Shock tube parameters

Obtaining chemical equilibrium compositions for assigning thermodynamic states on the basis of temperature, pressure, density, enthalpy, entropy, shock tube parameters, or detonations. 

Calculating shock tube parameters for both incident and reflected shocks. 

Our data can be used to estimate the effective temperatures reached in each site through comparative rate thermometry, a technique developed for similar use in shock tube chemistry (32). Using the sonochemical kinetic data in combination with the activation parameters recently determined by high temperature gas phase laser pyrolysis (33), the effective temperature of each site can then be calculated (8),(34) the gas phase reaction zone effective temperature is 5200 650°K, and the liquid phase effective temperature is 1900°K. Using a simple thermal conduction model, the liquid reaction zone is estimated to be 200 nm thick and to have a lifetime of less than 2 usee, as shown in Figure 3. 

The overall stoichiometric equation for this decomposition leading to equilibrium depends on the temperature. A considerable amount of the final products are H, OH, and O. Bauer et al.3 were the first to report an investigation of the water dissociation by the shock-tube method. The temperature range for this study was 2400-3200 °K. They followed the reaction by measuring the uv absorption of the hydroxyl radical produced during the decomposition. The apparent activation energy for the parameter (1/ [H20])(d [OH]/df) of about 50 kcal.mole-1 seemed to indicate that the reaction... 

The homogeneous thermal decomposition of HC1 has only been studied in shock tubes. Fishbume51 investigated the shock pyrolysis of HC1 diluted with Ar in the temperature region 3300-5400 °K and obtained Arrhenius parameters for... 

The solution procedure to this equation is the same as described for the temporal isothermal species equations described above. In addition, the associated temperature sensitivity equation can be simply obtained by taking the derivative of Eq. (2.87) with respect to each of the input parameters to the model. The governing equations for similar types of homogeneous reaction systems can be developed for constant volume systems, and stirred and plug flow reactors as described in Chapters 3 and 4 and elsewhere [31-37], The solution to homogeneous systems described by Eq. (2.81) and Eq. (2.87) are often used to study reaction mechanisms in the absence of mass diffusion. These equations (or very similar ones) can approximate the chemical kinetics in flow reactor and shock tube experiments, which are frequently used for developing hydrocarbon combustion reaction mechanisms. 

When the commodity chemical propylene oxide is heated to high temperature in the gas phase in a shock tube, unimolecular rearrangement reactions occur that generate the CsHgO isomers allyl alcohol, methyl vinyl edier, propanal, and acetone (Figure 15.9). Dubnikova and Lifshitz carried out a series of calculations to determine the mechanistic pathway(s) for each isomerization, with comparison of activation parameters to those determined from Arrhenius fits to experimental rate data to validate the theoretical protocol. 

Several years later the process analyzed in Ya.B. s article became the basis for the most powerful method for experimental study of physico-chemical kinetics in gases at high temperatures—shock tubes. For two decades practically all measurements of the probabilities of excitation of molecular oscillations and of dissociation of molecules, i.e., everything that was needed for calculations of the motion of space vehicles through the atmosphere, were performed in shock tubes by recording current parameters in the relaxation layer. We may note that even in the experimental study of ignition in a shock tube, the first work was done by Ya.B. with Ya. T. Gershanik and A. I. Rozlovskii [19],... 

The shock tube technique employed in the pyrolytic decomposition of polyfluorohydro-carbons22,27,28 showed that the elimination of molecular hydrogen fluoride is the predominant reaction. Yet, a side process of C—C bond breaking becomes important as the temperature is increased beyond 1300 K. Several fluoroethanes have been found to react by molecular dehydrofluorination in chemical activation process29 and Table 2 summarizes the kinetic parameters for the gas-phase pyrolysis of this type of compound. In the case of 1,1,2-trifluoroethane, three olefin products were obtained (equations 3-5). 

The general problem has been to extend the usefulness of the induction parameter model proposed by Oran et al. (1). This induction parameter model (IPM) is proposed as a means to enable one to estimate, relatively easily, the energy necessary to achieve ignition when using a thermal heating source Much of the calibration of this model, for example the effect of deposition volume (quench volume), can be done with one-dimensional models, and shock tube experiments. There are phenomena, however, which must be studied in two or three dimensions. Examples are turbulence and buoyancy. This paper discusses the effect of buoyancy and possible extensions to the IPM. 

As well as conventional kinetic methods, the shock-tube method and the toluene vapour-flow method have also been used for studying the unimolecular elimination of hydrogen iodide from alkyl iodides. Table 12 summarises Arrhenius Parameters for these reactions. 

The parameter regimes in a detonation are similar to those in shock tubes, so the most important test of this type of mechanism is its ability to reproduce shock tube ignition data. One example of this validation process compared computed ignition delay times (2) with experimental results of Burcat et al. 

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