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.

DNS Simulation of Erosive Burning in Planar Periodic Rockets

Abstract: We examine the combustion response of a flame anchored to two 1/4-spaces of solid fuel and oxidizer, a configuration relevant to the combustion of heterogeneous solid propellants. A time-periodic shear flow is applied to model the shear that can be generated by the presence of acoustics or turbulence in a rocket chamber. To estimate the magnitude and frequency of the shear for the case of a turbulent flow, we present DNS results of a planar periodic rocket, a configuration that has its roots in a multiscale analysis. Such a configuration allows for the determination of the shear parameters as functions of motor geometry and downstream location. The response of the flame to this shear, the heat flux to the surface, and the burning rate are calculated numerically. Significant enhancement to the burn rate, commonly known as erosive burning, is found.

Effect of magnesium metal in the characteristics performance of a sucrose-based solid rocket propellant

Abstract: This research work aimed at investigating the effects of magnesium metal (powder) and carbon on a potassium nitrate-sucrose (KNSU) solid propellant formulation. Characterization of propellant is very important to determine its performance before it can be suitable for use for a rocket flight or any mission. Ballistic loadcell method was used. The ballistic load cell instrumentation measured the thrust generated by the propellant, the propellant burn time and the exit temperature of the burning hot propellant gases. The carbon constituent which acts as an opacifier and coolant was kept constant at 2% in order to arrest some of the heat during the combustion process and helped to lower the combustion temperature, because high combustion temperature could lead to combustion chamber rupture or failure. Also, carbon was not increased beyond 2%, so as not to make the propellant excessively smoky because of presence of magnesium oxide and other solids in the combustion products that can cause air pollution, and could be harmful to human lives and the environment. The propellant specific impulse (117.9s), combustion temperature (1818K), heat ratio (1.1508), propellant molecular weight (38.88g/mole), propellant density (1874.6kg/m3), characteristics velocity (997.2m/s) and burn rate (0.00906m/s) were obtained. The effect of addition of magnesium which was optimized for 3% in the formulation contributed significantly in improving the overall performance of the propellant as parameters such as the specific impulse, chamber temperature, characteristics velocity and heat ratio were found to have higher values as compare to the KNSU propellant when magnesium was not present in the formulation. Basically, higher values of these parameters suggest better propellant performance. Also, in this case, when carbon was increased beyond 2%, the propellant was excessively smoky because of presence of magnesium oxide and other solids in the combustion products that can cause air pollution, and could be harmful to human lives and the environment.

Determination of gun propellant ballistic parameters with a focus on flame spread and grain dimensional variation

Abstract: In interior ballistic simulations, the burn time can be affected by the burn rate, propellant dimensions and flame spread. Standard IB models assume that grains are symmetric with no variation in dimensions, with instantaneous homogeneous ignition. This paper evaluates the contribution of grain dimensional variation (specifically the web), asymmetry and flame spread in a single base propellant with a single perforated grain geometry. It is shown that flame spread has the dominant effect on burn time, followed by web dimensional variation and lastly asymmetry. The implementation of these effects also leads to a simulated result that is more representative of the experimental curve in the closed vessel especially in the burnout phase.

Adiabatic Pyrolysis of Solid Propellants

Abstract: Several one-step, irreversible, zero-order pyrolysis models (Arrhcnius, KTSS, and Merzhanov Dubovitskii high activation energy pyrolysis), commonly used to study adiabatic burning of energetic materials with arbitrary pressure and initial temperature, are revisited. Motivated by experimental and theoretical work performed in 1984 by students of this laboratory, a relationship among the several interplaying parameters is found under steadystate conditions. This relationship corresponds to the Jacobian of the sensitivity parameters used in the Zeldovich Novozhilov approach. If the Vieille steady burn rate law is enforced, consistency requires an explicit pressure dependence for both Arrhenius and KTSS pyrolysis. But if the normal (or Zeldovich) steady burn rate is enforced, no explicit pressure dependence is required for both Arrhenius and KTSS pyrolysis. Other constraints arise for the Merzhanov Dubovitskii pyrolysis model. The unifying concept for these different trends is the Jacobian consistency between the implemented steady pyrolysis and ballistic laws. The dependence of the pre-exponential factor on surface activation energy (known as kinetic compensation) is shown to be linear (Arrhenius) or almost linear (Merzhanov Dubovitskii), for any given experimental data set under steady burning. Experimental results are reported for a variety of solid propellants of different nature. NOMENCLATURE * Copyright © 1997 by Luigi DeLuca. Published by the American Institute of Aeronautics arid Astronautics, Inc. with permission. ' Professor, Dipartimento di Energetica; Fax: (39-2) 2399-3940, e-mail: DeLuca@icil64.cilea.it. Associate Fellow. ' Professor, Dipartimento di Matematica ' PhD. Candidate, Dipartimento di Energetica ' Lab. Technician, Dipartimento di Energetica " MSc. Candidate, Dipartimento di Energetica a&, &(, = multiplicative factors denned by Eq. 3.3, Eq. 3.4 A, B = nondim. functions used in frequency response analysis Ac = multiplicative factor used in the Merzhanov-Dubovitskii pyrolysis, 1/s, in Eq. 2.3 AS, Bs = multiplicative factors defined by Eq. 2.1 (Arrhenius ), Eq. 2.2 (KTSS) c = specific heat, cal/g K £{...) = activation energy, cal/mole J5(...) = .Z?(...)/9J/T(...) , riondim. activation energy Is = external radiant flux intensity, cal/cmPs j = running counter, integer k = ZN steady sensitivity parameter defined in Eq. 6.3 ra = mass burn rate, g/crn s Ms = pre-exponential factor of Zeldovich (or normal) mass burn rate, g/cms, in Eq. 2.6 n = pressure exponent of ballistic steady burn rate defined by Eq. 2.4 n., = pressure exponent of pyrolysis law denned by Eq. 2.1 (Arrhenius ) and Eq. 2.2 (KTSS) IT-TS — pressure exponent of steady surface temperature defined by Eq. 3.1 p = pressure, atm Pref, Tref = reference pressure (68 atm), reference temperature (298 K) Q = heat release, cal/g (positive if exothermic) r =ZN steady sensitivity parameter denned in Eq. 6.4 rj, — burn rate, cm/s n,ref>TSiref = reference burn rate n(pref), reference surface temperature Ts(pTnf) 5R = universal gas constant; 1.987 cal/moleK T = temperature, K TI = initial propellant temperature, K ws = power of KTSS pyrolysis law, denned in Eq. 2.2 Greek Symbols a = thermal diffusivity, cm/s 8 = ZN Jacobian defined in Eq. 6.5 fj,, v = ZN steady sensitivity parameters defined in Eq. 6.2, Eq. 6.1 p = density, g/cm cTp = steady temperature sensitivity of burn rate, 1/K, denned by Eq. 2.4 T« = pressure exponent of surface temperature defined by Eq. 3.1 if} = variable defined in Eq. 4.19 Subscripts Arr = Arrhenius pyrolysis law bal = ballistic c = condensed g = gas hig = high KTSS = KTSS pyrolysis law low = low p = pressure pyr = pyrolysis ref = reference s = burn surface Vi = Vieille burn rate law Ze = Zeldovich burn rate law (...)1 = cold boundary value Superscripts (...) = steady-state value (...) = dimensional value (...) — average value