Composition Of Combustion Products Research Articles

Condensed combustion products of aluminized propellants. II. evolution of particles with distance from the burning surface

Condensed combustion products of a model propellant on the basis of ammonium perchlorate and aluminum were studied using the sampling technique. The granulometric composition of combustion products and the content of metal aluminum in particles of size from 1.2 µm to maximum were determined within the pressure range of 0.6–7.5 MPa at a distance from the burning surface up to 190 mm. A multimode structure of mass distributions of oxide particles within the size range of 1.2–40 µm was found. An empirical dependence of burnout of metal aluminum from agglomerates on the residence time of particles in the plume of combustion products of the propellant sample was obtained.

Relaxation of the composition of combustion products in cylindrical channels

The results of an experimental study and numerical simulation of the relaxation of the composition of the flow of high-temperature combustion products in cylindrical channels with cooled and uncooled walls are presented. Primary attention is given to the effect of parameters such as the channel radius, the oxidizer excess coefficient in the initial mixture, and the wall temperature on the relaxation of carbon monoxide CO and on the level of its concentration at the channel outlet.

Investigation of a pulsating-combustion chamber

The results of experimental investigations of a tangential chamber of pulsating combustion with an aerodynamic valve are discussed. The composition of combustion products, the level of sound pressure, and the temperature field are analyzed.

Treatment of systematic errors in intrusive concentration and temperature measurements

Typical systematic errors that are made during intrusive concentration and temperature measurements in combustion chambers are illustrated. To decrease the errors, it is necessary to ensure rapid quenching of combustion gases and freezing of the composition of combustion products. Analysis is performed using a simple analytic model for heat transfer in a sampling probe. Results are given in the form of temperature-time dependences, temperature profiles, and quench rates inside the probe. The measurement results are validated on the basis of formulation of a material balance (conservation of number of atoms). The main errors of high-temperature thermocouple measurements are discussed in detail, with emphasis on the radiation correction.

The structural peculiarities of the transition metals carbohydrides produced by combustion synthesis

We present experimental data regarding the combined influence of hydrogen and carbon on obtaining titanium carbohydrides. For processing, the self-propagating high-temperature synthesis (SHS) technique was used. The parameters of the SHS process were established by producing two modifications for ternary phases: fcc, TiCxHy (0.43<x<1); and hcp, TiC0.38–0.41H1.12–1.20). It is shown that the addition of a Va group metal led to significant changes in structure and composition of combustion products. On the concentration triangle Ti–V–C–H the fcc carbohydride regions are separated.

Calculation of thermodynamic parameters of combustion products of propellants under constant volume conditions using the virial equation of state. Influence of values of virial coefficients

The thermodynamic aspects of the propellant combustion under constant volume conditions are considered. The combustion model and computer program named BOMBA8 for the calculation of the thermodynamic and interior ballistics parameters of combustion products are described. The applicability of the presented combustion model and computer program is tested on several different types of propellants under different combustion conditions. The equilibrium composition of combustion products is calculated by applying the Gibbs energy minimization method. The pressure and thermodynamic parameters of combustion products are calculated by applying the virile equation of state. The virile coefficients of individual species are calculated in different manners — applying equations derived from experimental measurements and using different potential equations.

Combustion of ammonium dinitramide

The burning rate of ammonium dinitramide (ADN) has been studied as a function of pressure and different additives, the temperatures in the combustion front, and the composition of combustion products. Some kinetic characteristics of decomposition have been also obtained. A combustion model has been used that accounts for decomposition and evaporation, and calculated parameters of combustion are compared with experimental data. The mechanism of ADN combustion is similar to that of many other onium salts. Its peculiarities are conditioned by a rather high decomposition rate in the liquid state, low reactivity of decomposition products, and formation of ammonium nitrate as an intermediate product at low pressures.

A PHENOMENOLOGICAL THEORY OF PROPELLANTS' IGNITION AND SUBSEQUENT UNSTEADY COMBUSTION IN HIGH PRESSURE CHAMBERS

The goal of this paper is to show significant influence of ignition conditions on subsequent combustion of a condensed propellant and on the pressure diagram of combustion chamber. Emphasis is placed on the effect of accelerated combustion (AC-effect) after ignition in a high pressure closed bomb and in a chamber with moving piston. An analysis of such typical problems is carried out using an original phenomenological theory. Intermediate asymptotic solutions for the temperature and composition of combustion products as well as for the transitional combustion rate are presented. These asymptotic solutions show how the ignition conditions influence the subsequent unsteady combustion and pressure diagram in a high pressure chamber. The AC-effect of propellant surface layers and its dependence on ignition characteristics is demonstrated. A modification of Drozdov’s solution of the basic problem of gun interior ballistics has been obtained taking into account the AC-effect. It is shown that AC-effect can be responsible for the anomalous increasing of pressure-peak with decreasing of initial temperature of propellant charge in a gun-chamber.

