| Abstract: | In this study the flow field and the nanoparticle collection efficiency of supersonic/hypersonic impactors with different nozzle shapes were studied using a computational modeling approach.The aim of this study was to develop a nozzle design for supersonic/hypersonic impactors with the smallest possible cut-off size d_(50) and rather sharp collection efficiency curves.The simulation results show that the changes in the angle and width of a converging nozzle do not alter the cut-off size of the impactor;however,using a conical Laval nozzle with an L/D_n ratio less than or equal to 2 reduced d_(50).The effect of using a cap as a focuser in the nozzle of a supersonic/hypersonic impactor was also investigated.The results show that adding a cap in front of the nozzle had a noticeable effect on decreasing the cut-off size of the impactor.Both flat disks and conical caps were examined,and it was observed that the nozzle with the conical cap had a lower cut-off size. |
