Turbine Nozzle Vane Offset Cooling for Oxidation Resistance
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Solution Overview
Problem
In gas turbine engines, the pressure variations and hot gas injections caused by bow waves at the turbine nozzle vane leading edges lead to localized oxidation, high temperatures, and decreased efficiency due to non-uniform gas pressure distribution and horseshoe vortex formation.
Innovation Solution
The design includes a turbine nozzle with an inner and outer band, where the vane leading edge is positioned downstream from the band leading edges, and a plurality of circumferentially-spaced cooling openings that bias cooling air towards the vane leading edge, reducing hot gas injections and enhancing aerodynamic efficiency by accelerating flow momentum and reducing vortex formation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the vane leading edge is aligned with the band leading edges (fish-mouth seal configuration), then the structural simplicity and ease of assembly are improved, but localized oxidation, high temperature exposure, and decreased efficiency occur due to pressure variations and hot gas injections
Solution Approach 1:
The turbine nozzle is divided into distinct components: the band platform and the vane. By positioning the vane leading edge downstream from the band leading edge, the design segments the flow path to eliminate direct alignment between the band and vane leading edges. This segmentation prevents the formation of a fish-mouth seal configuration, thereby eliminating the pressure variations and hot gas injections that cause localized oxidation and high temperature exposure while maintaining structural integrity.
Solution Approach 2:
The invention introduces a downstream offset in the axial direction between the band leading edge and the vane leading edge. This dimensional change in the axial position eliminates the harmful alignment while maintaining the structural connection. By shifting the vane leading edge to a different axial position (downstream), the design resolves the contradiction between ease of assembly and nozzle durability without compromising structural simplicity.
2Reliability
If cooling openings are added to redirect cooling air towards the vane leading edge, then surface heating is reduced and nozzle life is extended, but device complexity increases
Solution Approach 1:
Cooling openings are strategically positioned in the band platform to direct cooling air specifically toward the vane leading edge region. This localized cooling approach targets the area most susceptible to high temperature exposure and localized oxidation. By concentrating cooling resources at the critical vane leading edge rather than uniformly cooling the entire nozzle, the design extends nozzle useful life while minimizing the complexity of the cooling system.
Solution Approach 2:
The cooling air acts as an intermediary substance that mediates between the hot combustion gases and the vane leading edge. The cooling openings introduce this intermediary cooling air to create a protective layer or cooling effect at the vane leading edge, reducing surface heating and extending nozzle life without requiring complex active cooling mechanisms or thermal barrier coatings.
3Loss of energy
If the vane leading edge is positioned downstream from the band leading edges, then hot gas injections and vortex formation are reduced, but the aerodynamic flow path length increases
Solution Approach 1:
The downstream positioning of the vane leading edge relative to the band leading edge transforms a potentially harmful configuration (fish-mouth seal alignment) into a beneficial one. By deliberately offsetting the vane leading edge downstream, the design converts what would be a direct alignment causing pressure variations and hot gas injections into a configuration that reduces horseshoe vortex formation and hot gas impingement. The extended flow path length is accepted as a trade-off to eliminate the more severe energy losses from vortex-induced oscillations and localized heating.
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 reduces surface heating, extends the nozzle's useful life, and improves aerodynamic efficiency by minimizing horseshoe vortices and temperature increases, while providing a cost-effective and reliable assembly method.
Implementation Method 1
a plurality of circumferentially-spaced cooling openings that are oriented with respect to the turbine nozzle such that cooling air discharged therefrom during engine operation is biased towards the vane leading edge
Data Source
AI summary
A method facilitates the assembly of a gas turbine engine. The method comprises providing a turbine nozzle including an inner band, an outer band, and at least one vane extending between the inner and outer bands, wherein the vane includes a first sidewall and a second sidewall connected together at a leading edge and a trailing edge and coupling the turbine nozzle to a combustor that includes a plurality of circumferentially-spaced cooling openings that are oriented with respect to the turbine nozzle such that cooling air discharged therefrom during engine operation is biased towards the vane leading edge.