Fireball Formation Research Articles

Fireballs-Like Explosive Peroxides Produced by the Brown-rot Fungus

Abstract: Fireballs are unusual and rare phenomena usually associated with thunderstorms, although sometimes they have been observed during earthquakes, volcano eruptions or in fair weather. There are still questions about their origination, features and interaction with the environment. In this work, a new model is shown to explain the formation of fireballs in fair weather from poplar cotton and peroxides produced by brown-rot fungi. Light emission is produced via thermal decomposition of 1,2- dioxetane phenylcoumarane or 1,2-dioxetane monolignol, from lignin inside the poplar fibers. The energy released during the explosive decaying of fireballs was calculated as being about 3 kilojoules for each gram. This value is the same order of magnitude as the estimated for the explosive fireballs decaying.

On the significance of the external circuit, Langmuir and Bohm criterion for the stability of plasma fireballs

This paper is devoted to studying the influence of the external circuit as well as the Langmuir and Bohm criterion on the stability of plasma fireballs. A simple mathematical model is suggested that describes why plasma fireballs can get unstable up to the point where they start pulsating. The predictions of this model are compared to measured experimental data. Furthermore, it is argued that the Bohm criterion in particular determines whether a stable plasma fireball can be formed. This adds to the current understanding that fireballs are preliminarily formed due to a change in the space charge in front of a positively biased electrode in surrounding plasma. It is argued that the space charge distribution near the vicinity of the anode surface might play a role but that the initial stages of fireball formation are dominantly driven by the requirement of the double layer to satisfy Bohm’s sheath criterion and Langmuir’s criterion. The same holds for a collapsing fireball. This paper shows that if the Langmuir and the Bohm criterion are not satisfied simultaneously, a fireball cannot reach a stable state and will start pulsating with a frequency that is proportional to the square root of the mass of the working gas ions.

Comparison of the 3-Fluid Dynamic Model with Experimental Data

The article considers a way to compare large bulks of experimental data with theoretical calculations, in which the quality of theoretical models is clearly demonstrated graphically. The main idea of the method consists in grouping physical observables, represented by experiment and theoretical calculation, into samples, each of which characterizes a certain physical process. A further choice of a convenient criterion for comparing measurements and calculations, its calculation and averaging within each sample and then over all samples, makes it possible to choose the best theoretical model in the entire measurement area. Published theoretical data of the three-fluid dynamic model (3FD) applied to the experimental data from heavy-ion collisions at the energy range $\sqrt{s_{NN}}\,=\,2.7 - 63$ GeV are used as example of application of the developed methodology. When analyzing the results, the quantum nature of the fireball, created at heavy ion collisions, was taken into account. Thus, even at energy $\sqrt{s_{NN}}\,=\,63$ GeV of central collisions of heavy ions, there is a nonzero probability of fireball formation without ignition of the quark-gluon plasma (QGP). At the same time, QGP ignition at central collision energies above at least $\sqrt{s_{NN}}\,=\,12 GeV occurs through two competing processes, through a first-order phase transition and through a smooth crossover. That is, in nature, these two possibilities are realized, which occur with approximately the same probabilities.

Approval of a computational method for determining thermal loads during accidents accompanied by fireballs

