Preparation zone

The combustion wave structure of ADN consists of three zones the melt layer zone, the preparation zone, and the flame zone. The temperature remains relatively unchanged in the melt layer zone, then increases rapidly just above the melt layer zone to form the preparation zone, in which it rises from about 1300 to 1400 K. At some distance above the melt layer zone, the temperature increases rapidly to form the flame zone, in which the final combustion products are formed. 

Similar to the situation with nitrate esters, the two-stage gas-phase reaction resulting from the combustion of ADN occurs due to the reduction of NO to N2, which is reported to be a termolecular reaction. The heat flux transferred back from the preparation zone to the melt layer zone dominates the gasification process occurring in the melt layer zone. 

The soUd-phase reaction zone is also termed the subsurface reaction zone or condensed-phase reaction zone . As the dark zone reaction represents an induction zone ahead of the flame zone, the dark zone is also termed the preparation zone when it produces a luminous flame. Since the flame zone is luminous, it is also termed the luminous flame zone . 

Fig. 7.48 Variation of reaction rate in the preparation zone with pressure for non-catalyzed and catalyzed HMX composite propellants.

The propagation velocity of the TM does not exceed 85-87% of the theoretical detonation velocity DT. Calculation of DT is carried out under the assumption of a chemical reaction which runs after compression by the shock wave without any thermal or hydrodynamic losses. In the case of the TM, meanwhile, the very possibility of propagation of a fast flame with the velocity of the shock wave depends on a velocity redistribution as a result of braking of the layers adjacent to the wall. In constructing the equations for the motion as a whole, braking plays the role of a loss which reduces the velocity. In fact, the velocity will be even smaller than the value cited besides the losses in the hydrodynamic preparation zone (the zone of velocity redistribution between the shock wave front and the forward point of the flame front, zone I-II in Fig. 19) we must add the losses in the combustion zone (from the forward point of the flame front to the cross-section in which combustion has ended, zone II-III in Fig. 19). 

At the close of the dialysis the plasma was centrifuged to remove small amounts of precipitate and the clear plasma resulting was subjected to starch-block preparative zone electrophoresis by the technique of Kunkel and Slater (15). At the close of the electrophoresis 1-cm. segments of the starch block were cut and transferred to sintered glass funnels, and the proteins were quantitatively eluted with five successive 2-ml. aliquots of 0.9% sodium chloride. The filtrates containing the protein fractions were then made up to a constant volume and mixed, and small aliquots were analyzed for total protein content by the method of Lowry et al. (18). 

The gas phase reaction of HMX-GAP propellants occurs with two-stage zones 22 at the first-stage reaction zone the temperature increases rapidly on and just above the burning surface. At the second-stage reaction zone the temperature increases, also rapidly, at some distance from the burning surface. In the preparation zone... 

In addition, a pH control and the possibility to apply different temperatures in two or more preparation zones will be favorable. Moreover, the dosing system must be able to dose liquids as well as solids while the reaetion vessels are stirred and heated, i.e. when solvent vapor is present and a movement takes place in the vessel. 

One of the ways of improving wear resistance and reliability of sealing elements is filling of porous semis by components able to form a secondary porous system [146]. For example, a blank of a polyurethane foam is impregnated with a mixture of dispersed PE with an inhibited lubricant. The formation of a gel under certain temperature regimes is accompanied by phase distribution within the material. The contact surface of the blank is cleaned by acetone to remove the lubricant. As the acetone evaporates, the prepared zones are zinc-plated and pores freed from the lubricant become filled with zinc. This makes the coating adhere strongly to the surface and allows zinc to penetrate to a depth acceptable for wear limits. 

Formation of concentration-prepared zones proceeding from segregation at grain boundaries or other defects. 

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