Gas Turbine Casing Boss with Internal Pedestals for Bolt Thread
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Solution Overview
Problem
Existing casing designs for gas turbine engines require thicker boss regions to accommodate bolt threads, leading to excess material and increased weight and cost, as the minimum boss height must meet stress requirements and thread length demands simultaneously.
Innovation Solution
The method involves using coaxially aligned canister portions to create a casing with a boss and inner pedestals, where the second canister portion includes holes or recesses that form pedestals aligned with the boss, allowing for reduced material usage and weight by minimizing the combined depth of the boss and casing wall only where necessary to accommodate bolt threads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the boss height and casing wall depth are increased to accommodate bolt threads, then the thread accommodation capability is improved, but the material usage and weight increase
Solution Approach 1:
The invention divides the thread accommodation function into two separate segments: the boss structure on the outer wall and the internal pedestals within the casing wall. This segmentation allows each component to be optimized independently - the boss provides the external mounting surface while the internal pedestals provide the thread reception space, eliminating the need for excessive boss height or wall depth.
Solution Approach 2:
The invention transitions from a single-dimensional approach (increasing boss height or wall depth linearly) to a multi-dimensional solution by creating internal pedestals that protrude into the casing wall from the inner surface. This adds a radial dimension to thread accommodation, allowing threads to be received within the wall thickness rather than requiring increased axial depth.
2Reliability
If the boss height is increased to meet both stress requirements and thread length requirements, then the structural integrity is improved, but the material cost increases
Solution Approach 1:
The structural functions are segmented between the boss (providing external strength and mounting surface) and the internal pedestals (providing internal support and thread reception). This allows the boss height to be minimized for stress considerations while the pedestals provide the necessary depth for threads, reducing overall material consumption.
Solution Approach 2:
The invention applies local quality by creating pedestals only in specific regions where thread accommodation is needed, rather than uniformly thickening the entire casing wall. The pedestals are positioned to align with bolt hole locations, providing localized structural reinforcement exactly where required.
3Ease of operation
If the casing wall is made thicker to accommodate bolt threads, then the thread reception capability is improved, but the manufacturing complexity increases
Solution Approach 1:
The invention merges the formation of the boss and internal pedestals into a single PHIP manufacturing process step. Both features are created simultaneously by configuring the canister portions with appropriate geometry, eliminating the need for separate machining operations to create internal pedestals and reducing overall manufacturing complexity.
Solution Approach 2:
The canister portions are pre-configured with the geometry needed to form both the boss and internal pedestals before the PHIP process. The canister walls are machined or formed with recesses and protrusions that define the final geometry, allowing the complex internal pedestal structure to be created in advance of the actual casing formation.
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 reduces the weight and material costs of the casing while ensuring sufficient structural integrity and thread accommodation, making the manufacturing process more economical and efficient.
Implementation Method 1
The canister is then sealed, placed in a pressure vessel and heated to a high temperature in conditions of high pressure. This causes the powder to amalgamate into a solid structure
Implementation Method 2
aligning the first and second canister portions coaxially and introducing the material from which the casing is to be manufactured into a void defined between the canister portions, the material being introduced in a powdered form and under vacuum conditions
Data Source
AI summary
The manufacture of a casing which has a boss includes providing two canister portions a first defining an outer wall geometry of a casing including a boss and a second defining an inner wall geometry of the casing. The casing is made using known PHIP methods. The second canister portion includes an array of holes or recesses which, when the canister portions are aligned, face a recess on the first canister portion which defines the boss such that in the nett shape COS an array of pedestals is provided aligned with the boss. The dimension from an exposed end of a pedestal to an exposed surface of the boss is sufficient to receive a bolt thread of the minimum length required to secure a component to the boss.