Aircraft Engine Heat Exchanger Cover System for Exhaust Backflow Prevention
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Aircraft engines with air-cooled heat exchangers are susceptible to temperature-related damage due to hot exhaust gases flowing through them during shutdown, as the heat exchangers may draw ambient air and vent outwards when the engine stops, potentially causing damage to temperature-sensitive materials like aluminum.
Innovation Solution
A cover system is implemented in the heat exchanger duct, which includes a plate with apertures and a biasing member that moves between open and closed positions based on pressure changes, preventing hot exhaust gases from flowing into the heat exchanger during shutdown by transitioning to a closed position when the engine is not operational.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If the heat exchanger duct remains open to allow cooling air flow during operation, then heat exchange efficiency is improved, but hot exhaust gases can flow into the heat exchanger during shutdown causing temperature-related damage
Solution Approach 1:
The closure is made movable between open and closed positions based on operating conditions. During operation, the closure opens to allow cooling air flow through the heat exchanger for efficient heat exchange. During shutdown, the closure automatically closes to prevent hot exhaust gases from entering the heat exchanger, thereby protecting temperature-sensitive materials from thermal damage.
Solution Approach 2:
The closure acts as an intermediary element between the heat exchanger duct and the exhaust duct. It selectively controls the flow path, allowing cooling air to pass through during operation while blocking the path for hot exhaust gases during shutdown, thus mediating between the need for heat exchange and the need for thermal protection.
2Object-affected harmful factors
If a closure is added to prevent hot exhaust gas flow, then protection from temperature damage is improved, but device complexity increases
Solution Approach 1:
The closure system is designed to operate automatically based on the pressure differential that naturally occurs during engine operation and shutdown. The biasing member provides the closing force, while the pressurized fluid provides the opening force during operation. The system self-regulates without requiring external control mechanisms, actuators, or complex control systems, thereby minimizing added complexity while achieving reliable protection.
3Object-affected harmful factors
If a biasing member is used to keep the closure closed, then prevention of hot gas flow is improved, but the force required to open the closure during operation must be greater
Solution Approach 1:
The system uses pneumatic pressure from the pressurized fluid to automatically overcome the biasing force during operation. The pressurized fluid exerts sufficient force on the closure to open it during normal engine operation when cooling air flow is needed, while the biasing member maintains the closed position during shutdown when the pressurized fluid force is insufficient. This eliminates the need for mechanical actuators or complex control systems.
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 cover system effectively prevents hot exhaust gases from reaching the air-cooled heat exchanger, thereby protecting temperature-sensitive components from damage during engine shutdown, ensuring the longevity and functionality of the heat exchanger.
Implementation Method 1
a biasing member operatively connected to the closure biasing the closure toward the closed position with a biasing force
Implementation Method 2
a first force generated on the closure by the source of pressurized fluid at the first pressure being greater than a second force generated on the closure by the source of pressurized fluid at the second pressure
Implementation Method 3
an air-cooled heat exchanger disposed in the heat exchanger duct between the air inlet and the air outlet
Data Source
AI summary
A cover system selectively allows a gas flow through a heat exchanger duct upstream of an exhaust duct in an aircraft engine. A fluid is at a first pressure during an engine operating condition and a second pressure lower than the first during shutdown. A plate extends across the heat exchanger duct with aperture(s) extending therethrough. A closure is movable between an open position with gas flowing through the apertures into the exhaust duct, and a closed position with the closure closing the apertures. A biasing member operatively connected to the closure closes the closure with a biasing force. During the engine operating condition, the first pressure creates a first force acting against and greater than the biasing force to urge the closure open. At shutdown, the second pressure creates a second force acting against and lower than the biasing force, the biasing force biasing the closure closed.