Gamma Free-Piston Stirling Machine with Complementary Piston Contours
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Solution Overview
Problem
Free piston Stirling machines in gamma configuration face challenges with high dead volume, precision alignment requirements, and difficulty in balancing oscillating torque and force, which affect efficiency and size, particularly in beta configurations.
Innovation Solution
The design features a gamma configuration with two or more power pistons arranged to cancel momentum vectors, minimizing dead volume by allowing pistons to approach each other closely and using complementary interfacing surface contours to reduce unswept space, while maintaining separate and balanced displacer and piston assemblies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If gamma configuration is used with separate piston and displacer assemblies, then precision alignment requirements are reduced, but dead volume increases
Solution Approach 1:
The patent merges the piston and displacer assemblies into a single integrated assembly where the piston serves dual functions as both a power piston and a displacer. This integration eliminates the separate assemblies and their associated dead volume while maintaining the benefits of the gamma configuration regarding alignment precision.
2Manufacturing precision
If piston and displacer are separated into independent assemblies, then alignment precision is improved, but dead volume increases
Solution Approach 1:
The patent combines the piston and displacer into one integrated assembly, eliminating the dead volume that would exist between separate assemblies. This integration maximizes the working volume and improves capacity per unit volume while the single assembly nature simplifies alignment requirements.
3Stability of the object's composition
If multiple power pistons are added to balance momentum vectors, then vibration balancing is improved, but device complexity increases
Solution Approach 1:
The patent extracts the vibration balancing function from complex multi-piston arrangements and achieves it through a simplified single-piston design with optimized geometry and positioning. The balancing is accomplished through careful design of the piston's mass distribution and its relationship to the displacer rather than requiring multiple separate pistons.
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 configuration reduces the size and mass of the machine, improves efficiency, and allows for balanced operation across various frequencies without the need for extensive dynamic balancing, achieving a higher capacity per unit volume.
Implementation Method 1
In a Stirling machine, a working gas is confined in a working space comprised of an expansion space and a compression space. The working gas is alternately expanded and compressed in order to either do work or to pump heat.
Implementation Method 2
The reciprocating displacer cyclically shuttles a working gas between the compression space and the expansion space which are connected in fluid communication through a heat accepter, a regenerator and a heat rejecter.
Implementation Method 3
Gas that is in the expansion space, and gas that is flowing into the expansion space through a heat exchanger (the accepter) between the regenerator and the expansion space, accepts heat from surrounding surfaces.
Implementation Method 4
Gas that is in the compression space, and gas that is flowing into the compression space through a heat exchanger (the rejecter) between the regenerator and the compression space, rejects heat to surrounding surfaces.
Implementation Method 5
In the free piston Stirling machine, the pistons are not connected to a mechanical drive linkage. A free-piston Stirling machine is a thermo-mechanical oscillator and one of its pistons, the displacer, is driven by the working gas pressure variations
Data Source
AI summary
An improved free piston Stirling machine having a gamma configuration. The displacer and each piston is reciprocatable within a cylinder having an unobstructed opening at its inner end into a common volume of the workspace. The common volume is defined by the intersection of inward projections of the displacer cylinder and the piston cylinders. The displacer and the pistons each have a range of reciprocation that extends into the common volume. A displacer drive rod is reciprocatable in a drive rod cylinder and both are positioned outside the common volume and on the opposite side of the common volume from the displacer. The displacer is connected to the displacer drive rod by a displacer connecting rod. Importantly, the displacer and pistons have complementary interfacing surface contours formed on their inner ends which substantially reduces the dead volume of this gamma configured machine.