Interior Ballistic Performance Research Articles

Optimization design in single wagon-wheel fuel grain of hybrid rocket motor

The grain design of hybrid rocket motor is a design of proper fuel grain geometry and flow adjustment scheme based on the total impulse, thrust, chamber pressure, length and outer diameter of combustion chamber. And the laws of various parameters in the working process of motor are obtained through the internal ballistic calculation. Based on the overall indicators of the upper stage motor of launch vehicles, the grain design process of single wagon-wheel and the internal ballistic calculation of adjusting the oxidizer flow according to the thrust feedback under the preset thrust condition are established. According to the indicators of power system, the constant thrust is F=11kN, the total impulse is I≥1100kN·s, the outer diameter is Dt≤400mm and the chamber length is L≤1000mm. Furthermore, the comparison and optimization design on star-shaped and single wagon-wheel grain are carried out. The oxidizer is 98% hydrogen peroxide (HP), the fuel is hydroxyl-terminated polybutadiene (HTPB) based fuel (including 58% Al), and the optimal oxygen-fuel ratio (O/Fopt) is 1.3. According to the theory of constant regression rate of the burning surface, the changes of the burning line length and channel area of the single wagon-wheel grain with the regression of the combustion surface are calculated. The results show that when the expansion ratio is 100 and average combustion chamber pressure is 5 MPa, the burning area of single wagon-wheel grain increases by 16.9% compared with the star-shaped grain, the O/F is reduced during motor operation, and the average specific impulse of the engine is increased by nearly 2%. In this paper, a typical uniform-thickness single wagon-wheel fuel grain is adopted. According to the optimization design, when the spokes number is 6, the average specific impulse of the motor is the largest. With increasing the spokes angle coefficient, increasing the height of the spokes, and reducing the angle of the spokes, the burning area is increased and the channel area is reduced, thereby the regression rate and fuel flow are increased and the O/F is reduced during the working process. Then the average specific impulse and overall performance are improved. This research provides a reference for single wagon-wheel fuel grain of hybrid rocket motor, calculation of interior ballistic performance under preset thrust, and flow adjustment by thrust feedback.

Numerical investigation of a muzzle multiphase flow field using two underwater launch methods

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.

Burning characteristics of high density foamed GAP/CL-20 propellants

The monolithic foamed propellants with high densities were prepared by casting and two-step foaming processes. Glycidyl azide polymer (GAP) and isocyanate were used as the binder system and 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazaisowurtzitane (HNIW, CL-20) was employed as the energetic component. The newly designed formulation containing 60 % CL-20 produced a force constant of 1077 J/g and low flame temperature of 2817 K. Two foamed propellants with densities of 1.32 g/cm3 and 1.53 g/cm3 were fabricated by a confined foaming process and examined by closed bomb tests. The results revealed that porosity significantly affects burning performance. A size effect on combustion behaviors was observed for the foamed propellant with 5.56 % porosity, and a double-hump progressive dynamic vivacity curve was obtained. At last, the 30 mm gun test was carried out to demonstrate the interior ballistic performance, and the muzzle velocity increased by 120 m/s at the same maximum chamber pressure when monolithic propellant was added in the charge.

Combustion Performance of Spherical Propellants Deterred by Energetic Composite Deterring Agents.

In order to achieve ideal burning progressivity and reduce harmful phenomena such as muzzle flame and smoke, energetic composite deterring agents (ECDAs) deterring spherical propellants were designed and prepared. The combustion performance of ECDA-deterred propellants was characterized by a closed vessel, and the interior ballistic performance was studied by a ballistic gun. High-speed photography and a smoke box were employed to capture muzzle flames and smoke. The results showed that triethylene glycol dinitrate (TEGDN) had a slight deterring effect weaker than that of poly(neopentyl glycol adipate) (PNA) on the propellants. The maximum pressure in the closed vessel bore of the ECDA-deterred propellants was 2.29 MPa higher than that of the dibutyl phthalate (DBP)-deterred propellants, though the L–B curve of the ECDA-deterred propellants was slightly lower and its combustion time was 0.44 ms longer. For ECDA containing 5 wt % PNA and 3.2 wt % TEGDN, 80 °C and 150 min are the best deterring conditions. The average velocity of the bullet propelled by ECDA-deterred propellants was increased by 93.4 m·s–1, while the average maximum pressure in the gun bore was decreased by 19 MPa, compared with the original propellants. The muzzle flame and smoke of the ECDA-deterred propellants were significantly reduced compared with the DBP-deterred propellants, where the smoke concentration was reduced by up to 44.5%.

