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.

Low Pressure Combustion of Composite Propellant

Abstract: The combustion behaviour of two batches of a new type of composite propellant was investigated in the pressure range between 5 kPa and 915 kPa absolute. A newly developed technique to determine simultaneously the burning rate, combustion efficiency, and the propellant's sensitivity for combustion instability is described together with a specially developed data reduction code. Notwithstanding the low pressure during the experiments no lower deflagration limit could be traced but a Vieille type burning rate law appeared to be applicable for the whole pressure range of interest. A large difference found in the combustion behaviour could be attributed to the fact that the two batches had been manufactured with AP from different suppliers. Combustion efficiency was poor while combustion instability occurred in the whole pressure range.

Solid propellant ignition studies: ignition of the reaction field adjacent to the surface of a solid propellant

Abstract: : The object of this research was to elucidate igni tion mechanisms of solid propellants, to identify the component processes, and to lay the basis for a theory of ignition. Experiments were performed in which composite propellant samples and polymeric fuel samples were exposed to high and low speed flows of oxygen containing gases at high temperature and pressure in a shock tunnel. Ignition of either propellant or fuel could not be obtained in high speed flows even in pure oxygen; in addition, no charring or decomposition of the fuel was observed. At low flow speeds, on the other hand, ignition of the composite propellant and the polymeric fuel did occur, and the ignition delay was found to depend on the gas phase oxygen concentration. The non-ignition at high flow speeds indicated that dilution or sweeping away of the gaseous reaction zone inhibited the ignition. Results strongly suggest that the site of ignition is in a gaseous reaction boundary layer adjacent to the surface of the propellant and not on the fuel surface itself.

Development of a dual-frequency microwave burn-rate measurement system for solid rocket propellant

Abstract: A DUAL-FREQUENCY microwave burn-rate measurement system for solid rocket motors has been developed. The system operates in the X-band (8.2-12.4 GHz) and uses two independent frequencies operating simultaneously to measure the instantaneous burn rate in a solid rocket motor. Computer simulation and limited laboratory testing of the system were performed to determine its ability to limit errors caused by secondary reflections and by uncertainties in material properties, particularly the microwave wavelength in the propellant. Simulations showed that the frequency ratio and the initial motor geometry determined the effectiveness of the system in reducing secondary reflections. Overall, the simulations showed that a dual frequency system can provide up to a 75% reduction in burn-rate error over that returned by a single-frequency system. The hardware and software for dual-frequency measurements was developed and tested; however, further instrumentation work is required to increase the data acquisition rate so its full potential can be realized.

Thermodynamic reaction drive

Abstract: A thermodynamic reaction drive or rocket engine which employs liquefiable solid propellant. An alkali metal, which is used as the propellant, is stored in the fuel tank of the rocket engine in the solid state and then, whenever engine operation is desired, liquefied by heating to the necessary temperature. The liquid propellant is fed from the fuel tank through a De Laval nozzle into the mixing or combustion chamber where it is combined with an oxidizer. The propellant, which can be forced through the nozzle primarily by means of its own vapor pressure, is changed over at the nozzle into a two-phase flow. The oxidizer, which is simultaneously introduced into the mixing chamber at a higher pressure than the pressure in the chamber, effects the combustion of the propellant so that the internal energy of the products of combustion may be converted to kinetic energy in an appropriate thrust nozzle.

Kinetic Modeling of Slow Energy Release in Non-Ideal Carbon Rich Explosives

Abstract: We present here the first self-consistent kinetic based model for long time-scale energy release in detonation waves in the non-ideal explosive LX-17. Non-ideal, insensitive carbon rich explosives, such as those based on TATB, are believed to have significant late-time slow release in energy. One proposed source of this energy is diffusion-limited growth of carbon clusters. In this paper we consider the late-time energy release problem in detonation waves using the thermochemical code CHEETAH linked to a multidimensional ALE hydrodynamics model. The linked CHEETAH-ALE model dimensional treats slowly reacting chemical species using kinetic rate laws, with chemical equilibrium assumed for species coupled via fast time-scale reactions. In the model presented here we include separate rate equations for the transformation of the un-reacted explosive to product gases and for the growth of a small particulate form of condensed graphite to a large particulate form. The small particulate graphite is assumed to be in chemical equilibrium with the gaseous species allowing for coupling between the instantaneous thermodynamic state and the production of graphite clusters. For the explosive burn rate a pressure dependent rate law was used. Low pressure freezing of the gas species mass fractions was also included to account for regions where the kinetic coupling rates become longer than the hydrodynamic time-scales. The model rate parameters were calibrated using cylinder and rate-stick experimental data. Excellent long time agreement and size effect results were achieved.