Experimental study of the combustion efficiency of two-phase gasification products of energetic boron-containing condensed compositions in a high-enthalpy airflow

This paper describes an experimental setup and a method for determining the combustion efficiency of the gas and condensed phases of gasification products of energetic boroncontaining condensed formulations in a high-enthalpy subsonic airflow. The results of investigation of the combustion of two-phase combustible mixtures in a channel of constant cross section at various temperatures, pressures, and component ratios are given. The combustion regularities of boron-containing condensed phases in a high-enthalpy airflow are identified. The obtained data can be useful in computational and experimental studies of propulsion system operation.     

Optical emission spectrum in combustion with formation of condensed reaction products

Broadband far ultraviolet (UV) emission (up to 200 nm) was recorded during combustion of heterogeneous systems with the formation of condensed reaction products. It was shown that UV emission occurred during combustion in various gases (He, Ar, and N₂) and had the highest intensity in helium at a pressure of 25 kPa. This emission is attributed to the chemiionization of gas, separation of charges in combustion products, and subsequent microbreakdowns.     

Experimental verification of models for induction heating of continuous-carbon-fiber composites

Heating of continuous-carbon-fiber-reinforced polymers (CFRPs) by the application of an alternating magnetic field has been shown to be due to dielectric losses in the polymer. Models that predict thermal generation in these composites are input to a finite element heat transfer analysis, providing the predicted transient thermal profile in the plane of the laminate. The validity of the global thermal generation model is established through an experimental test matrix in which various specimen configurations are evaluated and compared with theoretical predictions of transient surface temperatures.     

Analysis of unsteady solid-propellant combustion models (review)

Recent studies of solid-propellant combustion models are briefly analyzed. The models are divided into purely one-dimensional (classical and phenomenological models with various generalizations of the Zel’dovich approach) and non-one-dimensional. The latter include models with local non-one-dimensionality, which is always accompanied by local unsteadiness. This all can be eliminated by averaging. The main disadvantage of unsteady solid-propellant combustion models, which is no fault of their authors, is the same as in the case of steady-state models: the lack of detailed information on chemical and physical processes in the condensed phase. Impropriety of extending the purely one-dimensional approach to the instability region is noted. Possible directions for further development of unsteady (and quasi-steady-state) solid-propellant combustion models for homogeneous compositions may involve accounting for local non-one-dimensionality and the unsteadiness due to instability of the subsurface reactions zone and verification of the possibility of the existence of chemical instability capable of causing similar non-one-dimensionality and unsteadiness. __________ Translated from Fizika Goreniya i Vzryva, Vol. 44, No. 1, pp. 35–48, January–February, 2008.     

Fractal structure and features of energy-release (combustion) processes in heterogeneous condensed systems

In this work, the theory of fractals has been used to describe the structure of heterogeneous condensed systems (HCS). Features of energy-release processes with variation of the initial structure parameters have been investigated. The microstructure of HCS and the dynamics of its change have been studied as functions of the proportion and properties of their components. It is shown that particles of the components form fractal structures, which are characterized by fractional dimensions. The obtained images of the microstructure reflect the presence of the geometric phase transition “fractal cluster-percolation cluster.” Regularities of reaction-front propagation are determined. It is found that the concentration limits of energy release and combustion are associated with the evolution of fractal structures and the formation (disruption) of a continuous reaction surface. The electrical conductivity of the starting compositions is measured as an indicator of the formation of fractal structures of one or another configuration. Electrical and thermal-physics properties of the samples and energy-release (combustion) parameters are analyzed. The systems exhibit similar behavior in different processes. Near the critical point, the dependence of the parameters studied on concentration has an exponential character. The exponent is close to that determined in percolation theory. A computational algorithm for the contact surface of the components is developed and implemented. The computation results allow one to distinguish the “base block” that influences the combustion rate and to determine the critical concentrations of the components. The study of HCS in the context of the new direction in the geometry of disordered systems—the theory of fractals—is promising for generalization of available experimental data and for predicting the parameters of energy release in HCS with variation in the structural parameters. Institute of Chemical Physics, Russian Academy of Sciences, Moscow 117977. Translated from Fizika Goreniya i Vzryva, Vol. 33, No. 5, pp. 3–19, September–October, 1997.