A calculation method of interior ballistic two-phase flow considering the recoil of gun barrel

The theory of interior ballistic two-phase flow (IBTPF) is the primary means to study the distributions of physical quantities in gun chamber. In previous calculations, the gun breech is usually simplified as a fixed wall boundary, totally ignoring the effect of gun barrel recoil on interior ballistic processes. Thus to truly describe the interior ballistic process of the self-propelled gun (SPG), the transfer matrix method of multibody system (MSTMM) is combined with the theory of IBTPF in this paper. By simultaneously solving the generalized coordinate equations of multibody system and the conservation equations of IBTPF, the gun barrel recoil is converted to the moving boundary of the gun breech, and a more accurate calculation method of IBTPF is established. The results show that the simulated vibration characteristics, dynamic response during launch as well as interior ballistic performance of the SPG are all in good agreement with test values. Compared with no recoil, the gun barrel motion affects the growth regularity of the chamber volume behind the projectile, and eventually results in the changes of interior ballistic performance indexes such as maximum breech pressure and muzzle velocity. Overall, this study provides a more accurate prediction and simulation tool to enable better insight into such complicated interior ballistic processes, which is of great significance to the launch safety analysis and subsequent ballistic calculations.

Analysis of interior ballistic performance degradation of a worn gun barrel based on finite element method

A comprehensive accelerated life test of a 12.7mm caliber barrel gun barrel was carried out to study the variation in interior ballistic performance during the lifespan of a large- caliber machine gun. The wear mechanism at different positions in the bore was analyzed, and the wear data for the bore was obtained from the test. On this basis, a three-dimensional barrel- wear finite element model was established using the parametric model-ing method. The variation law of interior ballistic performance and the influence of wear location on ballistic performance were studied. The results showed that, after shooting 4300 rounds, the radial swing of the projectile head at the muzzle reached 0.35 mm and the projectile rotational speed decreased by 57.5% compared with the unworn performance. In addition, the wear on the initial position of the rifling not only caused the swing of pro-jectile in the barrel, but also aggravated the wear of other parts of the inner wall. The wear at the muzzle had a more obvious effect on the rotational speed of the projectile. Finally, it was concluded that the fundamental reason for interior ballistic performance degradation was wear on the initial position of the rifling.

Design optimization for a launching system with novel structure

A launching system with novel structure using optimization method is investigated to improve the muzzle velocity of guns in this article. This system has two tandem chambers of which the front one is ignited first and the other is ignited after a while. The launching process of this novel system is modelled and a series of different schemes are simulated, to discover the interior ballistic performance of this novel launching system. In order to obtain the optimal loading conditions, an optimization model combined with the combustion model is established. The optimal schemes can improve the muzzle velocity by 20.6% without changing the parameters of barrel. It means that this novel launch system could improve the interior ballistics performance significantly and it still has considerable potential to be ameliorated.

Study on the analysis method on ballistic performance of deterred propellant with large web size in large caliber artillery

As for the characteristics of combustibility of deterrent propellant with large web size which is used in large-caliber gun and interior ballistic performance, the combustion characteristics of deterrent propellant are obtained by using closed-bomb experiments. The combustion law of deterrent propellant and the classic interior ballistic model of composite charge are given. By simulation and analysis the results of the artillery firing test, the burning rate variation law and the interior ballistics simulation parameters of propellant A are determined, and the burning rate relationship between propellant A and propellant B obtained from closed-bomb, then the ballistic performance of propellant B is predicted. The results show that the predicted results are in good agreement with the experimental results. The study shows that the burning rate law of deterrent propellant with large web size can be obtained by closed-bomb experiment. Using the method provided in this paper can accurately predict the interior ballistic performance and provide an important basis for improving the accuracy of interior ballistic calculation.

Study on Dynamic Burning Rate Equation of Propellant

Aiming at the difficulty that the actual burning law of propellant in the gun bore couldn't be described exactly by static burning rate equation in the closed-bomb, propellant dynamic burning rate equation and its acquisition method were established in the paper, which are based on static burning rate equation and considering burning gas flow and loading density influence factors in bore. A numerical code for interior ballistic two-phase flow was successfully developed. And corresponding firing tests were also carried out. The comparison of simulations with interior ballistic code and firing test results show that the propellant dynamic burning rate equation makes the maximum errors of muzzle velocity and pressure in breech decreased from 2.97 % to 0.75 % and from 6.68 % to 0.38 %, respectively. This method not only improves simulation precision of gun muzzle velocity and pressure significantly, but also provides a means to improve the design accuracy for interior ballistic performance.

