Effect of Divergence Angle, Carrier Gas, and Back Pressure on Species Separation Using Convergent Divergent Micro-Nozzle

A numerical investigation of the species separation of a mixture of argon (Ar) and helium (He) flowing through the micro-nozzle at different divergent angles and in the presence of different concentrations of carrier gases (nitrogen and krypton) is reported. The study of varying back pressure effect on species separation is also included in the current literature. The Direct Simulation Monte Carlo approach has been adopted for the research, and the methodology was validated with the experimental study of Hao et al. (J Micromech Microeng 15:2069, 2005 [12]). Nozzle inlet is kept at a pressure of 120 kPa, while the exit is kept at hard vacuum. An equimolar mixture of argon and helium is inserted at the inlet of the nozzle with an inlet temperature of 300 K. The highest centerline argon mole fraction is obtained for a 45° divergence angle. The separation is found to be decreased with an increase in the concentration of carrier gases, and the heavier carrier gas (Kr) was found to further inhibit the separation. The species separation is found to be decreased with an increase in back pressure.