Gas Turbine Nozzle Compressive Contact Face
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Solution Overview
Problem
Gas turbine engine nozzles made from ceramic matrix composite (CMC) materials face shortened life due to high tangential loads, stress concentrations, and differential thermal growth, leading to localized stresses that exceed material capabilities.
Innovation Solution
The nozzle design incorporates an airfoil with a radially compressive contact face and an airfoil support frame, featuring engagement angles non-orthogonal to the engine centerline, which transmits compressive forces to alleviate tensile strain and reduce the need for retention pins, using CMC materials for the airfoil and metal for the support frame.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If radial pins are used to hold vanes in the turbine engine, then the vanes can be secured in position, but high tangential loads and stress concentrations are created that shorten the life of CMC nozzle segments
Solution Approach 1:
The invention removes the radial retention pins from the design entirely. Instead of using pins to hold the CMC nozzle segments, the design relies on the compressive contact faces and engagement angles to secure the segments without any penetrating retention features that would create stress concentrations.
Solution Approach 2:
Rather than using tensile retention pins that pull on the CMC material, the invention uses compressive forces applied at non-orthogonal engagement angles. This inverts the retention mechanism from tensile to compressive loading, which is much more favorable for CMC materials with low tensile ductility.
2Temperature
If CMC materials are used for nozzles to operate at higher temperatures, then engine efficiency is improved, but the low tensile ductility of CMC materials makes them susceptible to failure from moment stresses and concentrated loads
Solution Approach 1:
The invention changes the loading parameters by using compressive forces at non-orthogonal engagement angles rather than tensile pin loads. This parameter change in the force application method allows CMC materials to operate at their optimal compressive strength while avoiding their weak tensile regime.
Solution Approach 2:
The invention uses CMC materials for the nozzle segments while combining them with a support frame structure that provides mechanical retention. The composite approach leverages the high temperature capability of CMC while using the support frame to manage the mechanical loading and stress distribution.
3Stability of the object's composition
If retention pins are used to secure nozzles, then the nozzles are held in position, but high tensile loads are created that are especially harmful to CMC materials
Solution Approach 1:
The invention converts the potentially harmful tensile pin loads into beneficial compressive contact forces. By using compressive engagement at non-orthogonal angles, the design transforms the loading regime from harmful (tensile) to beneficial (compressive) for CMC materials.
4Stability of the object's composition
If conventional pin structures are used to restrain CMC components, then the components are secured, but stress concentrations develop at the interface leading to shortened nozzle life
Solution Approach 1:
The compressive contact faces act as an intermediary between the nozzle segments and the support frame. Instead of direct pin-to-nozzle contact that creates stress concentrations, the engineered contact faces distribute the compressive forces over a larger area at non-orthogonal angles, reducing peak stresses.
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 enhances load transmission, limits tensile strain, and extends the nozzle's life by distributing compressive forces effectively, reducing the risk of damage from thermal expansion and stress concentrations.
Implementation Method 1
a radially compressive contact face defined on the flange at an engagement angle non-orthogonal to a centerline of the engine. The compressive contact face is configured to transmit a compressive force perpendicular to the engagement angle.
Implementation Method 2
CMC materials have relatively low tensile ductility or low strain to failure when compared to metallic materials... These low-coefficient-of-thermal-expansion materials have higher temperature capability than similar metallic parts
Data Source
AI summary
A nozzle for a gas turbine engine, including an airfoil having an exterior surface, flange and radially compressive contact face. Also included is an airfoil support frame having a mating face positioned in engagement with the contact face. A non-orthogonal engagement angle is provided in order to transmit a compressive force to the airfoil.