Introduction. Large fires are quite often accompanied by the formation of fireballs (OSH), which create significant thermal loads. As a result of the fire coverage of a container containing an overheated liquid, a physical explosion occurs, which releases a significant amount of fuel forming a fireball. This phenomenon is dangerous because, with a short lifetime, it is capable of causing thermal injuries over considerable distances. The existing methods of predicting the consequences of a fireball, set out in various domestic regulatory documents and foreign literature, do not fully reflect the possible values of thermal loads. In this regard, a computational method for determining thermal loads was developed, taking into account the movement of the fireball.Goals and objectives. The purpose of this study is to test the developed computational methodology for determining thermal loads, which takes into account the kinematic characteristics of the fireball. The following tasks were solved in the study:● check the operability of the fireball lifting model;● to conduct a comparative analysis of thermal loads according to the developed methodology with the results of calculation of domestic and foreign methods;● conduct a computational experiment on the effect of air mobility (wind effect of 7 m/s) on thermal loads.Research methods. To check the operability of the OSH lifting model, footage of the formation of a fireball was used. According to the shooting frames, the position of the fireball in space and its kinematic characteristics were tracked. Using kinematic parameters, thermal loads were determined. To assess the adequacy of calculations of thermal loads, a comparative analysis of the results of calculations of the developed computational methodology with the results of calculations using existing domestic and foreign methods was used. To substantiate the application of the developed computational methodology for determining thermal loads, taking into account the kinematic parameters of the fireball, a computational experiment was conducted using the MATLAB software and computing complex.Results and their discussion.The results of the calculation of kinematic parameters are satisfactorily correlated with the results of mathematical modeling. The obtained values of thermal loads according to the developed computational methodology are in satisfactory agreement with the results of calculations according to existing domestic and foreign methods. Based on the calculations performed in the article, it is shown that a change in gas dynamic flows (wind demolition) leads to a significant change in the damaging factors of fireballs that are formed during fires in emergency situations.Conclusions. The results of the research made it possible to assess the adequacy of the performance of the improved computational methodology for determining thermal loads in accidents accompanied by fireballs, as well as to justify the relevance of the application of the developed method.

Influence of sequential fireballs on thermal safety distance estimations for organic peroxide drums

Organic peroxides are highly reactive and unstable substances that can undergo self-accelerating decomposition and develop sequential fireballs during storage and transportation. The available semi-empirical equations for the assessment of physical and radiative properties of organic peroxides and liquid hydrocarbon fireballs are based on a fixed mass of substance with an assumption of single fireball formation. However, the involvement of variable fuel mass in sequential fireballs developed in an overlapping and individual manner requires further modifications to the existing equations. Considering the complexities involved in large-scale experiments, Computational Fluid Dynamics (CFD) based open-source code Fire Dynamics Simulator (FDS) has been used in the present study to estimate the characteristics of such sequential fireballs. The existing equations are modified based on visible diameter of the overlapped fireballs. The safety distances are calculated and compared using different models viz. TDU, TNT equivalence and irradiation. Results indicated that the predicted Surface Emissive Power (SEP) for the overlapped fireballs are 9–27% higher compared to the individual fireballs. Moreover, the predicted safety distances as per NFPA 49CFR (5 kW/m2) for overlapped fireballs were ranging from 60 to 70 m compared to 15–25 m for the individually generated ones.

Turbulent flame propagation in corn dust clouds formed in confined and open spaces

Flame propagation stages in a corn dust cloud in a large room size confinement investigated. The clouds ignited by a weak heat source. The mass of the dust identified to be influenced the flame acceleration. Dust in the clouds burnt rapidly through several fluid dynamic mechanisms. Four types of instabilities contributed to fast flame development. Landau–Darrieus and Kelvin–Helmholtz instabilities increased the flame speed in the initial stages of the fireball. In the intermediate and final stages, corrugated and the wrinkled flame structure originated through Rayleigh–Taylor instabilities. In addition to flow aspects and instabilities, the shock waves also enhanced the flame speed. The shock overpressure measured with a dynamic pressure sensor. These shock waves induced Richtmyer–Meshkov instability in the fireball and developed turbulent flames. Density gradients across the fireball (due to higher temperature gradients) caused perturbations. Further, this gradient increased by the shock waves. The crosswind speed through the confinement windows was slower, therefore it has not enhanced the flame speed. Corn dust dispersed quickly to a wider area by the shock waves, established large dust clouds, and lead to explosions. The maximum surface temperature of the fireball predicted as 1384 K. The preheat zone around the fireball identified by an image processing tool. The turbulence parameters at the fireball obtained from qualitative and quantitative methods and analyzed. The clouds of a small quantity of corn dust lead to the formation of larger fireballs due to higher kinematic viscosity than the energy dissipation rate.

