Condensed-phase reaction zone

A schematic representation of the combustion wave structure of a typical energetic material is shown in Fig. 3.9 and the heat transfer process as a function of the burning distance and temperature is shown in Fig. 3.10. In zone I (solid-phase zone or condensed-phase zone), no chemical reactions occur and the temperature increases from the initial temperature (Tq) to the decomposition temperature (T ). In zone II (condensed-phase reaction zone), in which there is a phase change from solid to liquid and/or to gas and reactive gaseous species are formed in endothermic or exothermic reactions, the temperature increases from T to the burning surface temperature (Tf In zone III (gas-phase reaction zone), in which exothermic gas-phase reactions occur, the temperature increases rapidly from Tj to the flame temperature (Tg). 

The combustion wave of HMX is divided into three zones crystallized solid phase (zone 1), solid and/or liquid condensed phase (zone 11), and gas phase (zone 111). A schematic representation of the heat transfer process in the combustion wave is shown in Fig. 5.5. In zone 1, the temperature increases from the initial value Tq to the decomposition temperature T without reaction. In zone 11, the temperature increases from T to the burning surface temperature Tj (interface of the condensed phase and the gas phase). In zone 111, the temperature increases rapidly from to the luminous flame temperature (that of the flame sheet shown in Fig. 5.4). Since the condensed-phase reaction zone is very thin (-0.1 mm), is approximately equal to T . 

The combustion wave of GAP copolymer is divided into three zones zone I is a non-reactive heat-conduction zone, zone II is a condensed-phase reaction zone. 

The condensed-phase reaction zone of a burning-interrupted BAMO copolymer is identified by infrared (IR) spectral analysis. In the non-heated zone, the absorption of the N3 bond, along with the absorptions of the C-O, C-H, and N-H bonds. 

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 . 

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 curves of Figures 5 and 6 fit the data fairly well. Thus, Figure 5 gives no indication of heat release in the condensed phase below 450° C. Figure 6 shows the same result at least to 400° C. It may be further noted that at 0.5 atm., for the pressed strand (Figure 5) the condensed phase reaction zone was about 0.5 mm. thick while at 1 atm., for the tamped strand it was about 0.3 mm. thick. 

If there is exothermicity in the condensed-phase reaction zone illustrated in Figure 7.1, then the burning rate may be controlled by reactions that occur in this zone. Deflagration analyses paralleling those discussed in Chapter 5 may be developed for condensed-phase combustion. For illustrative purposes, let us assume that the condensed-phase reaction is the one-step process... 

The combustion wave of GAP copolymer is divided into three zones zone I is a non-reactive heat conduction zone, zone II is a condensed phase reaction zone, and zone III is a gas phase reaction zone in which final combustion products are formed. Decomposition reaction occurs at Tu in zone II, and gasification reaction is complete at Ts in zone II. This reaction scheme is similar to that of HMX or TAGN shown in Fig. 5-5. 

The condensed phase reaction zone of a buming-interrupted BAMO copolymer is identified by infrared (IR) spectra analysis. In the nonheated zone, the absorptions of N3, C-O, C-H, and N-H bonds are seen. In the surface reaction zone (0-0.5 mm below the burning surface), the absorption of N3 bonds is eliminated. However, the absorptions of C-O, C-H, and N-H bonds remain as observed in the nonheated zone. This suggests that an exothermic reaction occurs by decomposition of N3 bonds at the subsurface- and surface-reaction zones1301. 

Results for oscillatory combustion assuming quasi-steady gas and condensed phase reaction zone (surface reaction approximation) are presented in two groups. First, general characteristics of oscillatory combustion are discussed in the context of the non-dimensional formulation, similar to the steady-state benehmark problem of Table 1. Second, specific results for the common materials NC/NG and HMX are presented. 

Fig. 25 In-phase component of pressure-coupled response function for propellant-N (50 atm). Shaded region represents T-bumer measure-ments Horton and Price [35] NWC [36]. Model calculations are for quasi-steady model using parameters of Table 2. Condensed-phase reaction zone characteristic frequency is estimated to be // = 10,000 Hz quasi-steady assumption should be valid up to at least 3000 Hz.

In summary, the combustion of MTV pyrolant is determined by processes in both gas and condensed phase. Cudzilo [36] has proposed a combustion wave structure for MTV. In the pyrolant, an inert temperature increase occurs that is caused by heat conduction from the adjacent condensed-phase reaction zone. 

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