The present study investigated the effect of geometrical and non-geometrical parameters on the thrust performance of a pump-valve propulsion device consisting of a Coanda effect valve(CEV)and a pump.A more accurate th...The present study investigated the effect of geometrical and non-geometrical parameters on the thrust performance of a pump-valve propulsion device consisting of a Coanda effect valve(CEV)and a pump.A more accurate theoretical model was also developed to predict the thrust of the pump-valve device.Firstly,a rough thrust model was developed based on existing theory to predict the thrust and energy loss generated by the pump-valve device under different exit and nozzle areas.Considering the limitations of the theoretical analysis,numerical simulations were carried out to evaluate the effect of various geometrical and non-geometrical parameters,including nozzle shape,nozzle area,control port width,exit area,inlet flow rate,etc.,on the thrust performance of the CEV and the pump-valve device.Due to the margin between simulation thrusts and theoretical thrusts,we built an experimental platform and carried out relevant experiments.The experimental data verified the simulation results,and on this basis,the original thrust prediction model was corrected.展开更多
Mounds of spatter are generated in laser powder-bed fusion(L-PBF)additive manufacturing,which reduces build quality and laser lifetime.Due to the lack of supplemental airflow above the chamber,the conventional build c...Mounds of spatter are generated in laser powder-bed fusion(L-PBF)additive manufacturing,which reduces build quality and laser lifetime.Due to the lack of supplemental airflow above the chamber,the conventional build chamber with a single gas inlet exhibits a pronounced tendency for gas to flow upward near the outlet.This phenomenon results in the formation of a large vortex within the build chamber.The vortex leads to the chaotic motion trajectory of the spatter in the build chamber.The design defects of the existing build chamber based on dual gas inlets are shown in this paper.We established a coupled computational fluid dynamics-discrete phase model(CFD-DPM)model to optimize the build chamber by adjusting the position and structure of the second gas inlet.The homogeneity of the flow is increased with a distance of 379 mm between the two inlets and a wider-reaching second inlet.The Coanda effect is also crucial in the spatter-removal process.The Coanda effect is reduced by modifying the right sidewall of the build chamber and increasing the pressure difference between the inlet and outlet.Finally,we found that the spatter-removal rate rose from 8.9%to 76.1%between the conventional build chamber with a single gas inlet and the optimized build chamber with two gas inlets.展开更多
基金supported in part by the National Natural Science Foundation of China(NSFC)under grant U1813225,grant 61733014,grant U21B2047,grant U22A2066in part by the Doctorate Foundation of Northwestern Polytechnical University under grant CX201904.
文摘The present study investigated the effect of geometrical and non-geometrical parameters on the thrust performance of a pump-valve propulsion device consisting of a Coanda effect valve(CEV)and a pump.A more accurate theoretical model was also developed to predict the thrust of the pump-valve device.Firstly,a rough thrust model was developed based on existing theory to predict the thrust and energy loss generated by the pump-valve device under different exit and nozzle areas.Considering the limitations of the theoretical analysis,numerical simulations were carried out to evaluate the effect of various geometrical and non-geometrical parameters,including nozzle shape,nozzle area,control port width,exit area,inlet flow rate,etc.,on the thrust performance of the CEV and the pump-valve device.Due to the margin between simulation thrusts and theoretical thrusts,we built an experimental platform and carried out relevant experiments.The experimental data verified the simulation results,and on this basis,the original thrust prediction model was corrected.
基金supported by the Natural Science Foundation of Jiangxi Province(Nos.20224BAB214061 and 20224ACB214008)the National Natural Science Foundation of China(Nos.52165043 and 52166002)+2 种基金the Jiangxi Provincial Cultivation Program for Academic and Technical Leaders of Major Subjects(No.20225BCJ23008)the Anhui Provincial Natural Science Foundation(No.2308085ME171)the University Synergy Innovation Program of Anhui Province(Nos.GXXT-2023-025 and GXXT-2023-026),China。
文摘Mounds of spatter are generated in laser powder-bed fusion(L-PBF)additive manufacturing,which reduces build quality and laser lifetime.Due to the lack of supplemental airflow above the chamber,the conventional build chamber with a single gas inlet exhibits a pronounced tendency for gas to flow upward near the outlet.This phenomenon results in the formation of a large vortex within the build chamber.The vortex leads to the chaotic motion trajectory of the spatter in the build chamber.The design defects of the existing build chamber based on dual gas inlets are shown in this paper.We established a coupled computational fluid dynamics-discrete phase model(CFD-DPM)model to optimize the build chamber by adjusting the position and structure of the second gas inlet.The homogeneity of the flow is increased with a distance of 379 mm between the two inlets and a wider-reaching second inlet.The Coanda effect is also crucial in the spatter-removal process.The Coanda effect is reduced by modifying the right sidewall of the build chamber and increasing the pressure difference between the inlet and outlet.Finally,we found that the spatter-removal rate rose from 8.9%to 76.1%between the conventional build chamber with a single gas inlet and the optimized build chamber with two gas inlets.
