Temperature Sensitivity of Burning Rate

The temperature sensitivity of the burning rate defined in Eq. (3.72) is a parameter of considerable relevance in energetic materials. 

The temperature profile in the combustion wave of a double-base propellant is altered when the initial propellant temperature T0 is increased to T0 + AT0 as shown in Fig. 6-14. The burning surface temperature Ts is also increased to Ts + ATS and the temperature of the succeeding gas phase zones, the dark zone from Td to Td + ATd, and the final flame temperature from Tg to Tg + ATg. If the burning pressure is low (below about 1 MPa), no luminous flame is formed above the dark zone. The final flame temperature is Td at low pressures. The burning rate is determined by the heat flux transferred back from the fizz zone to the burning surface and the heat flux produced at the burning surface. The analysis of the temperature sensitivity of double-base propellants described in Section 3.5.4 in Chapter 3 is applied. 

Substituting the temperature, activation energy in the fizz zone, and burning rate data shown in Fig. 6-16 into Eqs. (3.86), (3.88), and (3.80), the temperature sensitivity of the gas phase, t , defined in Eq. (3.79) and the temperature sensitivity of the condensed phase, W, defined in Eq. (3.80) are obtained as1151 

The temperature sensitivity of the burning rate consists of 60 % O and 40 % W. The lower ap of the high energy propellant is due to the lower activation energy and higher temperature in the fizz zone when compared with these values for the low energy propellant. 

---

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... 

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- ... 

Kubota, N., and Miyazaki, S., Temperature Sensitivity of Burning Rate of Ammonium Perchlorate Propellants, Propellants, Explosives, Pyrotechnics, Vol. 12,... 

Fig. 8.19 Temperature sensitivity of burning rate decreases with increasing Ihmx. 3nd (gas phase) has a greater effect on than (condensed phase).

The burning rate of propellants is one of the important parameters for the design of rocket motors. The burning rate is obtained as a function of pressure and of initial temperature, from which pressure exponent of burning rate and temperature sensitivity of burning rate are deduced. 

The burning rate of any energetic materials depends also on the initial temperature of the materials, T0, even when the burning pressure is kept constant. The temperature sensitivity of burning rate, ap, is defined by the change of burning rate when T0 is changed as... 

---