Detonation Temperature Research Articles

Measuring the brightness temperature of a detonation front in a porous explosive

The detonation temperature of pressed PETN grains with a relative volumetric concentration of air pores of 0.0047–0.147 was measured using an optical fiber pyrometer at wavelengths of 678 and 487 nm. The nonequilibrium nature of the radiation of the detonation front was shown to be due to the presence of two radiation sources with different temperatures. One source was the explosion products and the other was the strongly compressed air pores, in which air was heated to a temperature above 104 K.

Ultrafine Oxides during Detonation Expanse at A Fast Quenching Rate

Nanostructured spherical lithium manganese oxide (Li-Mn-O) with about 30nm in diameter was synthesized for the first time by explosive method. The water-solubility explosive was prepared using a simple facility at room temperature. The growth of lithium manganese oxides via detonation reaction was investigated with respect to the presence of an energetic precursor, such as the metallic nitrate and the degree of confinement of the explosive charge. The detonation products were characterized by scanning electron microscopy. Powder X-ray diffraction and transmission electron microscopy were used to characterize the products. Lithium manganese oxides with spherical morphology and more uniform secondary particles, with smaller primary particles of diameters from 10 to 50 nm and a variety of morphologies were found. Lithium manganese oxides with a fine spherical morphology different from that of the normal is formed after detonation wave treatment due to the very high quenching rate. It might also provide a cheap large-scale synthesis method. Explosive detonation is strongly nonequilibrium processes, generating a short duration of high pressure and high temperature. Free metal atoms are first released with the decomposition of explosives, and then theses metal and oxygen atoms are rearranged, coagulated and finally crystallized into lithium manganese oxides during the expansion of detonation process. For detonation of the water-solubility explosive, the detonation pressure, the detonation temperature and the adiabatic gamma were close to 3 GPa, 2300 K and 3. The inherent short duration, high heating rate (1010 – 1011 K/s) and high cooling rate (108 – 109 K/s) prevent the lithium manganese oxides crystallites from growing into larger sizes and induce considerable lattice distortion.

Detonation temperature of high explosives from structural parameters

A new scheme is introduced for calculating detonation temperature of different classes of high explosives. The ratio of oxygen to carbon and hydrogen to oxygen as well as specific structural parameters are the fundamental factors in the new method. An empirical new correlation is used to calculate detonation temperature of energetic compounds without considering heat contents of explosives and detonation products. Calculated detonation temperatures for both pure and explosive formulations show good agreement with respect to measured detonation temperatures and complicated computer code using BKWR and BKWS equations of state. Predicted detonation temperatures have root-mean-square (rms) percent deviation of 4.6, 14.2 and 4.6 from measured values for new method, BKWR and BKWS equations of state, respectively.

A simple method to assess detonation temperature without using any experimental data and computer code

Detonation temperature of C a H b N c O d explosives can be predicted from a, b, c, d and calculated gas phase heat of formation of explosives without using any assumed detonation products and experimental data. Two new correlations are introduced for calculation of detonation temperature of aromatic and non-aromatic explosive compounds so that it is shown here how simply calculated heat of formation by additivity rule and atomic composition are only necessary data for this simple prediction. Calculated detonation temperatures by the introduced correlations for both pure and explosive formulations show good agreement with respect to measured detonation temperatures and complicated computer codes. The average mean absolute error in detonation temperature is within about 7.0%.

Shock-to-detonation transition of nitromethane: Time-resolved emission spectroscopy measurements

The objective of this work is to improve the knowledge of the shock-to-detonation transition of nitromethane. The study is based on a spectral analysis in the range 0.3–0.85 μm, with a 28-nm resolution, during experiments of plane shock impacts on explosive targets at 8.6 GPa. The time-resolved radiant spectra show that the detonation front, the reaction products produced during the superdetonation, and the detonation products are semitransparent. The temperature and absorption coefficient profiles are determined from the measured spectra by a mathematical inversion method based on the equation of radiative transfer with Rayleigh scattering regime. Shocked nitromethane reaches at least 2500 K, showing the existence of local chemical reactions after shock entrance. Levels of temperature of superdetonation and steady-state detonation are also determined.

Predicting the Detonation Velocity of CHNO Explosives by a Simple Method

AbstractA simplified method is shown, based on a semi‐empirical procedure, to estimate the detonation velocities of CHNO explosives at various loading densities. It is assumed that the product composition consists almost of CO, CO2, H2O and N2 for oxygen‐rich explosives. In addition solid carbon and H2 are also counted for an oxygen‐lean explosive. The approximate detonation temperature, as a second needed parameter, can be calculated from the total heat capacity of the detonation products and the heat of formation of the explosive by PM3 procedure. The detonation velocities of some well‐known CHNO explosives, calculated by the simple procedure, fit well with measured detonation velocities and the results from the well‐established BKW‐EOS computer code.

