Explosion Region Research Articles

High‐conversion polymerization. VII. A definition of the explosive region and the influence of free volume on it

AbstractThe easily observed autoacceleration of free radical Polymerization is defined as the explosive region and an arbitrary but quantitative definition of it is made. Using this definition it is shown that the explosive regions of solution polymerizations of methyl methacrylate occur at constant values of the product of polymer concentration times (molecular weight)1/2. This upholds the concept that polymer entanglements control the termination reaction in this region. It is also shown that this region does not, as previously suggested, occur at a constant value of free volume, but that free volume does play a role in determining the rate of termination at a given level of chain entanglements.

Calculation of the amount of gas in the explosive region of a vapour cloud released in the atmosphere

Formulae were derived and calculations made for the amount of gas in the explosive region of a vapour cloud or plume. It appears that, for an instantaneous source, a large fraction of the total amount released (e.g. 50% for methane) can be in the explosive region, irrespective of source strength and meteorological conditions. On the other hand, for a continuous source, the amount in the explosive region is strongly dependent on source strength and meteorological conditions. To assist in the hazard analysis, a computer program was written to calculate the concentration as a function of time for a quasi-instantaneous spill of LNG on water.

The Rio Blanco Experiment-Its Objectives, Design, and Execution

Project Rio Blanco is a joint government-industry experiment utilizing nuclear explosives to stimulate gas production from thick, relatively impermeable, gas-bearing lenticular sand and shale sequences. Three 30-kt explosives spaced vertically in a single wellbore at intervals of 390 and 460 ft were detonated simultaneously on May 17, 1973. No significant adverse effects were experienced, and damage resulting from ground motion was as predicted. The initial reentry into the upper explosive region indicates that coalescense of the top cavity and fracture region with the lower ones did not occur as expected. Reentry into the bottom cavity indicated that similarly, communication does not exist between the lower two chimneys. The fracture height of the upper region was about as predicted from previous experience with single-chimney geometry as was the cavity radius resulting from the bottom detonation. All indications are that yields were as predicted, and to date there is no valid explanation as to the lack of intercommunication between the fracture regions of the three explosives. Production test data from the top chimney indicated a reservoir capacity of only 0.73 md-ft, which is 6 to 10 times lower than expected. Subsequent testing of an evaluation well and other data lends further evidencemore » that, although significant stimulation most surely occurred, the gas contained in the sandstones was much less than had been originally anticipated. Properties deduced from production test data from the bottom chimney are in much better agreement with predetonation estimates. Further investigations are required to fully evaluate the experiment. (auth)« less

Acoustic fuel vapor monitor

The speed of sound as a function of the average molecular weight in a gaseous mixture has been used to determine the concentration level of fuel vapor in air, in the range from 1.0% to 8.0% by volume. This method of measurement yields an error due to a 1°C change in temperature of only 0.18% and can be applied to many different types of fuel. The range can be extended to wider limits, but our interest included only the explosive region for gasoline fuel vapor, i.e., 1.6% to 7.8% by volume. Using this device, fuel vapor levels can be continuously monitored without altering the system in any way. Thus, error introduced by sampling, temperature change, and time delay are virtually eliminated. Sensitivity of the system to changes in fuel vapor levels is proportional to the ratio of the molecular weight of air. This method of measurement is applicable down to ratios of 1.51 and has been typically applied with a ratio of 3.9 with total success. Instrumentation has been developed to indicate fuel vapor levels by either meter movement or digital readout.

Experimental study of the explosion characteristics of metal dust clouds

An experimental investigation of the explosion characteristics of dust clouds of aluminum and magnesium was carried out for a wide range of dust concentrations up to 7000 g/m 3 , using a new closed experimental apparatus. The explosion characteristics of aluminum and magnesium did not show much difference. The explosion pressure for aluminum and magnesium tended toward maximum values at concentrations roughly 3 to 5 times higher than the stoichiometric concentrations in the reactions of Al to Al 2 O 3 and Mg to MgO. The explosion pressure for aluminum decreased rapidly whereas that of magnesium decreased fairly showly with increasing dust concentration. The optimum dust concentration, at which the explosion pressure was highest, increased for aluminum and decreased for magnesium as the amount of oxygen available for the reaction decreased. The time-to-peak pressure/dust concentration curve for aluminum was convex downwards with the minimum value near the optimum dust concentration, whereas the curve for magnesium was constant after it reached the minimum. In the relation between the amount of residual oxygen and the concentration of the dust cloud, the trend was the same for both aluminum and magnesium as that of the time-to-peak pressure/dust concentration curve for magnesium. The amount of oxygen available for the reaction was changed by diluting the air with nitrogen [case (I)] and by decreasing the initial pressure [case (II)]. It was found that the explosion region of case (II) was wider with respect to both oxygen and dust concentrations than that of case (I), although the explosion pressure was higher in case (I) than in case (II), except near the explosion limit.

