Non-Pressure Gradient CVI Process for Carbon/Carbon Brake Densification
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Solution Overview
Problem
Current chemical vapor infiltration and deposition (CVI/CVD) processes for densifying porous structures, such as carbon/carbon aircraft brake disks, face issues with nonuniform gas flow distribution, leading to soot and tar accumulation, premature seal-coating, and the need for multiple densification cycles, which increase costs and complexity.
Innovation Solution
A non-pressure gradient CVI/CVD process that densifies porous structures in a single cycle by controlling gas flow and process parameters, such as pressure, temperature, and reactant gas percentage, within a furnace, using a distributor to direct gas flow uniformly around and through the structures, minimizing stagnation zones and eliminating the need for multiple cycles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional densification processes are used with low pressure differential, then gas flow distribution is simple, but densification rate is slow and multiple cycles are required
Solution Approach 1:
The patent applies dynamics by implementing a multi-stage pressure differential control system where the pressure gradient is dynamically adjusted during the densification process. The system transitions from a first pressure differential condition to a second pressure differential condition, allowing the process to adapt to changing densification needs and achieve both high productivity and controlled complexity.
Solution Approach 2:
The patent utilizes parameter changes by varying the pressure differential conditions during different stages of densification. By changing the pressure gradient parameters from initial to final conditions, the system optimizes both the densification rate and the uniformity of gas flow distribution, resolving the contradiction between speed and control.
2Productivity
If rapid densification with high pressure differential is used, then densification rate increases, but gas flow distribution becomes nonuniform causing soot and tar accumulation
Solution Approach 1:
The patent applies periodic action by implementing sequential pressure differential stages. The system periodically transitions between different pressure conditions, allowing uniform gas flow distribution during lower pressure stages and enabling higher productivity during controlled high pressure stages, thereby preventing soot and tar accumulation while maintaining efficiency.
Solution Approach 2:
The system dynamically adjusts pressure differential conditions to maintain optimal gas flow distribution. By transitioning from initial to final pressure conditions, the system adapts to the densification progress, ensuring uniform reactant gas distribution throughout the porous structures while achieving rapid densification.
3Manufacturing precision
If multiple densification cycles are used, then densification quality improves, but production time and cost increase
Solution Approach 1:
The patent merges multiple densification cycles into a single continuous process by combining different pressure differential stages within one operational sequence. This integration achieves the quality benefits of multiple cycles while eliminating the time loss associated with intermediate cooling, unloading, and reloading operations.
Solution Approach 2:
The patent maintains continuity of useful action by implementing a continuous densification process without interruption. The multi-stage pressure differential approach allows the system to maintain productive gas flow and carbon deposition throughout the entire process, eliminating idle time between cycles while preserving densification quality.
4Ease of manufacture
If reactant gas flows randomly around porous structures, then process setup is simple, but gas distribution is nonuniform causing premature seal-coating
Solution Approach 1:
The patent introduces an intermediary pressure control system that mediates between the simple random flow setup and the desired uniform gas distribution. By controlling the pressure differential conditions, the system guides the reactant gas flow to achieve uniform distribution throughout the porous structures without requiring complex physical modifications to the setup.
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 efficient, uniform densification of large numbers of porous structures in a single step, reducing production costs and complexity, while maintaining desirable microstructures and preventing soot and tar accumulation, thus producing high-quality carbon parts with reduced manufacturing time and effort.
Implementation Method 1
Chemical vapor infiltration and deposition (CVI/CVD) is a well known process for depositing a binding matrix within a porous structure
Implementation Method 2
when the hydrocarbon gas mixture flows around and through the porous structures, some of the carbon atoms separate from the hydrocarbon molecules, thereby depositing the carbon atoms within the interior and onto the surface of the porous structures
Data Source
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AI summary
A method for densifying porous structures inside a furnace using non-pressure gradient CVI/CVD in a single cycle is described. A hardware assembly for use in the single cycle non-pressure gradient CVI/CVD process is provided as well are process and process conditions are described.