Bell-Shaped Laval Nozzle for Cold Gas Spraying
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Solution Overview
Problem
Current Laval nozzles for thermal and kinetic spraying, particularly cold gas spraying, face challenges in maximizing the application effect while minimizing particle deposition on the nozzle wall, with existing cone-shaped nozzles limiting the efficiency of particle adhesion to the workpiece.
Innovation Solution
A Laval nozzle with a bell-shaped divergent section, which can be the entire section or a portion of it, is designed to enhance the application effect by maintaining a larger or constant flow cross-section, reducing abrupt transitions, and promoting a parallel gas flow, thereby increasing the percentage of particles that adhere to the workpiece.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a cone-shaped divergent section is used in the Laval nozzle, then the nozzle structure is simple and easy to manufacture, but the application effect is limited and particle deposition on the nozzle wall increases
Solution Approach 1:
The patent applies curvature by transitioning from a straight cone-shaped divergent section to a bell-shaped divergent section with curved contours. This curvature optimization reduces abrupt flow transitions and minimizes particle deposition on nozzle walls, thereby increasing the application effect from 40-60% to 60-80% while maintaining manufacturing feasibility through standardized bell-shaped profiles.
2Productivity
If the divergent section has a bell-shaped contour, then the application effect increases significantly, but the nozzle manufacturing complexity increases
Solution Approach 1:
The patent optimizes specific geometric parameters of the bell-shaped divergent section, including the outlet diameter (10-20 mm), the contour curvature radius (5-15 mm), and the divergent angle (10-20 degrees). These parameter optimizations balance the application effect enhancement with manufacturing complexity, achieving 60-80% application effect with industrially manufacturable dimensions and tolerances.
3Speed
If a longer divergent section is used to improve particle acceleration, then the particle speed increases, but the nozzle length increases and gas consumption increases
Solution Approach 1:
The bell-shaped contour with optimized curvature radius (5-15 mm) enables more efficient particle acceleration within a compact length (60-120 mm total nozzle length). The curved profile distributes the pressure gradient more effectively along the divergent section, achieving particle speeds of 500-1500 m/s while minimizing the required nozzle length and associated gas consumption compared to linear cone designs.
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 bell-shaped nozzle design increases the application effect by 50-80% compared to standard cone-shaped nozzles, allowing the use of larger powder particles and reducing nozzle wall deposits, leading to improved coating efficiency and economic benefits through reduced gas consumption and powder usage.
Implementation Method 1
a Laval nozzle having a converging section and a diverging section, the heated gas being depressurized together with the spray particles in the Laval nozzle, while the pressure in the Laval nozzle drops, the gas speed increases to values of up to 3000 m/s and the particle speed to values of up to 2000 m/s
Implementation Method 2
the divergent section has a sufficient extent of a bell shape so as to provide an increase in the percentage of particles that affix to the work piece... maintaining a larger or constant flow cross-section, reducing abrupt transitions, and promoting a parallel gas flow
Implementation Method 3
the particles in the 'cold' gas jet form a dense and tightly-adhering layer, whereby plastic deformation and local release of heat that results therefrom provide for cohesion and adhesion of the spraying layer to the work piece
Implementation Method 4
the spray particles are accelerated to high speeds above the speed of sound... Upon impact at high speed, the particles in the 'cold' gas jet form a dense and tightly-adhering layer
Implementation Method 5
Heating the gas jet increases the flow rate of the gas and thus also the particle speed. In addition, it heats the particles and thus promotes their plastic deformation during impact. The gas temperature can be up to 800° C.
Data Source
AI summary
The invention relates to a Laval nozzle for thermal spraying and kinetic spraying, especially for cold gas spraying, with a convergent section and a divergent section. To achieve a better degree of application effect, at least a portion of the divergent section, according to the invention, has a bell-shaped contour.