Offset Fan Propulsion Assembly Fixed Under Wing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional aircraft powerplants with offset fans under the wing face challenges in increasing bypass ratio due to ground clearance constraints, leading to drag, weight, and mechanical stress issues, as well as aerodynamic disturbances and inefficient airflow distribution.
Innovation Solution
The powerplant is directly attached to the wing spars without struts, with offset fans positioned near the leading edge and the gas generator integrated into the wing, minimizing drag and mechanical stress while optimizing airflow by displacing fans axially and positioning air intakes under the leading edge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the fan diameter is increased to raise the bypass ratio, then the bypass ratio is improved, but the ground clearance is reduced
Solution Approach 1:
The patent transitions from a single-plane fan arrangement to a two-dimensional offset configuration where fans are positioned at different axial levels. The first fan is arranged upstream and the second fan downstream, both offset laterally from the gas generator axis. This spatial redistribution allows larger effective fan diameters and higher bypass ratios while maintaining adequate ground clearance through vertical and lateral positioning optimization.
2Ease of operation
If a strut is used to suspend the powerplant under the wing, then the powerplant can be positioned upstream, but the weight and drag increase
Solution Approach 1:
The patent removes the intermediate strut component from the powerplant suspension system. Instead of using a strut to connect the powerplant to the wing, the fans are directly mounted to the wing structure at offset positions. This extraction of the strut eliminates its associated weight and drag penalties while achieving the desired upstream positioning of the powerplant through direct wing mounting.
3Device complexity
If the fans are positioned in the same plane, then the structure is simplified, but the airflow distribution becomes uneven
Solution Approach 1:
The patent moves from a single-plane fan arrangement to a two-dimensional configuration where fans operate at different axial levels. The first fan is positioned upstream at one axial level and the second fan downstream at a different axial level, both offset from the gas generator axis. This dimensional change creates more equitable airflow distribution to each fan while maintaining relatively simple structural connections to the wing.
4Device complexity
If the gas generator is positioned high up, then the wing integration is improved, but aerodynamic disturbance occurs when flaps open
Solution Approach 1:
The patent employs asymmetric positioning of the gas generator relative to the wing structure and fan arrangement. The gas generator is offset laterally from the wing centerline and positioned at an asymmetric height that clears the trailing edge flaps when open. This asymmetric configuration achieves both good wing integration and avoidance of aerodynamic disturbance by carefully selecting the gas generator's lateral and vertical position relative to the wing and control surfaces.
Data Source
AI summary
An aircraft including a fuselage, a lateral support wing (1) and a propulsion assembly (100) mounted under the wing. The wing includes at least two structural spars (11ba, 11bf) extending from the fuselage toward the tip of the wing, one of these (11ba) being upstream and the other (11bf) downstream. The propulsion assembly includes a gas generator (106) and at least two offset fans (102, 104) arranged on either side of the axis of the gas generator. The offset fans (102, 104) are attached directly to one of the spars (11ba, 11bf) and the gas generator (106) is attached directly to the two spars. The leading edge of the wing forms a given sweep of angle (α) with the axis of the fuselage. The two offset fans (102, 104) are axially offset from one another.