Composite Piston Ring Structure for Liquid Hydrogen Pressure Pumps
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Solution Overview
Problem
Conventional piston rings used in pressure boosting pumps face challenges in maintaining sealing performance, low friction, and high strength when dealing with ultra-high pressures of low-temperature fluids, particularly liquid hydrogen.
Innovation Solution
The pressure boosting pump incorporates a piston ring design with a piston ring main body and an inner ring having different hardness levels, where the inner ring is softer than the piston ring main body, formed from materials like PEEK and PTFE, respectively, to counteract rotational moments and ensure proper contact with the cylinder, enhancing sealing performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional piston rings with uniform hardness are used, then the structure is simple and easy to manufacture, but sealing performance deteriorates at ultra-high pressures
Solution Approach 1:
The piston ring is designed with different hardness values at different radial positions: the inner ring portion (closer to the piston center) has lower hardness while the outer ring portion (closer to the cylinder wall) has higher hardness. This local quality differentiation allows the softer inner portion to deform and counteract rotational moments, ensuring uniform contact pressure and improved sealing performance at ultra-high pressures up to 100 MPa.
Solution Approach 2:
The piston ring employs a composite structure with two distinct material regions having different hardness properties. The inner ring is made of softer material (e.g., PTFE-based) while the outer ring uses harder material (e.g., PEEK-based), creating a composite piston ring that combines the deformation capability of soft materials with the structural integrity of hard materials to maintain sealing under extreme pressure conditions.
2Strength
If harder materials are used for the piston ring, then strength and wear resistance improve, but friction increases and sealing performance deteriorates
Solution Approach 1:
Different radial zones of the piston ring are assigned different hardness levels to simultaneously achieve strength and sealing. The outer ring portion uses harder material for strength and wear resistance, while the inner ring portion uses softer material that can deform to counteract rotational moments and maintain uniform contact with the cylinder wall, ensuring reliable sealing performance.
3Reliability
If the piston ring is made of softer material, then friction and wear decrease, but strength and ability to maintain contact at high pressure deteriorate
Solution Approach 1:
The piston ring structure assigns softer material to the inner ring portion where deformation is needed to counteract rotational moments and maintain contact pressure, while assigning harder material to the outer ring portion where structural strength and wear resistance are critical. This spatial differentiation of material properties resolves the contradiction between softness for sealing and hardness for strength.
4Reliability
If a single-material piston ring is used, then manufacturing is simple, but performance at ultra-high pressure deteriorates
Solution Approach 1:
The piston ring is manufactured as a composite structure with inner and outer portions made of different materials having different hardness values. While this increases manufacturing complexity compared to single-material rings, it enables the piston ring to maintain sealing performance at ultra-high pressures up to 100 MPa by combining the deformation capability of soft inner material with the structural support of hard outer material.
Data Source
AI summary
In a pressure boosting pump and a hydrogen supply system, included are a cylinder having a compression chamber, a suction valve configured to cause a low-temperature fluid to be sucked into the compression chamber, a piston movably supported on the cylinder and configured to compress the low-temperature fluid in the compression chamber, a discharge valve configured to cause the low-temperature fluid in the compression chamber to be discharged, and a piston ring provided on an outer periphery of the piston. The piston ring has a piston ring main body positioned closer to an inner peripheral face of the cylinder and an inner ring positioned closer to the center of the piston than the piston ring main body is. The inner ring has a hardness lower than a hardness of the piston ring main body.