Mid Turbine Frame Oil Purge System

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Solution Overview

Problem

Oil leakage from the seal between the oil transfer tube and the bearing housing in a gas turbine engine's mid turbine frame can ignite due to the high temperature environment, posing a risk to the engine's components.

Innovation Solution

An oil purge system is implemented, featuring a heat shield tube surrounding the oil transfer tube to create an annular cavity, which is filled with pressurized air to purge leaked oil downward and direct it to a dumping area outside the engine case, preventing ignition.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If an oil transfer tube is used to deliver oil through the inter-turbine duct, then oil can be supplied to bearings, but oil leakage may occur from the seal between the tube and bearing housing

Engineering Contradiction:

Improveoil supply to bearingsVSAvoidseal leakage

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

A heat shield tube is introduced as an intermediary component surrounding the oil transfer tube. This heat shield tube creates an annular cavity that serves as a containment zone for any leaked oil, preventing it from entering the turbine disk hub cavities. The heat shield tube effectively mediates between the oil transfer function and the leakage prevention requirement.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The harmful element (leaked oil) is extracted from the dangerous environment (high temperature turbine cavity) by directing it through a separate pathway. The annular cavity formed by the heat shield tube extracts leaked oil from the main oil transfer path and channels it to a safe dumping area away from the turbine components.

Inventive Principle:

Principle #2Taking out (Extraction)

2Ease of operation

If leaked oil enters the turbine disk hub cavities, then bearing lubrication is maintained, but the oil may ignite due to high temperature

Engineering Contradiction:

Improvebearing lubricationVSAvoidignition risk

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The potential harmful effect of oil leakage is converted into a beneficial outcome by using the leaked oil's natural flow path to feed the annular cavity purge system. Instead of preventing all leakage (which is difficult), the system accepts the leakage and uses it to demonstrate the effectiveness of the purge system in preventing ignition.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The annular cavity acts as an intermediary zone between the oil transfer tube and the turbine cavity. It provides a buffer space where leaked oil can be contained and purged by pressurized air, preventing direct contact between leaked oil and the high-temperature turbine environment that would cause ignition.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If a heat shield tube with annular cavity is added to purge leaked oil, then ignition risk is reduced, but device complexity increases

Engineering Contradiction:

Improveignition preventionVSAvoidsystem structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The heat shield tube serves multiple functions: it provides thermal shielding to protect the oil transfer tube from high temperatures, creates the annular cavity for oil containment, and facilitates the purge system operation. By combining multiple functions into a single component, the overall system complexity is minimized.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The oil transfer tube is nested within the heat shield tube, creating a compact concentric structure. This nesting arrangement allows the annular cavity to be formed naturally between the two tubes, eliminating the need for separate cavity structures and reducing overall system complexity.

Inventive Principle:

Principle #7Nested doll (Nesting)

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

Effectively prevents oil leakage from entering turbine cavities and reduces the risk of ignition, maintaining engine safety and efficiency by ensuring oil is properly managed and drained.

Implementation Method 1

introducing pressurized air into the cavity adjacent the port of the bearing housing for purging the leaked oil down along the cavity and out of the outer case

Methodology Applied

Scientific EffectPressurized air flow: Pressure Gradient

Data Source

PatentUS8944749B2Oil purge system for a mid turbine frame

Publication Date: 2015.02.03 PRATT & WHITNEY CANADA CORP

AI summary

An oil purge system for a mid turbine frame (MTF) of a gas turbine engine has an oil transfer tube surrounded by a heat shield tube. The oil transfer and heat shield tubes extend at their respective inner ends downwardly from an oil port of a bearing housing and terminate at their respective outer ends projecting outwardly from an annular wall of an outer case of the MTF. Oil leaked from the oil port is purged by pressurized air through an annular cavity formed between the oil transfer and heat shield tubes, and is discharged out of the MTF.