Three-Stream Gas Turbine Engine Accessory Packaging
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Solution Overview
Problem
Conventional turbofan engine designs face challenges in increasing fan diameter to improve fuel efficiency while maintaining propulsive efficiency and reducing weight, as larger fans require more complex and heavier engine accessory packaging, and the removal of the outer nacelle complicates installation and increases drag.
Innovation Solution
A three-stream gas turbine engine design with an unducted primary fan and a ducted secondary fan, where the secondary fan provides airflow to a third stream, allowing for a larger fan diameter without overloading the primary fan, reducing the core engine's axial length, and optimizing the core cowl diameter and length ratios to accommodate engine accessories while maintaining propulsive efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If fan diameter is increased to improve fuel efficiency, then fuel efficiency is improved, but engine accessory packaging becomes more complex and heavier
Solution Approach 1:
The fan system is segmented into two separate fans: a primary unducted fan for thrust generation and a secondary ducted fan for auxiliary functions. This segmentation allows each fan to be optimized independently, with the primary fan having larger diameter for fuel efficiency while the secondary fan handles accessory packaging requirements separately.
Solution Approach 2:
The patent utilizes three-dimensional space around the engine core by positioning accessories on the core cowl surface rather than only within traditional nacelle boundaries. This dimensional reorganization allows adequate packaging space for accessories while maintaining a compact overall engine footprint.
2Use of energy by moving object
If fan diameter is increased to improve fuel efficiency, then fuel efficiency is improved, but engine weight increases
Solution Approach 1:
By dividing the fan function into two separate fans, the patent avoids the need for a single oversized fan. The primary fan provides the necessary thrust with appropriate diameter, while the secondary fan handles auxiliary functions, resulting in lower total engine weight compared to a single large fan design.
Solution Approach 2:
The patent extracts the auxiliary fan function from the primary fan system, separating it into an independent secondary ducted fan. This extraction allows the primary fan to be optimized for thrust with smaller diameter, reducing overall engine weight while maintaining fuel efficiency.
3Weight of moving object
If outer nacelle is removed to reduce weight and complexity, then weight and complexity are reduced, but installation becomes more difficult and drag increases
Solution Approach 1:
The patent removes the traditional outer nacelle structure and extracts the fan system from its conventional enclosed configuration. The unducted primary fan and ducted secondary fan are positioned directly around the engine core, eliminating the need for a separate nacelle while maintaining structural integrity and reducing weight.
Solution Approach 2:
The core cowl structure serves multiple functions: it provides the mounting surface for accessories, defines the engine boundary, and supports the fan systems. This multi-functionality eliminates the need for separate nacelle components, simplifying installation while reducing weight.
4Volume of stationary object
If core engine axial length is reduced to optimize packaging, then packaging space is improved, but power output may be compromised
Solution Approach 1:
The patent transitions from a linear power transmission approach to a three-dimensional arrangement where the secondary ducted fan is positioned adjacent to the primary fan. This spatial reconfiguration allows the core engine to have reduced axial length while maintaining sufficient power output through the combined action of both fans.
Solution Approach 2:
By segmenting the fan system into two independent fans with separate drive mechanisms, the patent allows the core engine to be more compact. Each fan can be driven by appropriately sized turbines, enabling reduced core length while maintaining total power output through the combined thrust of both fans.
Data Source
AI summary
A gas turbine engine, comprising a turbomachine and a housing at least partially encasing a portion of the turbomachine, the housing having an inner surface and defining in part a void between the inner surface and the portion of the turbomachine, the housing moveable relative to the portion of the turbomachine; and an engine component selectively coupled to the portion of the turbomachine or to the housing.