Machine spring displacer for Stirling cycle machines
OwnerRoberto O. Pellizzari, David Gedeon +1inventors
InventorsRoberto O. Pellizzari, David Gedeon, Laurence Penswick
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Abstract
A displacer spring and displacer/spring assembly for use in an FPSE and with improved wear characteristics. One embodiment calls for the use of a single machined spring operating alternately in a tension mode and a compression mode and wherein the operating frequency of displacer movement can be controlled therewith to a desired resonant frequency. The machined spring of the present invention provides enhanced structural accuracy which, in turn, leads to the elimination of lateral and side loads as compared to prior art wire-wound helical springs.
Claims21
A displacer in a free piston Stirling engine comprising:
- a displacer rod;
- a displacer housing within which said displacer rod reciprocates;
- and
- a machined spring attached at a first end to at least a portion of said displacer rod and providing a constraining force upon said displacer rod when said displacer rod moves in either a first axial direction or a second axial direction within said displacer housing, said machined spring further including first and second end portions and a plurality of helical coils located therebetween;
- wherein said machined spring is characterized such that the mass of said displacer and said displacer rod and the force constant of said machined spring results in mechanical resonance at the operating frequency of a free piston Stirling engine containing said displacer.
A free piston Stirling engine comprising:
- a displacer;
- a housing within which displacer reciprocates in both a first axial direction and a second axial direction;
- and
- a machined spring having a first end and a second, said first end attached to said displacer and providing a constraining force upon said displacer when said displacer moves in either said first axial direction or said second axial direction, said second end at said machined spring attached to a displacer rod, said machined spring further including first and second end portions and a plurality of helical coils located therebetween;
- wherein said machined spring is characterized such that the mass of said displacer and said displacer rod and the force constant of said machined spring results in mechanical resonance at the operating frequency of said free piston Stirling engine.
A method of optimizing a free piston Stirling engine having a displacer and displacer rod, comprising the steps of:
- (a) machining a displacer spring having a first end, a second end and a length defined by the distance between the first end and the second end;
- (b) positioning a plurality of coils within the length of the displacer spring so as to optimize a natural frequency of the spring;
- and
- (c) installing the spring so machined by attaching the first end to at least a portion of the displacer rod and providing a constraining force upon the displacer rod when the displacer rod moves within a displacer housing of the free piston Stirling engine in either a first axial direction or a second axial direction;
- wherein in step (b) positioning the coils closer to the second end of the spring reduces total moving mass, thereby increasing the natural frequency of the free piston Stirling engine and positioning the coils closer to the first end of the spring increases total moving mass, thereby decreasing the natural frequency of the free piston Stirling engine.
The method of 18, wherein the plurality of coils is of helical configuration.
The method of 18, wherein the material of the displacer spring is steel.
Dependencies are inferred from the claim text.