Three-Stream Gas Turbine Engine Fan Segmentation
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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 dealing with weight and installation issues.
Innovation Solution
A three-stream gas turbine engine design with an unducted primary fan and a ducted secondary fan, along with a third stream, allows for a higher fan diameter, reduced fan pressure ratio, and improved propulsive efficiency, while also reducing the axial length and weight of the core engine.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If fan diameter is increased to improve fuel efficiency, then propulsive efficiency improves, but engine weight and installation issues worsen
Solution Approach 1:
The fan system is segmented into two separate fans: a primary unducted fan and a secondary ducted fan. This segmentation allows each fan to be optimized independently for its specific function, enabling the primary fan to be smaller (reducing weight) while the secondary fan handles additional airflow requirements, thus resolving the contradiction between fuel efficiency and weight.
Solution Approach 2:
The invention introduces a third airflow stream through the ducted secondary fan, creating a multi-dimensional airflow configuration. This additional dimension allows the engine to achieve higher propulsive efficiency without requiring a single oversized fan, thereby reducing overall engine weight while maintaining performance.
2Loss of energy
If fan diameter is increased to improve fuel efficiency, then propulsive efficiency improves, but installation and performance penalties worsen
Solution Approach 1:
By segmenting the fan system into primary and secondary fans with different ducting configurations, the invention eliminates the need for a single large-diameter fan that would cause installation and performance penalties. Each fan can be installed in optimized locations, avoiding harmful interference with engine performance.
Solution Approach 2:
The ducted secondary fan acts as an intermediary component that bridges the gap between the primary unducted fan and the required total airflow. This intermediary structure allows the primary fan to operate at optimal sizes while the secondary fan compensates for any performance penalties, maintaining overall engine efficiency.
3Volume of stationary object
If core cowl diameter is increased to accommodate accessories, then packaging space improves, but drag and installation difficulties worsen
Solution Approach 1:
The engine accessories are segmented and distributed across multiple locations: some are mounted on the core cowl while others are mounted on the engine case. This segmentation allows sufficient packaging space without requiring a uniformly large core cowl diameter, thereby reducing drag and installation difficulties.
Solution Approach 2:
The invention utilizes multiple spatial dimensions for accessory mounting: radial mounting on the core cowl and axial mounting on the engine case. This multi-dimensional arrangement provides adequate packaging space without increasing the core cowl diameter, thus avoiding increased drag and installation problems.
Data Source
AI summary
A gas turbine engine defines an axial direction and a radial direction and comprises a turbomachine having an unducted primary fan, a core engine a combustor casing enclosing a combustor and defining an outer surface, a core cowl surrounding at least a portion of the core engine. The outer surface of the core cowl defines a peak cowl diameter in the radial direction, and the outer surface of the combustor casing defines a maximum combustor casing diameter along the radial direction. The core engine defines an overall core axial length along the axial direction and an under-core cowl axial length along the axial direction. The gas turbine engine defines a core cowl diameter ratio equal to the peak cowl diameter divided by the maximum combustor casing diameter and a core cowl length ratio equal to the under-core cowl axial length divided by the overall core axial length.