Ducted Fan Aircraft Propulsion With Flared Ducts for Hover Lift
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Solution Overview
Problem
Ducted fan aircraft propulsion systems face challenges with high disk loading and low hover lift efficiency, leading to reduced payload capability and increased power consumption.
Innovation Solution
A duct design with an outwardly flared inlet and outlet, featuring a decreasing and increasing sectional area respectively, combined with a spheroidal payload portion, enhances airflow efficiency and lift by encouraging larger air volumes and reducing obstruction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a ducted fan is used with a straight duct design, then the rotor size is reduced and noise is lowered, but the hover lift efficiency decreases and power consumption increases
Solution Approach 1:
The duct geometry parameters are changed from a straight cylindrical design to a flared design with varying cross-sectional area. The inlet end has a larger cross-sectional area than the outlet end, creating a gradual contraction that optimizes airflow parameters and improves hover lift efficiency while reducing power consumption
Solution Approach 2:
The duct incorporates curved surfaces with specific flare angles at the inlet and outlet ends. The curved geometry smooths airflow transitions and reduces turbulence, improving overall system efficiency and reducing energy loss compared to straight-edged duct designs
2Productivity
If the duct has a flared inlet end with decreasing sectional area, then airflow efficiency and lift are improved, but the device complexity increases
Solution Approach 1:
The duct design applies different geometric properties to different sections: the inlet end features a flared configuration with a larger cross-sectional area to capture and guide airflow, while the outlet end has a smaller cross-sectional area optimized for thrust generation. This local differentiation of geometric quality optimizes airflow efficiency without requiring complete redesign of the entire duct structure
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
The design improves hover lift efficiency by 67% compared to a simple straight duct, achieving lift efficiency comparable to tilt wing aircraft, with a 49% increase during ground effect.
Implementation Method 1
The reducing air flow passage encourages a larger volume of air into the duct, which aids lift due to the flared inlet end of the annular wing
Implementation Method 2
A rotor provided within the interior of the duct forces airflow through the duct 200 from an inlet 207 to the outlet 206, providing thrust for an aircraft
Implementation Method 3
The reducing air flow passage encourages a larger volume of air into the duct, which aids lift due to the flared inlet end of the annular wing
Data Source
AI summary
The disclosure relates to a ducted fan aircraft propulsion system and to an aircraft incorporating such a propulsion system. Example embodiments include a ducted fan aircraft propulsion system (300),including: a duct (301); a central body portion (302) having first and second ends (303, 304) and extending through the duct (301); a payload portion (305) extending from the first end (303) of the central body portion (302); and a rotor (306) extending across an internal volume (307) of the duct (301) from the central body portion (302), wherein the duct (301) includes an outwardly flared inlet end (308) such that an inlet air flow passage (309) between the central body portion (302) and an inner surface (310) of the duct (301) has a sectional area that decreases from the inlet end (308) of the duct (301) to the rotor (306).