Shock Wave Mechanical Seal for High-Pressure Gas Leakage Control
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Solution Overview
Problem
Conventional end face mechanical seals are inefficient in sealing high pressure and ultrahigh pressure compressible fluids, as they rely heavily on viscous stresses which lead to viscous heating and are unsuitable for large pressure differentials.
Innovation Solution
The end face mechanical seal employs supersonic regions within the seal gap, where the fluid is accelerated to a supersonic condition and undergoes a shockwave, reducing stagnation pressure and minimizing viscous heating, allowing for effective sealing over a shorter distance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional end face mechanical seals rely on viscous stresses to seal high pressure compressible fluids, then sealing effectiveness is achieved, but viscous heating occurs and the seal is unsuitable for large pressure differentials
Solution Approach 1:
The patent changes the physical state and flow parameters of the compressible fluid by creating supersonic flow conditions through carefully designed seal gap geometry. The gap width is optimized to accelerate the fluid to supersonic speeds, fundamentally altering the flow regime from subsonic viscous flow to supersonic flow with shockwaves, thereby reducing viscous heating while maintaining sealing effectiveness
Solution Approach 2:
The patent employs a contoured or curved seal gap profile rather than a straight parallel gap, creating a converging-diverging geometry that guides the fluid acceleration to supersonic conditions. This curvature in the seal gap path enables the fluid to follow a trajectory that maximizes velocity while controlling pressure distribution and minimizing viscous dissipation
2Reliability
If conventional end face mechanical seals use viscous stresses for sealing, then sealing is achieved, but the seal face size must be large to handle high pressure differentials
Solution Approach 1:
By transforming the flow regime to supersonic conditions, the patent dramatically changes the pressure-drop characteristics of the fluid. The shockwave-induced backpressure provides much stronger sealing force per unit area, allowing the same sealing effectiveness to be achieved with a significantly smaller seal face area, thereby reducing material costs and device complexity
3Reliability
If the seal gap is made very narrow to reduce leakage, then sealing effectiveness improves, but viscous stresses increase leading to excessive viscous heating
Solution Approach 1:
The patent resolves this contradiction by changing the flow regime parameter from subsonic to supersonic. The supersonic flow conditions allow the fluid to pass through the narrow seal gap with dramatically reduced viscous dissipation. The shockwave formation converts kinetic energy to pressure energy in a manner that minimizes viscous heating, enabling narrow gap dimensions to be used without excessive temperature rise
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 significantly reduces viscous heating and enables effective sealing of high pressure and ultrahigh pressure fluids by creating a backpressure that minimizes leakage, while allowing for smaller seal face sizes and reduced material costs.
Implementation Method 1
the fluid is accelerated to a supersonic condition and undergoes a shockwave, reducing stagnation pressure and minimizing viscous heating
Data Source
AI summary
An end face mechanical seal for a high pressure, compressible fluid includes metal or ceramic seal faces separated by a seal gap having at least one supersonic region that accelerates the fluid in the leakage direction, producing a shockwave that reduces fluid pressure to significantly reduce viscous heating and gap length. A choke width of the seal gap formed between the converging and diverging segments of the first supersonic region is between 50 and 200 micro-inches, and upper and lower boundaries thereof are flat, with combined slopes of less than 10 degrees. A total length of all of the supersonic regions is less than 0.1 inches. A non-supersonic region can further reduce fluid pressure by inducing viscous stresses. The seal can be configured axially or radially, and can be used as a pre-conditioner in combination with a conventional downstream mechanical fluid seal.