A hybrid time-frequency domain approach for numerical modeling of reciprocating compressors

In the reciprocating compressor field, strong attention is paid to the study of pressure wave propagation in the discharge and suction pipelines. Oscillating pressure waves may lead to mechanical vibrations and failures and affect the machine performance. For this reason, an accurate analysis of the acoustic response of suction and discharge pipelines in a reciprocating compressor plant is of great interest. By solving a linear system of equations, the acoustic domain of a piping system can be easily determined. Usually, the acoustic pulsation analysis of the pipelines is carried out without considering the interaction between the machinery and the pipelines. Consequently, the reciprocal interaction between the compressor and the pipelines can not be considered. The aim of this work is to perform a fluid-dynamic analysis of the full compressor-pipelines system. For this purpose, a hybrid time-frequency domain approach is adopted. The reciprocating compressor thermodynamic cycle is simulated with a 0D time-domain model, while the pressure wave propagation in the pipelines is modelled by mean of a transfer matrix approach in the frequency domain. This analysis allows one to take into account the mutual interaction between the compressor and its pipelines by using the FFT and the Inverse FFT alternatively. The methodology was assessed by comparing the results of the simulation of a test case performed with both the hybrid approach and a commercial 1D code.