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8212218 
Book/Book Chapter 
Unsteady combustion of solid propellants: Simplified kinetics modeling 
Brewster, MQ 
2000 
American Institute of Aeronautics and Astronautics 
Reston, VA 
36th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit 
English 
is part of a larger document 8222349 36th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit 2000
Simplified kinetics will continue to play an important role in computational simulation of solid propellant combustion for the foreseeable future, particularly in simulating unsteady combustion. The first part of this article reviews some recent progress made in connection with the Multi-disciplinary University Research Initiative (MURI) on solid propellant combustion instability with regard to simplified kinetics modeling for steady and particularly unsteady combustion. For homogeneous energetic materials (HMX and NC/NG) simplified kinetics combustion models have developed to the point that macroscopic generic features (e.g., burning rate, temperature, reactant, product) can be described within the modeling approximations and a priori predictive capability is a reasonable expectation. For composite propellants, however, ability to describe essential macroscopic behavior of even steady burning-for example, burning rate sensitivity to pressure and initial temperature-is still limited by lack of understanding of kinetics. The second part of this paper reviews MURI program progress in measuring pressure-coupled frequency response function Rp which is the primary quantity for comparison between experiment and theory for unsteady combustion. The de facto standard method for measuring Rp in the U.S. still appears to be the T-burner. Several other techniques for measure Rp are being developed; however, the results by various techniques show significant variation in the results for the same propellant at the same conditions. There is still a need for new techniques that are quick, inexpensive, use small amounts of material, and have high spectral resolution. The main feature of measured pressure-responses for both homogeneous and composite propellants is a broad, low-frequency, solid-phase thermal relaxation response peak which occurs around a non-dimensional frequency of Ω ~ 5 to 20. For Ω < Ec/RTs the response of various propellants at various pressures are correlated fairly well by the non-dimensional frequency Ω, which is based on quasi-steady (QSHOD) theory. The significance of Ec/RTs is that this is the value of Ω where the quasi-steady assumption (specifically, the quasi-steady condensed phase decomposition zone) assumption breaks down. For Ec ~ 40 kcal/mol (HMX), EcRTs ~ 25. For Ec ~ 20 kcal/mol (AP), Ec/RTs ~ 12. Thus breakdown of quasi-steady conditions begins near the response peak or at just slightly higher Ω-values. 
36th AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit 2000 
Huntsville, AL 
July 16-19, 2000