Analyses of gas pulsation characteristics in the pipelines of a hydrogen diaphragm compressor

A numerical method for calculating the gas pulsation in compressor pipelines based on the thermophysical properties of real gas has been developed. The one-dimensional flow dynamic equations for piping flow are derived under the condition of real gas working fluid. Given the pipeline element parameters and boundary conditions, the flow dynamic equations are discretized at the inner points of pipeline elements by the Lax-Wendroff scheme, and the characteristic equations are discretized at the boundary points by the trapezoidal integration scheme. Thereby the time-domain solution of flow data of pulsating gas at various pipeline locations is obtained. By developing the numerical analysis program, the calculations and analyses of gas pulsations in the interstage and exhaust pipelines of a two-stage hydrogen diaphragm compressor were performed. The pressure pulsation results agree well with the data calculated by PULS, and the relative magnitudes of different harmonic amplitudes are similar. The pressure pulsation level is highest at the outlet of the cylinder, and drops to the lowest level at the downstream snubber. Within a range of ±10% of the rated speed, the pressure pulsations at various locations fluctuate with the change in rotational speed, and the peak-to-peak value of pressure pulsation is generally lower than 10% of the average pressure. An appropriate inner diameter of the expansion tube can minimize pressure pulsation in the pipeline.