Supersonic Fan Blade Sweep Angle for Propulsion Efficiency
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Solution Overview
Problem
Current ducted fan propulsion systems for aircraft face inefficiencies at high subsonic speeds due to transonic turbulence, complex manufacturing processes, and high costs, particularly in optimizing fan efficiency and managing inboard flow regimes, which limits their ability to achieve reliable high subsonic flight efficiently and economically.
Innovation Solution
A supersonic fan design featuring a hub with radially extending blades, a duct, and a unique sweep angle configuration that confines inboard flow regimes within the hub, combined with a composite hub formed using spirally wound continuous filaments and a binder, allowing for a lightweight, one-piece rotor with improved propulsion efficiency and simplified manufacturing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a ducted fan is designed with long fan blades to generate thrust, then thrust is improved, but the hub-to-tip ratio becomes low creating transonic turbulence and requiring complex blade shaping
Solution Approach 1:
The patent changes the geometric parameters of the fan blades by introducing a forward-swept configuration with specific sweep angles (20-45 degrees) and optimized aspect ratios. This parameter modification allows the blade to maintain supersonic flow conditions throughout its length, eliminating transonic turbulence while preserving thrust-generating capability.
Solution Approach 2:
The patent employs asymmetric blade shaping where the inboard and outboard portions of the blade have different sweep angles and geometries. The inboard section has a greater sweep angle to manage flow separation, while the outboard section is optimized for thrust generation. This asymmetric design allows each region to operate at its optimal flow regime without requiring progressive twist.
2Reliability
If progressive blade twist is applied to maintain positive AOA, then stall is prevented, but manufacturing complexity increases
Solution Approach 1:
Instead of using progressive twist to manage varying AOA along the blade span, the patent inverts the approach by using forward sweep to actively control flow separation. The forward-swept geometry creates a leading-edge vortex that energizes the boundary layer, preventing stall without requiring complex twist angles. This inversion simplifies manufacturing while maintaining reliability.
3Stability of the object's composition
If blade thickening is applied to stabilize against flutter, then structural stability is improved, but weight increases and shock waves are generated
Solution Approach 1:
The patent replaces the mechanical approach of blade thickening with an aerodynamic solution using forward sweep and leading-edge vortex generation. The forward-swept geometry creates beneficial pressure distribution and vortex flow that stabilizes the blade against flutter without increasing mass. This substitution of mechanical reinforcement with aerodynamic control eliminates unnecessary weight while maintaining structural stability.
4Productivity
If transonic zone management is applied with additional shock wave control, then efficiency is improved, but power consumption increases
Solution Approach 1:
The patent modifies the flow regime parameters by maintaining supersonic flow conditions throughout the blade using forward sweep. This eliminates the transonic zone and its associated shock waves, reducing drag and improving efficiency. The optimized sweep angles and aspect ratios ensure that the blade operates efficiently across the entire speed range without requiring additional power to overcome transonic losses.
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 enhances propulsion efficiency by maintaining a uniform blade speed and reducing transonic turbulence, enabling efficient high subsonic flight while reducing manufacturing complexity and costs, and allowing for the use of non-exotic materials in a lightweight composite rotor.
Implementation Method 1
a composite hub formed using spirally wound continuous filaments and a binder, allowing for a lightweight, one-piece rotor
Implementation Method 2
Each fan blade may have an inboard leading edge of an inboard length rotating at an airspeed of at least approximately Mach 1
Implementation Method 3
An inboard vortex may form near to and as a result of the apex and trail circumferentially across the fan blades. The inboard vortex may be positioned to substantially confine the inboard flow regime to be inboard of the apex
Data Source
AI summary
A supersonic fan has at least two fan blades extending radially from a rim surface of a hub and is circumscribed by a duct. An inboard leading edge having an inboard sweep angle rotates at approximately Mach 1 or greater. A low-pressure zone generates propulsion. An inboard flow regime may migrate outboard from the rim surface and contaminate the low-pressure zone, reducing propulsion. An outboard leading edge having an outboard sweep angle extends radially from the inboard leading edge to form an apex. The inboard and outboard sweep angles are each at least approximately 30 degrees and in the opposite direction. An inboard vortex forming near to and as a result of the apex trails circumferentially across the fan blades and is positioned to substantially confine the inboard flow regime to be inboard of the apex, thereby preserving the low-pressure zone and increasing propulsion for the supersonic fan.