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.

Regression fronts in random sphere packs: Application to composite solid propellant burning rate

Abstract: The burning rate of a composite solid propellant may be estimated by global modeling, such as the widely used BDP model. The backbone of such models is the “mixture law” that links the propellant burning rate rp with the burning rate of its own components, i.e., oxidizer rox and binder rb. However, different laws are available in literature which all read: 1/rp = q(ξ)/rox + (1 − q(ξ))/rb, with q(ξ) a function of oxidizer volume fraction ξ. This work attempts in analyzing numerically the validity of those empirical formulations by surface regression computation. Composite propellants are modeled by a random packing of monomodal spheres and the evolution of the regression front is computed via the resolution of Hamilton–Jacobi equations. It is shown that the popular choice q(ξ) = ξ is fairly valid but only provided that burn rate ratio Z = rox/rb is about 1. When Z > 1, combustion surface is no longer plane and global burning rate deviates from postulated laws. A special regime is also noticed for high rate ratio Z (typically Z > 5) because combustion then preferentially takes place through adjacent oxidizer particles. Computed results occur to be correctly modeled by percolation theory. This hints that percolation is a common feature of propellant combustion and a critical percolation threshold on volume fraction is numerically found to be about ξc ∼ 0.2. First validations show encouraging correlations with experimental data.

Solid Strand Burn Rate Technique for Predicting Full-Scale Motor Performance

Abstract: : The objective of this program was to perform and evaluate solid strand burn rate measurements on the Titan 3 propellant taken from cartons which were cast during motor manufacture. The results of this evaluation would determine if the solid strand burn rate technique would be an acceptable approach toward re-establishing the correlation between full-scale motor performance, and small ballistic test motors, and liquid strand burn rate tests. The effects of strand preparation, sample selection, burn rate variability within the carton, and particle orientation were briefly investigated. During the program, an improved monitoring system was developed and demonstrated.

Study on Friction Sensitivity of Passive and Active Binder based Composite Solid Propellants and Correlation with Burning Rate

Abstract: Friction sensitivity of composite propellants and their ingredients is of significant interest to mitigate the risk associated with the accidental initiation while processing, handling, and transportation. In this work, attempts were made to examine the friction sensitivity of passive binder: Hydroxy Terminated Polybutadiene/Aluminium/Ammonium Perchlorate and active binder: (Polymer + Nitrate Esters)/Ammonium Perchlorate/Aluminium/Nitramine based composite propellants by using BAM Friction Apparatus. As per the recommendation of NATO standard STANAG–4487, the friction sensitivity was assessed by two methods: Limiting Frictional load and Frictional load for 50% probability of initiation (F50). The test results showed that the active binder based formulations were more vulnerable to frictional load as compared to the formulations with passive binders. Examination of a comprehensive set of propellant compositions revealed that the particle size distribution of Ammonium Perchlorate and burn rate catalysts were the most influential factors in dictating the friction sensitivity for HTPB/Al/AP composite propellants. For active binder/AP/Al/Nitramine composite propellants, the formulation with RDX was found more friction sensitive with a sensitivity value of 44 N as compared to its HMX analog (61 N). The correlation studies of friction sensitivity, burning rate, and thermal decomposition characteristics of HTPB/Al/AP composite propellants is described.

Modeling techniques for liquid propellant rocket combustion processes

Abstract: A qualitative physical processes description of stable and unstable combustion in rockets is presented to establish the basis for choosing model hardware design criteria. It is concluded that it is not possible to scale rocket combustion processes in the usual sense of the term. The studies conducted at Rocketdyne have shown that model chambers which satisfactorily model the steady state behavior of large engines must be designed to maintain (1) the propellant injection density, and (2) the chamber to throat contraction ratio (hence chamber pressure). For studies of destructive acoustic modes of combustion instability a third parameter, the frequency, must also be maintained.

Deuterium isotope effects during RDX combustion : mechanistic burn rate-controlling step determination

Abstract: High pressure (500 psig/3.55 MPa and 1000 psigl6.99 MPa) burn rate comparisons from the combustion of solid RDX (hexahydro- 1.3,.5-trinitro-1,3,5-triazine) and perdeuterio-labeled RDX-dh cylindrical pressed pellets reveals a large kinetic deuterium isotope cffect (KDIE). This experimental KDIE confirms that chemical reaction kinetics are a significant mechanistic factor in controlling the inherent RDX burn rate and further shows the six-membered RDX hcterocycle's rate-controlling mechanistic step during com- bustion is the same as that previously reported for its larger eight-membered HMX (octahydro-l.3,5,7-tetranitro-l.3.5,7 tetrazocine) homologuc. As with HMX. This experimental KDTE approach also demonstrates a direct mechanistic relationship between RDX's higher order cornbustion regime and its ambient pressure thermochemical decomposition process.