this condition, a deep dehydration process can be obtained and most of the water vapor is expected to be removed. That is, a large expansion ratio improves the dehydration performance of a supersonic separator since natural gas is expanded further.
4.4. Effect of expansion ratio on PRC
The computational fluid dynamics (CFD) technique was employed to predict the PRC of the supersonic separator. In this simulation, the Redlich–Kwong equation of state was used to evaluate the real gas effect in the high pressure and low temperature. The various gas Mach numbers were achieved by adapting the expansion ratio of the nozzle involved in a supersonic separator. The numerical results of the PRC along with the gas Mach number are shown in Fig. 7. We can see that the PRC also declines with the increase of the Mach number in the upstream of the shock wave. Furthermore, increasing the Mach number will enlarge this drop of the coefficient. The maximum PRC in simulation reaches 92.60% with the gas Mach number of 1.15. While the Mach number reaches 1.87, the maximum PRC is only about 71.00%.
The theoretical value, calculated by the Eq. (14), was depicted in Fig. 7 to evaluate the difference between the real and ideal values. It can be seen that the numerical results are smaller than the ideal data in the whole computed gas Mach number from 1.15 to 1.87.