Investigation of supersonic flow in a Laval nozzle with different convergent and divergent geometries

Abstract

Supersonic separators have emerged from researches of new technologies to eliminate impurities from natural gas. The nozzle geometry plays an important role on the flow stability and on the condensation of components of the natural gas. Notable attention has been devoted to the design of the convergent section, whereas the impact of the divergent part on internal nozzle flow remains understudied. This paper puts forward a numerical investigation of the supersonic air flow inside a Laval nozzle for different designs of both convergent and divergent sections. The results have shown that the flow is more affected by the divergent geometry than by the convergent design. Disturbances on the flow were observed when a linear shape is used in the later part. The disturbances formed when a linear divergent section were progressively reduced as the length of the constant area portion increases. By using an Arina divergent section, smaller velocity gradients were observed, which can be a positive aspect for phase separation during the condensation process. Different pressures were assigned at inlet and outlet of the nozzle and the results indicates that moderate pressures can mitigate re-evaporation and provides sufficient time for droplet nucleation and growth during the condensation.