Essays on Introduction to Physics and Chemistry of Combustion: Explosion, Flame, Detonation Assignment

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The paper "Introduction to Physics and Chemistry of Combustion: Explosion, Flame, Detonation" is a wonderful example of an assignment on chemistry. A thermal explosion is the rapid or sudden inflammation of uniformly heated materials. In order for a thermal explosion to occur, two conditions must be met. First, the temperature of the reacting medium must rise above the ambient temperature past the critical temperature (To) defined by the Semenov Diagram during self-heating (Glassman, 1996). This rise of the temperature of the reacting medium relative to the ambient temperature is due to the self-accelerating reaction of the medium.

Second, this increase in temperature must occur faster than the heat transfer between the reacting medium and its surroundings as a result of the consumption of reactants; otherwise, no explosion could occur. When the thermal equilibrium between the system and its environment is disrupted, the reaction produces an explosion after a given time, called the induction period. The self-accelerating reaction occurs because of the formation of active particles which may result from two things: first, from the thermal motion of these particles and second from the branching of the chain reaction due to the excess energy (Liberman, 2008).

When the rate of chain branching exceeds the rate of chain termination, an explosion occurs. The induction period is the time it takes for the reacting substances to explode from the time they react. It is typically seen as the slow phase of the chemical reaction of reacting substances (Ayeni, 1982). More precisely, it is the time it takes for the buildup of active particles to reach measurable values for them to continue rising without limit (Liberman, 2008). Using Semenov diagrams, explain the effect of heat transfer on thermal heat balance in a vessel with cold walls, critical conditions of the thermal explosion, and pre-explosion heating. There are three critical conditions for the thermal explosion determined by the Semenov diagram.

First, the heat production rate would exceed the heat loss rate in which an explosion occurs after some time. If the heat loss exceeds heat production after a given induction period, the temperature rises to a peak and then gradually decays as the heat production and speed of reaction is slowed by the consumption of reactants.

References

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Bull, D. (1979). “Concentration limits to the initiation of unconfined detonations in fuel/air mixtures”. Chem E 57:219-227

Delichatsios, M. (1992). Transition from momentum to buoyancy-controlled turbulent jet diffusion flames and flame height relationships. Combustion and Flame. 92(4). 349-364

Fickett W, Davis WC (1979) Detonation. University of California Press.

Glassman I (1996) Combustion. 3rd edition, Academic Press.

Liberman, M. (2008). Introduction to Physics and Chemistry of Combustion: Explosion, Flame, Detonation. Springer-Verlag Berlin Heidelberg.

Quintere, J. (1997). Principles of Fire Behavior. Delmar Publishers.

Semenov, N.N., (1959). Some Problems in Chemical Kinetics and Reactivity Part 1 and 2, Pergamon Press, London.

Simmons, R. & Wolfhard, H. (1957). Combustion. Flame 1, 155-161

Strehlow RA (1984) Combustion fundamentals. McGraw-Hill.

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