Unducted Propulsion Housing and Counter-Rotation for Drag Reduction
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Solution Overview
Problem
Existing aircraft propulsion systems face inefficiencies in thrust production due to energy losses, swirl, vortices, frictional drag, and shockwave-related drag, which are exacerbated at high subsonic cruise speeds, leading to poor fuel efficiency and increased power requirements.
Innovation Solution
An unducted propulsion system with two blade assemblies, where one assembly counteracts the swirl of the other, and optimized external housing flowpath curves to minimize drag and pressure loss, allowing high subsonic cruise flight with improved efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional ducted fan propulsion systems are used, then thrust is produced by accelerating air through the fan, but energy losses occur due to swirl, vortices, and frictional drag on external surfaces
Solution Approach 1:
The patent removes the traditional ducting structure from the propulsion system, extracting the harmful interaction between the duct and the airflow. By eliminating the duct, the system avoids the energy losses associated with air entering and exiting the duct, as well as the frictional drag on the external surfaces of the duct.
Solution Approach 2:
Instead of using a duct to guide and contain the airflow (conventional approach), the patent inverts the approach by allowing the airflow to be uncontained and free-form. The blade assemblies operate in an open environment, and the counter-rotating blades actively manage the airflow patterns rather than relying on duct constraints.
2Speed
If high subsonic cruise speeds are achieved, then propulsion efficiency improves, but shockwave-related drag and frictional drag increase
Solution Approach 1:
The patent employs counter-rotating blade assemblies that dynamically adjust the airflow patterns. The second blade assembly rotates in the opposite direction to the first, creating a dynamic interaction that counteracts swirl and vortex formation. This dynamic control of airflow reduces the harmful effects of drag at high subsonic speeds.
Solution Approach 2:
The system changes the rotational parameters of the blade assemblies, specifically using counter-rotating motion with carefully controlled speeds and directions. This parameter change transforms the airflow characteristics, reducing shockwave formation and minimizing frictional drag on the aircraft surfaces.
3Loss of energy
If blade assemblies counteract swirl to reduce energy losses, then propulsion efficiency improves, but device complexity increases
Solution Approach 1:
The patent combines two blade assemblies into a single integrated propulsion system, where the first and second blade assemblies work together in counter-rotating fashion. This merging of functions into a unified system allows the counter-swirl effect to be achieved while managing the complexity through coordinated operation of the two assemblies.
Solution Approach 2:
The counter-rotating second blade assembly acts as an intermediary element that receives the swirl and vortex energy from the first blade assembly and transforms it into useful thrust. This intermediary action neutralizes the harmful rotational components while preserving the forward propulsion function.
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 system enables high subsonic cruise speeds with reduced energy losses and drag, enhancing propulsion efficiency and fuel efficiency by counteracting swirl and optimizing flowpath surfaces.
Implementation Method 1
a fan of an aircraft propulsion system produces thrust by accelerating air passing through the fan
Implementation Method 2
one assembly counteracts the swirl of the other
Implementation Method 3
optimized external housing flowpath curves to minimize drag and pressure loss
Data Source
AI summary
Apparatuses and systems are provided herein for unducted propulsion systems. The system includes an aft housing for low drag for high subsonic sustained flight. A plurality of blades are affixed to the aft housing, wherein the housing defines a flowpath curve extending from the axial extent of the aft blade root to the aft end of the aft housing. The flowpath curve is described by an axial direction parallel to an axis of rotation and a radius from the axis of rotation. The flowpath curve includes first point having a first radius where the radius reaches a maximum aft of the aft blade root and a second point forward of the first point having a second radius where the radius stops decreasing. The ratio of the first radius to the second radius is greater than or equal to 1.081.