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.

Analysis of the combustion, burn rate, and grain structure of ammonium nitrate and badge based propellant

Abstract: A rocket solid propellant is a compacted grain of a mixture of a fuel, an oxidant, and a binder. During the combustion process it produces a flux of hot gases intended to produce work through a rocket propulsion system. Two important and most desirable characteristics of a solid propellant are grain high stability and non-toxic trace. Ammonium nitrate oxidant releases low production of toxic traces, such as nitrogen oxides and chlorinated compounds. As a binder, BADGE presents easy handling and good resistance to shock and humidity when cured in a grain. Grains of ammonium nitrate and BADGE with aluminum and iron oxide III, as catalysts, were built and tested. Three different formulations were tested with fixed 8% in mass of aluminum or iron oxide, and varying ammonium nitrate from 60% up to 75%. The measurements of burn rate were conducted in standard ambient temperature and pressure. Gravimetric comparison of ashes and calculation of burning products via numerical simulation methods were carried out. The results presented a significant relationship between the burn rate and the ammonium nitrate concentration. The use of aluminum and iron oxide modified this relationship due to changes in oxygen consumption dynamics, leading to a change in flame temperature. It was also shown that a presence of aluminum elevates the production of CO, while iron oxide III maintained approximated values of non-catalyzed process. The soot formation was present in all formulations.

Agglomerate Size Evolution in Solid Propellant Combustion under High Pressure

Abstract: Solid propellant combustion and flow are significantly affected by condensed combustion products (CCPs) in solid rocket motors. A new aluminum agglomeration model is established using the discrete element method, considering the burning rate and formulation of the propellant. Combining the aluminum combustion and alumina deposition model, an analytical model of the evolution of CCPs is proposed, capable of predicting the particle-size distribution of completely burned CCPs. The CCPs near and away from the propellant burning surface are collected by a special quench vessel under 6~10 MPa, to verify the applicability of the CCP evolution model. Experimental results show that the predicted error of the proposed CCP evolution model is less than 8.5%. Results are expected to help develop better analytical tools for the combustion of solid propellants and solid rocket motors.

Theory of nonsteady propellant combustion. Combustion in the presence of harmonically varying pressure

Abstract: It is shown that in order to construct a theory of nonsteady propellant combustion it is necessary to know the steady-state dependences of the burning rate u0 °, surface temperature Ts °, and flame temperature TF ° on the external parameters and the initial temperature of the propellant. The combustion processes in an unbounded space, when one of the external parameters varies according to a harmonic law, are examined within the framework of such a theory.

Linear Analysis of Erosive Burning in Solid Propellant Motors

Abstract: A theoretical investigation of the coupling between the core flow process and combustion sublayer process in a rocket chamber flow is presented. The focus of the investigation is on penetration of chamber disturbances into the sublayer and on the burn rate characteristic responses. Characteristic solutions to the local non parallel instability problem supported by gasifying propellant in a double slab geometry are sought. In the fully decoupled limit the only characteristic solution response is a pressure response, thus comparisons between coupled and decoupled pressure responses are presented. The propellant is typified by a set of burning characteristics, and their effect on the coupling is explored. The goal of the analysis is to clarify the extent strand burning characteristics (i.e., in zero cross flow conditions) can affect burn rate perturbations leading to the phenomenon of erosive burning. The findings of this research agree with experimental studies as it regards the effect of burning parameters on erosive behavior. Change in erosive sensitivity with propellant characteristics is thus correlated with a change in the core-sublayer interaction. n this paper we present an investigation of erosive burning in rocket motors by performing a linear analysis of the coupling between combustion sublayer and turbulent chamber flow. Erosive burning describes burn rate augmentation in solid rocket engines as a result of cross-flow conditions. Erosive burning is responsible for strong overpressure at the rocket firing stage. A better understanding of the influence of burning characteristics on erosive sensitivity can improve rocket design techniques and propellant choices. There have been many attempts to identify the mechanism responsible for the measured increase in burn rate over the zero-cross flow burn rate. “Flame bending”, “heat transfer from core to propellant surface”, “increase in heat flux due to turbulence” are classical examples. Most analyses have relied on empirical fits often based on turbulent profiles over a flat plate; none have been based on a rigorous analysis of the equations. Due to the large difference in length scales between combustion sublayer and chamber core flow, as discussed in more detail in §II of this paper, the development of the instability and the ensuing turbulent field are fairly independent of the burning characteristics. Therefore, the experimentally established link between erosive burning augmentation and propellant characteristics (e.g., King 3 ) cannot be resolved without hypothesizing an effect of the instability on the micron-size combustion profile; that is, hydro-dynamic considerations alone are not sufficient. Mukunda and Paul 2 argue that the effect of the burning characteristics can be taken into account by simply scaling the port mass flow rate by the strand value. Still, the proposed effect of the Reynolds number on erosive burning cannot be explained based on the relationship between the same parameter and the instability growth rate. The present paper attempts to provide a more rigorous analysis of the effect of burning parameters on the core flow-sublayer coupling by seeking characteristic solutions to the linearized and localized solid-gas fully-coupled problem. Although the linearized analysis does not provide a clear quantitative answer on the burning rate augmentation, burn rate eigenfunctions (fluctuation intensity) quantify the importance of

Solid Propellant Rockets

Abstract: Solid rocket motors and various solid propellant grain configurations are described. Burning rate and grain design effects on thrust-time tailoring are discussed, as well as the sensitivity of the solid propellant to temperature. Analysis of the transient behavior and equilibration of the combustion chamber pressure, the stability of the combustion chamber pressure, and the effects of erosive burning is presented. Solid rocket performance characteristics, dual-thrust solid rockets, rocket motor casings, and transient operation are discussed. Rocket motor nozzle heat transfer and ablative and film-cooling techniques are described. Hybrid rocket motors are introduced and their characteristics and operation are covered.