CFD Simulation of Fuel Dispersion and Fireball Formation Associated with Aircraft Crash on NPP Structures

ABSTRACT The accidental or intentional crash upon structures of Nuclear Power Plant (NPP) by an aircraft cause the fuel spreading followed by a fireball formation. This fireball is large enough to engulf the entire NPP and radiates a large amount of heat. This engulfment may lead to a local rise in temperature, which causes the spallation of concrete structure and fatalities to the human being. This may affect the integrity of NPP structures and has safety implications. The building structures influence the spatial evolution of fireball due to the generation of large turbulent structures, which further increases the local temperature. The evolution of fireball following fuel dispersion due to the aircraft crash upon an NPP is presented in this article. Numerical simulation to study the effect of fireball on the target NPP structure and its surrounding has been performed using a three-dimensional computational fluid dynamics (CFD) code. This analysis is used to study the evolution of fireball and thermal hazard associated with the radiated heat. It is found that some parts of fireball energy go as heat input to containment and the remaining portion is dissipated to the atmosphere by convection and radiation. Abbreviations CCPS: Centre for Chemical Process Safety; CID: Controlled Impact Demonstration; CFD: Computation Fluid Dynamics; EDC: Eddy Dissipation Concept; FAA: Federal Aviation Administration; FDS: Fire Dynamic Simulator; FVDOM: Finite Volume Discrete Ordinate Method; GAMG: Geometric Algebraic Multi-Grid; HRR: Heat Release Rate; IAEA: International Atomic Energy Agency; NIST: National Institute of Standards and Technology; NPP: Nuclear Power Plant; NTSB: National Transport Safety Board; OpenFOAM: Open Field Operation And Manipulation; PBiCG: Preconditioned Bi-Conjugated Gradient; PISO: Pressure Implicit with Splitting of Operator; SMD: Sauter Mean Diameter; TNO: The Netherlands Organization of applied scientific research; VTT: Technical Research Centre of Finland; WTC: World Trade Centre

On the hysteresis in fireball formation and extinction

A model is proposed to explain hysteresis observed in fireball formation and extinction as electrode bias is varied in partially ionized plasmas. Formation is predicted after a sufficiently deep potential well for electrons is established in the electron sheath of the electrode. Under the experimental conditions considered, once the fireball forms, the plasma potential rapidly increases, resulting in electrons being only lost to the electrode. Previous predictions suggest that once formed, the fireball double layer must maintain a potential close to the ionization potential of the neutral gas to remain in a steady state. In this paper, it is predicted that changes in electrode bias after formation result in a corresponding change in the fireball size and plasma potential. This change in plasma potential allows the double layer potential to be maintained at biases both above and below the electrode bias at onset. The fireball extinguishes when the required double layer potential can no longer be maintained with the balance of current loss of the bulk plasma. These predictions are tested experimentally and are found to be in good agreement with the measurements.

Theoretical studies on fuel dispersion and fireball formation associated with aircraft crash

ABSTRACTThe accidental or intentional crash of an aircraft causes the fuel dispersion followed by a fireball formation that may affect the integrity of structures by thermal hazards. The fireball arising from the aircraft crash has been studied and analyzed using Eddy Dissipation Concept (EDC) combustion model in the computational fluid dynamic (CFD) platform openFOAM. The simulations have been performed with two methods. In first method, the fuel is injected in complete vapor form and in the second method, fuel is injected as dynamic fuel spray. The input to analyze fireball by dynamic spray model has been obtained from droplet spray model reported earlier (Shelke et al., 2018). The diameter and lift-off height obtained in CFD analyses are compared with a video footage reported in literature and it is found to be in good agreement. To illustrate the transient behavior of fireball, evolution of mass fractions of fuel and combustion products and developed pressure are studied. It has been found that both methods give similar predictions for fireball diameter and lifting height.

