The effect of pressure exponent on temperature sensitivity

Abstract

The paper presents a technique for theoretically determining the motor temperature sensitivity coefficient, π k , from burning rate information generated by a theoretical combustion model, the Petite Ensemble Model, thereby permitting a parametric study of several factors affecting π k that are influenced by the initial propellant temperature: characteristic velocity, burning rate constant and exponent, and burning rate temperature sensitivity. The study is for an AP/HTPB propellant having a unimodal oxidizer distribution with a mode width parameter of 1.5 about a mass mean diameter of 100 microns. The content of AP is varied from 60 to 90%, while the values for the propellant area ratio, K n , range from 200 to 400. The results indicate that at the higher values of oxidizer loading the value of π k appears to be invariant with pressure or K n . At the lower oxidizer loading, the value of π k appears to slightly decrease with increasing pressure or K n . The temperature sensitivity of the burn rate constant and the characteristic velocity both serve to increase the value of π k and both appear to be relatively invariant with pressure and K n . The influence of the pressure exponent on the value of π k appears to be linked with the oxidizer loading. At the higher values of oxidizer loading the n effects term is positive and increases the value of π k , while at the lower oxidizer loading, the n effects term is negative and reduces the value of π k .