Drain Tube Diffuser for Bearing Sump Scavenge Protection
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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, especially in small, high-speed compartments, and the use of restriction devices like orifices to reduce airflow can result in blockages due to debris.
Innovation Solution
A diffuser device is attached to the drain tube, featuring a flow chamber with side and end openings that diffuse gas flow, reducing velocity and minimizing the risk of blockage by debris, while maintaining effective mass flow and scavenge capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a drain tube is introduced into a sealed bearing compartment under positive pressure, then oil can be returned to the bearing compartment, but significant airflow enters the compartment through the drain tube which interferes with the scavenge capability of the sump
Solution Approach 1:
A diffuser device is introduced as an intermediary component between the drain tube and the bearing compartment. The diffuser includes a flow chamber with multiple openings that mediate the airflow, converting the high-velocity jet into a distributed, low-velocity flow pattern that returns oil to the bearing compartment while minimizing interference with sump scavenging operations
Solution Approach 2:
The diffuser device changes the flow parameters by expanding the high-velocity, high-pressure airflow from the drain tube into a low-velocity, distributed flow through multiple openings in the flow chamber. This parameter transformation reduces the kinetic energy of the air jet while maintaining oil return functionality
2Productivity
If a restriction device (orifice) is introduced into the drain tube to reduce mass flow of air, then the impact on scavenge capability is reduced, but the orifice may become blocked by debris
Solution Approach 1:
The single restricted flow path of an orifice is segmented into multiple parallel flow paths through the multiple openings in the diffuser's flow chamber. This segmentation distributes the airflow into several channels, reducing the risk that debris will block the entire flow path, while still achieving the goal of reducing overall air mass flow impact on scavenging
Solution Approach 2:
The diffuser acts as an intermediary that replaces the restrictive orifice. Instead of forcing air through a single small opening that is vulnerable to blockage, the diffuser mediates the flow through multiple larger openings that are less susceptible to debris accumulation and blockage
3Reliability
If the end of the drain tube is located as low into the compartment strut as possible, then back flow is avoided and head height is increased, but the impact of debris from the buffer cavity on components within the bearing compartment is increased
Solution Approach 1:
The diffuser device serves as an intermediary barrier between the drain tube outlet and the bearing compartment components. It allows the drain tube to be positioned optimally for back flow prevention while the diffuser's flow chamber and multiple openings filter and distribute the flow, reducing the direct impact of debris on sensitive components within the bearing compartment
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 reduces airflow velocity and prevents blockages, enhancing the scavenge capability of the sump without restricting mass flow, thus improving the overall efficiency of the oil drainback system.
Implementation Method 1
A diffuser device is attached to the drain tube, featuring a flow chamber with side and end openings that diffuse gas flow, reducing velocity and minimizing the risk of blockage by debris
Data Source
AI summary
A diffuser for an oil drainback system drain tube includes a flow chamber configured for attachment to an open end of a drain tube, wherein the flow chamber has a side wall and an end wall, and openings in at least the side wall.