Source Characteristics of Earthquakes, Explosions and Afterevents

Summary Broad-band seismic data available on the magnetic tape library at Berkeley have been used in a study comparing P, and Rayleigh waves from earthquakes, explosions and explosion afterevents, both collapse and earthquake types. Eighty-one events equidistant from Berkeley at 500-550 km provided the data for wave amplitude and spectra comparisons. Explosions exhibit characteristic low Rayleigh wave (12-s period) generation, for given P,, amplitude, relative to earthquakes as well as explosion afterevents. This discriminant, for events recorded at Berkeley, is well developed down to local magnitude M,, 4.0 or less (m; R 3.6) and shows no indication of convergence, although scatter increases, for smaller events. Rayleigh wave spectra for explosions and collapses are quite similar, the similarity continuing up to frequencies of 0.5 Hz for proximate events. However, they differ significantly from spectra of shallow earthquakes in the same source region. This implies the explosions, including those large ones with appreciable surface faulting, Love wave generation, and aftershock sequences, are sources with small time and space dimensions, relative to shallow earthquakes at the same site. Extensive fault displacements near large explosions is proposed as passive medium response to strong shaking and Love wave generation with Rayleigh wave asymmetry is suggested to occur through processes acting in the relatively small high stress explosive source region.

A flash photolytic study of the explosive reaction between hydrogen and oxygen sensitized by nitrogen dioxide, chlorine and bromine

When hydrogen and oxygen were flashed in the presence of nitrogen dioxide, chlorine or bromine under suitable conditions explosion occurred. The results are compatible with the accepted mechanism for the hydrogen–oxygen reaction, with the addition of steps involving molecules and radicals produced from the sensitizers, when the unusual conditions pertaining to the flash system are considered. In addition to the chain branching mechanism there is a considerable thermal contribution to the explosion, since heat must be evolved at a sufficient rate to compensate for the heat lost to the surroundings. This was confirmed by direct observation of the temperature of the system by following the vibrational temperature of nitric oxide throughout the incubation period and explosion. With nitrogen dioxide as sensitizer, the nitric oxide formed during the flash exhibited a sensitizing effect attributed to the reaction proposed by Ashmore & Tyler (1962) HO 2 + NO → NO 2 + OH which interrupts the normal termination sequence. With halogen sensitizer ( X 2 ), H X formed during the flash exhibits an inhibiting effect, more pronounced with bromine, owing to the reaction: H X +H → H 2 + X . A peninsular explosion region was observed, for which the upper limit was analogous to the second limit in conventional thermal systems, but the lower limit did not involve heterogeneous termination steps. The onset of explosion at this limit was found to be chain-thermal in nature. During the explosion sensitized with chlorine a transitory continuous spectrum was observed, but not identified.

Spontaneous ignition of methane—air mixtures at high pressure II—the explosive region of reaction

The rates of temperature and pressure rise during spontaneous ignition at initial pressures up to 110 atmospheres have been followed for relatively slow explosions of rich mixtures of methane and air. The activation energy for the reaction in the initial stages of explosion was 20 to 25 kcal/mole. The reaction rate was relatively independent of pressure above 63 atmospheres and was approximately proportional to the square of the oxygen mole fraction. Explosion products include relatively large amounts of hydrogen and ethane. It is suggested that the marked differences between the reaction during the ignition delay and that during explosion are due to a take-over of control of the reaction by hydrogen atom reactions. In consequence, the fast reaction has characteristics typical of an oxidation-sensitized pyrolysis.

