Gas Turbine Fan Blade Axial Stacking Offset Design
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Solution Overview
Problem
Gas turbine engine fan blades experience irreversible propulsive losses due to flow discontinuities and turbulence, making it challenging to identify and optimize design factors for improved propulsive efficiency.
Innovation Solution
The design of the fan blade features a curve with critical and inflection points, specific axial stacking offsets, and slope ratios that vary along the span, optimizing the axial stacking offset ratio to reduce losses and enhance aerodynamic functionality and thermal efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the fan rotates at a high rate of speed, then the propulsive efficiency is improved, but flow discontinuities and shocks are created resulting in irreversible propulsive losses
Solution Approach 1:
The patent applies local quality by varying the axial stacking offset at different span positions along the fan blade. The offset is not uniform but is specifically tailored for different regions (root, mid-span, tip) to optimize airflow characteristics locally, reducing shocks and flow discontinuities that cause energy losses while maintaining high rotational speeds
Solution Approach 2:
The invention changes the geometric parameter of axial stacking offset to optimize performance. By adjusting the offset values at different span positions and their rates of change, the patent modifies the blade geometry to reduce propulsive losses while maintaining high rotational speed operation
2Loss of energy
If the axial stacking offset is optimized to reduce propulsive losses, then the propulsive efficiency is improved, but the design complexity increases
Solution Approach 1:
The patent introduces dynamic characteristics to the blade design by defining the axial stacking offset as a varying parameter along the span rather than a fixed value. This dynamic approach allows the offset to change continuously from root to tip, optimizing performance while providing a systematic method for design that manages complexity through mathematical relationships
Data Source
Figure 1
Figure 2A~2C
Figure 3A~3B
AI summary
An airfoil for a turbine engine includes pressure and suction sides that extend in a radial direction from a 0% span position at an inner flow path location to a 100% span position at an airfoil tip. The airfoil has a relationship between a stacking offset and a span position that is at least a third order polynomial curve that includes at least one positive and negative slope. The positive slope crosses an initial axial stacking offset that corresponds to the 0% span position at a zero-crossing position. A first axial stacking offset X1 is provided from the zero-crossing position to a negative-most value on the curve. A second axial stacking offset X2 is provided from the zero-crossing position to a positive-most value on the curve. A ratio of the second to first axial stacking offset X2/X1 is between 1.5 and 2.0 or less than 1.4.