Pressure exponent

Modification of the burning rates, pressure exponents, and temp coefficients of burning rate of the fluorocarbon composites has been accomplished with copper, lead, tin, sodium, ammonium and potassium fluoborates sodium, potassium, lithium, lead, copper and calcium fluorides potassium and ammonium dichromate lead and zinc stearate cesium carbonate potassium and ammonium sulfate copper chromite oxides of magnesium, copper and manganese boron zinc dust and carbon black (Ref 75)... 

The value of the pressure exponent was the same at each of the three test temps,... 

The possibility of significant heat release below the surface suggests the importance of a number of variables which do not enter into analyses based on purely gas-phase processes. Among these are (1) binder mechanical properties, and (2) coatings on the solid oxidizer, since they affect the burning rate and the pressure exponent. 

In general, the internal pressure in a gun barrel exceeds 200 MPa, and the pressure exponent, n, of the propellant burning rate given by Eq. (1.80) is 1. When n = 1, the burning rate of a gun propellant is represented by... 

The burning rate of GAP copolymer increases linearly with increasing pressure in an In rversus Inp plot, as shown in Fig. 5.17. The pressure exponent of burning rateat a constant initial temperature, as defined in Eq. (3.71), is 0.44. The temperature sensitivity of burning rate at constant pressure, as defined in Eq. (3.73), is 0.010 K"h... 

Fig. 6.1 Burning rate increases with increasing energy density of NC-NG double-base propellants at constant pressure the pressure exponent remains unchanged when the energy density is changed.

Though both propellants contain equal amounts of NC and NG, the burning rate of NC-NG-GAP is approximately 70% higher than that of NC-NG-DEP at Tq = 293 K. The pressure exponent of burning rate remains relatively unchanged at = 0.7 by the replacement of DEP with GAP. However, the temperature sensitivity of burning rate defined in Eq. (3.73) is increased significantly from 0.0038 K" to 0.0083 K- ... 

Table 6.10 Overall reaction order, m, in the dark zone determined from the pressure exponent of burning rate, n, and the dark zone index, d.

In order to clarify the combustion wave structure of AP composite propellants, photographic observations of the gas phase at low pressure are very informative. The reaction rate is lowered and the thickness of the reaction zone is increased at low pressure. Fig. 7.3 shows the reduced burning rates of three AP-HTPB composite propellants at low pressures below 0.1 MPa.FI The chemical compositions of the propellants are shown in Table 7.1. The burning rate of the propellant with the composition ap(0-86) is higher than that of the one with ap(0-80) at constant pressure. However, the pressure exponents are 0.62 and 0.65 for the ap(0-86) and Iap(0.80) propellants, respectively that is, the burning rate is represented by r for the p(0.86) propellant and by r for the p(0.80) propellant. 

---