Composition of combustion products of explosives and their mixtures

The compositions of combustion products of explosives and their mixtures are studied numerically and experimentally. It is shown that combustion of explosive mixtures results in the formation of toxic substances whose content exceeds by an order of magnitude the maximum permissible concentrations in working areas.

Effects of reaction medium on combustion of the Zr-Nb-C system

Self-propagating high-temperature synthesis was used to study combustion of theZr-Nb-C system in argon, nitrogen, and a nitrogen-hydrogen mixture. In combustion in argon a deviation from the carbon stoichiometry facilitates the mutual dissolution of the formed phases and leads to the formation of single-phase complex carbides. The homogenizing role of hydrogen in the formation of the complex combustion products of theZr-Nb-C-N-H system was shown. It was found that there is competition among the effects of nitrogen, hydrogen, and carbon in this system. Concentration triangles of theZr-Nb-C system were constructed which show the evolution of the phase composition of combustion products depending on the reaction medium.

Analytical study of pollutants and their control in MHD generators

Analytical investigations have been carried out to evaluate the combustion temperature and composition of combustion products of various fuels—methane (CH 4), liquified petroleum gas (LPG) (C 3.7H 8.8), acetylene (C 2H 2), water gas (CO + H 2), diesel oil (CH 1.88) and heavy fuel oil (CH 1.53)—under different conditions of combustion to determine the amount of pollutants, such as CO, CO 2, NO x , present in the combustion products. Calculations have been carried out to study the dependence of the amount of these pollutants on air enrichment, combustion pressure and equivalence ratio (/gf). Efforts have been made to determine the optimum conditions when the amount of pollutants, CO, CO 2 and NO, in the combustion products remains under reasonable limits, and the combustion temperature is high enough for MHD utility.

Determination of zero components in the composition of a system

A method is proposed for determing components whose concentration in a system of chemically reacting components is zero without necessity of computing the composition of the entire system. Theoretical considerations are applied to the case of the equilibrium composition of combustion products of hydrocarbons with air and an ionization additive, K2CO3.

Determination of the equilibrium compositions of combustion products

Determination of the equilibrium compositions of combustion products

Nonuniqueness of stationary states in combustion of mixtures of zirconium and soot powders in hydrogen

This article attempts to clarify the question of the existence of the nonuniqueness of regimes accompanying the combustion of a three-component system of zirconium-carbon-hydrogen. Values of the rates and temperatures of combustion, as well as the phase composition of combustion products of mixtures of zirconium with soot for three different cases of ignition, are presented. The results indicate that all the compositions investigated burn in the low-temperature regime with the formation of zirconium hydrides. It is concluded that the theoretically predicted nonuniqueness of stationary regimes of combustion and the critical transition from the high-temperature regime to the low-temperature regime using ignition sources with different temperature can be observed experimentally in the combustion of zirconium-carbon-hydrogen systems.

