Closed Impeller Brazing Sheet for Stronger Blade-Shroud Joints
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional brazing methods for manufacturing closed impellers from aluminum alloys result in lower joint strength between the blades and shroud due to void formation from gas reactions, leading to reduced operational efficiency and increased manufacturing costs.
Innovation Solution
A closed impeller design using a brazing sheet with a core material containing Mg and a filler material layer of Al-Si alloy, brazed without flux in an inert gas, where Mg diffuses to break down oxide films and enhance joint strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If dip brazing is used to join aluminum alloy impeller main body and shroud, then the manufacturing process is simple and constraints on shape are small, but gas reactions during brazing create voids that reduce joint strength
Solution Approach 1:
The patent applies inert atmosphere brazing by performing the brazing process in a nitrogen or argon atmosphere. This prevents gas reactions between the flux and aluminum alloy that cause void formation, thereby maintaining joint strength while preserving the simplicity of the dip brazing process. The inert gas environment eliminates harmful chemical reactions during heating.
Solution Approach 2:
The patent extracts and removes the flux from the brazing process entirely. By eliminating the flux, the source of gas reactions and void formation is removed. The process uses direct contact brazing between the impeller main body and shroud without any flux intermediary, thus achieving high joint strength without the harmful side effects of conventional dip brazing.
2Ease of manufacture
If conventional brazing with flux is used, then manufacturing process is established and simple, but oxide films on aluminum alloy surfaces prevent proper brazing and reduce joint quality
Solution Approach 1:
The patent uses an inert atmosphere (nitrogen or argon) during brazing to prevent oxidation of the aluminum alloy surfaces. This eliminates the oxide film formation problem while maintaining an established manufacturing process. The inert gas protects the molten filler material and base metal surfaces from reacting with oxygen.
Solution Approach 2:
The patent introduces inert gas as an intermediary medium between the aluminum alloy components and the oxygen in air. This mediator prevents direct contact between oxygen and the aluminum surfaces, thereby preventing oxide film formation without requiring complex surface treatment processes.
3Adaptability or versatility
If precision casting is used to manufacture the closed impeller, then constraints on impeller shape are small, but dimensional accuracy is low which decreases compressor operation efficiency
Solution Approach 1:
The patent divides the impeller manufacturing into two segments: the impeller main body (hub and blades) is manufactured by precision casting with flexible shape design, and the shroud is separately manufactured and then joined by brazing. This segmentation allows the impeller main body to achieve complex shapes while the brazed joint provides the necessary dimensional precision for efficient operation.
Solution Approach 2:
The patent changes the manufacturing parameter approach by combining precision casting for the impeller main body with precision brazing for the shroud attachment. This hybrid approach leverages the shape flexibility of casting while achieving the dimensional accuracy needed for compressor efficiency through controlled brazing processes.
4Manufacturing precision
If cutting processes are used to integrally form hub, blades, and shroud, then dimensional accuracy is high, but the range of achievable shapes is constrained by fabrication apparatus and tools
Solution Approach 1:
The patent segments the impeller into the impeller main body (manufactured by precision casting for shape flexibility) and the shroud (joined by brazing for dimensional accuracy). This allows each component to be manufactured using the most appropriate process for its requirements, combining the advantages of both casting and precision joining.
Solution Approach 2:
The patent creates a composite structure by joining the impeller main body and shroud through brazing. This composite approach allows the use of different manufacturing processes for each component, combining the shape flexibility of casting with the precision of brazed joints to achieve both geometric freedom and dimensional accuracy.
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 significantly increases the joint strength of brazed joints, improving durability under high-speed rotation and pressure, while eliminating voids and reducing manufacturing costs.
Implementation Method 1
Mg diffuses to break down oxide films and enhance joint strength
Implementation Method 2
the shroud and the impeller main body are brazed to one another
Data Source
AI summary
A closed impeller (1) includes an impeller main body (2), which is composed of an aluminum alloy and has blades (22) that protrude from a hub (21). A shroud (3) covers the blades. The blades and the shroud are joined together by brazed joints (4). The shroud (3) is formed from a brazing sheet (30) that comprises a core material (31), which is composed of an aluminum alloy, and a filler material layer (320), which is disposed on an outermost surface (33) of the shroud that opposes or faces the blades when the shroud is brazed to the blades.