| Unloading inlet valves at partial stroke is one means of capacity regulating for reciprocating compressor, and it possesses economic, full-range and easy-using character. With inlet valves unloaded by some device, gas flows back into suction cavity before being compressed, which can save the energy. Changing the duration of unloading inlet valves conduces to varying capacity theoretically in the range of 0-100%.Compress circulation of an ideal-gas reciprocating compressor with unloaded inlet valves was analyzed and a formula was deduced to calculate capacity. Numerical simulation of unloaded valve dynamics shows influence of the unloading structure, and some advice was given for design of unloading system. Experiment on capacity control system with rotational hydraulic distributor represents the real regulation effect.Through this research task, the following topics can be obtained:1. Combined with the simplified thermodynamics circulation of compressor, the theoretical calculation of capacity and indicated power has been deduced, and the regulation principle was revealed.2. Differential equations of gas flow and valve motion were established, and computer aided analysis with varied unloading time was carried out. Means to reduce the impact between valve plate and valve seat were suggested.3. A simple capacity regulation system with rotational hydraulic distributor was introduced, and the theory of rotator and distributor control by microprocessor was explained. Result of theoretical experiment shows that the unloading time can be controlled.4. Experiment of the control system on a real reciprocating compressor has been accomplished. The results indicate: With the duration of the unloading force continuously regulated, the capacity varies from 90% to 30% accordingly. |
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