Burn rate (chemistry)

About: Burn rate (chemistry) is a research topic. Over the lifetime, 847 publications have been published within this topic receiving 8908 citations. The topic is also known as: Burning rate.

Development and characterization of high performance solid propellants containing nano-sized energetic ingredients

Abstract: This paper addresses the development of a pair of layered solid propellants suitable for use in a fast-core gun-propellant charge application. A baseline propellant combination was formulated using RDX particles and thermoplastic-elastomer binder as the major ingredients and CL-20 and nitroguanadine as separate additives for high- and low-energy propellants. The propellant’s burning rate was characterized and insufficient burning-rate ratio between the fast and slow baseline propellants was found. Impetus obtained from the combustion of the combined baseline propellants was also found to be far from the demanded value of 1300 J/g. Several modifications were made by introducing nano-sized aluminum particles and ultra-fine boron particles as well as high-energy oxidizer HNF into the propellant formulation. It was found that the addition of nano-sized aluminum particles can enhance the propellant burning rate only when the propellant contains oxidizers with a positive oxygen balance. Without the presence of positive oxygen balance oxidizer, the exothermic reaction of aluminum and boron particles occurs at a large distance from the burning surface introducing an energy-sink effect. The results obtained from the combustion of the advanced propellants show that an average impetus of 1299 J/g, a flame temperature of 3380 K with a burn rate ratio around 3 between the fast- and the slow-burning layers can be achieved. These conditions are desired for fast-core layered propellant applications. The impact sensitivities of the baseline, intermediate and advanced propellants were measured. The results show that addition of HNF and nano-sized aluminum exhibited improved impact sensitivity at levels that can be considered acceptable for deployment.

Theory of Flame Front Propagation in Porous Propellant Charges under Confinement

Abstract: : Ultra-high burning rates can be achieved by combustion of porous media. A theoretical model is developed to describe the flame propagation in a packed bed of granular propellant. The calculated pressure-time-distance transients, wave propagation speed, and mass fraction of propellant burned during flame propagation, all agree well with experimental data obtained for the same conditions. Results demonstrate that the combustion-generated strong pressure gradient causes the hot product gas to deeply penetrate the unburned region. A continental divide forms automatically in the pressure distribution as the wave progresses into the charge. In the particular case studied the flame front reaches a speed about 5000 times the normal propellant burning rate and continues to accelerate as the internal pressure increases. (Modified author abstract)

Solid Rocket Motor Internal Ballistics Simulation Using Three-Dimensional Grain Burnback

Abstract: Internal ballistics simulations of solid rocket motors have been conducted with the propellant grain's 3-D burning surface geometry described by a new minimum distance function approach and the internal flowfield represented by 1-D, time-dependent, single-phase compressible flow equations. The combustion model includes erosive burning and unsteady, dynamic burning corresponding to transient energy storage in the heated surface layer of the propellant. The integrated internal ballistics code (Rocballist) is used to investigate the role of these two burning rate augmenting mechanisms in solid rocket motor performance. Two tactical motors are used as test cases. Results indicate that dynamic burning can be the dominant factor in producing a short-duration ignition pressure spike in low-L* motors, particularly if the L/D ratio is not too large and the port cross section is nonrestrictive (e.g., center perforated grain). However, when L/D is large and the port cross section is noncircular in the aft section (aft fins/slots), erosive burning can take over in dominating the burning rate to the extent that an otherwise progressive pressure-time trace becomes regressive/neutral. That is, erosive burning can effectively prolong the initial pressure spike in some star-aft motors. The results also show that with sufficiently accurate models of dynamic burning and erosive burning, it is reasonable to expect reliable internal ballistics predictions with suitable simplified flowfield models, thereby realizing significant reductions in computation time compared with 3-D, multiphase reacting flow simulations.

Burn Rate Measurements of HMX, TATB, DHT, DAAF, and BTATz

Abstract: : In this paper we present new burn rate results for several energetic materials. The burn rates of octahydro- 1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), HMX and estane-based binder (PBX 9501), 1,3,5-triamino- 2,4,6-trinitrobenzene (TATB), and TATB and KelF binder (PBX 9502), are reported and compared with existing data. Burn rate data of these common explosives complement and extend existing data sets. Burn rate data of three novel high-nitrogen materials are presented in this work. Specifically, the high-nitrogen monopropellants considered are 3,6-dihydrazino-s-tetrazine (DHT), 4,4'-diamino-3,3' -azoxyfurazan (DAAF), and 3,6-bis(1H-1,2,3,4-tetrazol-5-amino)-s-tetrazine (BTATz). High-nitrogen compounds may be key to meeting the advanced performance objectives of next-generation solid propellants. High-nitrogen solids offer the possibility of high performance, reduced emissions, and lower plume signature (low temperature and no HCl) than current propellant systems. The theoretical specific impulse is comparable to HMX. In contrast to HMX, however, high-nitrogen materials tend to be insensitive to impact. Because high-nitrogen energetic materials have intrinsically large positive heats of formation and produce low-molecular-weight reaction products, they may be suitable for consideration in high-performance propellant applications. BTATz appears particularly interesting because of its rapid burn rate, relatively low-pressure exponent, and high heat of formation. The effect of a small amount of binder is investigated for all but one of these materials.

Cigarette sidestream smoke and free-burn rate control device

Abstract: A device for minimizing cigarette sidestream smoke and reducing free-burn rate of a burning cigarette, the device comprises: i) a non-combustible tubular element (12) encasing an effective length of a tobacco charge (22) of a cigarette (14) located in the tubular element; and ii) the tubular element having a means for both minimizing sidestream smoke emission from a burning tobacco charge and reducing free-burn rate of such burning tobacco charge to increase number of puffs from the burning tobacco charge.