The use of Hugoniot analysis for the propagation of vapor explosion waves (original) (raw)

A mathematical model of melt/water detonations

Applied Mathematical Modelling, 1989

We describe a new mathematical model of melt/water detonations. This model has been developed to study the escalation and propagation stages of a vapor explosion. After describing the physics of this problem, we give a complete description of the conservation equations and constitutive relations which form the model. We then describe the solution procedure and present some results from example simulations.

Numerical Model for Boiling Liquid Vapor Explosion (BLEVE)

42nd AIAA Aerospace Sciences Meeting and Exhibit, 2004

The depressurization of a vessel containing saturated or subcooled liquid may occur in a variety of industrial processes and often poses a potentially hazardous situation. A 1D plane numerical model was developed for estimating the thermodynamic and the dynamic state of the boiling liquid during a boiling liquid expanding vapor explosion (BLEVE) event. Based on the choice of the initial nucleation sites density, the model predicts, simultaneously, the bubble growth processes in the liquid at the superheat-limit state, the front velocity of the expanding liquid, and the shock wave pressure formed by the liquid expansion through the air.

An improved mathematical model of melt/water detonations—II. A study of escalation

International Journal of Heat and Mass Transfer, 1991

In this paper, the model presented in Part I is used to perform a detailed study of the effect of various model parameters and constitutive assumptions on the escalation stage of a vapour explosion. In particular, the roles played by the chosen heat transfer rate and fragmentation law, the effect of geometry, and of a non-uniform premixture are examined. Finally, the requirements for experimental validation of the model are discussed.

Preliminary result on unconfined vapor cloud explosion using vertical tube on hot surface

The unconfined vapor cloud explosion (UVCE) is fire accidents that could cause severe damage and it sometimes leads to high potential of casualties. Severity caused by UVCE is due to its wide spread fire explosion and that the source mostly comes from a relatively small amount of gasoline or gas leak that has happened long enough leading to the occurrence of an explosion. Since the awareness to this situation relatively low. Research on flammability levels from various liquid and gas fuels has been conducted extensively and it has even been shown in MSDS which ease users in utilizing fuel handling and the selection of safety factors. There have been many studies completed on discovering the cause of fire occurrence especially after the incident of several UVCE-related accidents. Similarly, many dispersion models of fuel leakage and liquid followed by evaporation process have been developed at an applicable level. UVCE still leaves some questions related to the initiation of the explosion. Some research on the phenomenon of explosions on UVCE has been carried out to find out the conditions so as to enable an explosion. Moreover, there is still one question unanswered on UVCE concerning on how do high velocity of deflagration arises in the conditions of an open space explosion. From an accident evaluation so far, it can be believed that the obstacle in the flame path will make the escalated flame velocity reach the Deflagration to Detonation Transition (DDT) level. This was supported by the results of a large scale experimental study conducted by several researchers whose results were reported in line with these assumptions. In addition, some researchers believe that the explosion of UVCE is sequential, beginning with the initial fire. The flame formed will generate heat quickly through radiation heat transfer to the unburned vapor cloud section. This phenomenon is considered responsible for the occurrence of a larger explosion and covers a large area on several accidents.This paper presents preliminary results from lab scale research to characterize the deflagration velocity of vapor cloud flame which is affected by the temperature of the environment. Visual observation is processed from the camera record on deflagration in an open vertical tube with a hot plate. By using gasoline as a vapor cloud source, tests were carried out in three conditions: lean mixture, stoichiometric mixture and rich mixture. In experiments with lean mixture does not occur or it is difficult to fire. For stoichiometric mixture, deflagration occurs quickly and causes an explosion sound. In rich mixture conditions a loud explosion occurs. Especially for the 1.8 stoichiometric concentration, two fires were produced and with the loudest explosion sound. On first fire combustion occurs quickly with a large fireball, after which a second explosion is followed which depletes the rest of the unburned vapor cloud. In experiments with very rich mixture (concentrations of 2 x stoichiometric conditions) occur fire with a slow flame velocity and form soot significantly.

1D plane numerical model for boiling liquid expanding vapor explosion (BLEVE)

International Journal of Heat and Mass Transfer, 2007

Theoretical and experimental study of cylindrical shock and heterogeneous detonation waves

Acta Astronautica, 1974

A simplified theory of blast initiation of detonations in clouds of fuel in gaseous or droplet form is developed and agrees with the experiments described below. The flow is at first dominated by the strong blast wave but transition from blast to detonation behavior occurs near a critical radius r. where the blast energy and the heat of combustion contained in r < r. are equal. The complex flow in this transition region cannot be determined analytically. In the simplified theory the details of the transition region are ignored but the flow is represented by the self-similar solution for a strong blast wave for r < r. and by the self-similar detonation solution for r > r..

