Second-stage reaction zone

The combustion wave of an HMX composite propellant consists of successive re-achon zones the condensed-phase reachon zone, a first-stage reaction zone, a second-stage reaction zone, and the luminous flame zone. The combustion wave structure and temperature distribution for an HMX propellant are shown in Fig. 7.47. In the condensed-phase reaction zone, HMX particles melt together with the polymeric binder HTPE and form an energetic liquid mixture that covers the burning surface of the propellant. In the first-stage reaction zone, a rapid exother-... 

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... 

The combustion wave of an NC-NG-GAP propellant consists of successive two-stage reaction zones.0 1 The first gas-phase reaction occurs at the burning surface and the temperature increases rapidly in the fizz zone. The second zone is the dark zone, which separates the luminous flame zone from the burning surface. Thus, the luminous flame stands some distance above the burning surface. This structure... 

Extension of the hydrodynamic theory to explain the variation of detonation velocity with cartridge diameter takes place in two stages. First, the structure of the reaction zone is studied to allow for the fact that the chemical reaction takes place in a finite time secondly, the effect of lateral losses on these reactions is studied. A simplified case neglecting the effects of heat conduction or diffusion and of viscosity is shown in Fig. 2.5. The Rankine-Hugoniot curves for the unreacted explosive and for the detonation products are shown, together with the Raleigh line. In the reaction zone the explosive is suddenly compressed from its initial state at... 

II Second-stage gas-phase reaction zone (O/F flame)... 

Condition at end of first-stage gas-phase reaction zone (A/PA flame) 2 Condition at end of second-stage gas-phase reaction zone (O/F flame)... 

Figure 6.16 displays the temperature profile and liquid-phase molar fractions for cumene and DIPB. It may be observed that the temperature is practically constant over the reactive sections with a first plateau at 200 °C and a second one at 210 °C. The top temperature is at 198 °C while the bottom temperature climbs to 242 °C. The explanation may be found in the variation of concentrations for cumene and DIPB in the liquid phase. The maximum reaction rate takes place on the stages where propylene is injected. The cumene concentration increases rapidly and reaches a flat trend corresponding to the exhaustion of the propylene in liquid phase. It may be seen that the amount of DIPB increases considerably in the second reaction zone. This variation is very different from that with a cocurrent PFR. The above variations suggest that the productivity could be improved by providing several side-stream injections and/or optimizing the distribution of catalyst activity. 

The general redox mechanism of metal-oxide catalyzed oxidation of hydrocarbons involves two major stages in the catalytic process, reduction of the surface layers by hydrocarbons and their reoxidation by interaction with oxygen. While these two stages occur simultaneously in a reactor with the catalyst working under steady-state conditions, they can be carried out in two separate reaction zones in a reactor with catalyst circulation [37]. A hydrocarbon is fed into the first zone where a desirable intermediate product of partial oxidation is formed after interaction with the oxidized catalyst. In the second zone, gas phase oxygen reoxidizes the catalyst. Obviously, the residence time of the catalyst in the first zone should be short enough to prevent formation of an inactive reduced state of the catalyst. If only surface layers participate in the interaction with hydrocarbons, the time of catalyst reduction is approximately several seconds. 

Species profiles have not been measured directly for dry CO/air or CO/O2 flames in the same way as they have for hydrogen flames. Several investigations, however, have been concerned with the oxidation of carbon monoxide in lean hydrocarbon flames (e.g. refs. 406, 413, 417, 429) or in moist CO flames flames of H2 /CO mixtures in air [167, 406, 414, 418] or O2 [523]. The interest in the oxidation in hydrocarbon flames has arisen since the overall reaction in such flames is a two stage process. In the first rapid stage (the main flame reaction zone) the hydrocarbon is essentially converted to CO and water, with traces of hydrogen also appearing. The second, more extended, stage is devoted to radical recombination and to the slower oxidation of CO, predominantly by reaction (xxiii). 

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