Low Acceleration Overload Catapult Technique for Throwing the Small Scout Robot

The small scout robot is generally thrown into the war zone by soldier. The short thrown distance and the danger of soldier exposed to the enemy limit the application of the small scout robot. So this paper presents a type of low acceleration overload catapult device of no flash, no smoke and no sound. It can throw the small scout robot covertly to long distances with low acceleration overload, and avoid the danger that soldier be exposed to the enemy when artificial throwing. The high and low pressure chambers of the catapult device achieve the low acceleration overload launching, and eliminate the risk of robot damaged by huge acceleration overload. The covert launching of no flash, no smoke and no sound is achieved by the piston to seal the gun propellant gas in barrel. Based on the interior ballistic model, the interior ballistic performance is calculated. The experiment for measuring the acceleration overload of the projectile is achieved by using the catapult device prototype and the measurement system developed by authors. The simulation and test results show that this catapult device can meet the requirement to throw the small scout robot into the war zone.

3D numerical simulation and analysis of railgun gouging mechanism

Abstract A gouging phenomenon with a hypervelocity sliding electrical contact in railgun not only shortens the rail lifetime but also affects the interior ballistic performance. In this paper, a 3-D numerical model was introduced to simulate and analyze the generation mechanism and evolution of the rail gouging phenomenon. The results show that a rail surface bulge is an important factor to induce gouging. High density and high pressure material flow on the contact surface, obliquely extruded into the rail when accelerating the armature to a high velocity, can produce gouging. Both controlling the bulge size to a certain range and selecting suitable materials for rail surface coating will suppress the formation of gouging. The numerical simulation had a good agreement with experiments, which validated the computing model and methodology are reliable.

Theoretical study on ignition compensating temperature sensitivity

Temperature sensitivity of the propellant has significant influence on the interior ballistic performance of guns. Many physical and chemical approaches are employed to decrease this temperature sensitivity of the propellant. In this article, it is proposed that the temperature sensitivity of the propellant is changed by altering the factors required to ignition. A one-dimensional two-phase flow interior ballistic model is established to analyze the relation between ignition factors and temperature sensitivity. The simulation results show that the propellant temperature sensitivity is changed by altering the ignition factors. That is, the interior ballistic performance is affected by altering the size of fire hole, breaking liner pressure, and ignition location. Based on the simulation results, the temperature sensitivity can be controlled by matching of charges and intelligent control ignition system.

Modeling of combustion and propulsion processes of a new concept gun using a gaseous propellant

The combustion light gas gun (CLGG) uses a low molecular weight gas as the propellant to burn, expand and propel the projectile out of the barrel with higher muzzle velocities. In order to better understand the interior ballistic process of CLGG, an multidimensional combustion and flow model for CLGG is established. It contains unsteady Reynolds-averaged Navier-Stokes (RANS) equations, the RNG k-ε two equation turbulence models, and the Eddy-Dissipation Model (EDM) of combustion. Simulation of the interior ballistic process of CLGG is carried out with a propellant of hydrogen and oxygen mixture charged at a particular initial condition. Results show that the spherical front flames spread from the ignition points which divide the flow field as burned and unburned regions in the initial period and expand to the whole flow field subsequently. The filling error of propellants in the chamber will affect the interior ballistic performance, but the impact is relatively small.

Study on the Burning of the Modified Single Base Gun Propellant

The modified single base gun propellant (MSBP) was prepared from single base propellant grain by impregnation with blasting oil, followed by deterring with deterrent in water medium. The combustion performance of this propellant was investigated by means of closed-bomb, interior ballistic and barrel erosion test. The interior ballistic property of this propellant after accelerated aging at high temperature was researched, too. Compared with the single base gun propellant, the MSBP burns more progressively and the value of Pr increases from 0.035 to 0.445. The interior ballistic performance for this propellant charge is improved obviously. The muzzle velocity increases by 5.0% from 886.6 m/s to 931.3 m/s. The MSBP has the characteristic of low temperature sensitivity and the barrel erosion of this propellant decreases by 16.6% at least. The interior ballistic performance of the MSBP has slightly changes after long-term storage. The MSBP has the advantages of higher muzzle velocity, higher combustion progressivity, low temperature sensitivity, low erosion and it can be satisfied with the actual storage demand.