Metallurgical examination of an M107 projectile fragment

A fragment of steel from a detonated M107 projectile was examined in order to determine whether the temperature produced by the explosion was extreme enough to melt the bronze rotating band. There was an environmental concern that the detonation temperature may have been high enough to melt and/or vaporize the bronze alloy. Extensive metallographic analysis, hardness testing and scanning electron microscopy were conducted in an attempt to determine the temperature imparted on the projectile. Based on the results of this testing and examination, as well as information provided by the probable manufacturer of this ordnance, it was determined that the temperature reached most likely did not approach the melting point of the bronze rotating band.

New method for estimating the heat of formation of CHNO explosives in crystalline state

For CHNO explosives, a new correlation is derived, which has the form Q c o r r /cal = 0.196T a d /K + 755 in the range Q c o r r > 1100 cal between Kamlet's corrected heat of detonation, Q c o r r , and approximate detonation temperature, T a d . The semi-empirical PM3 procedure is used for calculating the approximate heat of formation of the explosive in the gas phase, which is required for the computation of T a d . In calculating Q c o r r , it is assumed that the decomposition products of any CHNO explosives consist of CO, CO 2 , H 2 O, N 2 , H 2 , solid carbon, and in the next step the carbon monoxide is converted to carbon dioxide and solid carbon. The calculated Q c o r r can be used for the determination of the heat of formation of any CHNO explosives in the solid state.

Analysis of a Pulsed Detonation Thermal Spray Applicator

Pulsed detonation thermal spray applicators are used to deposit particulate-based coatings on metal components. The coatings usually consist of a unique class of thermal spray materials that are widely employed in numerous industries to enhance the surface of metal components. This paper presents an analysis and numerical simulation of an open tube pulsed detonation thermal spray applicator. Calculations are made to determine the theoretical detonation states attainable for typical operating conditions and to track the particle trajectories as they traverse the barrel, eventually impacting the target workpiece. The present investigation focuses on the combustion of acetylene in oxygen, diluted with nitrogen. Key parameters studied are: nitrogen dilution percentage, oxygen-carbon ratio, barrel location of solid-particle axial injection, and size of the injected particles. Results are presented on the effect of these design parameters on several important quantities including: detonation speed, velocity of the detonation product gases, detonation pressure, detonation temperature, temperature and velocity profiles of the solid particle as it travels through the pulsed detonation thermal spray applicator, percentage melt history of the solid particles, and temperature, velocity, and percentage melt of the solid as it impacts the workpiece.

Anisotropic shock sensitivity and detonation temperature of pentaerythritol tetranitrate single crystal

Shock temperatures of pentaerythritol tetranitrate (PETN) single crystals have been measured by using a nanosecond time-resolved spectropyrometric system operated at six discrete wavelengths between 350 and 700 nm. The results show that the shock sensitivity of PETN is strongly dependent on the crystal orientation: Sensitive along the shock propagation normal to the (110) plane, but highly insensitive normal to the (100) plane. The detonation temperature of PETN is, however, independent from the crystal orientation and is determined to be 4140 (±70) K. The time-resolved data yielding the detonation velocity 8.28 (±0.10) mm/μs can be interpreted in the context of a modified thermal explosion model.

JCZS: An Intermolecular Potential Database for Performing Accurate Detonation and Expansion Calculations

