Boundary Layer Ingestion Open Rotor for Aircraft Drag Reduction
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Solution Overview
Problem
Fixed-wing aircraft experience parasitic drag due to boundary layer effects, which do not provide corresponding lift benefits and are considered undesirable, affecting the efficiency and performance of the aircraft.
Innovation Solution
A boundary layer ingestion-open rotor system is introduced, featuring an unshrouded multi-bladed prop fan positioned aft of the empennage within the fuselage's boundary layer, controlled during various flight phases to reduce parasitic drag and increase propulsion efficiency, using a mechanical linkage assembly and energy storage systems for operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the aircraft uses conventional propulsion systems, then thrust is provided, but parasitic drag from boundary layer effects reduces efficiency
Solution Approach 1:
The patent applies boundary layer ingestion (BLI) technology that captures the harmful boundary layer airflow and converts it into useful work by driving the open rotor assembly. The rotor is positioned to ingest the boundary layer flow that would otherwise create parasitic drag, transforming this harmful effect into a source of rotational energy that generates thrust.
Solution Approach 2:
The invention positions the open rotor assembly in a unique location aft of the empennage, utilizing the three-dimensional structure of the boundary layer flow around the fuselage. This spatial arrangement allows the rotor to access and utilize boundary layer flow that would not be available in conventional propulsion configurations.
2Force
If flight control surfaces are adjusted to increase lift, then lift is improved, but drag increases
Solution Approach 1:
The open rotor assembly serves multiple functions: it provides thrust during cruise, assists during takeoff and landing, and can operate in motoring or generating modes during various flight phases. This multi-functionality allows the system to address both lift and drag concerns across different flight conditions without requiring separate dedicated systems.
3Productivity
If the open rotor assembly is positioned within the boundary layer, then parasitic drag is reduced, but the system complexity increases
Solution Approach 1:
The boundary layer flow itself provides the energy to rotate the rotor assembly, eliminating the need for an external power source for the rotor during cruise. The system is self-sustaining by utilizing the available boundary layer flow to drive the rotor, which then generates useful thrust without requiring additional energy input.
Solution Approach 2:
The mechanical linkage assembly allows the open rotor assembly to be dynamically positioned and adjusted during flight. The system can transition between different operational modes (motoring, generating, idle) and adjust rotor pitch and position to optimize performance for different flight phases, providing adaptability without excessive complexity.
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 system reduces parasitic drag, enhances propulsion efficiency, and provides additional thrust functions during takeoff, landing, and taxiing, while also passively recharging energy storage systems, thereby improving fuel efficiency and reducing the load on main propulsion engines.
Implementation Method 1
The term 'boundary layer' refers to a narrowly-defined band of laminar or turbulent airflow passing over and around an aircraft's external surfaces. Air viscosity and resulting friction slow airflow within the boundary layer
Implementation Method 2
Other types of drag, including wake drag induced by the boundary layer effect of airflow passing over and around the fuselage of the aircraft, do not provide a corresponding lift benefit, and therefore are considered to be undesirable parasitic drag
Implementation Method 3
with some configurations actuating the mechanical linkage assembly using onboard hydraulic and/or electrical power to raise or lower the open rotor assembly as needed
Implementation Method 4
at least one energy storage system is selectively connected to the rotor hub. Each energy storage system is configured to selectively energize and thereby rotate the rotor hub within the pre-identified boundary layer in response to an electronic control signal
Implementation Method 5
The ECU may be configured to operate the open rotor assembly as an electric generator or wind turbine, such as during a descent phase of flight, to thereby passively recharge the supercapacitor bank
Implementation Method 6
an open rotor assembly in the form of an unshrouded multi-bladed prop fan is positioned aft of the empennage within a pre-identified boundary layer around the fuselage
Data Source
AI summary
A boundary layer ingestion-open rotor system for use with an aircraft having a fuselage, wings, and an empennage includes an open rotor assembly, one or more energy storage systems, and an electronic control unit (ECU). The open rotor assembly includes fan blades connected to and extending radially from a rotor hub, and a linkage assembly connecting the hub to the fuselage aft of the empennage within a predefined boundary layer of airflow around the fuselage. The energy storage systems are connectable to the rotor hub. In response to an electronic control signal, the system(s) selectively energize the open rotor assembly to cause rotation of the hub to occur within the boundary layer. The ECU selectively generates the electronic control signals to energize the open rotor assembly during one or more predetermined flight operating phases of the aircraft, e.g., cruise, takeoff, landing, and descent.