Inert second limit

There is general agreement that increasing the O2 /CO ratio above stoichiometric raises the second limit pressure, whilst the addition of the inert gases helium, argon, or nitrogen, lowers the partial pressure of combustible gas at the limit. Von Elbe et al. [367] found that the... 

According to eqn. (109a), only CO may be replaced by inert gas without lowering the overall second limit pressure, and this is contrary to experiment. The situation can be modified by inclusion of further reactions, so that some semblance of agreement is obtained. However, there is a stronger objection. There is no evidence that CO reacts directly with O3 at 350 °C, the formation of CO2 in these conditions being due to reaction with oxygen atoms which arise from the thermal decomposition of the ozone[379, 380]. 

Finally it should be realized that quadratic branching may occur where there is no net increase in radicals. Reaction (59) is a key step in determining the second limit of the H2 -I- O2 reaction under conditions where HO2 is inert, so that effectively one active radical gives two active radicals. Similarly reaction (54) is a very important branching reaction in alkane oxidation between 700 and 1000 K. 

Figure 4.1 Variation of the rate of reaction in a system containing a 2 1 mole ratio of hydrogen to oxygen as a function of the total pressure. First, second, and third explosion limits are labeled a, b, and c, respectively. Displacement of the first and second limits to lower pressures occurs on addition of an inert gas or enlarging the volume of the reactor (dashed lines). (Adapted from J. W. Moore and R. G. Pearson, Kinetics and Mechanism, 3rd ed., p. 409. Copyright 1981 by John Wiley Sons, Inc.)...

Figure 6.3.2 shows the feed-forward design, in which acrolein and water were included, since previous studies had indicated some inhibition of the catalytic rates by these two substances. Inert gas pressure was kept as a variable to check for pore diffusion limitations. Since no large diffusional limitation was shown, the inert gas pressure was dropped as an independent variable in the second study of feed-back design, and replaced by total pressure. For smaller difftisional effects later tests were recommended, due to the extreme urgency of this project. 

In summary, in the equilibrium-chemistry limit, the computational problem associated with turbulent reacting flows is greatly simplified by employing the presumed mixture-fraction PDF method. Indeed, because the chemical source term usually leads to a stiff system of ODEs (see (5.151)) that are solved off-line, the equilibrium-chemistry limit significantly reduces the computational load needed to solve a turbulent-reacting-flow problem. In a CFD code, a second-order transport model for inert scalars such as those discussed in Chapter 3 is utilized to find ( ) and and the equifibrium com-... 

Cubic Phase of Boron Nitride c-BN. The cubic phase of boron nitride (c-BN) is one of the hardest materials, second only to diamond and with similar crystal structure. It is the first example of a new material theoretically predicted and then synthesized in laboratory. From automated synthesis a microcrystalline phase of cubic boron nitride is recovered at ambient conditions in a metastable state, providing the basic material for a wide range of cutting and grinding applications. Synthetic polycrystalline diamonds and nitrides are principally used as abrasives but in spite of the greater hardness of diamond, its employment as a superabrasive is limited by a relatively low chemical and thermal stability. Cubic boron nitride, on the contrary, has only half the hardness of diamond but an extremely high thermal stability and inertness. 

Since the dipoles of chromophore molecules are randomly distributed in an inert organic matrix in amorphous PR materials, the material is centrosymmet-ric and no second-order optical nonlinearity can be observed. However, in the presence of a dc external field, the dipole molecules tend to be aligned along the direction of the field and the bulk properties become asymmetric. Under the assumption that the interaction between the molecular dipoles is negligible compared to the interaction between the dipoles and the external poling field (oriented gas model), the linear anisotropy induced by the external field along Z axis at weak poling field limit (pE/ksT <[Pg.276]

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