In order to realize safe and accurate homing of parafoil system,a multiphase homing trajectory planning scheme is proposed according to the maneuverability and basic flight characteristics of the vehicle.In this scena...In order to realize safe and accurate homing of parafoil system,a multiphase homing trajectory planning scheme is proposed according to the maneuverability and basic flight characteristics of the vehicle.In this scenario,on the basis of geometric relationship of each phase trajectory,the problem of trajectory planning is transformed to parameter optimizing,and then auxiliary population-based quantum differential evolution algorithm(AP-QDEA)is applied as a tool to optimize the objective function,and the design parameters of the whole homing trajectory are obtained.The proposed AP-QDEA combines the strengths of differential evolution algorithm(DEA)and quantum evolution algorithm(QEA),and the notion of auxiliary population is introduced into the proposed algorithm to improve the searching precision and speed.The simulation results show that the proposed AP-QDEA is proven its superior in both effectiveness and efficiency by solving a set of benchmark problems,and the multiphase homing scheme can fulfill the requirement of fixed-points and upwind landing in the process of homing which is simple in control and facile in practice as well.展开更多
A two-dimensional axisymmetric model, employing a dynamic mesh and user-defined functions, is used to numerically simulate the transient multiphase flow field produced by an underwater gun. Furthermore, a visualized s...A two-dimensional axisymmetric model, employing a dynamic mesh and user-defined functions, is used to numerically simulate the transient multiphase flow field produced by an underwater gun. Furthermore, a visualized shooting experiment platform with a high-speed camera is built to observe the evolution process of such a multiphase flow field. The simulated phase distribution diagram is agreed well with the shadow photo of the experiment, indicating that the numerical model is reasonable. Further examinations of the multiphase flow fields by using the submerged and sealed launch methods show that use of the sealed launch can significantly improve the interior ballistic performance of an underwater gun. In the cases by using these two types of underwater launch methods, the displacement of the projectile within the range of the muzzle flow field meets the exponential law over time. Moreover, a not fully developed bottle-shaped shock wave is formed when t = 0.4 ms, but this bottle-shaped shock wave expands more rapidly for the sealed launch. In addition, the amplitude of pressure oscillation for the sealed launch is larger than that of the submerged launch, but the pressure oscillation of the sealed launch lasts shorter.展开更多
This study calculates the combustion characteristics of various gas-generating and micro gas pyrotechnic charges,including aluminium/potassium perchlorate,boron/potassium nitrate,carbon black/potassium nitrate,and sil...This study calculates the combustion characteristics of various gas-generating and micro gas pyrotechnic charges,including aluminium/potassium perchlorate,boron/potassium nitrate,carbon black/potassium nitrate,and silicon-based delay compositions,using thermodynamic software.A multiphase flowthermal-solid coupling model was established,and the combustion process of the pyrotechnic charges within a closed bomb was simulated.The pyrotechnic shock generated by combustion was predicted.The combustion pressures and pyrotechnic shocks were measured.The simulation results demonstrated good agreement with experimental results.Additionally,the mechanism of shock generation by the combustion of pyrotechnic charges in the closed bomb was analyzed.The effects of the combustion characteristics of the pyrotechnic charges on the resulting pyrotechnic shocks were systematically investigated.Notably,the shock response spectrum of the gas-generating pyrotechnic charges is greater than that of the micro gas compositions at most frequencies,particularly in the mid-field pyrotechnic shocks(3-10 kHz).Furthermore,the pyrotechnic shocks increase approximately linearly with the impulse of the gas-generating pyrotechnic charges.展开更多
Wei-Zhong Qian(骞伟中)Prof. Weizhong Qian received a Ph.D. at Tsinghua University in 2003 and worked as a faculty member in Tsinghua University since2002. He has been visiting associate professor of department of mate...Wei-Zhong Qian(骞伟中)Prof. Weizhong Qian received a Ph.D. at Tsinghua University in 2003 and worked as a faculty member in Tsinghua University since2002. He has been visiting associate professor of department of materials science and engineering, Cornell University at 2008. He has been a full professor of chemical engineering at Tsinghua University since 2015. His research interests include carbon nanomaterials production and electrochemical energy storage application, and the multiphase chemical reaction technology to prepare high value chemicals.展开更多
