Tail Boom Duct Shroud Airfoil Profile for Forward-Flight Drag
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Solution Overview
Problem
Existing rotorcraft designs suffer from significant aerodynamic drag in forward flight conditions due to the transverse ducts of the shroud, despite improvements in aerodynamic efficiency, primarily caused by suction and compression effects.
Innovation Solution
The rotorcraft incorporates a shroud with aerodynamically improved vertical forward and rearward middle sections shaped like airfoil profiles, featuring a trailing edge with a sharp edge and varying depth along the circumferential direction, reducing drag by minimizing suction and compression effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a shroud with a transverse duct is used to generate counter-torque thrust in hover flight, then counter-torque thrust is improved, but aerodynamic drag increases significantly in forward flight condition
Solution Approach 1:
The shroud is divided into multiple sections (first section connected to tail boom, second section spaced apart and diametrically opposed), with the first section having an airfoil-like aerodynamic profile. This segmentation allows different parts of the shroud to have optimized functions for both hover thrust generation and forward flight drag reduction.
Solution Approach 2:
The first section of the shroud is given an airfoil-like aerodynamic profile with curved surfaces, replacing the conventional cylindrical or flat profile. This curvature optimization reduces suction and compression effects on the transverse duct during forward flight, significantly decreasing aerodynamic drag while maintaining counter-torque thrust generation capability.
2Device complexity
If the transverse duct has a constant depth over its circumference, then structural simplicity is maintained, but aerodynamic efficiency deteriorates in forward flight due to suction and compression effects
Solution Approach 1:
Instead of giving the entire shroud a uniform structure, the invention applies airfoil-like aerodynamic profiles specifically to the first section of the shroud that is connected to the tail boom. This localized quality change optimizes the aerodynamic characteristics where they are most needed for drag reduction during forward flight, while maintaining structural simplicity elsewhere.
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 significantly reduces aerodynamic drag in fast forward flight while maintaining counter-torque thrust generation comparable to conventional designs, enhancing overall efficiency.
Implementation Method 1
The first section comprises an airfoil-like aerodynamic profile
Implementation Method 2
the transverse duct itself produces such comparatively large amount of drag due to suction and compression effects occurring in the forward flight condition on the transverse duct
Implementation Method 3
suction and compression effects occurring in the forward flight condition on the transverse duct
Data Source
AI summary
A rotorcraft with at least one main rotor and a fuselage, comprising: a tail boom connected to the fuselage, the tail boom extending in a longitudinal direction from the fuselage toward a duct-type portion; a shroud provided at the duct-type portion and forming a transverse duct comprising a circumferential direction and a longitudinal extension oriented at least essentially perpendicular to the circumferential direction and the longitudinal direction of the tail boom; and at least one ducted tail rotor rotatably arranged in the transverse duct; wherein the shroud comprises a first section connected to the tail boom and a second section spaced apart from the tail boom and diametrically opposed to the first section, the first section comprising an airfoil-like aerodynamic profile.