Passive Variable Air Passage Cover for Propeller Blades
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Solution Overview
Problem
Existing boundary layer blowing techniques for aerofoils in propellers and turbines are complex, costly, and energy-intensive, with high power requirements and drag augmentation, making them unsuitable for widespread deployment.
Innovation Solution
A passive boundary-layer blowing system using a variable air passage mechanism that reacts to air speed and rotational speed, allowing the cover to adjust the air passage cross-section, reducing the need for external energy sources and minimizing drag.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple spanwise slots with dedicated control valves are integrated for boundary layer blowing, then flow separation is delayed and lift is increased, but device complexity and manufacturing cost increase significantly
Solution Approach 1:
The blade is divided into multiple spanwise sections, each with its own slot for boundary layer blowing. This segmentation allows independent control of flow separation delay at different spanwise positions, optimizing lift enhancement while managing system complexity through modular design
Solution Approach 2:
A single control valve is designed to serve multiple slots across different spanwise positions, rather than dedicating one valve per slot. This multi-functional valve reduces the number of control components, simplifying the actuation system while maintaining the ability to regulate boundary layer blowing at various locations
2Reliability
If blow-type flow control with multiple slots and control valves is implemented, then aerodynamic performance is improved, but weight and manufacturing cost increase
Solution Approach 1:
A single control valve is designed to regulate flow to multiple spanwise slots, reducing the total number of valves required. This multi-functional approach significantly reduces the weight of control components while maintaining effective boundary layer blowing capability across the blade span
Solution Approach 2:
Multiple slot outlets are combined under a single control valve system, merging what would otherwise be separate control assemblies. This consolidation reduces the overall weight of the actuation system while preserving the distributed flow control capability needed for aerodynamic performance
3Reliability
If compressed air is used for boundary layer blowing, then flow separation is delayed and lift is increased, but power consumption increases significantly
Solution Approach 1:
Boundary layer blowing is implemented as a pulsed or periodic action rather than continuous compression. The control valve opens and closes at optimized intervals, delivering compressed air in controlled bursts that effectively delay flow separation while reducing the average power demand of the compression system
Solution Approach 2:
Compressed air is supplied at high pressure for short durations only when and where needed to prevent flow separation, rather than maintaining continuous compression. This partial action approach provides sufficient flow separation delay while minimizing the energy consumption of the air compression system
4Reliability
If slots are carved in the aerofoil for boundary layer blowing, then flow control is achieved, but drag augmentation occurs
Solution Approach 1:
Slots are positioned and sized with locally optimized characteristics at different spanwise locations. The slot geometry, width, and orientation are tailored to specific local flow conditions, providing effective boundary layer control while minimizing disruption to the overall aerodynamic profile and reducing drag augmentation
Solution Approach 2:
The slots are designed to provide just sufficient boundary layer blowing to delay flow separation without excessive air injection that would create strong wakes and increase drag. The partial action approach maintains flow control capability while limiting drag penalties through optimized slot dimensions and operating parameters
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 aerodynamic performance by delaying flow separation, increasing lift and power generation, while reducing power consumption and drag, and simplifying the design of propellers and turbines.
Implementation Method 1
a passive mechanism, configured to react passively to the oncoming air speed of oncoming air in the axial direction of the propeller or turbine
Implementation Method 2
boundary layer blowing... injecting a high-energy air flow on the suction surface at a position upstream to the point of flow separation. This results in a re-energisation of the boundary layer on the suction surface, which enables the air flow on the suction surface to remain adhered for longer, thereby delaying the onset of flow separation
Data Source
AI summary
An aerofoil module for use in a blade of a propeller or turbine comprising: a body comprising a suction surface and a pressure surface; an air passage traversing the body, the air passage having an entrance opening on the pressure surface and an exit opening on the suction surface; a cover for covering a variable portion of a cross-section of the air passage; and a mechanism for varying the portion of the cross-section of the air passage covered by the cover, wherein the mechanism reacts passively to the oncoming air speed of oncoming air in the axial direction of the propeller/turbine; wherein the mechanism varies the portion of the cross-section covered by the cover such that the cover covers a smaller portion of the cross-section in response to a higher oncoming air speed, and covers a larger portion of the cross-section of the air passage in response to a lower oncoming air speed.