Hα Shock Wave and Winking Filaments with the Flare of 20 September 1963.

view Abstract Citations (30) References Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Hα Shock Wave and Winking Filaments with the Flare of 20 September 1963. Moreton, G. F. Abstract and Ha -0.5 A, with 30 sec between filtergrams at one wavelength. The flare starts at 23h49m; a 1-min duration explosive phase commences at 23h58m, during which parts of the flare expand at 120 km/sec. A shocklike disturbance propagates from near the explosive region across the sun to a distance of 420 000 km, maintaining a constant transverse velocity of 750 km/sec. Radio data from J. P. Wild and A. A. Weiss show an outstanding type III burst extending from 2000 Mc/sec coincident with the explosive phase, and a type II coincident with the visible shock front. Two dark filaments are encountered by the front near the end of its visible trajectory, and the filaments are caused to undergo a "winking" activation: at Ha the filaments momentarily disappear; in the Ha wings they momentarily darken. The three-wavelength coverage confirms earlier observations of fast disturbances expelled from explosive type flares (Athay, R. G., and Moreton, G. F., Astrophys. J. 133, 935,1961), and provides new data: the activated filaments darken first in the red wing, then in the violet wing. This effect, observed first by Dodson-Prince (NASA-AAS Symposium on Flare Physics, October 1963) may be attributed to a Doppler shift, caused by the filament moving first down, then up. Each filament executes three oscillations, with a period 7 min. These observations show the moving disturbance only in the wings of Ha, as has been demonstrated previously. It is now found that the leading edge of the front is darker than the chromospheric background in the red wing, and brighter in the violet wing. This suggests that the disturbance is an effed, caused by an invisible agency that depresses the chromosphere and mottling as it passes tangentially through the solar atmosphere. Publication: The Astronomical Journal Pub Date: 1964 DOI: 10.1086/109375 Bibcode: 1964AJ.....69Q.145M full text sources ADS |

水による熔融〓の爆発について (第2報)

The explosion phenomena were studied'from the standpoint of the chemical reaction, which was carried out by blowing steam into the matte at 1, 250°C in the presence of Si02, SOC, HLS and H2 were detected in the outlet gas and determined quantitatively.The reaction velocities between the molten matte and steam given by the above experiment were listed in Table 1.In general it was observed that the higher the Fe content of the matte was, the larger the reaction velocity was, till the Fe content was 20% and at the matte over 20% Fe it did not so varied corresponding to the Fe content.The results of the reports I and II were discussed on the equilibrium constants of the reactions considered in the above experiments, gas explosion region, etc. It was concluded that the molten matte reacted with steam to yield the explosive gases, H2 and H2S, and when those accumulated gases mixed with the oxidizing atmosphere, the explosion took place.

Kinetics of the hydrogen/oxygen reaction II. The explosion region in salt- and alkali-coated vessels

The first, second and third explosion limits for the hydrogen/oxygen reaction have been examined over a wide range of temperature, mixture composition, vessel size and wall coating. An expression has been derived from general chain theory which can account for the observed features of the complete explosion region. It includes and relates previously given expressions for the individual limits. The reactions found to be necessary and apparently sufficient to account for the hydrogen/oxygen spontaneous ignition peninsula are those of chain destruction in triple collisions, destruction at the wall of three different chain carriers, first-order branching, second-order branching, the regeneration of ‘dead’ chains and a chain-initiating process.

The Thermal Hydrogen-Oxygen Reaction at Relatively Low Temperatures

In the behavior of the thermal hydrogen-oxygen reaction there is an apparent discrepancy. The second explosion of the thermal reaction occurs over a wide range of low temperatures down to 350°C, even though the rate of steady thermal reaction is very nearly zero. The authors used a criterion stated by Lewis and von Elbe to show that the same volume chain which explains the reaction at higher temperatures applies to the low temperature range. The inhibition period within the low pressure explosion region and the branching of the chains are briefly discussed.

Kinetics of the hydrogen/oxygen reaction I. The explosion region in boric acid-coated vessels

The region of low-pressure explosion for hydrogen/oxygen mixtures in boric acid-coated vessels has been observed over a wide range of temperature, vessel size and mixture ratio. The results obtained cannot be explained by any of the existing mechanisms, and appear to conflict with the present interpretation of the effects of boric-acid coating. The explosion boundary is described by a simple mathematical expression which demands the participation of a second-order chain-branching process not operative in salt-coated vessels. The previously excluded reaction H + HO2→ OH + OH is postulated. A mechanism is outlined which successfully accounts for the shape and temperature dependence of the newly observed explosion region.

