Plateau burning

Plateau burning characteristics are dependent on the chemical components and the nature of the catalysts. The effects of aromatic lead and copper salts on burning rate behavior are shown in Fig. 6.24. The addition of PbSa (1 %) increases the burn-... 

Flg. 6.24 Various types of plateau burning obtained by the addition of different types of catalysts. 

As the burning rate increases in the high-pressure region, the formation of carbonaceous materials diminishes and hence the super-rate burning also diminishes and becomes plateau burning. This negative catalytic effect of lead compounds is considered to produce mesa burning. 

Fig. 6.31 Super-rate and plateau burning are suppressed by the addition of KNO3, but not by the addition of K2SO4.

Kubota, N., Determination of Plateau Burning Effect of Catalyzed Double-Base Propellant, 17th Symposium (International) on Combustion, The Combustion Institute, Pittsburgh, PA, 1979,... 

It is well known that the super-rate burning of nitropolymer propellants diminishes with increasing pressure in the region 5-100 MPa and that the pressure exponent of burning rate decreases. - ] This burning rate mode is called plateau burning. As for these nitropolymer propellants catalyzed with LiF and C, HMX propellants catalyzed with LiF and C also show plateau burning. 

The burning surface of an HMX propellant only becomes covered with carbonaceous materials when the propellant is catalyzed with both LiF and C. This surface structure is similar to the burning surface of an HMX propellant catalyzed with a lead compound and C. The results indicate that the combushon mode and the action of LiF are the same as those resulting from the use of lead compounds to produce super-rate and plateau burning of nitramine propellants. 

Like double-base propellants, CMDB propellants show super-rate and plateau burning when they are catalyzed with small amounts of lead compounds. Fig. 8.21 shows a typical plateau burning for a propellant composed of NC-NG and HMX.P I The chemical composition of the catalyzed propellant is shown in Table 8.1. 

Fig. 8.21 Plateau burning over a wide pressure range (1.6-3.6 MPa) following the addition of 3.2% PbSt.

Table 8.1 Chemical composition of super-rate and plateau burning propellant.

Fig. 8.22 The luminous flame front of the platonized propellant approaches the burning surface more rapidly than that of the non-catalyzed propellant when the pressure is increased in the plateau-burning pressure region.

Fig. 8. 23 Temperature gradient in the fizz zone increases in the super-rate burning region and then remains unchanged in the plateau-burning pressure region for the catalyzed propellant.

The effective overall order of the fizz zone reaction, k, is determined to be zero for plateau burning, and approximately 1.4for super-rate burning. The reaction order for the non-catalyzed propellant is also determined to be approximately 1.7, that is, nearly equal to the order of a conventional gas-phase reaction. 

Fig. 13.10 Burning rate characteristics of an AP-PU composite propellant, showing plateau burning.

If finite chemical reaction times are put into the columnar diffusion flame theory (76), burning rates are predicted to be linearly proportional to pressure at low pressure and independent of pressure (plateau burning) at high pressure. Based on this model, von Elbe et al. (97) proposed the simple equation ... 

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