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.

Solid Rocket Motor Combustion Instability Modeling in COMSOL Multiphysics

Abstract: Combustion instability modeling of Solid Rocket Motors (SRM) remains a topic of active research. Many rockets display violent fluctuations in pressure, velocity, and temperature originating from the complex interactions between the combustion process, acoustics, and steady-state gas dynamics. Recent advances in defining the energy transport of disturbances within steady flow-fields have been applied by combustion stability modelers to improve the analysis framework [1, 2, 3]. Employing this more accurate global energy balance requires a higher fidelity model of the SRM flow-field and acoustic mode shapes. The current industry standard analysis tool utilizes a one dimensional analysis of the time dependent fluid dynamics along with a quasi-three dimensional propellant grain regression model to determine the SRM ballistics. The code then couples with another application that calculates the eigenvalues of the one dimensional homogenous wave equation. The mean flow parameters and acoustic normal modes are coupled to evaluate the stability theory developed and popularized by Culick [4, 5]. The assumption of a linear, non-dissipative wave in a quiescent fluid remains valid while acoustic amplitudes are small and local gas velocities stay below Mach 0.2. The current study employs the COMSOL multiphysics finite element framework to model the steady flow-field parameters and acoustic normal modes of a generic SRM. The study requires one way coupling of the CFD High Mach Number Flow (HMNF) and mathematics module. The HMNF module evaluates the gas flow inside of a SRM using St. Robert's law to model the solid propellant burn rate, no slip boundary conditions, and the hybrid outflow condition. Results from the HMNF model are verified by comparing the pertinent ballistics parameters with the industry standard code outputs (i.e. pressure drop, thrust, ect.). These results are then used by the coefficient form of the mathematics module to determine the complex eigenvalues of the Acoustic Velocity Potential Equation (AVPE). The mathematics model is truncated at the nozzle sonic line, where a zero flux boundary condition is self-satisfying. The remaining boundaries are modeled with a zero flux boundary condition, assuming zero acoustic absorption on all surfaces. The results of the steady-state CFD and AVPE analyses are used to calculate the linear acoustic growth rate as is defined by Flandro and Jacob [2, 3]. In order to verify the process implemented within COMSOL we first employ the Culick theory and compare the results with the industry standard. After the process is verified, the Flandro/Jacob energy balance theory is employed and results displayed.

Study on Burning Rate Inhibitors of HTPB/AP/Al Propellants

Abstract: The effect of ammonium oxalate,lithium fluoride,calcium carbonate,strontium carbonate,quaternary ammnium salt and etc.as burning rate inhibitors on burning rate of HTPB/AP/Al propellant have been investigated.Considerable decrease in burning rate has been observed when quaternary ammonium salt composite with carbonate or lithium fluoride are used as depressant,and above-mentioned composite inhibitors have excellent effect on decreasing the burning rate of propellants.In HTPB/AP/Al propellants,the quaternary ammonium salts composite with carbonates are more pronounced on decreasing burn rate than ammonium oxalate inhibitor which is now used for many practical low burning rate propellant.The firing tests of BSFФ75mm motors indicate that quaternary ammonium salt composite with carbonate also could decrease the pressure exponent of the propellant from 0.33 to 0.20 in the pressure range of 3.45～12.17MPa.The firing test of BSFФ165mm motors loaded with HTPB/AP/Al propellant grain containing quaternary ammonium salt and carbonate as inhibitor gives more stable chamber pressure-time and thrust-time histories than that containing ammonium oxalate,and the results show that the density-specific impulse of obtained formulation is 2.8% higher than that containing ammonium oxalate with the same burning rate.

Combustion Property Character of Variable-burning Rate Gun Propellant

Abstract: The principle and realizable approach of variable-burning rate propellant, the burning rate of inner layer is higher than that of the outer layer are introduced. The combustion character of two layered variable-burning rate propellant in closed bomb test is analyzed and the interior ballistic performance on 30mm gun is construced. Contrast with single base gun propellant with polymer coating layer, the two-layered variable-burning rate propellant has good properties of progressive combustion and low temperature coefficient.

The Optimization of Base Bleed Grain Parameters for Maximum Ballistic Performance

Abstract: Solid propellant Base bleed unit is one of the effective methods to increase the range of artillery projectiles. As far as we search, no published study focuses on the optimal dimensions of the base bleed grain. However, few studies focus on the effect of base bleed grain parameters on its ballistic performance in which each parameter was studied separately. The present optimization study is performed on base bleed grain which performed as longitudinally slotted tubular cylinder. Different case studies have been introduced according to the number of design variables which are: grain outer, inner radius, length, burn rate, base bleed grain unit orifice diameter. Moreover, the study is extended to demonstrate the effect of these parameters on the innovative multi-burn rate base bleed grain. In this new idea, the grain is splitted into two horizontal parts one with higher burn rate than the other part. The idea is to have a grain that provides high mass flow rate in the first seconds of projectile flight, while keeping long bleeding time. The optimization constrains are the upper and lower limits of each design variable. An analytical model has been developed in C++ environment to accurately evaluate the range of the projectile. This model is then utilized in combination with design of experiment (DOE) and the response surface method (RSM) to develop a smooth response function which can be effectively used in the design optimization formulation as the objective function. The objective of the optimization is to find the design variables which contribute the maximum range.

Measurement of solid propellant burning rates during rapid depressurization

Abstract: : A microwave continuous measurement technique has been used to measure burning rates of a carboxyl-terminated polybutadiene and ammonium perchlorate composite solid propellant during rapid decompression. A microwave signal oscillating at a known source frequency is passed through the end of a burning propellant strand opposite the burning surface and allowed to reflect off the burning surface. By continuously comparing the phase angle of this reflected signal with the phase angle of another signal oscillating at the original source frequency, a relative phase angle of another signal oscillating at the original source frequency, a relative phase angle between the two signals is obtained. The rate of change of this relative phase angle with time is proportional to the propellant's burning rate. Possible errors were investigated and conclusions reached concerning them.