Solid Rocket Motor Internal Ballistics Simulation Using Three-Dimensional Grain Burnback

Abstract

Internal ballistics simulations of solid rocket motors have been conducted with the propellant grain's 3-D burning surface geometry described by a new minimum distance function approach and the internal flowfield represented by 1-D, time-dependent, single-phase compressible flow equations. The combustion model includes erosive burning and unsteady, dynamic burning corresponding to transient energy storage in the heated surface layer of the propellant. The integrated internal ballistics code (Rocballist) is used to investigate the role of these two burning rate augmenting mechanisms in solid rocket motor performance. Two tactical motors are used as test cases. Results indicate that dynamic burning can be the dominant factor in producing a short-duration ignition pressure spike in low-L motors, particularly if the L=D ratio is not too large and the port cross section is nonrestrictive (e.g., center perforated grain). However, when L=D is large and the port cross section is noncircular in the aft section (aft fins/slots), erosive burning can take over in dominating the burning rate to the extent that an otherwise progressive pressure-time trace becomes regressive/neutral. That is, erosive burning can effectively prolong the initial pressure spike in some star-aft motors. The results also show that with sufficiently accurate models of dynamic burning and erosive burning, it is reasonable to expect reliable internal ballistics predictions with suitable simplified flowfield models, thereby realizing significant reductions in computation time compared with 3-D, multiphase reacting flow simulations.

Simple Surface-Tracking Methods for Grain Burnback Analysis

“…Based on the previous methodologies, many researchers in academies or rocket companies in the United States and several European countries have developed sophisticated internal ballistics codes to deal with fluid-structure interactions with moving grain boundary [13][14][15][16][17][18]. A substantial use of the level set and its related methods has been observed in these sophisticated internal ballistics codes.…”

Finocyl Grain Design Using the Genetic Algorithm in Combination with Adaptive Basis Function Construction

“…Due to the wide use of solid propellant motors in the aerospace industry, the accurate prediction of a solid propellant motor decreases the number of expensive tests of motors. Therefore, it decreases the development cost of motors [17]. To reach this goal, there is an intense requirement to determine the pressure time and thrust time of the SRMs which greatly depend on the changes of the burning surface area and volume of the combustion chamber through time.…”

Analytical Prediction for Grain Burn Time and Burning Area Kinematics in a Solid Rocket Combustion Chamber

“…The alternative model, in [13], focuses on transient conditions and also describes erosive burning, which may be of interest in contrast to the erosive burning that can be accounted for in this chapter's proposed method based on kinematics. One evident advantage of this chapter's proposal is that it does not require any calculation of the fluid flow field, whereas even the alternative simplified 1D flow calculation proposed in [14] necessitates further computational expense, potentially.…”