The formation of hydrogen peroxide in the combustion of hydrogen at low pressures

Hydrogen peroxide has been obtained in appreciable concentrations when a flame of hydrogen and oxygen burning at pressures of 3 to 4 cm. mercury was directed against a surface cooled to —180° C ( c . 5 to 10%), and when an oxy-hydrogen mixture was exploded by the action of a spark, in glass or aluminium vessels c . 2 x 15 cm., cooled in liquid air, the products were shown to contain up to 30% hydrogen peroxide ( w / v ), depending on the conditions. The conditions controlling the formation of hydrogen peroxide in such explosions have been investigated more fully than was done by previous authors. It was found that as the overall gas pressure was decreased the yield of peroxide passed through a maximum value. The effects were also investigated of varying the dimensions of the vessels, the gas composition, the external temperature, and other factors. A series of experiments was carried out in order to ascertain whether the hydrogen peroxide was formed in the gas phase or only on the walls. In these experiments, the ultra-violet absorption spectrum of the explosion region was studied. It was found that a considerable quantity of hydrogen peroxide was present in the gas phase, even when the walls of the reaction tube were not cooled. The results are discussed in the light of modern views regarding the combination of hydrogen and oxygen. It would appear that the peroxide is formed by two mechanisms; one of these consists of recombination of hydroxyl radicals on the cold walls, the other involves the formation of an excited HO 2 radical, and its subsequent reaction with a hydrogen molecule to give a hydrogen atom and a molecule of excited hydrogen peroxide, which then decomposes unless it is stabilized and frozen on the walls. No other explanation has been found to account for all the observed facts, and at the same time not to contradict established mechanisms for the hydrogen oxygen reaction.

Second pressure limits in gaseous explosion regions: II. Experimental data on explosions of CO and CH4 with oxygen and air

AbstractThe authors investigated the explosion limit as a function of the pressure (below about 120 cm Hg). With CH4‐O2, CH4‐air, CO‐O2 and CO‐ air mixtures no shapes of explosion regions were found which were reminiscent of the lowpressure‐inflammation regions of these mixtures at higher temperatures. Though at the upper limit of mixtures with CO a “second pressure limit” was found, this was not at all comparable with the shape of the explosion region observed with H2‐O2 mixtures1). The “second pressure limit” of CH4‐air mixtures found by Lavrov and Bestchastny cannot have been an explosion limit, but must be attributed to secondary effects.

Theoretical considerations on the relation between explosion and inflammation regions

AbstractThe author emphatically distinguishes between explosion and inflammation. The shape of the inflammation regions (with pressure and composition of the mixture as variables) is discussed for such gas mixtures as possess a “low pressure inflammation region” in addition to a thermal inflammation region at a higher pressure (e.g. H2‐O2, CO‐O2, CH4‐O2).From experiments on the influence of a spark on the shape of the inflammation region and of the temperature on the position of the explosion limits, the author derives a general shape of the explosion region (as determined at room temperature). It follows from this that indentations in the explosion region may sometimes be expected in the place where thermal and low pressure inflammation regions merge. The “second pressure limits” which then occur were actually found with H2‐O2 and H2 ‐ air mixtures. The “second pressure limit” found by Lavrov and Bestchastny for CH4 ‐ air mixtures must have been due to secondary effects.The inflammation regions cannot be accounted for by one theory, although all the cases are instances of chain reactions. For, these reactions have in the thermal inflammation region a normal relationship between temperature and reaction rate, whereas this relationship is abnormal in the low pressure inflammation region. The various parts of the explosion regions can, therefore, not be accounted for by one theory either.Former attempts to explain the shape of explosion regions by either the thermal or the chain theory were wrong.A simple explanation of the association between explosion and inflammation is given.

On the inhibition of an explosive reaction in methane‐air mixtures

AbstractFor the correct appreciation of the extinguishing action, which a gas or vapour exerts on explosive binary gas mixtures, it is necessary to determine the whole ternary explosion region.

Ternary and quaternary explosion regions and Le Chatelier's formula

AbstractThe author investigated a number of quaternary and ternary explosion regions of gas (gas and vapour) mixtures in which ethylene and air throughout were two of the components. These gases were combined in the quaternary systems with hydrogen and carbon monoxide, hydrogen and carbon dioxide, nitrogen and carbon dioxide; in the ternary systems with vapours of ethylene chloride, ethylene bromide and n‐butyl bromide. It is considered whether in the limit mixtures of these systems Le Chatelier's law and formula was satisfied; in connection with this consideration the result of the investigations is summarized in graphs and tables. A closed explosion region was found in the system C2H4‐air‐H2‐CO2. Moreover a description is given of an apparatus in which a part of the experiments was carried out.

XXVI. On the origin of the line spectrum emitted by iron vapour in the explosion region of the air-coal gas flame

XXVI. <i>On the origin of the line spectrum emitted by iron vapour in the explosion region of the air-coal gas flame</i>