Turbomachine Fan Rotor Reduction Gearbox Integration
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Solution Overview
Problem
Current turbomachine designs face challenges in achieving high propulsive efficiency while minimizing mass, drag, and installation difficulties, particularly with large fan diameters and complex technologies required for low-pressure rotor fairing, which are exacerbated by the need for increased mass flow and external dimensions, limiting flight speed and installation on aircraft.
Innovation Solution
A ducted fan architecture with a reduction gear interposed between the fan rotor and low-pressure turbine shaft, featuring a compact nacelle that provides aerodynamic fairing without guiding or pressure control functions, and variable pitch blades for efficient operation across flight conditions, along with a cylindrical vein and spherical recess design to minimize clearance and efficiency losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the fan diameter is increased to treat larger mass flow and improve propulsive efficiency, then the propulsive efficiency is improved, but the external dimensions of the containment casing and nacelle increase, making under-wing installation difficult
Solution Approach 1:
The patent repositions the reduction gearbox from a traditional lateral placement to an axial placement within the fan hub. This dimensional reorganization allows the gearbox to occupy the central axial space rather than extending the radial dimensions, enabling larger fan diameters for improved propulsive efficiency without proportionally increasing the overall engine envelope volume for under-wing installation.
Solution Approach 2:
The reduction gearbox is nested within the fan hub structure itself, with the gearbox housing integrated into the hub assembly. This nesting approach allows the gearbox to be contained within the existing fan structure boundaries, avoiding additional external dimension increases while accommodating the necessary gear reduction mechanism for high-bypass ratio operation.
2Productivity
If the fan diameter is increased to handle larger mass flow, then the propulsive efficiency is improved, but the mass of the propulsion system increases significantly due to larger fan casing
Solution Approach 1:
By moving the gearbox axially into the hub, the patent eliminates the need for lateral extension of the fan casing to accommodate the gearbox. This allows the fan casing to be sized primarily for aerodynamic and centrifugal containment functions rather than also housing the reduction mechanism, reducing unnecessary mass while maintaining the large fan diameter needed for high-bypass propulsive efficiency.
Solution Approach 2:
The gearbox is extracted from the traditional external or lateral position and relocated to the central hub area. This extraction from the conventional arrangement allows the fan casing to be optimized for its primary aerodynamic function without the mass penalty of oversized casing required to accommodate laterally-placed gearbox assemblies.
3Productivity
If a reduction gearbox is added to enable high-bypass operation with large fan diameter, then propulsive efficiency is improved, but the device complexity increases
Solution Approach 1:
The gearbox housing is merged with the fan hub structure, creating an integrated assembly where the gearbox is contained within the hub rather than being a separate external component. This merging reduces the number of discrete parts and simplifies the overall system architecture, making the reduction gearbox integration less complex than traditional separate-mounted arrangements.
Solution Approach 2:
The fan hub is given multiple functions: it serves both as the aerodynamic hub for the fan blades and as the housing for the reduction gearbox. This multi-functionality eliminates the need for separate gearbox housings and mounting structures, reducing overall system complexity while enabling the high-bypass ratio operation required for improved propulsive efficiency.
4Ease of manufacture
If the reduction gearbox housing diameter is increased to accommodate the gearbox, then the gearbox can be integrated, but the inner radius of the blower is reduced, impacting aerodynamic performance
Solution Approach 1:
The gearbox is positioned in the axial dimension within the hub rather than extending radially outward. This axial placement allows the gearbox housing diameter to be minimized while still accommodating the reduction mechanism, preserving the blower's inner radius and aerodynamic performance by avoiding radial encroachment on the airflow path.
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 enhances propulsion efficiency, reduces mass and drag, and allows for integration under aircraft wings with minimal impact on dimensions, enabling higher flight speeds and thrust reversal capabilities while maintaining efficient operation across varying conditions.
Implementation Method 1
a reduction gear interposed between the fan rotor and low-pressure turbine shaft
Implementation Method 2
reduction gear housed in a gearbox casing between the fan and the low-pressure turbine shaft
Implementation Method 3
variable pitch blades for efficient operation across flight conditions
Implementation Method 4
spherical recess design to minimize clearance and efficiency losses
Data Source
Figure 1
Figure 2
Figure 3a
AI summary
A turbomachine comprising a ducted fan, a low-pressure turbine shaft and a reduction gearbox housed in a casing between the fan and the low-pressure turbine shaft, the fan rotor supplying airflow to a primary stream and a secondary stream and comprising a hub of diameter D1, wherein - the diameter D3 of the fan rotor is greater than 82 inches (2.08 metres), - the pressure ratio of the fan is between 1.10 and 1.35, the turbomachine comprises a low-pressure compressor separate from the fan, the reduction gearbox being interposed between the fan rotor and a turbine shaft of the low-pressure compressor, and wherein the reduction gearbox casing has an outside diameter D2 greater than the diameter D1 of the hub, the pitch diameter D4 of the reduction gearbox ring being between 0.15 and 0.35 times the fan rotor diameter.