The purpose of this study is to investigate means of controlling the interior ballistic stability of a bulk-loaded propellant gun（BLPG）.Experiments on the interaction of twin combustion gas jets and liquid medium in...The purpose of this study is to investigate means of controlling the interior ballistic stability of a bulk-loaded propellant gun（BLPG）.Experiments on the interaction of twin combustion gas jets and liquid medium in a cylindrical stepped-wall combustion chamber are conducted in detail to obtain time series processes of jet expansion,and a numerical simulation under the same working conditions is also conducted to verify the reliability of the numerical method by comparing numerical results and experimental results.From this,numerical simulations on mutual interference and expansion characteristics of multiple combustion gas jets（four,six,and eight jets） in liquid medium are carried out,and the distribution characteristic of pressure,velocity,temperature,and evolutionary processes of Taylor cavities and streamlines of jet flow Held are obtained in detail.The results of numerical simulations show that when different numbers of combustion gas jets expand in liquid medium,there are two different types of vortices in the jet flow field,including corner vortices of liquid phase near the step and backflow vortices of gas phase within Taylor cavities.Because of these two types of vortices,the radial expansion characteristic of the jets is increased,while changing numbers of combustion gas jets can restrain Kelvin-Helmholtz instability to a certain degree in jet expansion processes,which can at last realize the goal of controlling the interior ballistic stability of a BLPG.The optimum method for both suppressing Kelvin-Helmholtz instability and promoting radial expansion of Taylor cavities can be determined by analyzing the change of characteristic parameters in a jet flow field.展开更多
To explore further the launch mechanism of the new underwater launching technology proposed in this paper, the expansion characteristics of four wall combustion-gas jets in confined liquid space must be studied firstl...To explore further the launch mechanism of the new underwater launching technology proposed in this paper, the expansion characteristics of four wall combustion-gas jets in confined liquid space must be studied firstly. The experimental device is designed, and the high-speed digital photographic system is adopted to obtain the expansion sequence processes of Taylor cavities formed by the four wall jets. Meanwhile, the influence of the injection pressure on the axial expansion property of the four wall jets is discussed. Based on the experiments, a three-dimensional unsteady mathematical model is established to simulate the turbulent flow process of the four wall jets expanding in liquid, and the temporal and spatial distribution laws of phase, pressure, temperature, and velocity and the evolution rules of vortices are illustrated in detail. Results show that, accompanied by the jets expanding downstream, the four wall combustion-gas jets get close to each other and achieve convergence eventually under induction of the interference effect between multiple jets. Meanwhile, the heads of the Taylor cavities separate from the observation chamber wall and offset to the central axis of the observation chamber with time going on. The numerical simulation results of the four wall combustion-gas jets coincide well with the experimental data.展开更多
The expansion process of ablation plasma jet in liquid was experimentally investigated by using high speed digital camera. The sequential pictures show that, in the initial stage of the jet, the Taylor cavity expands ...The expansion process of ablation plasma jet in liquid was experimentally investigated by using high speed digital camera. The sequential pictures show that, in the initial stage of the jet, the Taylor cavity expands in the axial and radial directions simultaneously, and then, is subjected to the constraint of chamber wall, in axial direction mainly. The maximum axial speed of the cavity's head ranges from 240m/s to 280m/s. Some strong heat conduction and mass transmission effects can be found in the surface of Taylor cavity, where the plasma cools down and condenses as solid particles while the liquid vaporizes as gas. Compared the expansion processes of the cavities among the different discharge energies and the nozzle diameters, it can be seen that the expansion speed of the cavity is directly proportional to the discharge energy and inversely to the nozzle diameter, and the effect of the discharge energy is stronger than that of the nozzle diameter. A set of equations describing the expansion process of ablation plasma jet was derived under the assumption of momentum conservation. The calculated results by use of the equations coincide with the experimented results better.展开更多
基金supported by National Natural Science Foundation of China(Grant 11372139)
文摘The purpose of this study is to investigate means of controlling the interior ballistic stability of a bulk-loaded propellant gun（BLPG）.Experiments on the interaction of twin combustion gas jets and liquid medium in a cylindrical stepped-wall combustion chamber are conducted in detail to obtain time series processes of jet expansion,and a numerical simulation under the same working conditions is also conducted to verify the reliability of the numerical method by comparing numerical results and experimental results.From this,numerical simulations on mutual interference and expansion characteristics of multiple combustion gas jets（four,six,and eight jets） in liquid medium are carried out,and the distribution characteristic of pressure,velocity,temperature,and evolutionary processes of Taylor cavities and streamlines of jet flow Held are obtained in detail.The results of numerical simulations show that when different numbers of combustion gas jets expand in liquid medium,there are two different types of vortices in the jet flow field,including corner vortices of liquid phase near the step and backflow vortices of gas phase within Taylor cavities.Because of these two types of vortices,the radial expansion characteristic of the jets is increased,while changing numbers of combustion gas jets can restrain Kelvin-Helmholtz instability to a certain degree in jet expansion processes,which can at last realize the goal of controlling the interior ballistic stability of a BLPG.The optimum method for both suppressing Kelvin-Helmholtz instability and promoting radial expansion of Taylor cavities can be determined by analyzing the change of characteristic parameters in a jet flow field.
基金supported by the National Natural Science Foundation of China (Grant 11372139)
文摘To explore further the launch mechanism of the new underwater launching technology proposed in this paper, the expansion characteristics of four wall combustion-gas jets in confined liquid space must be studied firstly. The experimental device is designed, and the high-speed digital photographic system is adopted to obtain the expansion sequence processes of Taylor cavities formed by the four wall jets. Meanwhile, the influence of the injection pressure on the axial expansion property of the four wall jets is discussed. Based on the experiments, a three-dimensional unsteady mathematical model is established to simulate the turbulent flow process of the four wall jets expanding in liquid, and the temporal and spatial distribution laws of phase, pressure, temperature, and velocity and the evolution rules of vortices are illustrated in detail. Results show that, accompanied by the jets expanding downstream, the four wall combustion-gas jets get close to each other and achieve convergence eventually under induction of the interference effect between multiple jets. Meanwhile, the heads of the Taylor cavities separate from the observation chamber wall and offset to the central axis of the observation chamber with time going on. The numerical simulation results of the four wall combustion-gas jets coincide well with the experimental data.
基金Sponsored by the National Nature Science Foundation of China (10302102)
文摘The expansion process of ablation plasma jet in liquid was experimentally investigated by using high speed digital camera. The sequential pictures show that, in the initial stage of the jet, the Taylor cavity expands in the axial and radial directions simultaneously, and then, is subjected to the constraint of chamber wall, in axial direction mainly. The maximum axial speed of the cavity's head ranges from 240m/s to 280m/s. Some strong heat conduction and mass transmission effects can be found in the surface of Taylor cavity, where the plasma cools down and condenses as solid particles while the liquid vaporizes as gas. Compared the expansion processes of the cavities among the different discharge energies and the nozzle diameters, it can be seen that the expansion speed of the cavity is directly proportional to the discharge energy and inversely to the nozzle diameter, and the effect of the discharge energy is stronger than that of the nozzle diameter. A set of equations describing the expansion process of ablation plasma jet was derived under the assumption of momentum conservation. The calculated results by use of the equations coincide with the experimented results better.
