Centrally located linear actuators for driving displacers in a thermodynamic apparatus
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Solution Overview
Problem
The existing actuation system in Vuilleumier heat pumps experiences high electrical energy losses and potential overheating due to high current draw at the middle of the stroke, along with issues like shaft buckling, friction, and complex sealing requirements, which affect efficiency and reliability.
Innovation Solution
The linear actuator is positioned between the hot and cold displacer cylinders, featuring coils and armatures with springs and gas springs to manage displacement, reducing shaft length and eliminating concentric shaft friction, while using a power electronics module and position sensors for controlled actuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the linear actuator is positioned at the lower half of the heat pump with long shafts, then the displacers can be actuated, but shaft buckling and friction occur
Solution Approach 1:
The patent repositions the linear actuator from the lower half to the central region between the hot and cold displacer cylinders. This spatial relocation changes the dimensional arrangement of the actuation system, allowing the actuator to drive both displacers through short coupling shafts rather than long shafts extending from the bottom, thereby eliminating shaft buckling issues while maintaining actuation capability
Solution Approach 2:
The patent introduces a central actuator position as an intermediary location between the hot and cold displacer cylinders. This intermediary positioning allows the actuator to serve both displacers through short coupling shafts, eliminating the need for long shafts that would buckle, while the short shafts also eliminate concentric friction problems
2Ease of operation
If the coils are positioned to act on the armature at the middle of the stroke, then the displacer can be actuated, but high current draw increases energy losses and overheating
Solution Approach 1:
The patent replaces the coil-based electromagnetic actuation system with a spring-based mechanical actuation system. The springs are pre-loaded to provide the necessary force for displacer actuation throughout the stroke, eliminating the need for coils to generate force at the middle of the stroke. This mechanical substitution eliminates high current draw and associated energy losses and overheating issues
Solution Approach 2:
The patent changes the actuation mechanism from electromagnetic (coils) to mechanical (springs), fundamentally altering the physical parameter of force generation. The springs are configured with appropriate pre-load and stiffness to provide continuous actuation force throughout the displacer stroke, eliminating the high current draw problem inherent in coil-based systems
3Ease of operation
If concentric shafts are used for actuation, then the displacers can be driven, but friction and complex sealing requirements increase
Solution Approach 1:
The patent extracts the concentric shaft arrangement from the actuation system by repositioning the linear actuator centrally. Each displacer is now driven by its own short coupling shaft from the central actuator position, eliminating the need for concentric shafts. This extraction removes the associated friction and complex sealing requirements while maintaining the ability to drive both displacers
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 shaft bending, friction, and conduction losses, simplifies assembly, improves alignment, and enhances sealing, leading to lower energy consumption and increased reliability by leveraging mechatronics for efficient displacement control.
Implementation Method 1
Armature 116 has a plate portion that extends outwardly from a cylindrical portion through which a spring 124 passes and to which a spring 114 is coupled
Implementation Method 2
Actuator 110 has coils 112 and 118 on either side of armature 116. When coil 112 is activated, armature 116 is attracted toward coil 112
Implementation Method 3
Each of actuators 110 and 120 have a ferromagnetic bucket, 116 and 126, respectively. Ferromagnetic buckets 116 and 126 act as armatures
Implementation Method 4
it has been found to be advantageous to provide a gas spring that acts between displacers 102 and 104
Data Source
AI summary
A heat pump is disclosed that has a hot displacer section and a cold displacer section with a linear actuator section disposed between the hot and cold displacer sections. By providing the linear actuator section between the displacers, the shafts that couple the actuators in the linear actuator section to their respective displacer is shorter than if the linear actuator section were located at the bottom of the cold displacer. The shorter shaft can be less stiff to avoid buckling. Due to a lesser propensity to cock, there is less friction of the shaft when reciprocating.