Performance study on a single-screw compressor for a portable natural gas liquefaction process

Portable natural gas liquefaction devices are widely used to exploit unconventional natural gas resources and one of key components is a compressor. In this paper, a new natural gas liquefaction process is simulated and optimized and a single-screw compressor with 200 mm diameter is designed to be applied in this process. To verify the performance of the single-screw compressor, an experimental system was set up and performance parameters were studied, including volumetric efficiency, specific power rate, shaft efficiency, irreversible loss rate and cooling efficiency of the lubricating oil. The influence of the lubricating oil on the volumetric efficiency was also observed. Furthermore, the impact of actual compressor performance on the liquefaction process was also analyzed. The results indicate that the performance of the compressor changes greatly when it operates deviating from its design condition. The maximum volumetric efficiency, shaft efficiency, irreversible loss rate and cooling efficiency of the lubricating oil are 0.91, 0.64, 0.56 and 0.22, respectively. The minimum specific power rate is 6.5 kW·(m³·min⁻¹)⁻¹. In addition, the lubricating oil has a good effect of sealing so that the volumetric efficiency can be improved by 10.5%. Considering the actual performance of the single-screw compressor, specific power consumption of the process increases by 43.3%.