Booster Rotor Blade Sweep Angle Profile for Stall Margin
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Solution Overview
Problem
Conventional gas turbine engine compression systems face a trade-off between efficiency and stall margin, where increasing efficiency reduces stall margin and vice versa, particularly in high-performance jet engines, and this is exacerbated in boosters which operate at lower wheel-speeds with high throughflow velocities, leading to radial incidence swings that compromise operability.
Innovation Solution
The design incorporates rotor and stator airfoils with tailored leading edge sweep angles and exit swirl angle distributions to reduce incidence angle swings in the hub region, enhancing stall margin without sacrificing efficiency, by optimizing the aerodynamic profiles of stator vanes and rotor blades to manage airflow effectively across the compressor stages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If airfoil efficiency is increased by optimizing velocity distributions and reducing wetted surface area, then compressor efficiency improves, but stall margin decreases
Solution Approach 1:
The patent applies different leading edge sweep angles to different regions of the rotor blade - a first sweep angle in the hub region and a second sweep angle in the tip region. This local differentiation allows optimization of velocity distributions in specific areas to improve efficiency while maintaining adequate stall margin through region-specific aerodynamic characteristics
Solution Approach 2:
The patent modifies the aerodynamic parameters by implementing specific leading edge sweep angle profiles and aspect ratios for rotor blades. By changing these geometric parameters, the velocity distributions over pressure and suction sides are optimized to improve compressor efficiency while the hub region sweep angle configuration maintains sufficient stall margin
2Reliability
If rotor speed is increased to achieve adequate stall margin, then operability improves, but efficiency decreases due to increased airfoil Mach numbers and drag
Solution Approach 1:
The patent implements a first leading edge sweep angle specifically in the hub region that is optimized for maintaining stall margin at lower rotor speeds, while the tip region has a different sweep angle optimized for efficiency. This allows adequate stall margin to be achieved without increasing overall rotor speed, thereby avoiding the efficiency penalty of increased Mach numbers
3Reliability
If solidity is increased to achieve high stall margin in the hub region, then operability improves, but axial flow compressor efficiency decreases
Solution Approach 1:
The patent applies a first leading edge sweep angle in the hub region that provides adequate stall margin without requiring increased solidity, while the tip region employs a second sweep angle that optimizes efficiency. This local differentiation eliminates the need to increase overall solidity, thereby maintaining high compressor efficiency
Data Source
AI summary
A rotor airfoil having a leading edge extending from a root to a tip, an inner span region and an outer span region the leading edge having a sweep angle profile such that the sweep angle increases from the root a first height location at a first rate of change of sweep angle that is substantially constant and thereafter increases at a second rate of change of sweep angle that is substantially constant.