Variable Diameter Pump Piston for Friction and Leakage Control
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Solution Overview
Problem
High-pressure pumps used in gaseous fuel applications, such as those powered by natural gas, face challenges with fuel leakage past pistons due to tight tolerances which increase friction and wear, and existing solutions like U.S. Pat. No. 4,813,342 still exhibit significant friction and seal wear.
Innovation Solution
A pump piston design with a varying outer diameter along its axial length, featuring an annular wall with a cavity and a head that occupies most of the cavity, and tapers to accommodate pressure and temperature differentials, reducing friction and leakage by adjusting clearance between the piston and barrel.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If tight tolerances are maintained between piston and barrel to reduce leakage, then sealing performance is improved, but friction between piston and barrel increases
Solution Approach 1:
The piston diameter is made variable along its axial length rather than uniform, allowing different clearance zones along the piston. The larger diameter at the pressurizing end and smaller diameter at the actuating end create dynamic clearance variation that reduces friction while maintaining sealing effectiveness through the annular wall geometry.
Solution Approach 2:
Different sections of the piston have different diameters to optimize local conditions. The pressurizing end has a larger diameter for reduced friction under high pressure, while the actuating end has a smaller diameter for reduced friction during actuation, with each section optimized for its specific functional requirements.
2Reliability
If tight tolerances are maintained between piston and barrel to reduce leakage, then sealing performance is improved, but wear of seals increases
Solution Approach 1:
The variable diameter piston creates dynamic clearance that reduces contact pressure and friction on seals. By having a larger diameter at the pressurizing end, the piston maintains optimal clearance under pressure, reducing seal wear and extending seal lifespan while still preventing leakage.
Solution Approach 2:
The piston diameter parameter is changed along the axial length to optimize seal performance. The transition from larger diameter at the pressurizing end to smaller diameter at the actuating end creates favorable pressure distribution and reduces seal contact stress, thereby reducing wear and extending seal life.
3Reliability
If expanding members push seal rings against the cylinder to reduce leakage, then sealing performance is improved, but wear of seal rings increases
Solution Approach 1:
The variable diameter piston geometry creates dynamic clearance that naturally reduces the need for high seal ring contact pressure. The larger diameter at the pressurizing end maintains optimal clearance under pressure, reducing the force required from seal rings and thereby reducing wear while maintaining sealing effectiveness.
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 design effectively reduces friction and leakage by optimizing the piston's outer diameter profile and using an annular wall to flex and adjust clearance, improving the efficiency and lifespan of the pump.
Implementation Method 1
an annular wall having a fixed end attached to the body, a free end opposite the fixed end
Implementation Method 2
wherein the outer diameter varies between the pressurizing end and the actuating end without increasing to form an outer diameter profile
Data Source
AI summary
A pump piston is disclosed. The pump piston may include a body having an actuating end, a pressurizing end opposite the actuating end, and an outer diameter that is greater at the pressurizing end than at the actuating end, wherein the outer diameter varies between the pressurizing end and the actuating end without increasing to form an outer diameter profile.