Investigation of interaction between thermodynamic processes and pressure pulsation based on transient CFD model of a reciprocating compressor

Abstract

This paper presents a transient computational fluid dynamics (CFD) model of a reciprocating compressor to study the interaction of the thermodynamic process and pressure pulsation. To realize the interaction between the thermodynamics and the pressure pulsation, the most difficult procedure lies in dealing with the valve motion and flow through the valve channel both precisely and effectively. Therefore, a discretization method for the flow channel of the ring valve to generate structured grids is proposed. Then, the subsequent model is embedded in the flow channel of the compressor model. User-defined functions are employed to calculate the independent velocity of each valve plate based on the real-time pressure differences across the valve plates. After verified, the influences of the discharge pipeline configuration, pressure ratio, and rotational speed were examined. The results of the numerical model agreed well with the experiment. The maximal deviation between predictions and experiments at the pressure ratio of 3 was 6.14% of indicated power. The maximum deviation increased to 7.42% at the rotational speed of 480 rpm. The results for the discharge pipeline configuration verified that the buffer tank directly following the nozzle of the compressor contributed greatly to attenuating the pressure pulsation. A fast Fourier transform analysis of pressure pulsation showed that at all speeds, the amplitudes were almost the same below the eighth harmonic, and then gradually increased for the higher harmonics.