Direct Drive Engine Under Wing Installation
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Solution Overview
Problem
Indirect drive gas turbine engines face increased risks and inefficiencies due to high-speed LP turbines, additional weight, and complexity from reduction gearboxes, which are not present in direct drive engines, necessitating a solution that balances low-speed LP turbine benefits with improved aircraft efficiency.
Innovation Solution
A direct drive gas turbine engine configuration with a fan assembly and LP turbine coupled via a driveshaft, where the LP turbine is positioned underneath the wing, and a containment shield is used to mitigate risks, optimizing the fan to turbine diameter ratio and pressure ratio for reduced weight and complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If indirect drive configuration with reduction gearbox is used, then fan assembly speed is reduced relative to LP turbine rotor speed, but device complexity and weight increase due to additional gearbox structures
Solution Approach 1:
The patent removes the reduction gearbox from the engine architecture, transitioning from indirect drive to direct drive configuration. This extraction of the gearbox eliminates the complex mechanical transmission system while maintaining the desired speed relationship through direct coupling of the LP turbine rotor to the fan assembly, thereby reducing device complexity while preserving speed control benefits
Solution Approach 2:
The patent merges the functions previously performed by separate components (LP turbine rotor and fan assembly) into a directly coupled system. By eliminating the gearbox intermediary, the LP turbine rotor and fan assembly are merged into a single rotational system, reducing the number of moving parts and simplifying the overall engine architecture while maintaining operational efficiency
2Speed
If indirect drive configuration with reduction gearbox is used, then fan assembly speed is reduced relative to LP turbine rotor speed, but weight increases due to additional gearbox structures
Solution Approach 1:
The patent extracts and removes the reduction gearbox from the engine system, eliminating the significant weight associated with gearbox housing, gears, bearings, and supporting structures. This extraction achieves weight reduction while maintaining the functional relationship between LP turbine rotor speed and fan assembly speed through direct drive coupling
Solution Approach 2:
By merging the LP turbine rotor and fan assembly into a directly coupled system, the patent eliminates the weight of the gearbox transmission system. The combined direct drive configuration reduces overall engine weight by removing redundant mechanical components while preserving the speed ratio benefits through direct rotational coupling
3Use of energy by moving object
If LP turbine rotates at high speed in indirect drive, then efficiency is improved, but reliability decreases due to increased rotor failure risks
Solution Approach 1:
The patent changes the operational parameters of the LP turbine by directly coupling it to the fan assembly, which modifies the speed relationship and operational characteristics. This parameter change allows the turbine to operate at optimized speeds that balance efficiency with reduced mechanical stress and failure risk, eliminating the extreme speed differentials inherent in gearbox-driven systems
Solution Approach 2:
By removing the reduction gearbox, the patent eliminates the mechanism that creates extreme speed differentials between the LP turbine rotor and fan assembly. This extraction prevents the high-speed operation of the LP turbine that leads to increased failure risks, while maintaining efficient energy transfer through direct coupling at more moderate, reliable speeds
4Device complexity
If direct drive configuration is used, then device complexity and weight are reduced, but fan assembly speed ratio control is reduced compared to indirect drive
Solution Approach 1:
The patent optimizes the direct drive configuration by adjusting design parameters such as the diameter ratio between fan assembly and LP turbine rotor, and the pressure ratio across the fan. These parameter changes enable the direct drive system to achieve speed ratio control comparable to indirect drive systems, compensating for the absence of a gearbox while maintaining simplicity
Data Source
AI summary
The present disclosure is directed to a gas turbine engine defining a radial direction, a longitudinal direction, and a circumferential direction, an upstream end and a downstream end along the longitudinal direction, and an axial centerline extended along the longitudinal direction. The gas turbine engine includes a fan assembly including a plurality of fan blades rotatably coupled to a fan rotor in which the fan blades define a maximum fan diameter and a fan pressure ratio. The gas turbine engine further includes a low pressure (LP) turbine defining a core flowpath therethrough generally along the longitudinal direction. The core flowpath defines a maximum outer flowpath diameter relative to the axial centerline. The gas turbine engine defines a fan to turbine diameter ratio of the maximum fan diameter to the maximum outer flowpath diameter. The fan to turbine diameter ratio over the fan pressure ratio is approximately 0.90 or greater.