Two-phase flow modeling of solid propellants has great potential for simulating and predicting the ballistic parameters in closed vessel tests as well as in guns. This paper presents a numerical model describing the c...Two-phase flow modeling of solid propellants has great potential for simulating and predicting the ballistic parameters in closed vessel tests as well as in guns. This paper presents a numerical model describing the combustion of a solid propellant in a closed chamber and takes into account what happens in such twophase,unsteady,reactive-flow systems. The governing equations are derived in the form of coupled,non-linear axisymmetric partial differential equations. The governing equations with customized parameters are implemented into Ansys Fluent 14. 5. The presented solutions predict the pressure profile inside the closed chamber. The results show that the present code adequately predicts the pressure-time history. The numerical results are in agreement with the experimental results. Some discussions are given regarding the effect of the grain shape and the sensitivity of these predictions to the initial pressure of the solid propellant bed. The study demonstrates the capability of using the present model implemented into Fluent,to simulate the combustion of solid propellants in a closed vessel and,eventually,the interior ballistic process in guns.展开更多
Initial firing temperatures play an important role on the combustion rate of propellant. In gun propellants, initial temperature is a key factor for both accuracy and safety. Ideally, the initial temperature of the pr...Initial firing temperatures play an important role on the combustion rate of propellant. In gun propellants, initial temperature is a key factor for both accuracy and safety. Ideally, the initial temperature of the propellant should not influence the ballistic properties of the round. Nevertheless, constant initial temperature coefficients can not be achieved easily. This work focuses on the influence of the firing temperature on the ballistic properties, the mechanical integrity and the sensitivity to impact of nitrocellulose based propellants. Combustion rates have been determined by closed vessel tests. Ballistic properties have been investigated by firing 5.56 cartridges. The propellants have been conditioned at temperatures ranging from -54 ℃ to ＋71 ℃ before firing. The largest temperature coefficient is observed at high temperatures. The temperature sensitivity of the peak pressure in the combustion chamber can not be fully explained by the results from the closed vessel test. The authors speculated that the mechanical behaviour of the propellant grains at low temperatures influences also the overall ballistic properties of the round. Impact tests with propellants conditioned at low and high temperatures permit to investigate their mechanical strength under extreme temperatures and to better understand the propellant performance during firing. Tests on aged propellants have been conducted as well.展开更多
At low temperatures,gun propellant grains may become brittle and this can lead to fracture or shatter of the grains during gun firing.Should this event occur then it will result in an increase in the burning surface o...At low temperatures,gun propellant grains may become brittle and this can lead to fracture or shatter of the grains during gun firing.Should this event occur then it will result in an increase in the burning surface of the propellant and will give rise to a change in ballistic performance.Also,if the resultant over pressure is sufficient,a breech failure may result.Understanding the propensity of a grain to fracture or shatter is therefore important in determining its safety in use.This document describes a test that may be used to derive knowledge and to quantify the physical behaviour of a gun propellant grain at the low temperatures at which fracture or shatter is most likely to occur.展开更多
Power Cartridges are pyrotechnic devices where hot combustion gases utilized to do mechanical work for disruption of suspected Improvised Explosive Devices(IEDs). It plays a vital role either in destroying the suspici...Power Cartridges are pyrotechnic devices where hot combustion gases utilized to do mechanical work for disruption of suspected Improvised Explosive Devices(IEDs). It plays a vital role either in destroying the suspicious object or making them non-functional by generating the gas pressure on burning of propellant against the water column inside the barrel, Present work is focused on characterisation,numerical solution such as deformation; strain; stress using FEM(Finite Element Method), design qualification, performance and evaluation of power cartridge for disruptor application. Experimental trials for pressure-time(P-t) measurement in closed vessel(CV), various electrical parameters like all fire current(AFC), no fire current(NFC) and ignition delay have been measured. Further, mechanical properties for brass material have been determined. An attempt has been made to characterise the power cartridge by FEM and carrying out the experiments for water-jet application.展开更多
Propellants containing micro-aluminium particles have been shown to produce faster burn rates than conventional gun propellants.However,they are also more abrasive than conventional propellants.Nano-material propellan...Propellants containing micro-aluminium particles have been shown to produce faster burn rates than conventional gun propellants.However,they are also more abrasive than conventional propellants.Nano-material propellants have been reported to give similar benefits to micron-material propellants but without the disadvantage of increased abrasion.Tests were conducted to compare the burn rates,ignitability and wear rates of a propellant loaded with 0% aluminium,15% micro-aluminium and 15%nano-aluminium.Closed vessel tests showed a burn rate increase of 39% in the range 30-250 MPa,and 70% at low pressure(50-100MPa)for the nano-aluminium propellant compared with the baseline propellant.The micro-aluminium propellant showed only a 10%increase in the burn rate compared with the standard propellant.The ignition delay for the nano-aluminium propellant was slightly shorter than that of the baseline propellant.Substantially increased wear rates were measured for the micro-aluminium propellant.The nano-aluminium propellant showed reduced wear rates compared with the micro-aluminium propellant but these were still substantially greater than those for the baseline propellant.展开更多
基金Sponsored by the National Natural Science Foundation of China(Grant No.51176042 and 21276056)
文摘Two-phase flow modeling of solid propellants has great potential for simulating and predicting the ballistic parameters in closed vessel tests as well as in guns. This paper presents a numerical model describing the combustion of a solid propellant in a closed chamber and takes into account what happens in such twophase,unsteady,reactive-flow systems. The governing equations are derived in the form of coupled,non-linear axisymmetric partial differential equations. The governing equations with customized parameters are implemented into Ansys Fluent 14. 5. The presented solutions predict the pressure profile inside the closed chamber. The results show that the present code adequately predicts the pressure-time history. The numerical results are in agreement with the experimental results. Some discussions are given regarding the effect of the grain shape and the sensitivity of these predictions to the initial pressure of the solid propellant bed. The study demonstrates the capability of using the present model implemented into Fluent,to simulate the combustion of solid propellants in a closed vessel and,eventually,the interior ballistic process in guns.
