Variable Pitch Cross-Flow Fan for Rotorcraft Anti-Torque
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Solution Overview
Problem
Traditional tail rotors on rotorcrafts are susceptible to collision risks, produce high noise, and create profile drag, while cross-flow fan systems require complex gearing and redundancy for bidirectional thrust, necessitating an improved anti-torque system with reduced noise, impact risk, and drag.
Innovation Solution
A variable thrust cross-flow fan system with a cross-flow fan assembly and control assembly that changes the pitch angle of blades to generate variable thrust at a constant rotational speed, allowing for reversible thrust in multiple directions, reducing the need for multiple fans and complex gearing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional tail rotors are used, then anti-torque control is achieved, but noise level increases and collision risk increases
Solution Approach 1:
The tail rotor blade is segmented into multiple smaller blades arranged in a cross-flow fan configuration. This segmentation reduces the collision risk by distributing the rotating elements across a larger area with smaller individual components, while also reducing noise through distributed aerodynamic loading across multiple blade elements rather than a single large blade.
Solution Approach 2:
The invention transitions from a traditional horizontal axis rotor to a cross-flow fan configuration where blades are arranged radially outwardly from a longitudinal axis. This dimensional reconfiguration allows the blades to operate in a different spatial arrangement that reduces both noise signature and collision risk by distributing the rotating elements in a radial pattern rather than a single planar disk.
2Object-affected harmful factors
If cross-flow fan systems are used, then noise and collision risk are reduced, but system complexity increases due to required redundancy for bidirectional thrust
Solution Approach 1:
The invention employs dynamically adjustable blade pitch angles that can be varied during operation to change the direction and magnitude of thrust. This dynamic control allows a single cross-flow fan assembly to provide bidirectional thrust capability without requiring mechanical redundancy, clutches, or complex gearing schemes, as the same physical system can redirect thrust in different directions through pitch adjustment.
Solution Approach 2:
The invention changes the operational parameters of the cross-flow fan by allowing continuous variation of blade pitch angles. This parameter change enables the system to achieve bidirectional thrust control by modifying the aerodynamic characteristics of the blades rather than through mechanical reconfiguration, thereby simplifying the overall system architecture.
3Object-affected harmful factors
If cross-flow fan systems are used, then noise and collision risk are reduced, but device complexity increases due to redundancy requirements
Solution Approach 1:
The single cross-flow fan assembly is designed to perform multiple functions: it can generate thrust in both pro-torque and anti-torque directions, provide yaw control, and operate at variable thrust levels. This multi-functionality eliminates the need for separate fans or redundant components that would otherwise be required to achieve bidirectional thrust capability, thereby reducing the total number of components while maintaining noise and collision risk benefits.
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 provides effective anti-torque and yaw control with reduced noise, impact risk, and drag, while maintaining constant rotational speed, simplifying the system and enhancing operational efficiency.
Implementation Method 1
The plurality of blades are disposed radially outwardly from the longitudinal axis such that the plurality of blades have a generally circular path of travel when the cross-flow fan assembly rotates about the longitudinal axis
Implementation Method 2
The plurality of blades are moveable between a plurality of pitch angle configurations. A control assembly is coupled to the plurality of blades. The control assembly is operable to change the pitch angle configuration of the plurality of blades to generate variable thrust at a substantially constant rotational speed
Data Source
AI summary
In some embodiments, a rotorcraft includes a fuselage, a tailboom, a drive system and a variable thrust cross-flow fan system. The cross-flow fan system includes a cross-flow fan assembly that is mechanically coupled to a drive shaft and operable to rotate with the drive shaft about a longitudinal axis. The cross-flow fan assembly includes first and second driver plates having a plurality of blades rotatably mounted therebetween. The blades are disposed radially outwardly from the longitudinal axis and have a generally circular path of travel when the cross-flow fan assembly rotates about the longitudinal axis. The blades are moveable between a plurality of pitch angle configurations. A control assembly is coupled to the blades. The control assembly is operable to change the pitch angle configuration of the blades to generate variable thrust at a substantially constant rotational speed of the cross-flow fan assembly.