Turbine Airfoil Curvature Modification for Shock Loss Reduction
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Solution Overview
Problem
Turbines face efficiency limitations due to shock losses caused by supersonic working fluid velocities and varying pressure ratios, leading to reduced power output and increased losses at both high and low power levels.
Innovation Solution
The airfoil design incorporates increased curvature on either the pressure or suction surfaces near the trailing edge, including concave and convex sections, to dampen shock waves by enhancing the unguided turning angle, thereby reducing shock strength and reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the differential pressure of the compressed working fluid is increased to achieve higher power output, then the power level increases, but shock waves and shock losses increase drastically
Solution Approach 1:
The patent applies curvature modification to the airfoil surfaces, specifically adding a second convex section on the suction surface downstream from the throat with increasing curvature, and a second concave section on the pressure surface with increasing curvature. This curvature enhancement modifies the flow path to reduce shock wave intensity and reflection, thereby reducing shock losses while maintaining high power output capability
Solution Approach 2:
The patent implements local quality changes by modifying specific sections of the airfoil rather than the entire structure. The second convex section on the suction surface and second concave section on the pressure surface are localized modifications downstream from the throat, allowing the airfoil to maintain its overall structure while introducing local curvature enhancements that specifically address shock wave behavior in the critical trailing edge region
2Loss of energy
If the curvature of the airfoil surfaces is increased downstream from the throat to reduce shock losses, then shock losses are reduced, but the device complexity increases
Solution Approach 1:
The patent segments the airfoil surface into distinct functional sections: a first convex section on the suction surface, a throat, and a second convex section downstream from the throat; similarly on the pressure surface with a first concave section and a second concave section. This segmentation allows each section to be optimized independently for its specific flow control function, reducing overall shock losses while maintaining manageable geometric complexity through systematic division
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 design effectively reduces shock losses and enhances turbine efficiency, particularly at lower flow rates, by flattening pressure or shock waves across the airfoil, increasing the airfoil's efficiency and reducing cycle fatigue.
Implementation Method 1
reducing shock loss in a turbine by enhancing the airfoil curvature aft of the throat
Implementation Method 2
the compressed working fluid may reach supersonic velocities as it passes through the turbine, creating considerable shock waves and reflected shock waves
Data Source
AI summary
An airfoil includes a leading edge, a trailing edge downstream from the leading edge, a pressure surface between the leading and trailing edges, and a suction surface between the leading and trailing edges and opposite the pressure surface. A first convex section on the suction surface decreases in curvature downstream from the leading edge, and a throat on the suction surface is downstream from the first convex section. A second convex section is on the suction surface downstream from the throat, and a first convex segment of the second convex section increases in curvature.