Experimental investigation and numerical modeling of the condensed combustion products of micro and nano-aluminized solid propellants
- Paper number
IAC-06-C4.3.03
- Author
Dr. Luciano Galfetti, Politecnico di Milano, Italy
- Coauthor
Dr. Luigi T. DeLuca, Politecnico di Milano, Italy
- Coauthor
Prof. Febo Severini, Politecnico di Milano, Italy
- Coauthor
Dr. Laura Meda, Italy
- Coauthor
Dr. Gianluigi Marra, Italy
- Coauthor
Mr. Lucas Lentini, Politecnico di Milano, Italy
- Coauthor
Dr. Valery A. Babuk, Russia
- Coauthor
Ms. Sara Cerri, Politecnico di Milano, Italy
- Year
2006
- Abstract
The condensed combustion products significantly affect the behavior of solid rocket motors. Specific impulse losses, slag deposition in the motor and critical effects on motor components, but mainly the stability of the motor, depend on the CCP properties. The history of CCP begins at the propellant burning surface, where they are formed because of aggregation/agglomeration phenomena, and continues in the two-phase flow of the combustion gases. Traditionally CCP are divided into two groups: smoke-oxide particles (SOPs, characteristic size of about 1 micron) and agglomerates (characteristic size of hundreds or even thousands of micron). In aluminized propellants agglomerates consist of aluminum and aluminum oxide; their diffusive combustion process include very complex problems, involving the metal burning, the chemical interaction between metal and oxide, the SOPs deposition on the agglomerate, the change in the agglomerate structure and the change due to the agglomerate motion in the combustion gases. The experimental investigation performed in this paper aims to study the effects of the propellant composition on the formation and evolution of the CCP; in particular, the oxidizer particles size distribution (monomodal or multi-modal AP oxidizer), the nature of binder (HTPB or isoprene rubber) and the aluminum powder size (micro or nano powders) are considered in a compared evaluation. A constant volume bomb, operating at constant pressure, is used to burn propellant samples and to collect CCP; agglomerates quenching is obtained using an inert liquid placed at a variable distance from the propellant burning surface. A high-speed video recording system is used to visualize the aggregation/agglomeration formation at the burning surface and their evolution in the gas phase. A chemical analysis (traditional and with X-ray Photoelectron Spectroscopy (XPS)) is performed in order to measure the aluminum and aluminum oxide content in the quench-collected agglomerates and to evaluate the combustion efficiency. A X-ray Diffraction technique (XRD) allows to investigate the crystalline structure. The results of the experimental investigation show the main dependence of CCP on the oxidizer particles size, on pressure and on aluminum powder characteristic size. The experimental data base was used for the validation of the mathematical model, which follows assumptions and theoretical approaches proposed by Cohen and Babuk. The model describes the aluminum agglomeration and the evolution in the combustion gases of solid rocket composite propellants; it proved satisfactory to model the phenomena experimentally observed.
- Abstract document
- Manuscript document
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