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Modelling and Calculation of the Initial Ignition Gas Pressure Flow through a Rigid Porous Medium in a 100 mm Ignition Simulator

Xiao Z., Ying S., He W., Xu F.

Central European Journal of Energetic Materials

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2014

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Vol. 11, no. 4

475--489

EN

To acquire a better understanding of the early ignition phenomena in a 100 mm ignition simulator loaded with a packed propellant bed, a theoretical model of the ignition gas flow through the rigid porous medium was developed. Three pressure gauges were installed in the lateral side of the ignition simulator for post ignition measurement of the chamber pressure. The pseudo-propellant loaded into the chamber was similar in size to the standard 13/19 single-base cylindrical propellant. It was composed of a rigid ceramic composite with low thermal conductivity. It was assumed that the pseudo-propellant bed was rigid in contrast to the assumption of an elastic porous medium. The calculated pressure values were well verified by the experimental data at a low loading density of the pseudo-propellant bed of 0.18 g•cm-3. However, there was still error between the experimental and the calculated results in the early pressure peak position closest to the ignition primer when the loading density of the pseudo-propellant bed was increased to 0.73 and 1.06 g•cm-3. This error is attributed to the change in local permeability of the pseudo-propellant bed at high loading densities, which is assumed, for ease of modelling, to be constant in the model. These calculations may enable a better understanding of the physical processes of ignition gas flow in an ignition simulator loaded with a pseudo-propellant bed.

2

An investigation of the preparation and performance of microcellular combustible material

Yang W., Li Y., Ying S.

Central European Journal of Energetic Materials

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2014

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Vol. 11, no. 2

257--269

EN

Microcellular combustible materials, based on poly(methyl methacrylate) (PMMA) bonded RDX, were fabricated by the pressure quench method using supercritical CO2. After foaming, the bulk density, porosity, expansion ratio and cell density were analyzed. Scanning Electron Microscopy (SEM) has also been used to investigate the influence of the foaming conditions (temperature, saturation pressure and depressurization time) and the RDX ratio on the porous structure. The skin-core structure was also observed after the pressure quench process. The mechanical sensitivities and burning performance were investigated by the friction sensitivity test, the impact sensitivity test and the closed vessel test, respectively.

3

Morphological structure of polyetherketone membranes for gas separation prepared by phase inversion

Brown P. J., Ying S., Yang J.

Autex Research Journal

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2002

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Vol. 2, no. 2

101--108

EN

There has been increasing worldwide interest in the field of technical textile materials. Within this context the use of membranes for industrial separation processes has developed, and they can now compete effectively with conventional processes in terms of energy and capital costs. Membranes for gas separation have developed significantly in the last twenty years; however, there is still a need for high-temperature and chemically resistant membranes that exhibit good selectivity and gas permeability. In spite of the developments in gas separation membranes, only a few types of hollow-fibre membranes are still commercially available. Our study examines the fundamental properties of polyetherketone (PEK, a thermally stable and chemically resistant polymer) membranes prepared using concentrated sulphuric acid (98% H2SO4) as a solvent and dilute sulphuric acid (30%-60% H2SO4) as a non-solvent. Other non-solvents included acetic acid, ethanol, methanol, glycerol, and water. The concentration of the polymer-casting solutions was between 15% and 20%. The membrane structure was examined using SEM, and the gas separation properties were measured using a lab-scale test rig. The results show that formation and control of membrane structure are complicated, and that many preparation parameters affect membrane morphology and performance. Polymer concentration is a particularly important parameter. At each individual polymer concentration, the precipitant plays a crucial role, and has a determining influence on membrane structure. Membranes cast using 30-40% glycerol and 50-60% H2SO4 or 70-90% acetic acid as precipitants possessed sponge-type structures, and as such have an acceptable permeation rate. However, membranes cast into water display finger-like structures even at a low coagulation temperature of 3?C, and also exhibit lower permeation rates. It has also been shown that precipitated structures of PEK membranes are highly dependent upon the heat of mixing of the solvent with non-solvent, and that a reduction in this heat of mixing leads to sponge-like structures that are preferential for gas separation membranes.