Improvement of Interior Ballistic Performance Utilizing Particle Swarm Optimization

This paper investigates the interior ballistic propelling charge design using the optimization methods to select the optimum charge design and to improve the interior ballistic performance. The propelling charge consists of a mixture propellant of seven-perforated granular propellant and one-hole tubular propellant. The genetic algorithms and some other evolutionary algorithms have complex evolution operators such as crossover, mutation, encoding, and decoding. These evolution operators have a bad performance represented in convergence speed and accuracy of the solution. Hence, the particle swarm optimization technique is developed. It is carried out in conjunction with interior ballistic lumped-parameter model with the mixture propellant. This technique is applied to both single-objective and multiobjective problems. In the single-objective problem, the optimization results are compared with genetic algorithm and the experimental results. The particle swarm optimization introduces a better performance of solution quality and convergence speed. In the multiobjective problem, the feasible region provides a set of available choices to the charge’s designer. Hence, a linear analysis method is adopted to give an appropriate set of the weight coefficients for the objective functions. The results of particle swarm optimization improved the interior ballistic performance and provided a modern direction for interior ballistic propelling charge design of guided projectile.

Two Phase Flow Modeling of the Interior Ballistics for a Naval Medium Caliber Gun with Guided Projectile

This paper discusses the two phase (gas/Particles) flow effect of interior ballistic performance in a 76 mm naval medium caliber gun with guided projectile, using granular seven-perforated propellant. The theoretical and numerical simulation of the two phase flow in the interior ballistic cycle is carried out by using MacCromack technique depending on the governing equations of the two phase flow. This simulation is considered to be helpful for the prediction of the interior ballistic parameters which are required for endurance of guided projectile. A good agreement between the simulation results compared to the experimental results is fulfilled. Keywords: Guided projectile, two phase flow modeling, Interior ballistic, Computational fluid dynamics.

Interior Ballistic Modeling and Simulation for Different Charge Zones in Modular Charge System

The modular charge is developed to replace the conventional bagged charge systems for many advantages. In the interior ballistic cycle of a modular charge system, the nonsimultaneous ignition of propellant in different cases results in an increasing pressure wave, and can cause a launch safety problem of the gun. Because the charge structure is complicated, it is hard to simulate the interior ballistics process for the modular charge system currently. To simulate the interior ballistic of the modular charge system more accurately, an improved interior ballistic one-dimensional two phase flow model for modular charge system is established. The improvement of this model lies in that it takes account of the discontinuity of the propelling charge bed, the block of the cartridge wall to the flame spreading in propelling charge bed, effects of modular cartridge movement to the interior ballistic performance, the nonsimultaneous breakup of the modular charge cartridges, the ignition of the propelling charge in different cartridges, and flame spreading through the cap of the core tubes. Simulation for a full charge and three lower charge cases with different charge position were carried out based on the model. The simulation results proved that the model is reliable, and can be used to study the effects of cartridge mechanical properties, charge position, different charge zones on interior ballistic performance of modular charges.

A Novel Interior Ballistic Prediction of Gun Propellants Based on Experimental Pressure-Apparent Burning Rate Model in Closed Vessel

A new experimental pressure-apparent burning rate model was established based on the recorded pressure-time data in the closed vessel to study the actual burning gas generate rate of a propellant whose form function is not available. The new burning model can replace the Vieille’s law and form function of propellants in the interior ballistic equations to predict the interior ballistic performance of gun. As distinct from the traditional geometric form function based burning rate model, the new model introduced the concept of relative pressure impulse related to the actual burnt web thickness of propellant statistically. The apparent burning rate was expressed by the propellant mass fraction burnt vs. relative pressure impulse curve. The interior ballistic simulation of selected gun propellants was conducted using the new burning rate model. The results predicted by the new model show a good agreement with the classic interior ballistic predication results though the agreement with the experimental results is still to be improved.

The Influence of Loaded Conditions on the Interior Ballistic Performance

This paper mainly studies the change rules of interior ballistic performance under different loaded conditions, especially the maximum pressure and the muzzle velocity. There are six parameters affect the performance. The results show that, changing one of the all parameters, the maximum pressure and velocity will be increased with the increase of propellant shape coefficient χ; increased with the charge increases; increased as the propellant force increases; decreased with the chamber volume becoming bigger; increased with the engraving pressure increases; the maximum pressure increases while the velocity decreases with the mass of the projectile increases. In order to improve the interior ballistic performance, these loaded conditions must be paid attention.

Simulated Annealing Algorithm Optimization of the Deterred-Coating Propellant Charge Design

In order to get better interior ballistic performance of deterred-coating propellant charge (DCPC), the simulated annealing algorithm optimization of DCPC carries out in this paper. The interior ballistic model of DCPC and its model of simulated annealing algorithm optimization are established based on the characteristics of deterred-coating propellant. Two key parameters of DCPC, the mass ratio of deterred-coating propellants to total propellants and the average perforation pressure of deterred-coating propellant，are optimized for the search of the maximum muzzle velocity under the restricting conditions of maximum chamber pressure and the maximum relative end point of combustion. The optimization results agree well with the standard charge parameters, which justifies the feasibility of the model.