Diffusion Focusing Barrel for Cryogenic Jet Surface Treatment
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Solution Overview
Problem
Current surface treatment methods using pressurized jets of liquid nitrogen, supercritical cryogenic nitrogen, or hypercritical cryogenic nitrogen face issues such as clogging, inefficient particle aspiration, non-homogeneous treatment, and mechanical stress on materials due to high energy density, leading to suboptimal stripping and surface preparation.
Innovation Solution
A diffusion focusing barrel with a convergent, cylindrical neck, and divergent portions is used to accelerate and expand the nitrogen jet, ensuring efficient particle acceleration and distribution, reducing clogging, and controlling energy density for homogeneous treatment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a traditional focusing barrel with cylindrical outlet pipe is used, then the device structure is simple, but the jet expansion is insufficient leading to low treatment speed and poor productivity
Solution Approach 1:
The focusing barrel is divided into three distinct functional sections: a convergent portion for jet compression and acceleration, a cylindrical neck for transition, and a divergent portion for jet expansion. This segmentation allows each section to optimize its specific function, resulting in superior jet performance and treatment productivity while maintaining reasonable structural complexity
Solution Approach 2:
The barrel design incorporates dynamic geometry changes along the flow direction - the inner face transitions from convergent to cylindrical to divergent, creating a dynamic expansion profile that adapts to the jet development stages. This dynamic structure maximizes treatment speed without requiring overly complex mechanisms
2Force
If high pressure nitrogen jet is used for stripping, then the erosive power is high, but the energy density is too concentrated causing mechanical stress and substrate deformation
Solution Approach 1:
The divergent portion of the barrel creates a non-uniform expansion profile where the jet energy is redistributed across different spatial zones. This results in localized energy distribution that maintains erosive power on the surface while reducing concentrated energy density that causes substrate deformation and mechanical stress
3Productivity
If particles are added to the nitrogen jet for enhanced stripping, then the treatment effectiveness increases, but the mixing chamber becomes clogged and particle aspiration becomes inefficient
Solution Approach 1:
The convergent portion of the barrel pre-compresses and accelerates the nitrogen jet before particles are introduced, creating a high-velocity core flow that efficiently draws particles into the jet stream. This preliminary action ensures reliable particle aspiration and prevents mixing chamber clogging by maintaining strong flow dynamics
Solution Approach 2:
The design utilizes pneumatic principles where the high-pressure nitrogen jet itself serves as the transport medium for particles. The pressure gradient and flow dynamics within the barrel sections create automatic particle aspiration and distribution, eliminating clogging issues associated with mechanical mixing systems
4Area of stationary object
If the jet expansion is rapid and uncontrolled, then the treatment area increases, but the energy density decreases leading to non-homogeneous treatment
Solution Approach 1:
The barrel design systematically changes geometric parameters along the flow path - the divergent angle, section lengths, and diameter transitions are carefully controlled to regulate jet expansion. This parameter optimization ensures the jet expands to cover the required treatment area while maintaining sufficient energy density for homogeneous treatment across the entire surface
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 solution significantly increases treatment speed and quality, allowing for efficient removal of hard layers with reduced mechanical stress and improved productivity, while eliminating clogging issues and providing controlled surface modification.
Implementation Method 1
The principle of this process resides in the impact at high speed (from 500 to 800 m/s) of the jet resulting from the expansion of the nitrogen initially present under high pressure (up to 3,800 bars) and low temperature (down to −180° C.)
Implementation Method 2
A diffusion focusing barrel with a convergent, cylindrical neck, and divergent portions is used to accelerate and expand the nitrogen jet
Implementation Method 3
The particle-air mixture is then accelerated by the expansion of the air which occurs in a conduit called a 'nozzle'... using a Venturi effect created by the speed of the air
Data Source
AI summary
A device and a method for the surface treatment of a material by a pressurized jet of liquid nitrogen, supercritical cryogenic nitrogen or hypercritical cryogenic nitrogen that may be loaded with particles, use a device that includes a mixing chamber (10) closed by a downstream wall with an outlet orifice, and a diffusion focusing barrel (20) having an inlet and an outlet, the inlet being designed to be fastened to the mixing chamber (10) while being in fluid contact with the outlet orifice of the mixing chamber (10), the pressurized jet of nitrogen having to pass through the focusing barrel from the inlet to the outlet. The diffusion focusing barrel (20) includes a hollow tube having three successive portions placed one after the other, namely a convergent portion (21) located on the side of the inlet opening of the diffusion focusing barrel and whose inner face, considered in the direction of flow of the nitrogen jet, is convergent, a neck (22) whose inner face is cylindrical, and a divergent portion (23) ending in the outlet of the diffusion focusing barrel and whose inner face, considered in the direction of flow of the nitrogen jet, is divergent.