Counter-Rotating Low-Pressure Turbine Sections for Turbofan Engine
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Solution Overview
Problem
Increasing the bypass ratio in turbofans leads to larger fan sizes and higher fan tip speeds, necessitating more stages in the low-pressure turbine, which increases weight and complexity, and introduces challenges in maintaining engine efficiency, particularly due to the use of speed-reducing gearboxes.
Innovation Solution
The turbine engine assembly incorporates a low-pressure turbine with counter-rotating sections operating at different speeds, coupled to respective fan sections, allowing for reduced fan tip speed without a gearbox, thereby maintaining high bypass ratios and simplifying the engine design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the bypass ratio is increased to improve engine efficiency, then the fan size and fan tip speed increase, but the low-pressure turbine weight and complexity increase due to requiring more stages
Solution Approach 1:
The low-pressure turbine is divided into two separate counter-rotating turbine sections, each driving its own fan section at different speeds. This segmentation allows each turbine section to be optimized independently, reducing the overall weight and complexity compared to a single multi-stage turbine design.
Solution Approach 2:
The patent implements dynamic speed control by allowing the two turbine sections to rotate at different rotational speeds. The first turbine section rotates at a first rotational speed while the second turbine section rotates at a second rotational speed, enabling flexible optimization of fan tip speeds without increasing turbine weight.
2Speed
If more stages are added to the low-pressure turbine to control fan tip speed, then the turbine weight increases, but the device complexity increases
Solution Approach 1:
The turbine is segmented into two independent counter-rotating sections, each capable of operating at different speeds. This eliminates the need for multiple stages in a single turbine and removes the requirement for speed-reducing gearboxes, significantly reducing device complexity while maintaining control over fan tip speeds.
Solution Approach 2:
By allowing different rotational speeds for the two turbine sections, the system dynamically controls fan tip speeds without adding mechanical complexity. The first turbine section drives the first fan section at a first rotational speed while the second turbine section drives the second fan section at a second rotational speed.
3Speed
If a speed-reducing gearbox is used to decouple turbine speed from fan tip speed, then the fan tip speed can be controlled, but the engine weight and complexity increase
Solution Approach 1:
The patent extracts and eliminates the speed-reducing gearbox from the system by using counter-rotating turbine sections that naturally operate at different speeds. This removes the mechanical complexity and weight of the gearbox while maintaining the ability to control fan tip speeds through the differential rotation of the two turbine sections.
Solution Approach 2:
The system uses dynamic differential rotation of the two turbine sections to achieve speed decoupling without mechanical transmission components. The first turbine section rotates at a first rotational speed and the second turbine section rotates at a second rotational speed, providing flexible speed control without gearboxes.
Data Source
AI summary
A turbine engine assembly is provided. The assembly includes a low-pressure turbine assembly including a first turbine section configured to rotate in a first rotational direction at a first rotational speed, and a second turbine section configured to rotate in a second rotational direction at a second rotational speed. The second rotational direction is opposite the first rotational direction and the second rotational speed is lower than the first rotational speed. The assembly also includes a first drive shaft coupled to the first turbine section, and a fan assembly including a first fan section coupled to the first drive shaft such that the first fan section rotates in the first rotational direction at the first rotational speed, and a second fan section coupled to the second turbine section such that the second fan section rotates in the second rotational direction at the second rotational speed.