摘要
In this study, numerical simulation of flow field in a supersonic/hypersonic impactor with one or two nozzles was carried out using a commercial computational fluid dynamics （CFD） software FLUENT. The objective was to investigate the effects of working parameters such as pressure ratio （50 〈 Po]Pb 〈 800）, nozzle diameters （D=0.23, 0.27, 0.45 mm）, nozzle to plate distance （0.5 〈L/D〈 50）, particle diameter （1 nm〈 dp 〈 100 nm ） and angle between two nozzles. A single-phase 3D unsteady-state model was implemented by the software. For this purpose, a user-defined function （UDF） was employed to implement nanoparticles for different assumptions of Cunningham correction factor. An axisymmetric form of the compressible Navier-Stokes and energy equations was used for both fluid flow and temperature; Lagrangian particle trajectory analysis was used for particle motion. Using the variable Cunningham cor- rection factor showed suitable agreement with experimental data in comparison with other methods. Results show that increase of the distance between nozzle and impaction plate causes increase of Mach number, the distance between bow shock and impaction plate, and the collection efficiency. Maximum jet velocity, distance between bow shock and impaction plate and collection efficiency increase by using two nozzles in supersonic and hypersonic imoactors.
In this study, numerical simulation of flow field in a supersonic/hypersonic impactor with one or two nozzles was carried out using a commercial computational fluid dynamics （CFD） software FLUENT. The objective was to investigate the effects of working parameters such as pressure ratio （50 〈 Po]Pb 〈 800）, nozzle diameters （D=0.23, 0.27, 0.45 mm）, nozzle to plate distance （0.5 〈L/D〈 50）, particle diameter （1 nm〈 dp 〈 100 nm ） and angle between two nozzles. A single-phase 3D unsteady-state model was implemented by the software. For this purpose, a user-defined function （UDF） was employed to implement nanoparticles for different assumptions of Cunningham correction factor. An axisymmetric form of the compressible Navier-Stokes and energy equations was used for both fluid flow and temperature; Lagrangian particle trajectory analysis was used for particle motion. Using the variable Cunningham cor- rection factor showed suitable agreement with experimental data in comparison with other methods. Results show that increase of the distance between nozzle and impaction plate causes increase of Mach number, the distance between bow shock and impaction plate, and the collection efficiency. Maximum jet velocity, distance between bow shock and impaction plate and collection efficiency increase by using two nozzles in supersonic and hypersonic imoactors.