Extrapolation of the equilibrium composition of combustion products

Extrapolation of the equilibrium composition of combustion products

Kinetics of engine-generated nitrogen oxides and carbon monoxide

For temperatures characteristic of combustion in the spark-ignition automotive engine chemical equilibrium calculation of combustion product composition yields significant quantities of carbon monoxide and nitric oxide as well as atomic hydrogen, atomic oxygen and the hydroxyl radical. For continuous, equilibrium of combustion products during the engine expansion process, atomic species and free radicals must recombine, nitric oxide must decompose and carbon monoxide should to a considerable extent be oxidized. However, measurements indicate that carbon monoxide and nitric oxide concentrations appearing in engine exhaust correspond more closely to combustion temperature equilibrium values than to exhaust temperature values. It is therefore apparent that certain of the chemical reactions pertinent to carbon monoxide oxidation and nitric oxide decomposition may be kinetically limited during the expansion process. A theoretical analysis of the chemical kinetics of the internal combustion engine expansion process has been undertaken as the objective of the present work. Fourteen coupled non-linear differential equations based on thirty-two elementary chemical reactions were integrated numerically through use of a Runge-Kutta procedure. The integration was performed in a step-wise manner beginning at the initial point of expansion. Initial conditions included a chemical equilibrium distribution of species corresponding to average conditions of real engine combustion products just prior to expansion. Results were obtained in the form of concentration-time histories throughout expansion for each of the thirteen chemical species considered. It was found that the atomic species and the hydroxyl radical fail to recombine at a rate sufficient to maintain a continuous chemical equilibrium. Consequently these species persist in excess quantities throughout the process. Further, it was found that the persistence of excess concentrations of these species severely inhibits the oxidation of carbon monoxide during expansion. It was found that of the five elementary reactions directly involving nitric oxide, none was sufficiently rapid to effect an appreciable decomposition of nitric oxide.

A discussion on advanced methods of energy conversion- Magnetohydrodynamic power generation - Composition and thermodynamic properties of combustion products of methane containing potassium carbonate

The paper describes calculations and some computations of the composition of combustion products of methane and oxygen-enriched air between 1000 and 4000 °K. The effect of introducing potassium into the mixture is considered. This gives rise to the presence of electrons in large quantities and to certain redistributions in the proportions of some compounds and, at different temperatures, to the formation of a variety of potassium compounds. The formation of those compounds has a considerable effect on the concentration of electrons.

A Progress Report—Fundamentals of Thermochemical Corrosion Reactions

This paper describes original work on the reactions of sulfur with oxygen in flame systems of H2S-O2-Ar, where the stabilized thin flame was microprobed and the quenched products of reaction were examined with a mass spectrometer. Problems in identifying reaction products are described. Although the mass spectrometer was shown capable of checking wet analyses for mixtures of gases, the composition of combustion products was not determinable accurately by this method. Preliminary kinetic data are presented for both, homogeneously and heterogeneously (catalytically) produced SO2 and SO3.

Studies of industrial high intensity gas combustors

This paper describes theoretical and experimental studies of high intensity gas combustors, providing information from which practical combustors have been designed and applied in industrial furnaces and heating equipment. The combustors consist of combinations of an injector, in which low pressure air injects fuel gas, followed by a refractory-lined combustion chamber in which the air/gas mixture is burned, and the burned gases, at or near flame temperature, are accelerated through a refractory exit nozzle. The studies included investigations of the fluid dynamics of injection, the burner pressure loss characteristics, flame stability, completeness of combustion and combustion intensity. In designing a combustor of this type, the objective is to make the best possible use of the air supply pressure to obtain the highest exit velocity of the burned gases, or alternatively, the highest air/gas mixture velocity at the mixture nozzle (if a burner of wide stability range is required, i.e., high turndown). This necessitates minimizing the pressure losses in the whole burner, from fuel gas inlet to combustion exit. The pressure losses in the system may be characterized by defining a dimensionless pressure efficiency, i.e., the ratio of the dynamic pressure of combustion gases in the exit nozzle to the dynamic pressure of air in the injector air nozzle. Examples of the calculation of pressure efficiency have been given for both incompressible and compressible conditions. Experimental determinations of flashback rates have been carried out over a wide range of burner sizes and the results in the laminar flow range have correlated with the concept of a critical boundary velocity gradient. In the turbulent region no such correlation has been found. Compositions of combustion products at the burner exit have been determined experimentally and compared with the calculated equilibrium values to find the combustion chamber length required for complete combustion.

An Analog Computer for Flame Gas Composition

Specific impulse is an important parameter used to characterize the ballistic properties of a propellant. The calculation of this quantity has been a very tedious task, because a primary phase of this calculation involves the estimation of the composition of the products of combustion. This operation by standard techniques requires the simultaneous solution of ten equations containing ten unknown concentrations of reaction products for propellant systems composed of carbon, hydrogen, oxygen, and nitrogen. Iterative procedures have been found most efficient in solving these equations, but these are lengthy even when high speed calculating equipment is employed. An analog computer has been developed which simulates electrically the conditions of temperature, pressure, and composition of combustion products. These conditions are imposed as resistances in a series of interlocking Wheatstone bridges which, when balanced, produce the required resistances proportional to partial pressures. Mole fractions are obtained by dividing the partial pressures by the total pressure which also is produced as a proportional resistance by the computer.