Turbofan Fan Case Elastic Support for Blade Impact Absorption
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Solution Overview
Problem
Turbofan engine fan blades suffer damage from collisions with foreign objects, leading to whirling and increased clearance between blades and the engine casing, which reduces thrust and requires frequent maintenance of sacrificial abradable material layers.
Innovation Solution
A turbofan engine design featuring an elastic support device with compression springs that radially supports an annular member, allowing it to move and absorb impact from foreign objects, preventing blade damage while maintaining airflow efficiency and reducing thrust loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a sacrificial abradable material layer is provided on the engine casing to prevent fan blade damage, then fan blade protection is improved, but the clearance between fan blades and engine casing increases steadily causing thrust loss
Solution Approach 1:
The annular member is made movable relative to the engine casing through elastic support devices, allowing it to dynamically adjust its position. When fan blades contact the annular member, it moves radially outward to absorb the impact, then returns to its original position, preventing the steady clearance increase that occurs with fixed abradable material layers.
Solution Approach 2:
The clearance between the fan blades and the annular member is maintained at a predetermined value, and the annular member's radial position is changed elastically during impact events. This parameter change allows the system to accommodate blade contact without permanent clearance increase, resolving the contradiction between protection and thrust maintenance.
2Reliability
If a sacrificial abradable material layer is used to absorb impact, then fan blade damage is prevented, but the abradable material layer requires replacement and maintenance
Solution Approach 1:
The annular member serves its own protective function without being consumable. After absorbing impact through elastic deformation, it automatically returns to its original position and continues to protect the engine casing, eliminating the need for periodic replacement and maintenance of sacrificial materials.
Solution Approach 2:
The invention replaces the disposable abradable material layer with a durable, reusable annular member supported by elastic elements. This non-consumable design eliminates the maintenance cycle associated with replacing worn-out sacrificial materials while maintaining continuous protection.
3Reliability
If the annular member is rigidly fixed to prevent blade contact, then blade protection is improved, but airflow loss increases and thrust decreases
Solution Approach 1:
The annular member is positioned close to the fan blades with a small predetermined clearance, creating a dynamic barrier that only engages during abnormal conditions. During normal operation, the elastic support devices maintain the member at a position that minimizes airflow disruption while still providing protection when needed.
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 elastic support device effectively suppresses fan whirling and prevents blade damage without steady thrust reduction, allowing for quick return to original position and minimizing maintenance needs.
Implementation Method 1
an elastic support device (104) that supports the annular member to the fan case radially elastically
Implementation Method 2
the elastic support device (104) includes multiple spring members (112)
Implementation Method 3
compression springs (112) provided for the respective pins (108) such that each compression spring is disposed between a corresponding one of the sliders (110) and the bottom of the annular recess (12A) and urges the slider into contact with an outer circumferential surface (102A) of the annular member (102)
Data Source
AI summary
A turbofan engine includes: a cylindrical fan case; a fan rotatably disposed in the fan case and including a central member and multiple fan blades arranged on an outer circumference of the central member such that the fan blades are spaced apart from one another in a circumferential direction; an annular member disposed to surround the fan; and an elastic support device that supports the annular member to the fan case radially elastically such that a predetermined clearance is radially defined between the annular member and tips of the fan blades.