Variable Geometry Nacelle for Aircraft Engine Boundary Layer Control
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Solution Overview
Problem
The existing nacelle assemblies for turbofan gas turbine engines face inefficiencies due to thick inlet lip sections, which increase weight, drag, and reduce performance during normal cruise conditions, while attempts to reduce boundary layer separation have been complex and ineffective.
Innovation Solution
A nacelle assembly with a moveable cowl section that simulates a thick inlet lip section during specific flight conditions by increasing the boundary layer thickness, using a sensor and actuator system to adjust the cowl section's position and shape, thereby reducing the need for a thick inlet lip section during normal operations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a thick inlet lip section is used to support engine operation during specific flight conditions, then reliability is improved, but weight increases and drag increases
Solution Approach 1:
The inlet lip section is made variable in thickness through a movable cowl section that can extend or retract. During specific flight conditions (takeoff, climb, crosswind), the cowl section extends to simulate a thick inlet lip for reliable engine operation. During cruise conditions, it retracts to reduce weight and drag, achieving dynamic adaptation to different operational requirements.
Solution Approach 2:
The physical parameter of inlet lip thickness is changed dynamically based on flight conditions. The system transitions between thick and thin inlet lip configurations by moving the cowl section, allowing optimization of engine performance and aerodynamic efficiency for different operational phases.
2Reliability
If a thick inlet lip section is used to support engine operation during specific flight conditions, then reliability is improved, but drag increases
Solution Approach 1:
The inlet lip thickness is dynamically adjusted using a movable cowl section. During specific flight conditions requiring thick inlet lip for reliability, the cowl extends. During cruise conditions where drag is critical, the cowl retracts to minimize drag, thus dynamically balancing reliability requirements with drag reduction.
3Object-affected harmful factors
If the nacelle assembly diameter is increased to accommodate large diameter fan section, then noise decreases, but weight increases
Solution Approach 1:
The nacelle assembly diameter is made variable through the movable cowl section. During takeoff and climb, the cowl extends to provide the necessary diameter for noise reduction and engine performance. During cruise, the cowl retracts to reduce the effective diameter, thereby reducing weight and drag while maintaining the large diameter fan section capability.
4Reliability
If small vortex generators or synthetic jets are used to reduce boundary layer separation, then boundary layer separation is reduced, but device complexity increases
Solution Approach 1:
Instead of adding complex vortex generators or synthetic jets, the patent uses the dynamics of the movable cowl section itself to control boundary layer separation. By adjusting the cowl position, the inlet lip thickness is varied, which naturally manages the boundary layer and prevents separation during critical flight conditions, avoiding the need for additional complex devices.
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 design improves engine performance and efficiency by allowing a slim-line nacelle with reduced weight and drag, maintaining performance during diverse flight conditions while minimizing the nacelle's maximum diameter, thus reducing fuel burn and enhancing overall efficiency.
Implementation Method 1
A moveable portion 52 of the cowl section 50 is selectively introduced at the boundary layer 35 of the inlet lip section 38 to simulate a thick inlet lip section
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
A nacelle assembly (26) includes an inlet lip section (38) and a cowl section (50) positioned downstream of the inlet lip section (38). At least a portion (52) of the cowl section (50) is moveable to influence an effective boundary layer thickness of the nacelle assembly (26).