文摘Initial firing temperatures play an important role on the combustion rate of propellant. In gun propellants, initial temperature is a key factor for both accuracy and safety. Ideally, the initial temperature of the propellant should not influence the ballistic properties of the round. Nevertheless, constant initial temperature coefficients can not be achieved easily. This work focuses on the influence of the firing temperature on the ballistic properties, the mechanical integrity and the sensitivity to impact of nitrocellulose based propellants. Combustion rates have been determined by closed vessel tests. Ballistic properties have been investigated by firing 5.56 cartridges. The propellants have been conditioned at temperatures ranging from -54 ℃ to ＋71 ℃ before firing. The largest temperature coefficient is observed at high temperatures. The temperature sensitivity of the peak pressure in the combustion chamber can not be fully explained by the results from the closed vessel test. The authors speculated that the mechanical behaviour of the propellant grains at low temperatures influences also the overall ballistic properties of the round. Impact tests with propellants conditioned at low and high temperatures permit to investigate their mechanical strength under extreme temperatures and to better understand the propellant performance during firing. Tests on aged propellants have been conducted as well.
文摘At low temperatures,gun propellant grains may become brittle and this can lead to fracture or shatter of the grains during gun firing.Should this event occur then it will result in an increase in the burning surface of the propellant and will give rise to a change in ballistic performance.Also,if the resultant over pressure is sufficient,a breech failure may result.Understanding the propensity of a grain to fracture or shatter is therefore important in determining its safety in use.This document describes a test that may be used to derive knowledge and to quantify the physical behaviour of a gun propellant grain at the low temperatures at which fracture or shatter is most likely to occur.
文摘Power Cartridges are pyrotechnic devices where hot combustion gases utilized to do mechanical work for disruption of suspected Improvised Explosive Devices(IEDs). It plays a vital role either in destroying the suspicious object or making them non-functional by generating the gas pressure on burning of propellant against the water column inside the barrel, Present work is focused on characterisation,numerical solution such as deformation; strain; stress using FEM(Finite Element Method), design qualification, performance and evaluation of power cartridge for disruptor application. Experimental trials for pressure-time(P-t) measurement in closed vessel(CV), various electrical parameters like all fire current(AFC), no fire current(NFC) and ignition delay have been measured. Further, mechanical properties for brass material have been determined. An attempt has been made to characterise the power cartridge by FEM and carrying out the experiments for water-jet application.
基金funded by the Defence Science and Technology Laboratory(Dstl)part of the UK MoD,under the Hazard Modelling and Simulation task of the UK Energetics(UK-E)programme now consumed by the Weapons Science and Technology Centre(WSTC)
文摘Propellants containing micro-aluminium particles have been shown to produce faster burn rates than conventional gun propellants.However,they are also more abrasive than conventional propellants.Nano-material propellants have been reported to give similar benefits to micron-material propellants but without the disadvantage of increased abrasion.Tests were conducted to compare the burn rates,ignitability and wear rates of a propellant loaded with 0% aluminium,15% micro-aluminium and 15%nano-aluminium.Closed vessel tests showed a burn rate increase of 39% in the range 30-250 MPa,and 70% at low pressure(50-100MPa)for the nano-aluminium propellant compared with the baseline propellant.The micro-aluminium propellant showed only a 10%increase in the burn rate compared with the standard propellant.The ignition delay for the nano-aluminium propellant was slightly shorter than that of the baseline propellant.Substantially increased wear rates were measured for the micro-aluminium propellant.The nano-aluminium propellant showed reduced wear rates compared with the micro-aluminium propellant but these were still substantially greater than those for the baseline propellant.
