Variable Pitch Fan Design for Geared Turbofan Engines
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Solution Overview
Problem
The complexity of turbofan engines with gearboxes and variable pitch fans increases development and manufacturing difficulties, necessitating improved designs for more efficient and precise development of geared turbofan engines.
Innovation Solution
The use of specific fan parameters, such as the hub-to-tip radius ratio divided by the fan pressure ratio and bearing spanwise force divided by fan area, aids in the design and simplification of variable pitch fans and geared turbomachinery engines, incorporating a pitch change mechanism, vane assembly, and gearbox configuration to optimize engine performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a gearbox and variable pitch fan are included in a turbofan engine, then propulsive efficiency and power production are improved, but device complexity and manufacturing difficulty increase significantly
Solution Approach 1:
The patent applies parameter changes by optimizing specific fan parameters (hub-to-tip radius ratio divided by fan pressure ratio, and bearing spanwise force divided by fan area) to achieve improved propulsive efficiency while managing the complexity introduced by gearboxes and variable pitch mechanisms. This allows the system to operate at different rotational speeds for maximum efficiency without proportionally increasing complexity.
2Power
If a gearbox is added to allow different rotational speeds between power turbine and bypass fan, then maximum efficiency and power production are achieved, but manufacturing difficulty and development complexity increase
Solution Approach 1:
The patent optimizes the fan parameters specifically designed for geared configurations, using the hub-to-tip radius ratio divided by fan pressure ratio parameter to achieve maximum power production while managing manufacturing complexity. This parameter optimization allows the gearbox system to be designed more efficiently.
3Adaptability or versatility
If variable pitch fan blades are implemented, then propulsive efficiency improves across various operating conditions, but device complexity and development difficulty increase
Solution Approach 1:
The patent uses the bearing spanwise force divided by fan area parameter to optimize variable pitch fan blade designs, enabling improved adaptability across different operating conditions while managing the development complexity through focused parameter optimization rather than comprehensive redesign.
Data Source
AI summary
A turbomachinery engine can include a fan assembly with a plurality of variable pitch fan blades. The fan blades are configured such that they define a first VPF parameter and a second VPF parameter. The first VPF parameter is defined as the hub-to-tip radius ratio divided by the fan pressure ratio. The second VPF parameter is defined as the bearing spanwise force divided by the fan area. In some instances, the first VPF parameter is within a range of 0.1 to 0.25, and the second VPF parameter is within a range of 2-30 lbf/in2. In other instances, the first VPF parameter is within a range of 0.1 to 0.4 and the second VPF parameter is within a range of 5.25-30 lbf/in2. In certain examples, the turbomachinery engine further includes a pitch change mechanism, a vane assembly, a core engine, and a gearbox.