system drain tube includes a flow chamber (82) configured for attachment to an open end (84) of a drain tube (74), wherein the flow chamber (82) has a side wall (86) and an end wall (88), and openings (90) in at least the side wall (86).