Cobalt-Chromium Piston Ring for High-Temp Sealing
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Solution Overview
Problem
Air compressors operating at high temperatures (above 350° F) and pressures (above 2000 psi) face challenges with piston ring wear and cylinder scoring due to thermal expansions and viscosity breakdown of lubricants, leading to reduced operational lifetimes.
Innovation Solution
A piston ring design with a gap width 1.4 to 2.0 times its thickness and a height 4.5 to 6.4 times its thickness, made from a cobalt-chromium-tungsten-carbon alloy, providing ductility and a sharp leading edge for effective sealing without external lubrication, and capable of withstanding temperatures up to 450° F and pressures up to 5000 psi.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If piston rings are used to seal the piston/cylinder interface without external lubrication, then the compressor can operate at high temperatures and pressures, but the piston rings wear quickly and cylinder bores become scored
Solution Approach 1:
The invention changes the geometric parameters of the piston ring, specifically setting the gap width to 1.4-2.0 times the ring thickness and the height to 4.5-6.4 times the thickness. These parameter changes optimize the ring's flexibility and sealing characteristics, allowing it to maintain effective sealing under high temperature and pressure conditions without external lubrication, thereby improving wear resistance and reliability
Solution Approach 2:
The invention employs a composite material composition for the piston ring: 64-68 wt% cobalt, 26-30 wt% chromium, 3.5-5.5 wt% tungsten, and 0.5-2.0 wt% carbon. This composite material provides enhanced hardness, wear resistance, and thermal stability, enabling the piston ring to withstand the harsh operating conditions of high temperature and pressure without external lubrication
2Reliability
If piston rings are made with tight fits to prevent gaps, then sealing is improved, but the rings become brittle and prone to cracking during installation
Solution Approach 1:
The invention optimizes the geometric parameters by setting the gap width to 1.4-2.0 times the thickness and height to 4.5-6.4 times the thickness. These specific parameter ratios provide the optimal balance between sealing effectiveness and structural flexibility, preventing brittleness and cracking during installation while maintaining reliable sealing
3Reliability
If external lubrication is used to reduce wear, then piston ring and cylinder wall durability improve, but the lubricant viscosity breaks down at high temperatures above 350° F
Solution Approach 1:
The invention extracts the dependency on external lubrication by designing a piston ring that achieves effective sealing and wear resistance through its own geometric parameters and material composition. The ring operates without external lubrication, eliminating the problem of lubricant viscosity breakdown at high temperatures above 350° F while maintaining durability through inherent design characteristics
4Reliability
If the piston ring gap is minimized to improve sealing, then sealing effectiveness increases, but manufacturing precision requirements become extremely tight
Solution Approach 1:
The invention changes the gap parameter from a minimized value to a specific ratio of 1.4-2.0 times the thickness. This parameter change relaxes manufacturing precision requirements while maintaining effective sealing through the optimized geometric configuration that balances gap size with ring flexibility and contact pressure
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 piston ring design significantly reduces wear and scoring, extending the operational lifetime of air compressors by maintaining effective sealing and durability under extreme conditions, as demonstrated by test data showing minimal wear and extended cycle life compared to comparative examples.
Implementation Method 1
Sealing at temperatures above 350° F. and pressures in excess of 2000 psi may become difficult due to thermal expansions of the cylinder wall and piston
Implementation Method 2
viscosity breakdown of the lubricating oil
Data Source
AI summary
A piston ring for use at temperatures above 350° F. at pressures greater than or equal to about 2000 psi, comprising a gap having a gap width about 1.4 to about 2.0 times greater than a thickness of the piston ring; a height about 4.5 to about 6.4 times larger than the thickness, and a leading edge characterized by an arc having a radius of curvature of less than or equal to about 4 times the height. The piston ring may be formed of a material comprising cobalt, chromium, tungsten, and carbon. A gas compressor and method of sealing a piston using the above piston ring is also provided for.