Research And Simulation Of The Discrete Model Of The Large Caliber And High Speed Davis Gun

With the development of the Davis gun’s launching technology,the modern Davis gun presents the larger diameter,the heavier charge quality,the higher muzzle kinetic energy and the better stability.In order to improve the ventilation performance,the modularized tubular propellants are always used in the large-diameter Davis guns.Consequently,the two-phase flow process and combustion process in the chamber is becoming more complex.The instantaneous change process of the high temperature,high pressure and high speed brings a lot of difficulties to the study of the Davis guns’ internal ballistics.So the research of the two-phase flow model in the large diameter Davis Gun is important to its engineering design and the fire safety evaluation.In this study,in order to grasp the interior ballistics characteristics of the large caliber and high speed Davis guns,we designed a 480mm Davis gun device based on the designing requirements of a research project.In addition,not only experimental research,but also theoretical analysis and numerical simulation were all applied to study the Davis guns whole interior ballistics process,including the ignition process.The main work of this study includes the following aspects:(1)A gun firing test was designed and carried out for a 480mm Davis gun device.The experience results showed that the multi-point technology and the modularized tubular propellants were safe and reliable.The charge design in the Davis gun could obtain effective muzzle kinetic energy with the desired bore pressure range.(2)Based on the two-phase flow theory,we established a two-phase flow calculation model for the multi-point ignition system in the large caliber Davis gun.Considering the complexity of the multi-point ignition structure and the physical parameters distribution,we established the corresponding one-dimensional two-phase flow model and used the MacCormark format to simulate it.Thus we obtained the distribution of some characteristic parameters,such as the pressure,solid velocity,gas velocity,void and so on.The process of the multi-point fire spreading was analyzed,and the change rules of the gas pressure and the gas flow were discussed.The simulation results were verified to be right by comparing with the related experimental results.(3)A one-dimensional dispersion group two-phase flow model was established in the chamber of the 480mm Davis guns.Combined with the knowledge of the interior ballistics,combustion gas dynamics,and so on,we established the one-dimensional dispersion group two-phase flow model,which described the gas field by the Eulerian system and the tubular modules by the Lagrangian system.In addition,coupling with the multi-point ignition model and using the MacCormark scheme,we simulated the complex interior ballistics process of the large-caliber and high-speed Davis gun.By comparing the calculated results with the experimental results,the numerical model and methods were verified to be feasible and accurate.Through further analysis of the gas flow and the gunpowder motion in the chamber,we gained the tubular modules movement rules and the pressure distribution.The obtained results had important significance for the initial understanding of the large-caliber and high-speed Davis guns interior ballistics performance.(4)An assumption was put forward that the tubular modular was a linear distribution along the radial direction,and the movement was assumed along the axial direction.The gas filed would be settled using the Eulerian system and the solid filed would be settled using the Lagrangian system.Thus,a two-dimensional dispersion group two-phase flow model was established.By comparing the numerical simulation results and the test results,the correctness of the mathematical model was verified.Through the numerical simulation,we obtained both axial and radial gas flow rules in the chamber.(5)The main influencing actors of the large caliber and high speed Davis guns were analyzed.By using the numerical simulation method and changing interior ballistics parameters,such as the charge characteristics parameters,the propellant modules’ numbers and positions,the interior ballistics variation was investigated.In addition,by setting different situations that some of the ignition heads work failure,changes of the pressure and gas velocity characteristics in the chamber were obtained.This research was put forward to improve the energy release rules in the large caliber Davis guns and provide a theoretical basis for the design and optimization of the large caliber Davis guns.This study developed an approach to the research of the interior ballistics performance in the large caliber guns.It provided the references in application,and also has important meanings in theory and practical engineering.