Compact Low Pressure Turbine Design for High Bypass Ratio Engines
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Solution Overview
Problem
Current turbofan engines face challenges in achieving a high bypass ratio while maintaining a compact and efficient low pressure turbine section, as existing designs are constrained by the correlation between bypass ratio and turbine size, leading to weight and aerodynamic inefficiencies.
Innovation Solution
The implementation of a speed reduction mechanism, such as an epicyclic transmission, decouples the low pressure turbine section from the fan, allowing for a higher bypass area ratio and a lower airfoil count, enabling a compact turbine design with improved efficiency and reduced weight by optimizing the hub-to-tip ratio, disk structural design, and material selection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the bypass ratio is increased to improve fuel efficiency and reduce emissions, then the turbine section size must increase, leading to increased weight and reduced compactness
Solution Approach 1:
The turbine section is divided into multiple blade stages (3 to 6 stages) with optimized airfoil counts in each stage. This segmentation allows the overall turbine to achieve the necessary power output for high bypass ratios while keeping individual stage complexity and weight manageable through distributed architecture
Solution Approach 2:
The patent optimizes critical parameters including the ratio of total airfoils to bypass area ratio (less than about 170), hub-to-tip ratio (between 0.4 and 0.5), and the number of blade stages (3 to 6). These parameter changes enable the turbine to achieve high bypass ratio performance while maintaining compact dimensions and reduced weight compared to conventional designs
2Productivity
If the bypass area ratio is increased to improve engine efficiency, then the low pressure turbine section requires more airfoils, increasing device complexity
Solution Approach 1:
The patent establishes an optimized relationship where the ratio of total airfoils to bypass area ratio is maintained below about 170. This parameter constraint allows the turbine section to accommodate high bypass area ratios (greater than 6.0) while limiting the proportional increase in airfoil count, thereby controlling device complexity
Solution Approach 2:
The low pressure turbine section uses 3 to 6 adjustable blade stages with optimized airfoil distributions. This dynamic configuration allows the turbine to adapt to high bypass ratio requirements while maintaining manageable complexity through selective staging rather than uniform airfoil distribution across all stages
3Weight of moving object
If the low pressure turbine section is made compact to reduce weight, then the hub-to-tip ratio must be optimized, potentially reducing power output
Solution Approach 1:
The patent optimizes the hub-to-tip ratio to be between 0.4 and 0.5, which is a critical parameter change that enables compact turbine design. This specific ratio range achieves the best balance between compactness (reduced weight) and maintaining sufficient power output by optimizing the radial distribution of blade stages and airfoils within the constrained geometry
Solution Approach 2:
The patent addresses the power output constraint by optimizing the axial and radial distributions of 3 to 6 blade stages rather than simply increasing the hub-to-tip ratio. This multi-dimensional optimization allows the compact turbine to generate sufficient power through increased staging density and optimized airfoil configurations in the available radial and axial spaces
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for a high bypass ratio turbofan engine with a compact low pressure turbine section, achieving increased efficiency, reduced weight, and cost-effectiveness by balancing aerodynamic, structural, and design constraints, breaking the traditional correlation between bypass ratio and turbine size.
Implementation Method 1
The speed reduction mechanism may comprise an epicyclic transmission coupling the low speed shaft to a fan shaft to drive the fan with a speed reduction.
Data Source
AI summary
A gas turbine engine according to an example of the present disclosure includes, among other things, a propulsor including a circumferential array of blades, a low pressure compressor section including a low pressure compressor section inlet with a low pressure compressor section inlet annulus area and a low pressure turbine section. The low pressure turbine section includes a maximum gas path radius, the blades include a maximum radius, and a ratio of the maximum gas path radius to the maximum radius of the blades is equal to or greater than 0.35, and is less than 0.55.