Exponential-13,6 (EXP-13,6) potential parameters for 750 gases composed of 48 elements were determined and assembled in a database, referred to as the JCZS database, for use with the Jacobs Cowperthwaite Zwisler equation of state (JCZ3-EOS)(1). The EXP-13,6 force constants were obtained by using literature values of Lennard-Jones (LJ) potential functions, by using corresponding states (CS) theory, by matching pure liquid shock Hugoniot data, and by using molecular volume to determine the approach radii with the well depth estimated from high-pressure isentropes. The JCZS database was used to accurately predict detonation velocity, pressure, and temperature for 50 different explosives with initial densities ranging from 0.25 g/cm3 to 1.97 g/cm3. Accurate predictions were also obtained for pure liquid shock Hugoniots, static properties of nitrogen, and gas detonations at high initial pressures. JCZS: Eine intermolekulare Potential-Datenbank zur Durchführung von Detonations- und Expansionsberechnungen Exponential-13,6 (EXP-13,6) Potentialparameter von 750 Gasen, zusammengesetzt aus 48 Elementen, wurden bestimmt und gesammelt in einer Datenbank mit der Bezeichnung JCZS-Datenbank zur Anwendung in der Jacobs-Cowperthwaite-Zwisler Zustandsgleichung (JCZ3-EOS)(1). Die EXP-13,6 Kraftkonstanten wurden erhalten durch Verwendung von Literaturwerten der Potentialfunktionen von Lennard-Jones (LJ), durch Verwendung einer übereinstimmenden Zustandstheorie (CS), durch Anpassung der Hugoniot Stoßdaten für reine Flüssigkeiten, und durch Verwendung des Molekularvolumens zur Bestimmung der Näherungsradien mit der aus den Hochdruck-Isentropen abgeschätzten Potentialtiefen. Die JCZS-Datenbank wurde verwendet zur genauen Voraussage der Detonationsgeschwindigkeit, des Druckes und der Temperatur für 50 verschiedene Explosivstoffe mit Anfangsdichten zwischen 0,25 g/cm3 bis 1,97 g/cm3. Genaue Voraussagen wurden auch erhalten für Hugoniot Stoßdaten von reinen Flüssigkeiten, für statische Eigenschaften des Stickstoffs und für Gasdetonationen bei hohen Zünddrücken. JCZS: une base de données de potentiel intermoléculaire pour effectuer des calculs de détonation et d'expansion Les paramètres de potentiel exponentiel‒13,6 (EXP-13,6) de 750 gaz composés de 48 éléments ont été déterminés et rassemblés dans une base de données intitulée base de données JCZS destinée à être utilisée dans les équations d'état de Jacobs-Cowperthwaite-Zwisler (JCZ3-EOS)(1). La constante de force EXP-13,6 a été obtenue en utilisant des valeurs des fonctions de potentiel de Lennard-Jones (LJ) trouvées dans la littérature, en utilisant une théorie d'état correspondante (CS), en adaptant les données de choc d'Hugoniot des liquides purs et en utilisant le volume moléculaire en vue de la détermination des rayons d'approximation avec les profondeurs de potentiel estimées à partir des isentropes haute pression. La base de données JCZS a été utilisée pour prédire avec précision la vitesse de détonation, la pression et la température pour 50 explosifs différents avec des densités initiales allant de 0,25 g/cm3 à 1,97 g/cm3. On a également obtenu des prédictions précises pour les données de choc d'Hugoniot des liquides purs, pour les propriétés statiques de l'azote et les détonations de gaz à des pressions d'allumage élevées.

Experimental determination of detonation velocity

Abstract For the experimental determination of detonation parameters (such as detonation velocity, detonation pressure, detonation products mass velocity, detonation temperature, etc.) of an explosive, various dynamic methods, based on different physical principles, are applied. For this purpose, various experimental methods, as well as testing apparatuses and procedures, are used. At the same time, due to unusual (extreme) values of detonation parameters (detonation velocity reaches 10 mm/μs, detonation pressure up to 400 kbar, detonation temperature ranges from 2000 to 5000 K, duration time of the chemical reactions in the reaction zone is of the order of microseconds, and the width of the chemical reaction zone ranges from tenths of a micrometer to several millimetres), it is very difficult to achieve an entirely reliable experimental determination of some detonation parameters. Detonation velocity is one of the most important parameters of an explosive, which nowadays can be measured very accurately. ...

Ignition in conditions where a jet of fuel-air mixture interacts with the wall of a diesel combustion chamber

The dependence of the ignition delay and the limitting detonation temperature of fuel-air mixture on the geometric characteristics of the wall of a diesel combustion chamber at which a high-speed jet is incident is investigated experimentally on a motorless setup. It is shown that, to facilitate ignition in the characteristic conditions of diesel startup, glancing initial incidence of the jet at the wall is preferable, with sharp rotation of the fuel-mixture flow to return it to the free volume of the combustion chamber. This is explained by the additional heating of the mixture due to the sharp retardation and the continued accumulation of heat in the vicinity of the stagnation point.

Effect of explosion conditions on the structure of detonation soots: Ultradisperse diamond and onion carbon

Detonations of a number of pure and composite explosives with the negative oxygen balance in a hermetic tank filled with inert gas (N 2, Ar) have yielded the diamond containing solid carbonaceous products (soots). The influence of detonation parameters, namely (a) the inert gas pressure in the tank decreasing the effective temperature of detonation products, and (b) the composition of explosives determining the detonation pressure and temperature, on the nature and the yield of detonation soots have been investigated by TEM, XRD, SAXS, and auger spectroscopy. The soots contain ultradisperse diamond (UDD, 20–150 Å) along with amorphous carbon (40–250 Å), graphite ribbons (with length less than 200 Å), and spheres (20–40 Å) made of concentric graphite shells (onion-like carbon, registered only in the experiments with low initial inert gas pressure). It was shown that UDD thermally transformed into onion-like carbon particles. The detonation parameters have been optimized to increase the UDD yield.

