Investigation of characteristics of discharge pressure pulsation in a twin-screw refrigeration compressor

In this paper, characteristics of discharge pressure pulsation in a twin-screw refrigeration compressor are investigated. A thermodynamic model is developed and validated using data from a comprehensive experimental study. This validated model is then applied to investigate effects of key parameters including condensing temperature, compressor rotational speed, super-feed pressure, part-load operation, and design parameters on the discharge pressure pulsation. The results showed that the discharge pressure pulsation was mainly due to periodic variations of mass and energy flow from the working volumes to the discharge chamber. As the condensing temperature increased or decreased from the design condition, the compressor was in either over- or undercompression leading to an increase in the amplitude of the pressure pulsation. The gas super-feed pressure could increase the pressure pulsation at condensing temperatures below the design value and reduce the pressure pulsation at condensing temperatures above the design value. The analysis also demonstrated that the pressure pulsation was lower at part-load conditions. However, the compressor rotational speed increased both the amplitude and frequency of the pressure pulsation. Theoretical analysis of design parameters indicated that a large discharge volume with a high number of lobes could lower the pressure pulsation. These analyses provide useful information for the compressor design and optimization.