Working Principle Of A Fixed Displacement Compressor

A fixed displacement compressor operates based on a compression chamber with a fixed volume, such as the cylinder volume of a reciprocating compressor or the fixed scroll clearance of a scroll compressor. Its displacement is determined by its hardware structure, such as piston diameter, stroke length, or scroll height. During operation, the compressor runs at a fixed frequency, and the amount of compressed gas per unit time remains the same regardless of system load. This design results in an energy consumption mode of "fully on or fully off." When the system load decreases (e.g., when the ambient temperature drops), the compressor still needs to maintain pressure through frequent start-stop cycles or pressure relief via a bypass valve, which can easily lead to pressure fluctuations, component wear, and energy waste.