Propellants erosive burning

A. Jankowski, Mechanism of Erosive Burning of Solid Rocket Propellants , ArchProcesowSpalonia 3 (3), 249-77 (1972)... 

Green (G3) has proposed an alternate approach based on the concept of a critical mass-velocity required to produce a Mach number of 1 in a constant-area channel. Green showed this approach was able to correlate the erosive-burning data he obtained for both a double-base propellant and a composite propellant. 

Fig. 13.6 Erosive ratio and threshold velocity of erosive burning for high-energy, reference, and low-energy double-base propellants, showing that the low-energy propellant is most sensitive to the convective heat flux.

Though erosive burning is highly dependent on the cross-flow velocity, the physical structure of the propellant also plays a dominant role in determining the erosive... 

Fig. 13.21 shows another example of oscillatory burning of an RDX-AP composite propellant containing 0.40% A1 particles. The combustion pressure chosen for the burning was 4.5 MPa. The DC component trace indicates that the onset of the instability is 0.31 s after ignition, and that the instability lasts for 0.67 s. The pressure instability then suddenly ceases and the pressure returns to the designed pressure of 4.5 MPa. Close examination of the anomalous bandpass-filtered pressure traces reveals that the excited frequencies in the circular port are between 10 kHz and 30 kHz. The AC components below 10 kHz and above 30 kHz are not excited, as shown in Fig. 13.21. The frequency spectrum of the observed combustion instability is shown in Fig. 13.22. Here, the calculated frequency of the standing waves in the rocket motor is shown as a function of the inner diameter of the port and frequency. The sonic speed is assumed to be 1000 m s and I = 0.25 m. The most excited frequency is 25 kHz, followed by 18 kHz and 32 kHz. When the observed frequencies are compared with the calculated acoustic frequencies shown in Fig. 13.23, the dominant frequency is seen to be that of the first radial mode, with possible inclusion of the second and third tangential modes. The increased DC pressure between 0.31 s and 0.67 s is considered to be caused by a velocity-coupled oscillatory combustion. Such a velocity-coupled oscillation tends to induce erosive burning along the port surface. The maximum amplitude of the AC component pressure is 3.67 MPa between 20 kHz and 30 kHz. - ...

Razdan, M. K., and Kuo, K. K., Erosive Burning of Solid Propellants, Eundamen-tals of Solid-Propellant Combustion, Chapter 10, Vol. 90, Progress in Astronautics and Aeronautics, AlAA (Eds. ... 

Ishihara, A., and Kubota, N., Erosive Burning Mechanism of Double-Base Propellants, 21 St Symposium (International) on Combustion, The Combustion Institute, Pittsburgh, PA (1986), pp. 1975-1981. 

It is evident that erosive burning occurs only in the inihal stage of combustion and diminishes about 0.5 s after ignition in each of the cases shown in Fig. 14.19 the burning pressure then returns to the designed pressure, For example, the head-end pressure reaches more than 3.5 times the designed pressure of = 5 M Pa just after ignition at L/D =16, but the pressure decreases rapidly thereafter and the propellant continues to burn at constant pressure, p,.. ... 

A. Jaumotte, "Remarks on the Burning Mechanism and Erosive Burning of Ammonium Perchlorate Propellants , Ibid, pp 689-93 G2) G.K. Adams et al, "Combustion of Propellants Based on Ammonium Perchlorate , Ibid, p 693-705 Hj) J.Hershkowitz, F. Schwartz J.V.R. Kaufman, "Combustion of Loose Granular Mixtures of Potassium Perchlorate and Aluminum , Ibid, pp 720-27 H2) L.A. Dickinson et al, "Erosive Burning of Polyurethane Propellants in Rocket Engines , Ibid, pp 754-59 H ) S. Kumagai... 

Fig. 13.7 Erosive burning effect on the flame structure of a double-base propellant.

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