Metallic Fan Casing Heating for Clearance Control

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Solution Overview

Problem

In gas turbine engines, the clearance gap between fan blade tips and a composite fan casing is excessively large during cruise, reducing engine efficiency and performance due to the composite material's minimal thermal growth, leading to increased air leakage and specific fuel consumption.

Innovation Solution

A fan casing heating system that applies heat to the metal fan casing during takeoff and climb phases to expand it, and then removes heat during cruise to contract it, thereby adjusting the clearance gap to optimize efficiency and reduce specific fuel consumption.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a composite fan casing is used to accommodate maximum fan blade diameter during takeoff, then blade tip clearance is maintained during takeoff, but the clearance gap becomes excessively large during cruise, reducing fan efficiency

Engineering Contradiction:

Improveblade tip clearance maintenanceVSAvoidfan efficiency

Core Design Contradiction:

ReliabilityVSProductivity

Solution Approach 1:

The patent applies thermal expansion parameter changes to the fan casing. During takeoff, the fan casing is heated to expand and maintain optimal clearance gap despite blade thermal growth. During cruise, the heating is reduced or stopped, allowing the casing to contract and reduce the clearance gap, thereby improving fan efficiency and reducing air leakage.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent directly utilizes thermal expansion of the fan casing material. Heating elements apply controlled heat to the fan casing, causing it to expand radially outward to accommodate blade tip growth during high-power operations. This thermal expansion mechanism allows dynamic adjustment of the clearance gap based on operational requirements.

Inventive Principle:

Principle #37Thermal expansion

2Reliability

If the fan casing diameter is minimized to maintain clearance during takeoff, then blade tip clearance is adequate, but the casing must be thicker, increasing manufacturing complexity and cost

Engineering Contradiction:

Improveclearance gap maintenanceVSAvoidcasing thickness requirement

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent changes the thermal parameter of the fan casing through controlled heating. By applying heat during takeoff and climb phases, the casing expands to provide the necessary clearance without requiring a larger minimum diameter design. This allows the casing to be manufactured with optimal thickness while still maintaining adequate clearance through thermal management.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If the clearance gap is reduced during cruise to improve efficiency, then fan performance increases, but blade tips may contact the casing during takeoff

Engineering Contradiction:

Improvefan efficiencyVSAvoidblade tip clearance

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent implements a dynamic clearance gap control system that adjusts the fan casing diameter based on operational mode. During takeoff, the casing is heated to expand and increase clearance. During cruise, the heating is reduced or stopped, allowing the casing to contract and reduce clearance for improved efficiency. This dynamic adjustment prevents blade contact during high-power operations while optimizing performance during cruise.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent applies periodic thermal action to the fan casing, switching between heating and non-heating states based on flight phase. The heating elements are activated during takeoff and climb phases to expand the casing, then deactivated or reduced during cruise to allow contraction. This periodic thermal action maintains clearance when needed while improving efficiency when appropriate.

Inventive Principle:

Principle #19Periodic action

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 system effectively reduces the clearance gap by up to 0.1% of the fan diameter, improving fan efficiency and reducing specific fuel consumption by up to 0.7%, while also potentially reducing manufacturing costs and allowing for a thinner, more efficient fan casing.

Implementation Method 1

applying heat to the fan casing radially outboard and axially aligned with the fan such that the fan casing expands by a predetermined amount, increasing the clearance gap

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

removing the applied heat to contract the fan casing, decreasing the clearance gap

Methodology Applied

Scientific EffectThermal contraction: Thermal Contraction

Data Source

PatentUS10066630B2Method and system for metallic low pressure fan case heating

Publication Date: 2018.09.04 GENERAL ELECTRIC CO

AI summary

A fan assembly is provided. The fan assembly includes a fan, a fan casing circumscribing the fan, and a fan casing heating system in thermal communication with the fan casing. The fan includes a hub, and a plurality of fan blades extending from the hub. Each fan blade of the plurality of fan blades terminates at a respective blade tip. A clearance gap is defined between the fan casing and the blade tips. The fan casing heating system is configured to apply heat to the fan casing when the fan is operating in a first operational mode, and remove the applied heat when the fan transitions into a second operational mode.