Mathematical model for prediction of droplet sizes and distribution associated with impact of liquid-containing projectile

Abstract After the events of 9/11, the impact of fast flying commercial aircraft is considered as major hazard threatening the Nuclear Power Plant's (NPP) safety. The study of fuel spillage phenomenon and fireball formation is important to understand fire hazards due to burning of dispersed aviation fuel. The detailed analysis of fuel dispersion is very difficult to deliberate because both, large NPP structures and the large size of commercial aircrafts. Sandia National Laboratories, USA conducted impact tests using cylindrical projectiles filled with water to measure the associated parameters. Due to combustion properties and volatile nature of hydrocarbon fuels, the obtained parameters from impact studies using water are incomplete in fire analysis of flammable droplet clouds. A mathematical model is developed for prediction of droplet sizes and distribution associated with the impact of a liquid-containing projectile. The model can predict the transient behavior of droplet cloud. It is validated with experimental data available in literature. In the present study, the analysis has been performed using water and kerosene. The data obtained can be utilized as boundary and initial condition for CFD analysis. This information is useful for fire hazard analysis of aircraft impacts on NPP structures.

A statistical method to estimate low-energy hadronic cross sections

In this article we propose a model based on the Statistical Bootstrap approach to estimate the cross sections of different hadronic reactions up to a few GeV in c.m.s energy. The method is based on the idea, when two particles collide a so called fireball is formed, which after a short time period decays statistically into a specific final state. To calculate the probabilities we use a phase space description extended with quark combinatorial factors and the possibility of more than one fireball formation. In a few simple cases the probability of a specific final state can be calculated analytically, where we show that the model is able to reproduce the ratios of the considered cross sections. We also show that the model is able to describe proton\,-\,antiproton annihilation at rest. In the latter case we used a numerical method to calculate the more complicated final state probabilities. Additionally, we examined the formation of strange and charmed mesons as well, where we used existing data to fit the relevant model parameters.

Potansiyel Yaralama Etkileri Açısından Havai Fişekler

Amaç: Havai fişekler eğlence amacına yönelik bir piroteknik ürün çeşididir. Yapımında kullanılan malzemeler ve tasarımları nedeniyle bazı potansiyel riskler içermektedirler. Basit bir “silah” sistemi şeklinde kullanılabilirlikleri yanında, tasarımlarında kullanılan enerjik malzemeler de ev yapımı bombalarda kullanılabilir niteliktedir. Zaman zaman yangın, yaralanma ve ölüm olaylarına ilişkin haberlerle karşımıza çıkmaktadır. Çalışmamızda havai fişeklerin yaralama potansiyelini incelemek amaçlanmıştır. Gereç ve Yöntem: Yerli üretim havai fişek bataryalarının fiziki incelemesi, hızlı kamera eşliğinde havai fişek bataryasının fonksiyonu ile ateşlenmesi, fişeklerin namludan çıkış anının görüntülemesi ve hız ölçümü, fişeklerin infilak anının görüntülemesi ve basınç ölçümü olmak üzere dört farklı çalışma yapılmıştır. Havai fişeklerin fiziki incelemelerinde; fişek bataryalarının, silindirik yapıda kartondan mamül namluların birleştirilmesinden oluşturulmuş bloklar halinde olduğu, bataryayı oluşturan her bir namlunun alt kısmından geçirilmiş bir fitilin yakılması ile namlular içindeki fişeklerin belirli aralıklarla ve sırayla ateşlendiği, patlayarak görsel efekti oluşturan fişeklerin, tasarlanan efekti oluşturacak şekilde toz ve katı formda bir dizi piroteknik bileşikler ile toprak, tahıl gibi ilave maddeler kullanılarak tasarlandıkları gözlenmiştir. Bulgular: Bataryanın ateşlenmesi sırasında yoğun bir duman ve namlu ağızlarından ortalama 40,02 cm (SD= 7,21) yükseklikte alev püskürmesi oluştuğu, ortalama 28 g (SD:3,8) ağırlığındaki havai fişeklerin 0.5 m mesafede ortalama 52,61 m/sn (SD:6,92) hıza ulaştıkları belirlenmiştir. Fişeklerin infilak anında ortalama 144,42 cm (SD: 144.42) çapında alev topu oluştuğu ve aynı zamanda efekt materyali saçılımı gözlemlenmiş, fişeklerin patlama basıncı ortalama 89,10 kPa (SD: 16,62) olarak ölçülmüştür. Sonuç: Yapılan tespitler ışığında havai fişeklerin, içerdikleri piroteknik bileşiklerden kaynaklanan, namludan çıkışta alev püskürmesi, fişeğin ulaştığı hız, alev topu oluşumu ve parça tesiriyle yaralama potansiyeline sahip oldukları değerlendirilmiştir.

