Wingtip Vortex Drag Reduction Using Convergent Backwash
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Solution Overview
Problem
Lift-induced wingtip vortices account for a significant portion of airframe drag in fixed-wing transport aircraft, and existing solutions have limitations in reducing drag and recovering vortex energy efficiently.
Innovation Solution
A wingtip-mounted pusher type fan with a novel nacelle form and blade design that turns opposite to the vortex rotation, combined with secondary turbines that rotate in the same direction as the vortices, to dissipate and convert vortex energy into propulsion or electrical power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If wingtip-mounted turbines are used to extract energy from vortices, then vortex energy recovery is improved, but device complexity increases
Solution Approach 1:
The wingtip device integrates multiple functions into a single structure: the pusher fan provides primary propulsion while simultaneously generating vortex-dissipating backwash, and the secondary turbines extract energy from the vortex. This multi-functional integration resolves the contradiction by achieving energy recovery without proportionally increasing device complexity.
Solution Approach 2:
The invention merges the propulsion function and vortex management function into a unified wingtip system. The pusher fan's backwash and the secondary turbines work together in a coordinated manner to both reduce vortex drag and generate power, thereby improving energy recovery while maintaining manageable device complexity.
2Object-generated harmful factors
If pusher fan backwash is directed to converge centrally, then vortex dissipation is improved, but device complexity increases
Solution Approach 1:
The nacelle design incorporates localized flow control features including outward-aft swept blades and specific nacelle geometry that direct backwash convergence. These localized structural modifications achieve effective vortex dissipation without requiring complex active control systems, thus resolving the contradiction between vortex management effectiveness and device complexity.
3Power
If secondary turbines are mounted at blade tips, then electrical power generation is improved, but device complexity increases
Solution Approach 1:
The secondary turbines mounted at blade tips serve dual purposes: they extract energy from the vortex to generate electrical power while simultaneously helping to dissipate the vortex structure. This multi-functionality allows the system to improve power generation without proportionally increasing device complexity, as the same structural elements serve multiple functions.
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 solution significantly reduces airframe drag, enhances propulsion efficiency, and converts vortex energy into additional power, while also mitigating wake turbulence and improving fluid kinetic energy capture.
Implementation Method 1
The pusher fan is distinct from Patterson because its outward-aft blade sweep angle directs convergent backwash to a central high pressure flow volume that more efficiently dissipates the cyclonic structure of the vortex
Implementation Method 2
the outward-aft blade sweep angle directs convergent backwash to a central high pressure flow volume
Implementation Method 3
the same nacelle form supports secondary power-takeoff turbines mounted in high energy density flow at the turbine blade tips. In this arrangement, the secondary turbines turn in the same direction as the lift induced vortices. This reduces blade tip vortex drag and directly generates additional electrical power
Data Source
AI summary
A fuel efficient aircraft propulsion system comprises a wingtip mounted ducted pusher fan with convergent backwash and a skewed conical engine nacelle. The system both mitigates wingtip vortex drag and converts a portion of vortex energy into propulsion force and lift force. The forward-tapering nacelle skews both downward and inward, so the lower nacelle surface is flush with the lower wing surface and the inboard nacelle surface does not alter flow over the upper wing surface. This firstly preserves lift at the outboard wing end. Secondly, air displacement by the nacelle accelerates flow only on the outboard and upper nacelle surfaces, and because the nacelle occupies the core of the nascent wingtip vortex, rotational air velocity is greatest on the upper nacelle surface. The resultant pressure drop on the upper nacelle surface contributes to aircraft lift. And because the nacelle surface tapers forward, this pressure drop does not exert backward-acting drag on the aircraft. Aft of the nacelle, the pusher fan hub surface conforms with the aft nacelle surface and tapers aft. Propulsion foils project from the forward portion of the pusher fan hub at an outward-aft angle, which directs convergent high pressure backwash flow along the aft tapering hub surface. This isolates aft-facing hub surfaces from drag-inducing vortex core pressure drop. Downstream fan backwash convergence then forms a central volume of high pressure flow where the low pressure trailing vortex core would otherwise develop. This is an efficient means to dissipate the cyclonic structure of the vortex, because vortex persistence requires low pressure core persistence. The direction of pusher fan rotation opposes the direction of wingtip vortex rotation as described in the prior art. This cross-flow interaction increases the effective power of the fan and also further counters vortex formation. An integral peripheral duct links the outer ends of the fan propulsion foils to provide thrust efficiency similar to that of a high bypass fanjet engine, but without the internal air friction within a bypass channel. In an alternative horizontal axis wind turbine embodiment, the same nacelle form supports secondary power-takeoff turbines mounted in high energy density flow at the turbine blade tips.