Turbine Endwall Contouring and Vane Clocking for Pressure Loss Reduction
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Solution Overview
Problem
Gas turbine engines experience efficiency losses due to the formation of horseshoe vortices and associated pressure losses at the leading edges of turbine airfoils, which are exacerbated by non-uniform wake positioning caused by rotating blade speed variations.
Innovation Solution
The implementation of 3D-contoured endwalls and preferential clocking between rows of nozzle vanes, where the second-stage nozzle vanes are circumferentially clocked relative to the downstream nozzle vanes to align wakes with the leading edges, and the endwalls are contoured to reduce vortex strength and pressure losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional airfoil configuration is used, then manufacturing is simpler, but pressure losses increase due to horseshoe vortices
Solution Approach 1:
The endwalls are contoured with different radial positions at different axial locations along the airfoil chord. Specifically, the endwalls are positioned closer together at the leading edge and farther apart at the trailing edge, creating a non-uniform three-dimensional configuration that locally optimizes flow behavior to reduce horseshoe vortex formation and pressure losses.
Solution Approach 2:
The invention transitions from conventional two-dimensional airfoil sections to three-dimensional endwall contouring by introducing variation in the radial position of endwalls along the axial direction. This third dimension allows control over flow separation and vortex formation, reducing pressure losses while managing the increased geometric complexity.
2Object-generated harmful factors
If uniform wake positioning is maintained, then alignment is simpler, but vortex effects are not minimized
Solution Approach 1:
The airfoil configuration introduces asymmetric endwall positioning where the inner and outer endwalls are at different radial positions along the chord. This asymmetry is designed to compensate for wake positioning variations and optimize the interaction between wakes and downstream vanes, reducing vortex effects while requiring precise manufacturing control.
Solution Approach 2:
The invention accounts for the dynamic behavior of wakes by designing the endwall contour to optimize performance across varying operating conditions. The three-dimensional configuration adapts to changes in flow patterns, particularly the movement of horseshoe vortices and wake positioning, to maintain optimal flow control throughout the operating range.
3Loss of energy
If endwall contouring is applied, then pressure losses reduce, but manufacturing precision requirements increase
Solution Approach 1:
The invention specifies particular geometric parameters for the endwall contouring, including the radial position differences at leading edge and trailing edge locations, and the axial extent of the contoured portions. These parameter definitions provide guidance for manufacturing while achieving the goal of reducing pressure losses through optimized flow control.
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 configuration significantly reduces aerodynamic pressure losses and vortex strength, improving turbine efficiency by better aligning nozzle wakes and minimizing the impact of horseshoe and passage vortices, leading to enhanced performance and reduced heating of endwalls.
Implementation Method 1
the formation of horseshoe vortices generated as the combustion gases are split in their travel around the airfoil leading edges
Implementation Method 2
A total pressure gradient is effected in the boundary layer flow at the junction of the leading edge and endwalls of the airfoil
Implementation Method 3
wakes from the upstream vanes trailing edges to impinges on the downstream vane leading edges
Data Source
AI summary
A turbine apparatus includes: A first nozzle comprising an array of first vanes each including a concave pressure side, a convex suction side, and leading and trailing edges; A rotor downstream from the first nozzle comprising a plurality of blades carried by a rotatable disk; and a second nozzle disposed downstream from the rotor comprising an array of second vanes each including a concave pressure side, a convex suction side, and leading and trailing edges; wherein the first and second vanes of the first and second nozzles are circumferentially clocked relative to each other such that, in a predetermined operating condition, wakes discharged from the first vanes are aligned in a circumferential direction with the leading edges of the second vanes, wherein a stacking axis of the first vanes is nonlinear. An inner band of the first nozzle is contoured in a non-axisymmetric shape.