Impact Assessment of Thermal Radiation Hazard from LPG Fireball

The failure of the pressure vessel containing pressure liquefied petroleum gas leads to Boiling Liquid Expanding Vapour Explosion (BLEVE). Further, ignition of released gas results in the formation of fireballs. In the present paper the semi-empirical equations are presented that represent the impact assessment of thermal radiation hazards from the liquefied petroleum gas fireball. Also an attempt has been made to determine the safe separation distance.

Mechanism behind self-sustained oscillations in direct current glow discharges and dusty plasmas

An alternative explanation to the mechanism behind self-sustained oscillations of ions in direct current (DC) glow discharges is provided. Such description is distinguished from the one provided by the fluid models, where oscillations are attributed to the positive feedback mechanism associated with photoionization of particles and photoemission of electrons from the cathode. Here, oscillations arise as consequence of interaction between an ion and the surface charges induced by it at the bounding electrodes. Such mechanism provides an elegant explanation to why self-sustained oscillations occur only in the negative resistance region of the voltage-current characteristic curve in the DC glow discharges. Furthermore, this alternative description provides an elegant explanation to the formation of plasma fireballs in the laboratory plasma. It has been found that oscillation frequencies increase with ion's surface charge density, but at the rate which is significantly slower than it does with the electric field. The presented mechanism also describes self-sustained oscillations of ions in dusty plasmas, which demonstrates that self-sustained oscillations in dusty plasmas and DC glow discharges involve common physical processes.

Effect of finite chemical potential on QGP-Hadron phase transition in a statistical model of fireball formation

We study the effect of finite chemical potential for the QGP constituents in the Ramanathan et al. statistical model (Phys.Rev.C70, 027903,2004). While the earlier computations using this model with vanishing chemical potentials indicated a weakly first order phase transition for the system in the vicinity of 170 MeV (Pramana, 68, 757, 2007), the introduction of finite values for the chemical potentials of the constituents makes the transition a smooth roll over of the phases, while allowing fireball formation with radius of a few "fermi" to take place. This seems to be in conformity with the latest consensus on the nature of the QGP-Hadron phase transition. Keywords: Quark Gluon Plasma, Quark Hadron Phase Transition

Torqued fireballs in relativistic heavy-ion collisions

We show that the fluctuations in the wounded-nucleon model of the initial stage of relativistic heavy-ion collisions, together with the natural assumption that the forward- (backward-) moving wounded nucleons emit particles preferably in the forward (backward) direction, lead to an event-by-event torqued fireball. The principal axes associated with the transverse shape are rotated in the forward region in the opposite direction than in the backward region. On the average, the standard deviation of the relative torque angle between the forward and backward rapidity regions is $~$${20}^{\ifmmode^\circ\else\textdegree\fi{}}$ for the central and ${10}^{\ifmmode^\circ\else\textdegree\fi{}}$ for the midperipheral collisions. The hydrodynamic expansion of a torqued fireball leads to a torqued collective flow, yielding, in turn, torqued principal axes of the transverse-momentum distributions at different rapidities. We propose experimental measures, based on cumulants involving particles in different rapidity regions, which should allow for a quantitative determination of the effect from the data. To estimate the nonflow contributions from resonance decays we run Monte Carlo simulations with therminator, a thermal heavy-ion generator. If the event-by-event torque effect is found in the data, it will support the assumptions concerning the fluctuations in the early stage of the fireball formation, as well as the hypothesis of the asymmetric rapidity shape of the emission functions of the moving sources in the nucleus-nucleus collisions.

