Geared Turbofan Gearbox Layout for Reduced Core Flow Turning
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Solution Overview
Problem
Turbofan engine design faces challenges in optimizing flowpath geometry due to competing factors like weight, material strength, and aerodynamics, particularly in bearing arrangements that support rotating structures, which affect engine efficiency and radial turning of the core flow between high radius sections and lower diameter compressor sections.
Innovation Solution
A gas turbine engine design featuring a fan section with a specific ratio of inboard leading edge radius to peak tip radius, a core engine with multiple compressor and turbine stages, and a geared architecture that rotates the fan section at a different speed than the fan drive turbine, along with optimized bearing arrangements to manage radial and thrust loads, is proposed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a drive gear system is placed axially between the compressor and the fan, then the fan can be driven at a different speed than the compressor, but this causes relatively high core flowpath diameters and increased radial turning of the core flow
Solution Approach 1:
The patent moves the drive gear system from an axial arrangement between compressor and fan to a radial arrangement at the compressor discharge end. This dimensional change allows the gear system to be positioned in the radial direction rather than occupying axial space, thereby reducing the core flowpath diameter and minimizing radial turning of the core flow while still enabling independent fan speed control.
2Adaptability or versatility
If the core flowpath radius is increased to accommodate actuation mechanisms or variable pitch fan blades, then these features can be implemented, but this increases the hub diameter and causes high core flowpath diameters
Solution Approach 1:
By repositioning the drive gear system radially at the compressor discharge end, the patent creates space in the axial direction that can be utilized for variable pitch fan blade actuation mechanisms without increasing the core flowpath diameter. This allows adaptable fan blade control while maintaining optimized core flowpath geometry.
3Productivity
If radial turning of the core flow is minimized for efficiency, then engine efficiency is improved, but this conflicts with the need to accommodate high radius sections for bearing arrangements and gear systems
Solution Approach 1:
The patent positions the bearing arrangements and drive gear system in the radial direction at the compressor discharge end, allowing these necessary components to be accommodated without increasing the axial core flowpath diameter. This enables minimal radial turning of the core flow for improved engine efficiency while still providing adequate space for bearing arrangements through radial positioning.
Data Source
AI summary
A gas turbine engine according to the present disclosure includes, among other things, a propulsor section including a propulsor having a plurality of blades, the plurality of blades having a peak tip radius Rt and an inboard leading edge radius Rh at a first inboard boundary of a first flowpath, and a core engine including a first turbine that drives a first compressor and a second turbine that drives the propulsor section. A second inboard boundary of a core flowpath has a radius R1 defined at a first stage of a second compressor and has a radius R2 defined at a splitter rim that guides flow into the core flowpath.