Turbine Blade Labyrinth Seal Casting with Grain Jumper Gate
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Solution Overview
Problem
Conventional methods for producing turbine single-crystal gas turbine engine components with integrated labyrinth sealing structures, such as knife edges and hammerheads, face challenges in achieving precise dimensions and true positions due to limitations in casting techniques and machining difficulties, particularly with single-crystal grain structures and complex geometries.
Innovation Solution
An investment casting mold with a grain selection structure and grain jumper gate is used to facilitate single-crystal grain structure growth in labyrinth seal portions, allowing for the formation of precise and accurately positioned sealing structures directly on the turbine blades during the casting process, reducing the need for post-casting machining and enhancing design flexibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If labyrinth sealing structures are formed by machining after casting, then precise dimensions and true positions can be achieved, but manufacturing time and costs increase significantly
Solution Approach 1:
The mold cavity is designed with the final labyrinth seal geometry and dimensions built-in before casting. The grain selection structure and grain jumper gate are configured in advance to ensure single-crystal grain growth through the labyrinth seal portion, allowing the seal to be formed with precise dimensions and true position directly during casting, eliminating the need for subsequent machining operations
Solution Approach 2:
The casting process itself is enhanced to produce the labyrinth seal with the required precision. The grain selection structure and grain jumper gate enable the material to self-organize into a single-crystal structure during solidification, allowing the labyrinth seal to form with accurate dimensions and orientation without external intervention or post-processing
2Ease of manufacture
If conventional casting methods are used, then manufacturing simplicity is maintained, but sufficient dimension and true position tolerances for labyrinth sealing structures cannot be achieved
Solution Approach 1:
A grain selection structure is introduced as an intermediary element in the mold cavity. This structure acts as a mediator to control and direct the solidification process, ensuring that single-crystal grain growth occurs through the labyrinth seal portion. The grain jumper gate serves as another intermediary that facilitates the grain growth path from the grain selection structure through the labyrinth seal, enabling precise dimensional control while maintaining casting simplicity
3Strength
If single-crystal grain structure is required for turbine blades, then high temperature performance is achieved, but growth through complex structures like knife edges and hammerheads is not feasible
Solution Approach 1:
The grain jumper gate creates a dedicated vertical dimension or pathway for grain growth through the horizontally extending labyrinth seal structures. By establishing this vertical growth dimension, single-crystal grains can grow downward through the complex knife edge and hammerhead geometries, enabling high temperature performance in components with previously impossible grain structures
4Ease of manufacture
If turbine blades are cast in tip-down orientation, then standard casting practice is followed, but grain growth in sideways or downward direction required for labyrinth seals is not feasible
Solution Approach 1:
Instead of attempting to grow grains sideways or upward against gravity in the conventional tip-down orientation, the grain selection structure and grain jumper gate are configured to exploit gravity-driven downward grain growth. The labyrinth seal portion is designed to accommodate this downward grain growth direction, inverting the conventional approach of trying to make grains grow against gravity to achieve the required seal alignment
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
The method enables the production of turbine blades with labyrinth sealing structures that have precise dimensions and true positions as-cast, reducing manufacturing time and costs, and overcoming the limitations of conventional casting and machining methods.
Implementation Method 1
wherein the grain selection structure is configured to select a single crystal grain structure during casting when solidification begins at the grain selection structure
Implementation Method 2
a grain jumper gate connected between the grain selection structure and the labyrinth seal portion for facilitating single crystal grain structure through the labyrinth seal portion during casting
Data Source
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AI summary
Disclosed is an investment casting mold article (22) comprising a wall for retaining casting material, a cavity defined by the wall, the cavity comprising an airfoil portion (30), a root portion (32) adjacent to the airfoil portion and a labyrinth seal portion (34) extending from the root portion. Disclosed is also a method of casting a gas turbine engine component, the method comprising providing an investment casting mold having a cavity with an airfoil portion, a root portion adjacent to the airfoil portion, and a labyrinth seal portion extending from the root portion, supplying a metallic casting material to the cavity of the investment casting mold, solidifying the metallic casting material to form the gas turbine engine component with a single crystal grain structure, wherein a first feature of the gas turbine engine component defined by the labyrinth seal portion of the investment casting mold has a dimension and a true position defined as-cast.