Influence of CdZnTe/Au Contact on the Wire Bonding Property between the Down-Lead and Au Electrode

According to the need to make high quality X-ray or γ-ray detectors made by high resistance CdZnTe, the wire bonding technology between the Au contact layer of CdZnTe wafer and the down-lead has been studied in this paper. The influence of welding parameters and surface treatment of CdZnTe wafer on the welding quality between Au contact layer and down-lead have been discussed in detail, such as chemical and mechanical polishing technology of CdZnTe wafer before welding, thickness of the contact layer of CdZnTe wafer, welding energy, welding pressure, welding time, and etc. The results showed that the successful jointing between Au contact layer of CdZnTe and down-lead can be achieved when applying the suitable welding parameters and pretreatment technology of CdZnTe wafer. The optimized welding parameters for CdZnTe wafer were as follows: welding power 2w, welding pressure 60×10-3 kg, welding time 20ms and the power for fire ball formation 1.5w.

Strange Filamentary Structures (“Fireballs”) around a Merger Galaxy in the Coma Cluster of Galaxies

We found an unusual complex of narrow blue filaments, bright blue knots, and Hα-emitting filaments and clouds, which morphologically resembled a complex of fireballs, extending up to 80 kpc south from an E+A galaxy RB 199 in the Coma Cluster. The galaxy has a highly disturbed morphology indicative of a galaxy-galaxy merger remnant. The narrow blue filaments extend in straight shapes toward the south from the galaxy, and several bright blue knots are located at the southern ends of the filaments. The RC band absolute magnitudes, half-light radii, and estimated masses of the bright knots are ~–12 to –13 mag, ~200-300 pc, and ~106-107 M☉, respectively. Long, narrow Hα-emitting filaments are connected at the south edge of the knots. The average color of the fireballs is B − RC ≈ 0.5, which is bluer than RB 199 (B − R = 0.99), suggesting that most of the stars in the fireballs were formed within several times 108 yr. The narrow blue filaments exhibit almost no Hα emission. Strong Hα and UV emission appear in the bright knots. These characteristics indicate that star formation recently ceased in the blue filaments and now continues in the bright knots. The gas stripped by some mechanism from the disk of RB 199 may be traveling in intergalactic space, forming stars left along its trajectory. The most plausible fireball formation mechanism is ram pressure stripping by high-speed collision between the galaxy and the hot intracluster medium. The fireballs may be a snapshot of diffuse intracluster population formation, or halo star population formation in a cluster galaxy.

The Birth of Quark Stars: Photon-driven Supernovae?

In this Letter we propose a possible mechanism for trying to alleviate the current difficulty in core-collapse supernovae by forming a strange quark star inside the collapsing core. Although the initial long-time cooling behavior of nascent strange stars is dominated by neutrino emissions, thermal emissions including photons and e± pair plasma do play a significant role in the explosion dynamics in this scenario. The key to promoting a successful shock outside a bare strange star is more likely to be the radiation pressure caused by thermal photons rather than neutrinos in conventional models. We observed through calculation that radiation pressure can push the overlying mantle away through photon-electron scattering with energy (the work done by radiation pressure) as much as ~1051 ergs if protoquark stars are born with temperatures higher than ~30-40 MeV. This result not only indicates that strange quark stars are bare since their formations, it could also provide a possible explanation for the formation of fireballs in cosmic long-soft γ-ray bursts associated with supernovae.

Simple statistical model for analysis of quark-gluon plasma droplet (fireball) formation

We construct the density of states for quarks and gluons using the `Thomas - Fermi model' for atoms and the `Bethe model' for nucleons as templates. With parameters to take care of the plasma (hydrodynamical) features of the QGP with a thermal potential for the interaction, we find a window in the parametric space of the model where observable QGP droplets of $ \sim $ 5 fm radius can occur with transition temperature in the range 140 MeV to 250 MeV. By matching with the expectations of Lattice Gauge estimates of the QGP-hadron transitions, we can further narrow the window, thereby restricting the allowed values of the flow-parameters of the model.