Segmented Refractory Core for Turbomachine Blade Casting
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The existing lost-wax casting process for manufacturing turbomachine blades faces challenges with residual stresses and recrystallization due to differential thermal expansion between metal and ceramic cores, leading to blade damage and inefficiencies in cooling systems.
Innovation Solution
A refractory core with a main body and a shell defining a cavity is used, where the shell is designed to collapse under cooling stresses, reducing residual stresses and allowing for the free withdrawal of the metal blade, and reinforcements are strategically placed to manage rupture points and maintain structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a solid refractory core is used in lost-wax casting, then the blade can be properly formed and supported during manufacturing, but residual stresses and recrystallization occur due to differential thermal expansion between metal and core
Solution Approach 1:
The solid core is divided into two functional parts: a rigid main body that maintains structural integrity and positioning, and a collapsible shell that can deform to accommodate metal shrinkage. This segmentation allows different parts of the core to serve different functions - the main body provides support while the shell manages stress through controlled collapse
Solution Approach 2:
The shell is designed with specific geometric parameters (thin walls, convex shape) that enable it to collapse at controlled stress levels. By changing the physical state and geometry of the shell portion, it transitions from a rigid support structure to a deformable stress-relief mechanism during the cooling process
2Strength
If the core maintains rigid structural integrity, then it provides stable support during casting, but it prevents free contraction of the metal blade during cooling, inducing harmful stresses
Solution Approach 1:
The core structure separates the support function (main body) from the stress-management function (shell). The main body remains rigid to provide stable support during casting, while the shell portion is designed to collapse and allow metal contraction, thus resolving the conflict between structural stability and stress reduction
Solution Approach 2:
The shell's collapse, which might seem like a failure of structural integrity, is actually designed to be beneficial. The controlled collapse converts the harmful effect of rigid constraint into a beneficial stress-relief mechanism, allowing the metal to contract freely and reducing residual stresses
3Use of energy by moving object
If hollow blade geometries are manufactured, then cooling efficiency is improved, but stress concentrations increase leading to higher risk of recrystallization
Solution Approach 1:
The segmented core structure with collapsible shell portions positioned at high-stress zones provides localized stress relief where it is most needed. The shell can collapse independently in different regions, allowing differential contraction accommodation that protects against recrystallization in hollow blade geometries while maintaining cooling efficiency
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 approach enables the production of hollow monocrystalline blades with reduced residual stresses and prevents recrystallization, improving the durability and efficiency of turbomachine blades while maintaining rigidity and resistance to high cooling stresses.
Implementation Method 1
Due to the difference in coefficients of thermal expansion between the metal and the core, the metal blade contracts more than the ceramic core
Implementation Method 2
The ceramic core then exerts forces on the blade, inducing stresses within it
Implementation Method 3
the metal blade contracts more than the ceramic core
Data Source
Figure 1~4
AI summary
A refractory core (12) for manufacturing a hollow turbomachine blade (10) according to the lost-wax process comprises a main body (14) and at least one shell (16) connected to the main body (14) and defining a cavity (18) between the main body and the shell, the shell (16) being configured such that it contacts the blade (10) during manufacture.