CVI Module Stacking for Uniform Densification of Annular Substrates
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Solution Overview
Problem
Existing chemical vapor infiltration methods face challenges in controlling gas distribution and densification gradients between substrates of varying heights, leading to inefficiencies and potential soot deposits due to uncontrolled pressure differences.
Innovation Solution
Implementing a densification method with radial sealing rings and annular spacers to control gas circulation and pressure gradients, ensuring uniform gas distribution across stacks of porous annular substrates, using sealing rings and spacers to maintain radial sealing and facilitate even gas flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional directed flow method is used with stacks of varying heights, then loading capacity is maintained, but gas distribution becomes uncontrolled and soot deposits occur
Solution Approach 1:
The patent introduces height-adjustment elements (shims or spacers) under each substrate to locally equalize the height of all substrates in the stack. This local modification ensures uniform gas distribution across the entire stack without requiring complete redesign of the loading system, thereby maintaining loading capacity while preventing soot deposits caused by uncontrolled pressure differences.
Solution Approach 2:
The patent introduces intermediate elements (height-adjustment elements, sealing rings, and gas distribution channels) as mediators between the gas flow system and the substrates. These intermediaries control and regulate the gas distribution, ensuring uniform pressure and flow across substrates of varying heights, thus preventing harmful soot deposits while maintaining productivity.
2Manufacturing precision
If radial sealing rings and annular spacers are added to control gas circulation, then gas distribution improves, but device complexity increases
Solution Approach 1:
The patent designs sealing rings and spacers that serve multiple functions simultaneously: they provide radial sealing to control gas circulation, support and position substrates, and in some cases, act as height-adjustment elements. This multi-functionality reduces the need for separate components, thereby improving gas distribution uniformity without proportionally increasing device complexity.
Solution Approach 2:
The patent combines multiple functions into integrated components. For example, sealing rings are designed to simultaneously seal the radial gap between substrates and provide structural support. Annular spacers are merged with gas distribution channels to create unified gas circulation paths. This merging reduces the total number of discrete parts while achieving precise gas distribution control.
3Productivity
If pressure gradient is increased to enhance densification rate, then productivity improves, but soot deposits increase due to uncontrolled pressure differences
Solution Approach 1:
The patent implements a controlled pressure gradient system where the pressure difference across substrates is regulated through sealed gas circulation paths and adjustable flow control elements. This feedback mechanism ensures that while sufficient pressure gradient is maintained for high densification rates, excessive pressure differences that would cause soot deposits are prevented by continuous monitoring and adjustment of gas flow distribution.
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
Enhances gas distribution and reduces densification gradients, preventing soot deposits while maintaining or increasing the loading capacity of the furnace.
Implementation Method 1
The infiltration conditions, especially the composition and flow rate of the gas phase, and the temperature and pressure in the chamber, are chosen to allow diffusion of the gas phase within the accessible internal porosity of the substrates so that the desired material is deposited therein
Implementation Method 2
The densification of porous substrates by chemical vapor infiltration (CVI) consists of placing the annular preforms in a reaction chamber of an infiltration installation and admitting into the chamber a gas phase, one or more constituents of which form a precursor of the matrix material to be deposited within the substrates
Implementation Method 3
A pressure gradient will be established and increase as the preforms densify between the inside (where the gas arrives) and the outside of the stacks
Data Source
AI summary
A method for densifying porous annular substrates having a central passage by chemical vapor infiltration, the method including providing stacks of porous annular substrates, providing a plurality of individual modules including stacks disposed on a support plate having a perforated injection tube each mounted on a gas inlet opening, forming a stack of individual modules, aligning the individual modules of the stack in a sealed manner by means of an annular seal disposed between the injection tube of a second individual module and the gas inlet opening of a first individual module with which it cooperates, and injecting into the internal volume of each stack of porous annular substrates a gas phase including a gaseous precursor of a matrix material to be deposited within the porosities of the substrates.