Abstract
To acquire the erosive characteristics of two-channel combustion chambers, a quasi-one-dimensional internal ballistics model is proposed. Combining the model with two different erosive burning models, the modified L-R expression, and the Mukunda-Paul expression, the flow parameters and the internal ballistics performance of a test solid rocket motor are computed. The results show good agreement with experimental data. According to the results, the more severe the erosion is, the earlier, longer, and gentler the tail-off stage becomes. During the tail-off stage, the dramatic drop of pressure leads to a low normal burning rate and makes it easier for erosion burning to occur. For this reason, notable erosive burning might appear during tail-off if the case-to-throat area ratio is extremely low. The results also show that flows in the inner channel and the outer channel are similar but not identical. This leads to different erosive burning behaviours in the two channels. Also, the two erosive burning rate models involved in this paper are compared. It seems that the M-P expression provides better results than the modified L-R expression does, since it reveals the threshold phenomena. Besides, the M-P expression has great advantages for its universality for most propellants and different SRM geometries.
Highlights
In a solid rocket motor (SRM) with a high load fraction, the high flow velocity often induces an augmentation of the burning rate, which is called “erosive burning.” Erosive burning has been the subject of many studies, yet a satisfactory interpretation has not been proposed because of the complexity of its nature
Many studies [3, 4] were analysed by Landsbaum [5], and the erosive burning rate was processed as a function of mass velocity (i.e., G or ρV) beyond a threshold value
The 1D model described in Section 2 is implemented to obtain the 1D flow field in the combustion chamber and the internal ballistics performance of the test motor
Summary
In a solid rocket motor (SRM) with a high load fraction, the high flow velocity often induces an augmentation of the burning rate, which is called “erosive burning.” Erosive burning has been the subject of many studies, yet a satisfactory interpretation has not been proposed because of the complexity of its nature. Some empirical models have been derived by studies involving experimentation and theoretical analysis Among these theories, the expression that gives a linear relationship between erosive burning rate and velocity might be the simplest one. An implicit expression for the erosive burning rate was proposed, in which the distance to the head end of the grain is used as the characteristic length. To validate the models referred to for a specific SRM, there are always constants to be confirmed This makes it difficult to obtain a reliable internal ballistics prediction of an SRM before firing tests. A quasi-1D model is proposed, and, by combining this model with two different burning rate models (modified L-R expression and Mukunda-Paul expression), the authors calculate and discuss the internal ballistics performance of the combustion chamber and draw some interesting conclusions
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