Compressor Air Bleeding via Separate Flow Duct in Turbofan Engine
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Solution Overview
Problem
Existing methods for bleeding compressor air in turbofan engines often result in aerodynamic losses and require structural changes to functional components, particularly the intermediate casing, which is complex and costly to manufacture.
Innovation Solution
The compressor air is introduced into the secondary flow duct upstream of the fan stator and guided in a separate flow duct axially past the stator vanes, preventing mixing until downstream of the fan stator, thus avoiding aerodynamic losses and minimizing structural adaptations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If compressor air is introduced into the secondary flow duct between the fan and the fan stator, then the compressor air can be discharged from the low-pressure compressor, but aerodynamic losses occur due to mixing with swirling fan air
Solution Approach 1:
The secondary flow duct is segmented into a separate flow duct region and a main secondary flow region. The separate flow duct guides compressor air axially past the fan stator, keeping it separated from the swirling fan air in the main secondary flow region until downstream of the stator, preventing aerodynamic losses while enabling compressor air discharge.
Solution Approach 2:
The separate flow duct acts as an intermediary structure that transports compressor air from the discharge location to the mixing zone downstream of the fan stator. This intermediary pathway allows the compressor air to be introduced without direct mixing with swirling fan air, eliminating aerodynamic losses.
2Loss of energy
If the intermediate casing is adapted to guide compressor air axially rearwards, then aerodynamic losses are prevented, but structural changes are required which increase manufacturing complexity and cost
Solution Approach 1:
The flow guidance function is segmented from the intermediate casing structure. Instead of adapting the intermediate casing to guide air, a separate flow duct is introduced that performs the air guidance function independently, leaving the intermediate casing unchanged and avoiding increased manufacturing complexity.
Solution Approach 2:
The air guidance function is extracted from the intermediate casing and implemented through a separate flow duct. This extraction allows the intermediate casing to remain structurally simple while the separate flow duct handles the aerodynamic guidance, preventing both aerodynamic losses and manufacturing complexity increases.
3Device complexity
If compressor air is introduced upstream of the fan stator into the secondary flow duct, then structural changes to the intermediate casing are avoided, but aerodynamic losses occur due to premature mixing
Solution Approach 1:
The secondary flow duct is segmented into distinct regions: an upstream region where compressor air is introduced without mixing, a middle region with a separate flow duct that guides compressor air axially past the fan stator, and a downstream region where mixing occurs. This segmentation enables introduction upstream of the stator while preventing premature mixing.
Solution Approach 2:
The separate flow duct serves as an intermediary structure that receives compressor air upstream of the fan stator and transports it axially past the stator to a downstream mixing zone. This intermediary pathway prevents premature mixing while allowing introduction upstream of the stator, avoiding the need for structural changes to the intermediate casing.
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
This approach effectively introduces compressor air into the secondary flow duct without causing aerodynamic losses and avoids the need for structural changes to functional components, such as the intermediate casing, while ensuring efficient airflow management.
Implementation Method 1
compressor air to be released from the low-pressure compressor is passed into the secondary flow duct upstream of the fan stator and is there guided in a separate flow duct past the stator vanes of the fan stator in the axial direction
Data Source
AI summary
A device for bleeding compressor air in a turbofan engine includes a low-pressure compressor of a primary duct, a fan stator arranged in a secondary duct downstream of a fan, and an arrangement for discharging compressor air from the low-pressure compressor into the secondary duct. The arrangement includes air guiding devices to guide compressor air into the secondary duct upstream of the fan stator relative to the flow direction in the secondary duct, past the stator vanes of the fan stator in a separate duct in the axial direction and is only mixed with the air of the secondary duct downstream of the fan stator. The separate duct is formed by a plurality of hollow structures extending in the longitudinal direction each between two adjacent stator vanes of the fan stator, with the hollow structures having a closed circumference in cross-section.