Alternating Suction Cutoff Unloader Cycling for Valve Service Life
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Solution Overview
Problem
Current refrigeration and air conditioning systems face challenges in achieving tight temperature control and efficient capacity control due to limitations in unit cycling and the high cost and inefficiency of suction modulation valves, with existing solutions like suction cutoff unloader valves having reduced service life due to uniform cycling intervals.
Innovation Solution
A reciprocating compressor with two cylinders and suction cutoff unloader valves that utilize pulse width modulation cycling, where a controller alternates the cycling of the valves to distribute duty cycles and prevent over-cycling, ensuring one valve does not cycle more than the other, thereby extending service life and improving capacity control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If all suction cutoff unloader valves are operated with the same switching intervals to avoid balancing problems, then compressor balancing is maintained, but the service life of the valves is greatly reduced due to excessive cycling
Solution Approach 1:
The controller implements periodic action by cycling the suction cutoff unloader valves at different intervals. Specifically, when operating in a lower part-load range, the controller cycles at least a first suction cutoff unloader valve at a first switching interval while operating at least a second suction cutoff unloader valve at a second switching interval that is different from the first switching interval. This staggered periodic cycling maintains compressor balancing while reducing the total number of cycles each individual valve experiences, thereby extending valve service life.
2Measurement precision
If suction modulation valves are used for system capacity control, then tight temperature control is achieved, but the system becomes expensive and inefficient
Solution Approach 1:
The invention extracts the capacity control function from the expensive external suction modulation valve and relocates it to simpler suction cutoff unloader valves that are integral to the compressor. By moving the modulation function into the existing compressor structure and using the already-present unloader valves for capacity control, the system achieves tight temperature control without the high cost and inefficiency associated with external suction modulation valves.
3Device complexity
If unit cycling is used for capacity control, then system simplicity is maintained, but tight temperature control cannot be achieved
Solution Approach 1:
The invention applies dynamics by transitioning from static unit cycling (on/off) to dynamic capacity control through variable switching intervals of the suction cutoff unloader valves. The controller dynamically adjusts the switching intervals based on part-load conditions, cycling valves at different rates to achieve continuous capacity modulation. This dynamic approach maintains system simplicity while enabling tight temperature control that static unit cycling cannot provide.
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3A~3B
AI summary
A reciprocating compressor includes a first cylinder and a second cylinder, first and second suction cutoff unloader valve assemblies, and a controller. The first and second suction cutoff unloader valve assemblies are integral to the compressor and are capable of a rapid cycling to interrupt flow of refrigerant to the first and second cylinders. The controller operates at least one of the first suction cutoff unloader valve assembly or second suction cutoff unloader valve assembly in the rapid cycling and monitor a number of rapid cycles. In another aspect, a multi-stage compressor comprises a lower pressure stage and a higher pressure stage, and at least one suction cutoff unloader valve assembly capable of a rapid cycling to interrupt flow of refrigerant to a lower stage cylinder.