Thermal explosions resulting from fuel-coolant interactions: Analysis of single bubble hydrodynamics

Metallurgical Transactions B, 1988

High-speed photographic data and pressure traces of thermal explosions from the contact of single drops of iron oxide with water were analyzed according to models describing underwater chemical explosion and cavitation bubbles. The objective of the study was to develop a simple method for analyzing the microscale hydrodynamics of fuel-coolant interactions (FCI). We have found that for a given external pressure and liquid density essentially all the features of the radial motion of the explosion bubble, including the total energy release, are uniquely determined by a single parameter-the bubble period. Nearly all of the heat transfer from fuel to coolant occurs during the 10 -5 to 10 -4 sec timespan of coolant vapor film collapse during which the fuel fragments. The observable features of the resulting explosion bubble are not significantly affected by the degree of heat transfer from vapor to coolant liquid and the bubble can be modeled as an empty cavity. The method developed during this study should facilitate investigations on FCI by simplifying the analyses of thermal explosion data. Further attention can be given to experiments on the effects of fuel parameters, e.g., surface tension and viscosity, on fragmentation, heat transfer, and explosive yield.

Detonation onset in a thermally stratified constant volume reactor

Proceedings of the Combustion Institute, 2018

Understanding detonation development from a flame kernel initiated by a pre-ignition event is important for modern internal combustion (IC) engines operating at boosted conditions. To provide fundamental insights into the effects of bulk gas temperature stratification on the characteristics of detonation development, one-dimensional high fidelity simulations were conducted for a constant volume reactor filled with a thermally stratified reactive stoichiometric hydrogen/air mixture. A linear temperature variation in the upstream end-gas was introduced to represent the thermal stratification of the bulk mixture, and the evolution from the initial deflagration flame front to detonation development was examined. The results showed that the bulk-gas temperature gradient has a significant effect on the run-up time and intensity of the developing detonation. Detailed analyses further revealed that the mechanism of detonation development is qualitatively different for the positive and negative temperature gradient cases. In the former, the detonation development is initiated by the end-gas autoignition at the wall, while the latter exhibits detonation development following the process of the self-acceleration of the flame similar to the deflagration-to-detonation transition. This behavior is attributed to the longer residence time in the end-gas allowing the reinforcement by the interaction of incident and reflected pressure waves during the flame propagation, and results in the peak pressure even higher than the case with the same level of positive temperature gradient. Furthermore, yet another detonation development pattern was observed for the negative temperature gradient condition in the presence of a uniform temperature region just ahead of the flame. In this case, autoignition was found to start in the middle of the bulk end-gas, and subsequently leads to the transition to detonation. The results demonstrate the importance of the bulk gas conditions in predicting the detonation development, which corroborate the existing theoretical framework.

Gaseous detonations—A selective review

Progress in Energy and Combustion Science, 1991

lThis review confines itself to available information on gaseous detonations, including those in aerosols, clouds of flammable dusts and hybrid mixtures, from the standpoint of safety of chemical processing plant. In so doing, it examines recent extensions to work based on the concept of an ideal front with losses (non-ideal theory), showing how this may be applied to derive guidelines on the effects of tube diameter, of wall roughness and of initial pressure of the mixture on the velocity of a steady front. Further extension to the prediction of limits is considered for conditions likely to be experienced in actual plant, where walls are unlikely to be smooth and the presence of inert particles in the explosive medium is a possibility. However, the shortcomings of such an approach in dealing with the interactions of a real front with a complex component of plant is recognised. The experimental techniques which have been used to reveal the complex nature of real fronts are reviewed, prior to a description of studies of the structure of fronts which propagate transversely across the leading front and on how this structure is influenced by the properties of the explosive medium. Finally, experimental work on both non-reactive shocks and detonations in changing configurations of confinement is examined, in terms of possible measures for both reducing the destructive potential of a detonation and obtaining reliable design criteria for chemical plant. CONTENTS I. Introduction 328 2. Non-Ideal Detonations 2.1. Opening remarks 2.2. Detonation mechanisms in rough tubes 2.3. Theoretical considerations 2.4. Momentum and heat losses 2.5. Determination of momentum losses from shock attenuation 2.6. Detonations with homogeneous and boundary layer ignition 2.7. Influence of wall roughness on detonation velocity 2.8. Critical pipe diameter 2.9. Detonation in gaseous suspensions of inert particles 2.10. Detonation of gaseous mixtures in presence of evaporating particles 2.11. Comparison of experimental data with non-ideal unidimensional theory 2.12. Analysis of experimental data on dust clouds 3. Experimental Techniques 3.1. Opening remarks 3.2. Soot track method 3.3. Use of rings and gauges 3.4. Optical methods 3.5. Ionisation methods 4. Real Detonation Fronts 4.1. Opening remarks 4.2. Wave systems created by diffraction of shocks in inert media and their relationship to detonations 4.3. Uni-dimensional models of detonations 4.4. Initiation and the origin of structure 4.5. "Galloping' waves 5. Interactions of Wave Structure with Changes in Confinement 5.1. Opening remarks 5.2. Diffraction of a detonation at an abrupt increase in area 5.3. Methods of reducing and rendering more uniform local pressures 5.4. Reflection of detonation waves 6. Conclusions 364 Acknowledgements References 327

A Linear Stability Analysis of a Vapor Film in Terms of the Triggering of Vapor Explosions

Journal of Nuclear Science and Technology, 2002

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The use of Hugoniot analysis for the propagation of vapor explosion waves (original) (raw)

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