Boundary Layer Ingestion Fans for Aircraft Drag Reduction
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Solution Overview
Problem
Existing aircraft propulsion systems face challenges in reducing drag caused by boundary layer air across the fuselage, particularly at high speeds, and are inefficient during takeoff and climb conditions due to the proportion of thrust provided by distributed propulsion systems.
Innovation Solution
The system positions main gas turbine engines outwardly of the tail section and incorporates dedicated boundary layer ingestion fans with a scoop inlet and motor-driven fan rotors to ingest and remove boundary layer air, with the option to substitute a gear connection from the gas turbine engine, and operates the fans primarily during cruise conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If main gas turbine engines are positioned above the fuselage to ingest boundary layer air, then drag reduction is improved, but the aircraft requires a relatively wide body fuselage which increases structural complexity
Solution Approach 1:
The propulsion system is segmented into two distinct types: main gas turbine engines for primary thrust and smaller dedicated boundary layer ingestion fans for drag reduction. This segmentation allows each component to be optimized for its specific function without compromising the overall fuselage structure.
Solution Approach 2:
Boundary layer ingestion capability is applied locally at specific locations along the fuselage where boundary layer effects are most pronounced, rather than requiring the entire fuselage to be redesigned. The dedicated fans are positioned to target specific high-drag regions.
2Productivity
If distributed propulsion systems provide a high proportion of overall thrust, then propulsion efficiency is improved, but the system becomes inefficient during takeoff and climb conditions
Solution Approach 1:
The propulsion system dynamically adjusts the contribution of different engine types based on flight conditions. During takeoff and climb, the main gas turbine engines provide the majority of thrust. During cruise, the boundary layer ingestion fans are activated to enhance propulsion efficiency by ingesting the boundary layer and converting it into useful thrust.
Solution Approach 2:
The propulsion system is designed to perform multiple functions across different flight regimes. The main gas turbine engines provide primary thrust for all phases of flight, while the dedicated boundary layer fans provide supplemental thrust during cruise and can be adjusted to optimize performance for specific flight conditions.
3Object-affected harmful factors
If dedicated boundary layer ingestion fans are positioned in the tail section, then drag reduction is improved, but the system complexity increases
Solution Approach 1:
The dedicated boundary layer ingestion fans are merged with the existing tail section structure of the aircraft. This integration allows the fans to be positioned optimally for boundary layer ingestion while utilizing the existing structural framework, thereby reducing the overall system complexity compared to adding entirely separate structures.
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 configuration reduces drag and enhances propulsion efficiency by optimizing thrust distribution, with the boundary layer fans providing less than 20% of the overall thrust, allowing for improved aircraft performance at higher speeds while minimizing energy consumption during takeoff and climb.
Implementation Method 1
dedicated boundary layer ingestion fans with a scoop inlet and motor-driven fan rotors to ingest and remove boundary layer air
Implementation Method 2
The air is compressed in the compressor and delivered into a combustor where it is mixed with fuel and ignited. Products of this combustion pass downstream over turbine rotors driving them to rotate.
Data Source
Figure 1A~1B
Figure 2~3
AI summary
A propulsion system for an aircraft (20) comprises at least two main gas turbine engines (26) and a plurality of dedicated boundary layer ingestion fans (28). An aircraft (20) is also disclosed.