Ram Nozzle for Boundary Layer Ingestion
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Solution Overview
Problem
Adverse inlet distortions caused by fuselage curvature and viscous scrubbing reduce the efficiency of boundary layer ingestion in aircraft engines, leading to non-uniform airflow profiles and decreased fan efficiency.
Innovation Solution
A ram nozzle is placed in front of the fan inlet to accelerate boundary layer airflows near the fuselage and decelerate more distant airflows, providing a more uniform inflow velocity and optimizing the angle of attack for the fan, while a deployable nozzle element with step-wise and annular curvatures can be used to further homogenize airflow profiles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If boundary layer ingestion is implemented in aircraft engines, then propulsive efficiency is improved, but fan efficiency deteriorates due to non-uniform airflow profiles and inlet distortions
Solution Approach 1:
A nozzle element is positioned upstream of the fan inlet to pre-condition the boundary layer airflow before it enters the fan. This preliminary action accelerates the boundary layer air and modifies its velocity profile in advance, creating a more uniform inflow distribution that improves fan efficiency while maintaining the propulsive benefits of boundary layer ingestion
Solution Approach 2:
The nozzle element changes the velocity parameter of the boundary layer airflow by accelerating it. This parameter modification transforms the non-uniform boundary layer profile into a more uniform distribution, resolving the contradiction between maintaining propulsive efficiency and improving fan performance
2Reliability
If a nozzle element is added to homogenize airflow, then fan efficiency is improved, but device complexity increases
Solution Approach 1:
The nozzle is divided into multiple segments or sections with different curvature radii along its length. This segmentation allows each section to address specific airflow characteristics at different positions, achieving effective flow homogenization while keeping the overall structure manageable and not excessively complex
Solution Approach 2:
The nozzle element incorporates curved surfaces with varying radii of curvature to guide and reshape the boundary layer airflow. These curved geometries naturally redirect and homogenize the flow without requiring complex mechanical components, achieving flow conditioning through elegant geometric design
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
This solution enhances fan efficiency by ensuring more uniform boundary layer ingestion, maintaining propulsive efficiency benefits while overcoming pressure losses due to additional geometry, and allows for optimized angles of attack for improved performance.
Implementation Method 1
the engines ingest air flowing as a boundary layer along the fuselage via the respective fan sections of the engines
Implementation Method 2
adverse inlet distortions caused by fuselage curvature and viscous scrubbing reduce the efficiency of boundary layer ingestion
Data Source
Figure 1~2
Figure 3~5
AI summary
An aircraft (101) is provided and includes fuselage (110) having a nose (111), a main section (112) aft of the nose (111) and a tail (113) aft of the main section (112), an engine nacelle (130) partially embedded in the tail (113) and including a boundary layer ingestion (BLI) propulsor (131) with an inlet (132) directly adjacent to the fuselage (110) and a nozzle element (140) disposed upstream from the inlet (132) and configured to accelerate boundary flows flowing toward the interior side (1321) of the engine nacelle (130).