Turbojet Fairing Radial Debris Ejection for Downstream Fan Protection
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Solution Overview
Problem
Turbojet engines integrated into the rear of an aircraft's fuselage face significant risks when upstream fan blades break, as debris can damage the downstream fan, potentially leading to complete propulsive capability loss, especially when the turbojet engine is the sole propulsion means.
Innovation Solution
The design incorporates a fairing with an upstream section configured for radial ejection of broken fan fragments, preventing them from reaching the downstream fan, and includes a remedial casing system to restore aerodynamic guidance by deploying angular segments over ripped sections.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the upstream fan blades are retained in the fairing, then the downstream fan is protected from debris damage, but the aerodynamic guidance function of the fairing is compromised and the propulsive efficiency is reduced
Solution Approach 1:
The fairing is divided into two distinct sections: an upstream section that can be radially traversed by debris to allow ejection, and a downstream section that maintains aerodynamic guidance function. This segmentation allows each section to fulfill its specific function without compromising the other.
Solution Approach 2:
The harmful debris is extracted from the system by allowing it to be radially ejected through the upstream section of the fairing, preventing it from reaching and damaging the downstream fan, while the downstream section of the fairing continues to perform its aerodynamic guidance function.
2Productivity
If the fairing is designed to guide air flow through the fans, then aerodynamic efficiency is improved, but broken blades can be guided to the downstream fan causing catastrophic damage
Solution Approach 1:
Different sections of the fairing are given different functional qualities: the upstream section is designed with debris ejection capability (radial traversal) while the downstream section maintains aerodynamic guidance function. This local differentiation allows each section to optimize its specific function.
Solution Approach 2:
The harmful debris that would normally be guided toward the downstream fan by the aerodynamic fairing is instead utilized beneficially by being radially ejected through the upstream section, converting the potential harm into a protective mechanism that prevents downstream fan damage.
3Reliability
If blade retention means are added to the fairing, then downstream fan protection is improved, but device complexity and weight increase
Solution Approach 1:
The fairing is designed to perform multiple functions simultaneously: it maintains aerodynamic guidance, allows radial debris ejection, and provides blade retention capability through its structural design, eliminating the need for separate retention mechanisms and reducing overall system complexity.
Data Source
AI summary
The invention relates to an aircraft comprising a fuselage, flight control surfaces and a turbojet engine (20) integrated into the rear of said fuselage in the extension thereof, the turbojet engine (12) comprising two gas generators (22) that supply, via a common central duct (30), a power turbine (32) comprising two counter-rotating rotors (34, 36) respectively driving two upstream (38) and downstream (40) coaxial and counter-rotating fans each comprising a ring of vanes (42, 44), the set of fans (38, 40) being integrated into a fairing (46) of the turbojet engine (20) formed at the rear of the fuselage (12), characterised in that at least said fairing (46) is axially arranged behind the flight control surfaces and comprises an upstream section (50), surrounding the upstream fan (38), configured to be radially traversed by at least one fragment (43) of a vane (42) of the upstream fan (38) in the event of the breakage of a vane (42) of said upstream fan (38) and the ejection of said at least one fragment (43).