Reparameterization of the Becker-Kistiakowsky-Wilson equation of state for water-gel explosives

This paper describes the results of the reparameterization studies on the Becker-Kistiakowsky-Wilson (BKW) equation of state (EQS) for water-gel explosives. The original set of BKW parameters (α = 0.5, β = 0.1, κ = 11.85, and θ = 400) predicts a higher detonation velocity and detonation pressure and a lower detonation temperature compared with the experimental values for these explosives. Among the several combinations of parameters examined, the following set-α = 0.5, β = 0.1, κ = 8.85, and θ = 1850—is found to give realistic values for the various detonation properties. Moreover, the predicted and the experimental detonation velocities are seen to be in fair agreement. A comparison of the computed and the experimental (obtained from Crawshaw-Jones measurements) fume characteristics shows that (1) inclusion of the wrapper material in the explosive composition increases the concentration of fumes and gives correspondence between the two for products such as CO, H 2, NH 3, and CH 4, (2) the measured NO X concentration is difficult to get in these computations, and (3) calculations of the product compositions for the isentropic expansion of detonation products along the Chapman-Jouguet (C-J) isentrope give freeze-out temperatures in the range of 1000–1800K. These computations were also performed for two ammonium nitrate-fuel oil mixtures and are found to be in good agreement with the experimental data.

Detonation temperature of acetylene

Detonation temperature of acetylene

A numerical study of the charge diameter effect on unsteady detonation

A numerical study for the unsteady detonation of an unconfined tetryl charge of small diameter, which is assumed to be homogeneous, was performed by using the two-dimensional Lagrangian hydrodynamic computer code, 2 DL, with the first order Arrhenius equation of reaction rate. Becker-Kistiakowsky-Wilson (BKW) and Kihara-Hikita (KH) equations of state have been applied to the detonation products. In the case of BKW, it is shown that the rarefaction waves propagating inward from the lateral surface make the reaction rate slow and give a curvature to the front. Then after an induction time, a strong initiation occurs in the reaction zone near the lateral surface and higher pressure zone moves to the axis. This higher pressure accelerates the detonation propagation near the lateral surface and the curvature of detonation front is reduced. Then, the reaction at the lateral surface again begins to decay by the rarefaction waves. Such a sequence of process is repeated periodically. The possibility of the occurrence of the strong initiation depends on the pressure and temperature in the shocked zone near the surface. In a small diameter charge, the delayed explosion becomes weaker near the surface, while its frequency increases. No shock interaction occurs because the direction of the particle flow is always divergent. In the case of KH equation of state, the temperature of detonation is higher than that obtained by BKW and the behaviour of instability becomes rather different from the previous result, i.e. in the axis the pressure oscillates repeating the overdriven and underdriven detonation similar with the case of BKW.

Comments on the equation of state of the products of high density explosives

The problem of the thermal equation of state of the products of solid explosives is considered. It is assumed that the products are in chemical equilibrium, that the specific chemical heat released is independent of the loading density, and that the detonation density is proportional to the loading density. Using the energy conservation equation and thermodynamic relationships, it is then shown that the thermal equation of state must satisfy the following relationship: F [ T ( 1 − K ) / 2 K υ ; υ ( 1 + K ) / ( 1 − K ) p ] = 0 . where K is a constant and F is an arbitrary function of its two arguments. It is then argued that the experimental knowledge of detonation velocity, pressure, density, and particle velocity versus loading density is not enough to check the validity of an assumed thermal equation of state of the products and to compute the detonation temperature. In particular, it is explained why similar detonation pressures, densities, and particle velocities, but completely different detonation temperatures have been calculated by various authors, using similar detonation velocity data but different thermal equations of state.

Investigations of the Detonation Properties of Condensed Explosives with Equations of State Based on Intermolecular Potentials. I. RDX with Fixed Product Composition

An attempt is made to determine an average pair potential of intermolecular force for the mixture of product gases of the condensed explosive RDX (cyclotrimethylenetrinitramine) from measurements of the detonation velocity. The principal approximations are that the products of detonation consist of CO, H2O, and N2 in equimolar proportions and that the equation of state for this mixture can be calculated from theories of the free-volume type with the use of an average intermolecular potential. It was found that the average intermolecular potential was fairly well determined at distances somewhat less than the crossover distance. This result was almost independent of the choice of equation of state, although the calculated values of detonation temperature and pressure were not.

Detonation and other high temperature phenomena at high pressures. Introduction

Detonation and other high temperature phenomena at high pressures. Introduction