Cryocooler having variable-length inertance channel for tuning resonance of pulse tube
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Solution Overview
Problem
Conventional cryocoolers with fixed inertance channel lengths and diameters often face issues when the resonant mode of a larger system lies at a harmonic of the compressor's drive frequency, requiring costly and time-consuming redesigns to match resonance frequencies, leading to inefficiencies and delays.
Innovation Solution
A cryocooler with a variable-length inertance channel, adjustable via a seal mechanism that alters the functional length using different coefficients of thermal expansion, allowing for fine adjustments without venting the cooling fluid or changing the structural design, enabling resonance tuning to match the compressor's drive frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the inertance channel length and diameter are fixed during design, then the resonance frequency can be matched to the compressor drive frequency, but the system cannot adapt when resonant modes shift to harmonics, requiring costly redesigns
Solution Approach 1:
The inertance channel is designed with an adjustable seal that can move along the channel length, transforming the fixed structure into a dynamic one. This allows the functional length of the inertance channel to be varied, enabling resonance frequency tuning without redesigning the entire surge volume or inertance channel structure.
Solution Approach 2:
The invention changes the parameter of inertance channel length dynamically by positioning the seal at different locations along the channel. By adjusting the seal position, the effective length of the inertance channel is modified, which directly changes the resonance frequency of the pulse tube to match different compressor drive frequencies or system resonant modes.
2Reliability
If redesign of surge volume and inertance channel is performed to retune the pulse tube, then resonance matching can be achieved, but it results in increased costs and delays
Solution Approach 1:
The adjustable seal mechanism allows dynamic adjustment of the inertance channel length, enabling rapid retuning of the pulse tube resonance frequency without time-consuming redesign and manufacturing processes. The seal can be repositioned along the inertance channel to achieve the desired resonance matching quickly.
Solution Approach 2:
The inertance channel is effectively segmented by the movable seal, creating a variable-length functional section. This segmentation allows independent adjustment of the inertance channel length without affecting the overall surge volume structure, enabling quick retuning while maintaining system integrity.
3Adaptability or versatility
If the seal position is adjusted to change inertance channel length, then resonance frequency can be tuned, but the seal mechanism adds structural complexity
Solution Approach 1:
The seal mechanism is localized to a specific section of the surge volume, affecting only the inertance channel length without requiring complex modifications to the entire system. The seal provides a focused, local adjustment capability that achieves resonance tuning with minimal additional structural complexity.
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
Enables quick and cost-effective adjustments to the resonance frequency of the pulse tube, avoiding the need for redesigns and ensuring optimal performance without fluid venting, by allowing the seal to be positioned anywhere between its extreme positions, thus accommodating varying system resonant modes.
Implementation Method 1
A cryocooler with a variable-length inertance channel, adjustable via a seal mechanism that alters the functional length using different coefficients of thermal expansion
Data Source
Figure 1~2
Figure 3A~3B
Figure 4A~4B
AI summary
A system includes a pulse tube, a compressor (102, 202) configured to create pulses of fluid in the pulse tube (112, 312), and a surge tank (300). The surge tank includes a housing (302) that defines a surge volume (310) configured to receive the fluid from the pulse tube. An inertance channel (312) defines a passageway through which the fluid flows to and from the surge volume. At least part of the inertance channel has an open side to the surge volume. The surge tank also includes an adjustable seal (316) configured to block at least part of the open side of the inertance channel and to move in order to change a functional length of the inertance channel. The housing may include a material having a high coefficient of thermal expansion, and the adjustable seal may include a material having a low coefficient of thermal expansion.