Conformal Pylon Prop-Rotors for VTOL Drag Reduction
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Solution Overview
Problem
Vertical take-off and landing (VTOL) aircraft face challenges in transitioning between cruise and takeoff modes, optimizing lift-to-drag ratio for fuel efficiency, and reducing design complexity and points of failure, particularly due to the drag caused by inactive propulsors during cruise mode.
Innovation Solution
The design incorporates a conformal propeller rotor assembly with blades that can be stowed within a boom or fuselage, minimizing drag by matching the blade profile to the casing profile, and using a telescoping driveshaft to adjust the propeller position, allowing for efficient vertical lift and forward thrust while reducing aerodynamic turbulence and structural complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If propeller blades are stowed within the boom or fuselage during cruise mode, then drag is reduced and aerodynamic efficiency is improved, but the blade profile must match the casing profile which increases manufacturing complexity
Solution Approach 1:
The propeller blades are designed with varying cross-sectional shapes along their length, where each section is tailored to match the specific contour of the boom or fuselage casing it contacts during stowage. This local customization of blade geometry enables precise conformal integration without requiring complex manufacturing processes throughout the entire blade structure.
Solution Approach 2:
The blade profiles incorporate curved and rounded contours that naturally conform to the aerodynamic shaping of the boom or fuselage casing. By using smooth curved surfaces rather than sharp edges or flat surfaces, the blades integrate seamlessly with the airframe during stowage, reducing turbulence and drag while maintaining manufacturability through standard aerodynamic shaping techniques.
2Productivity
If a telescoping driveshaft is used to adjust propeller position, then transition between flight modes is smoothed and aerodynamic efficiency is enhanced, but device complexity increases
Solution Approach 1:
The driveshaft system transitions from a static fixed-length shaft to a dynamic telescoping shaft that can extend and retract. This dynamic adjustment allows the propeller to be positioned optimally for different flight modes - retracted during cruise to minimize drag and extended during takeoff/landing to maximize thrust efficiency - while the telescoping mechanism itself uses straightforward mechanical principles.
Solution Approach 2:
The telescoping driveshaft serves multiple functions: it adjusts propeller position for different flight modes, provides structural support for the propeller assembly, and acts as a guide for the propeller's movement. By combining these functions into a single mechanism rather than using separate components for each function, the overall system complexity is reduced despite the added telescoping capability.
3Reliability
If conformal propeller blades are designed to match the casing profile, then drag is minimized and lift-to-drag ratio is optimized, but the design complexity of the propulsor system increases
Solution Approach 1:
The conformal blade design applies varying geometric properties at different locations along the blade span. The root section of the blade is shaped to match the casing profile for optimal stowage, while the tip section maintains standard aerodynamic airfoil shapes for efficient operation. This localized differentiation allows the blade to achieve both low-drag stowage and high-performance operation without requiring complex conformal shaping throughout the entire blade.
Solution Approach 2:
The propeller blade is divided into multiple sections or segments along its length, each with different geometric characteristics. The root segment conforms to the casing profile, the middle section transitions between conformal and airfoil shapes, and the tip section uses standard aerodynamic profiles. This segmentation allows each portion to be optimized for its specific function while simplifying the overall manufacturing process compared to a fully conformal design.
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 configuration enhances aerodynamic efficiency, reduces drag, and minimizes points of failure, enabling smoother transitions between flight modes while maintaining high lift-to-drag ratios and reducing structural challenges associated with stowed propellers.
Implementation Method 1
The boom assembly includes a telescoping driveshaft that is extendable to raise the propeller assembly a determined distance above an upper surface of a casing of the boom
Data Source
AI summary
A vertical lift rotor propulsor assembly comprises a boom having a casing with a casing profile and a first propeller blade having a blade profile that corresponds substantially to at least a portion of the casing profile of the casing of the boom. A drive mechanism is at least partially housed within the boom and at the first propeller blade is rotatably mounted to the drive mechanism to be driven thereby. The drive mechanism is to operationally move the first propeller blade between a stowed position in which the first propeller blade is substantially flush with the casing of the boom, and a deployed position in which the first propeller blade is extended a determined distance from the casing of the boom.