Analysis On The Performance Of Solid Rocket Motor With Cracked Propellant Grain

Being differed from ancient research concentrated on the mechanical performance of solid propellant cracks during burning, this paper directly studies on how propellant grain cracks effect on the performance of solid rockets. In addition, elementary method for performance simulation and evaluation of solid rockets with defective propellant grain is established. New measures and ideas are put forward in this paper.Level Set interface capturing method is employed in burning surface area calculation of cracked propellant grains. Lately achievement in Level Set re-initialization technology is also utilized, which enhances universal capability Level Set method in burning surface area calculation. The method is tested by several cases and proved high accuracy as well as significant capability in dealing with burning back of complex surfaces. The method can be fixed to compute the burning perimeter of each grid along the axis of SRM, which makes the possibility of the combination with one dimensional internal ballistic model. All of these provide efficient measures for burning surface area computation of cracked propellant grains, and paves the way for the work of this paper.Considering the particularity of the pressure distribution along the axis of SRM, one dimensional internal ballistic model is introduced and deduced in details. Consequently, combining with Level Set method, a set of mathematical tools is finally established for analysis on SRM with cracked propellant grain. More over, its correctness is made certain by experiment. A certain SRM with different propellant grain cracks is analyzed, and it is found that: (1) If the initial crack area ratio is no more than 5%, the head-pressure and thrust of the SRM is only slightly disturbed. (2) If the initial crack area ratio is between 5% and 10%, the head- pressure and thrust of the SRM begins to be disturbed to some extend. (3) If the initial crack area ratio is higher than 10%, the head- pressure and thrust of the SRM is seriously disturbed.Finally, 3D flow field simulation model is built for normal SRM internal flow field calculation, which has been proved valid and rational in this paper, and is used in research of SRM internal flow field with cracked propellant grain. Different kinds of propellant grain cracks and debondings are considered in flow field calculation, conclusions of which are in according with those obtained by other scholars. It is revealed that the narrower of the grain cracks(or debondings) are, the higher the gradient of pressure and gas velocity near the chink, which does lots of harm to the structure integrality of the propellant grain.