基金Project(61273138) supported by the National Natural Science Foundation of ChinaProjects(KJ2016A169,KJ2015A242) supported by the University Natural Science Research Key Project of Anhui Province,ChinaProject(ZRC2014444) supported by the Talents Program of Anhui Science and Technology University,China
文摘In order to realize safe and accurate homing of parafoil system,a multiphase homing trajectory planning scheme is proposed according to the maneuverability and basic flight characteristics of the vehicle.In this scenario,on the basis of geometric relationship of each phase trajectory,the problem of trajectory planning is transformed to parameter optimizing,and then auxiliary population-based quantum differential evolution algorithm(AP-QDEA)is applied as a tool to optimize the objective function,and the design parameters of the whole homing trajectory are obtained.The proposed AP-QDEA combines the strengths of differential evolution algorithm(DEA)and quantum evolution algorithm(QEA),and the notion of auxiliary population is introduced into the proposed algorithm to improve the searching precision and speed.The simulation results show that the proposed AP-QDEA is proven its superior in both effectiveness and efficiency by solving a set of benchmark problems,and the multiphase homing scheme can fulfill the requirement of fixed-points and upwind landing in the process of homing which is simple in control and facile in practice as well.
基金This work was supported by the National Natural Science Foundation of China(No.11372139)the China Postdoctoral Science Foundation(2020M681596).
文摘A two-dimensional axisymmetric model, employing a dynamic mesh and user-defined functions, is used to numerically simulate the transient multiphase flow field produced by an underwater gun. Furthermore, a visualized shooting experiment platform with a high-speed camera is built to observe the evolution process of such a multiphase flow field. The simulated phase distribution diagram is agreed well with the shadow photo of the experiment, indicating that the numerical model is reasonable. Further examinations of the multiphase flow fields by using the submerged and sealed launch methods show that use of the sealed launch can significantly improve the interior ballistic performance of an underwater gun. In the cases by using these two types of underwater launch methods, the displacement of the projectile within the range of the muzzle flow field meets the exponential law over time. Moreover, a not fully developed bottle-shaped shock wave is formed when t = 0.4 ms, but this bottle-shaped shock wave expands more rapidly for the sealed launch. In addition, the amplitude of pressure oscillation for the sealed launch is larger than that of the submerged launch, but the pressure oscillation of the sealed launch lasts shorter.
文摘This study calculates the combustion characteristics of various gas-generating and micro gas pyrotechnic charges,including aluminium/potassium perchlorate,boron/potassium nitrate,carbon black/potassium nitrate,and silicon-based delay compositions,using thermodynamic software.A multiphase flowthermal-solid coupling model was established,and the combustion process of the pyrotechnic charges within a closed bomb was simulated.The pyrotechnic shock generated by combustion was predicted.The combustion pressures and pyrotechnic shocks were measured.The simulation results demonstrated good agreement with experimental results.Additionally,the mechanism of shock generation by the combustion of pyrotechnic charges in the closed bomb was analyzed.The effects of the combustion characteristics of the pyrotechnic charges on the resulting pyrotechnic shocks were systematically investigated.Notably,the shock response spectrum of the gas-generating pyrotechnic charges is greater than that of the micro gas compositions at most frequencies,particularly in the mid-field pyrotechnic shocks(3-10 kHz).Furthermore,the pyrotechnic shocks increase approximately linearly with the impulse of the gas-generating pyrotechnic charges.
文摘Wei-Zhong Qian(骞伟中)Prof. Weizhong Qian received a Ph.D. at Tsinghua University in 2003 and worked as a faculty member in Tsinghua University since2002. He has been visiting associate professor of department of materials science and engineering, Cornell University at 2008. He has been a full professor of chemical engineering at Tsinghua University since 2015. His research interests include carbon nanomaterials production and electrochemical energy storage application, and the multiphase chemical reaction technology to prepare high value chemicals.
