Overview of Experimental Research

At first glance, the science of vapor cloud explosions as reported in the literature seems rather confusing. In the past, ostensibly similar incidents produced extremely different blast effects. The reasons for these disparities were not understood at the time. Consequently, experimental research on vapor cloud explosions was directed toward learning the conditions and mechanisms by which slow, laminar, premixed combustion develops into a fast, explosive, and blast-generating process. Treating experimental research chronologically is, therefore, a far from systematic approach and would tend to confuse rather than clarify. 

Because the major causes of blast generation in vapor cloud explosions are reasonably well understood today, we can approach the overview of experimental research more systematically by treating and interpreting the experiments in groups of roughly similar arrangements. Furthermore, some attention is given to experimental research into the conditions necessary for direct initiation of a detonation of a vapor cloud and the conditions necessary to sustain such a detonation. 

This section is arranged as follows First, premixed combustion is discussed based on the experiments performed under controlled conditions. To establish these conditions the experiments were conducted in explosion vessels, balloons, plastic bags, and soap bubbles. Second, some experiments under uncontrolled conditions 

Fuel-pair mixtures, in soap bubbles ranging from 4 to 40 cm diameter and with no internal obstacles, produced flame speeds very close to laminar flame speeds. Cylindrical bubbles of various aspect ratios produced even lower flame speeds. For example, maximum flame speeds for ethylene of 4.2 m/s and 5.5 m/s were found in cylindrical and hemispherical bubbles, respectively (Table 4.1a). This phenomenon is attributed to reduced driving forces due to the top relief of combustion products. 

Obstacles introduced in unconfined cylindrical bubbles resulted only in local flame acceleration. Pressures measured at some distance from the cylindrical bubble were, in general, two to three times the pressure measured in the absence of obstacles. 

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This chapter is organized as follows. First, an overview of experimental research is presented. Experimental research has focused on identifying deflagration-enhancing mechanisms in vapor cloud explosions and on uncovering the conditions for a direct initiation of a vapor cloud detonation. 

In the overview of experimental research, it was shown that explosive, blastgenerating combustion in gas explosions is caused by intense turbulence which enhances combustion rate. On one hand, turbulence may be generated during a gas explosion by an uncontrolled feedback mechanism. A turbulence-generative environment, in the form of partially confining or obstructing structures, must be present for this mechanism to be triggered. 

TABLE 6.3. Overview of Experimental Research on Fireball Generation... 

In the rapidly developing field of cold molecules, Feshbach molecules play a particular role as the link to research on ultracold quantum matter. In this chapter, we have presented the basic experimental techniques and discussed some major developments in the field. In this final Section, we briefly point to some other recent developments not discussed so far, adding further interesting aspects to our overview of the research field. 

Taconis, R., Ferguson-Hessler, M.G.M. Broekkamp, H. (2001) Teaching science problem solving an overview of experimental work. Journal of Research in Science Teaching, 38, 442-468. 

In this chapter, we will start by briefly presenting an historical overview of PCET research, acknowledging the different meanings and mechanistic implications enclosed in the definition and establish the basic principles underlying this type of reactions. Experimental evidence and the importance of PCET in the catalysis of water oxidation in natural photosynthesis is explored, followed by a discussion of how those functional principles may be transposed to synthetic systems, both for fundamental studies and for practical applications in the context of solar energy conversion and solar fuel production. 

In this chapter we give an overview of our research on the chemistry of the CIMA reaction and experiments with Turing structures. We discuss the chlorite-iodide reaction and related systems, the effect of starch and its chemistry, the development of models for spatial studies and the results of experiments on Turing structures. We conclude by pointing out several unsolved mechanistic and experimental problems. 

This volume consists of two parts Chapters 1-6 and Chapters 7-9. Chapters 1 through 6 offer detailed background information. They describe pertinent phenomena, give an overview of past experimental and theoretical research, and provide methods for estimating consequences. Chapter 2 describes the phenomena covered, identifies various accident scenarios leading to each of the events, and describes actual accidents. In Chapter 3, principles such as dispersion, deflagration, detonation, blast, and radiation are explained. 

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