大长径比固体火箭发动机一阶纵向不稳定燃烧判据

In order to avoid the longitudinal medium⁃low frequency combustion instability of solid rocket motors with large as⁃ pect ratio and an internal burning cylindrical grain in the design stage as much as possible,based on the linear theory of combustion instability,a design criterion of the first⁃order longitudinal combustion instability was proposed,considering the influence of pressure coupling response,nozzle damping and particle damping in the combustion chamber on the growth rate of acoustic energy amplitude. In this criterion,some parameters such as grain length and nozzle throat diameter were selected as design constraints to calculate the criterion parameter Aim of the first⁃order longitudinal combustion instability of the motor,and then the parameter k_b that reflects the combustion response characteristics of propellant by means of engineering estimation were obtained.When Aim was less than k_b,the motor was considered to change from linear stability to first⁃order longitudinal linear instability.This criterion is applied to a small test motor,and the error between the calculated time and the tested time of unstable combustion is less than 6%,which verifies the applicability of this criterion for combustion stability prediction and design of solid rocket motor with large aspect ratio.