Floating Rod Seal for Stirling Cycle Machine Side Loads
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Solution Overview
Problem
Stirling cycle machines face challenges due to increased side loads on pistons, leading to engine noise, reduced efficiency, and shorter lifespan, which existing improvements have not adequately addressed, resulting in heavier and bulkier machines.
Innovation Solution
The design incorporates a rocking beam drive mechanism with a connecting rod and piston rod seal unit, including a floating rod seal assembly and airlock pressure regulator, to minimize side loads and maintain a pressure differential, enhancing piston motion linearity and engine efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional piston and drive mechanisms are used, then the machine can convert linear motion to rotary motion, but friction and side loads increase leading to higher noise, wear, and reduced efficiency
Solution Approach 1:
The patent employs a dynamically balanced rocking beam mechanism where the beam rocks back and forth to convert linear piston motion to rotary crankshaft motion. This dynamic mechanism distributes side loads more evenly compared to conventional rigid linkages, reducing friction and energy loss while maintaining smooth piston operation
Solution Approach 2:
The invention optimizes geometric parameters including the rocking beam length, crank radius, and piston rod positioning to minimize side loads. By carefully selecting these parameters, the mechanism achieves reduced friction forces and improved energy efficiency while maintaining effective motion conversion
2Reliability
If side loads on pistons are reduced through drive mechanism improvements, then friction and wear decrease, but the machine becomes heavier and bulkier
Solution Approach 1:
The patent divides the drive mechanism into separate functional components: pistons, piston rods, a rocking beam, and a crankshaft. This segmentation allows each component to be optimized independently for strength and weight, achieving reliable piston support without excessive overall machine weight
Solution Approach 2:
The invention utilizes composite construction in key components such as the rocking beam and crankshaft, combining materials with different properties to achieve optimal strength-to-weight ratios. This allows the mechanism to withstand side loads reliably while minimizing the weight of moving parts
3Reliability
If a piston rod seal unit is added to maintain pressure differential, then working fluid containment improves, but device complexity increases
Solution Approach 1:
The patent introduces a piston rod seal unit as an intermediary component between the working fluid chamber and the external environment. This seal unit, including the floating rod seal assembly, acts as a mediator that maintains the pressure differential while allowing piston rod movement, preventing direct exposure of the working fluid to atmospheric pressure
Solution Approach 2:
The floating rod seal assembly is designed to self-regulate and maintain sealing effectiveness through its floating mechanism. The seal automatically adjusts to pressure differential changes and piston rod position variations, maintaining reliable working fluid containment without requiring complex external control systems
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 solution reduces side loads on pistons, improving the efficiency and lifespan of Stirling cycle machines by maintaining piston motion linearity and reducing friction, thereby enhancing overall engine performance.
Implementation Method 1
reduces friction
Implementation Method 2
maintain a pressure differential
Data Source
AI summary
A piston rod seal unit. The piston rod seal unit includes a housing, a cylinder gland, and at least one floating rod seal assembly mounted in the cylinder gland, the floating rod seal assembly comprising at least one rod seal mounted onto the floating rod seal assembly.