Experimental investigation into pressure oscillations in the compression chamber of a rotary compressor

This study experimentally investigates the characteristics of the pressure oscillations within the compression chamber of a rotary compressor and evaluates their impact on compressor performance. Four fast-response pressure transducers are installed at circumferential positions in the upper cylinder to measure instantaneous pressure under varying rotational speeds (60–120 Hz) and suction pressures (0.4–1.0 MPa). Results reveal significant pressure oscillations during compression, with amplitudes increasing at higher rotational speeds. The oscillation frequency ranges from below 1000 Hz at the start of compression to approximately 4000 Hz near discharge. A finite element study is conducted to calculate the natural frequencies of the compression chamber assuming the shape at an instantaneous shaft angle. The calculated frequencies are identical to those observed in the experiments. It is revealed that the physical mechanisms of the pressure oscillations are the quasi-static acoustic resonance within the crescent-shaped chamber. Rapid volume changes with fast roller motions are identified as key triggers for the resonance. Performance tests demonstrate a decline in the coefficient of performance (COP) with increasing speed. The study highlights that acoustic resonance-induced pressure oscillations critically degrade energy efficiency, particularly at elevated rotational speeds. Mitigating these oscillations is essential for optimizing compressor performance at high speeds.