Bleed Duct Flap System for Turbojet Reverse Thrust Airflow Control
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Solution Overview
Problem
The inefficiency and potential operational jeopardy of gas generators in bypass turbojet engines due to air flow separation areas during reverse thrust mode, which reduces propulsion assembly efficiency and lifespan.
Innovation Solution
Incorporation of a bleed duct system with movable inner and outer flaps that allow controlled airflow from the secondary duct to feed the primary duct, minimizing mass and optimizing airflow during reverse mode operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the fan generates reverse thrust by circulating secondary flow from downstream to upstream, then counter-thrust is produced to slow down the aircraft, but air flow separation areas appear at the separation nozzle which reduce gas generator efficiency and may jeopardize its operation
Solution Approach 1:
The patent extracts the harmful separated air flow from the primary duct by providing a bleed duct that takes out the separated flow at the separation nozzle and redirects it to the secondary duct, eliminating the negative impact on gas generator operation while maintaining reverse thrust capability
Solution Approach 2:
The bleed duct acts as an intermediary element between the primary and secondary ducts, mediating the problematic air flow separation by capturing separated flow and transferring it to the secondary duct where it can be safely discharged without affecting gas generator performance
2Reliability
If a bleed duct system is added to remove separated air flow, then gas generator efficiency is improved, but the device complexity and mass increase
Solution Approach 1:
The bleed duct system is designed to perform multiple functions: removing separated air flow during reverse thrust, potentially regulating air flow during propulsive mode, and integrating with existing separation nozzle structure, thereby justifying the added complexity through multi-functionality
Solution Approach 2:
The bleed duct is nested within the existing duct structure, with the inlet integrated into the separation nozzle and the outlet discharging into the secondary duct, minimizing additional structural complexity by utilizing existing spatial arrangements
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
Enhances the efficiency and lifespan of the propulsion assembly by optimizing airflow and reducing pressure losses, thereby maintaining efficient operation during reverse thrust mode.
Implementation Method 1
at least one duct for bleeding said air flow to feed the primary duct
Data Source
AI summary
Propulsion assembly comprising:an inner casing (13);an outer casing (3);an inter-duct casing (15) delimiting a primary duct (12) between the inner casing (13) and an outer wall (14), and a secondary duct (16) between the outer casing (3) and an outer wall (17);a fan capable of generating an air flow (24) circulating from downstream to upstream in the secondary duct (16);the assembly further comprising:at least one duct (27) for bleeding air from said flow (24), this bleed duct (27) comprising an inlet port (28) in the outer wall (17) and an outlet port (29) in the inner wall (14);an outer flap (30) movable between an open position and a closed position of the inlet port (28);an inner flap (31) movable between an open position and a closed position of the outlet port (29).