Reciprocating Compressor Piston Positioning to Minimize Dead Volume
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Solution Overview
Problem
Conventional reciprocating compressors experience efficiency losses due to increased dead volume as the piston stroke length varies, particularly when reducing cooling capacity, leading to a greater spacing of the top dead center from the discharge valve.
Innovation Solution
A piston displacement device that includes a piston transfer unit with a rack gear and pinion gear system, driven by a separate piston transfer motor, allowing the piston to move axially in response to capacitance variations while maintaining a consistent top dead center, thereby minimizing dead volume.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the piston stroke length is reduced to decrease cooling capacity, then the cooling capacity is reduced, but the dead volume increases and compressor efficiency decreases
Solution Approach 1:
The patent applies dynamics by making the piston's top dead center position adjustable rather than fixed. The piston transfer unit enables the piston to dynamically shift its position along the cylinder axis, allowing the system to adapt to different stroke length requirements while maintaining optimal compression geometry. This resolves the contradiction by enabling both reduced cooling capacity (via shorter stroke) and maintained efficiency (via preserved top dead center alignment).
Solution Approach 2:
The piston transfer unit acts as an intermediary mechanism between the piston and the cylinder head. It mediates the relationship between stroke length reduction and top dead center position, allowing independent control of these two parameters. This intermediary enables the system to reduce stroke length for lower cooling capacity while simultaneously maintaining the top dead center alignment necessary for high compressor efficiency.
2Adaptability or versatility
If the piston stroke length is varied to control cooling capacity, then the cooling capacity control is achieved, but the top dead center spacing from discharge valve increases
Solution Approach 1:
The invention transforms the static top dead center position into a dynamic, adjustable position. The piston transfer unit enables the piston to shift axially, making the top dead center position variable rather than fixed. This allows the system to maintain optimal spacing between the top dead center and discharge valve across different operating conditions, resolving the contradiction between adaptability and dimensional constraints.
Solution Approach 2:
The patent segments the piston motion into two independent components: stroke length (controlled by reciprocating motor) and axial position (controlled by piston transfer unit). This segmentation allows independent optimization of each parameter, enabling cooling capacity control through stroke variation while simultaneously maintaining fixed top dead center spacing through axial position adjustment.
3Device complexity
If a fixed piston position is used, then the structure is simple, but the dead volume increases at reduced stroke lengths
Solution Approach 1:
The patent introduces dynamic adjustability to the piston positioning system. Rather than a completely fixed piston position, the system uses a transfer unit that enables controlled axial movement. This dynamic capability allows the system to compensate for increased dead volume at reduced stroke lengths by shifting the piston axially, maintaining compression efficiency while accepting the added complexity of the transfer mechanism.
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 maintains compressor efficiency by ensuring the piston remains aligned with the discharge valve even at reduced stroke lengths, reducing dead volume and preventing efficiency losses during low-capacity operations.
Implementation Method 1
a plurality of resonance springs for guiding a resonant motion of the piston
Implementation Method 2
a plurality of front resonance springs for supporting the front side of the spring supporting unit, and a plurality of rear resonance springs for supporting the rear side
Implementation Method 3
the reciprocating motor includes the outer stator having a winding coil and fixed between the front frame and the middle frame, the inner stator positioned at an inner side of the outer stator and fixed to the cylinder, and the mover having a magnet and linearly reciprocated between the outer stator and the inner stator along a flux direction
Data Source
AI summary
A piston displacement device for a reciprocating compressor comprises a piston linearly reciprocated in a cylinder and having a stroke length varied by a reciprocating motor, a plurality of resonance springs for guiding a resonant motion of the piston, and a piston transfer unit for moving the piston forward or backward in a motion direction of the piston according to a capacitance variation of a compressor and thereby maintaining the same top dead center. The piston is moved according to a capacitance variation of the compressor thereby to minimize a dead volume thereof and to increase the efficiency of the compressor.