Aft Engine Nacelle Curved Surface for Boundary Layer Ingestion
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Solution Overview
Problem
Conventional aircraft propulsion systems face inefficiencies due to drag caused by turbofan jet engines, which can be exacerbated by the nonuniform velocity profile of boundary layer air ingestion, and existing solutions like boundary layer ingestion propulsors may interfere with takeoff angles.
Innovation Solution
An aft engine with a nacelle designed to ingest boundary layer air from the fuselage without interfering with the takeoff angle, featuring a fan with a plurality of blades and a nacelle with a curved surface at the forward end, allowing for efficient energy reclamation of slow-moving air while maintaining optimal takeoff configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a dedicated boundary layer ingestion propulsor is added to the aircraft at the aft end, then drag is reduced by reenergizing the boundary layer airflow, but the takeoff angle of the aircraft is interfered with
Solution Approach 1:
The nacelle is designed with a curved surface at the forward end that redirects airflow from a non-parallel direction to enter the engine inlet. This dimensional change in airflow direction allows the boundary layer ingestion system to function without interfering with the aircraft's takeoff angle, as the curved surface accommodates both the angled boundary layer flow and the engine's axial requirement.
2Loss of energy
If boundary layer air is ingested into the turbofan jet engine, then drag is reduced, but the nonuniform velocity profile causes efficiency loss in the engine
Solution Approach 1:
The curved surface at the forward end of the nacelle modifies the airflow parameters by redirecting the boundary layer air to enter the engine inlet in a more uniform and axial direction. This parameter change in airflow direction and velocity distribution allows the engine to process boundary layer air with reduced distortion, maintaining engine efficiency while achieving drag reduction through boundary layer ingestion.
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 aft engine design enhances propulsive efficiency by capturing boundary layer air without compromising the aircraft's takeoff angle, thereby reducing overall drag and improving net thrust.
Implementation Method 1
ingest boundary layer air from the fuselage without interfering with the takeoff angle
Data Source
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AI summary
An aircraft (10) including a fuselage (20) and an aft engine (200) is provided. The fuselage (20) extends from a forward end (14) of the aircraft (10) towards an aft end (16) of the aircraft (10). The aft engine (200) is mounted to the fuselage (20) proximate the aft end (16) of the aircraft (10) and includes a fan (222) and a nacelle (224). The fan (222) is rotatable about a central axis (220) of the aft engine (200) and includes a plurality of fan blades (228). The nacelle (224) of the aft engine (200) surrounds the plurality of fan blades (228) and defines a bottom portion (248) having a forward end (14). Additionally, the nacelle (224) defines a curved surface at the forward end (14) of the bottom portion (248), the curved surface including a reference point where the curved surface defines the smallest radius of curvature (266). The nacelle (224) further defines a normal reference line (268) extending normal from the reference point. The normal reference line (268) defines an angle with the central axis (220) of the aft engine (200) greater than zero to, e.g., allow for a maximum amount of airflow into the aft engine (200).