Pocket Model for Aluminum Agglomeration Based on Propellant Microstructure

Maggi, F.; DeLuca, Luigi T.; Bandera, A.

doi:10.2514/1.j053992

Cited by 27 publications

(14 citation statements)

References 27 publications

(42 reference statements)

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“…It characterizes the reciprocal position of spheres, identifying repetitive structures in assemblies, or clusters in multimodal blends [12]. It does not supply a directional information.…”

Section: Monomodal Packsmentioning

confidence: 99%

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Parallel packing code for propellant microstructure analysis

Baietta

Maggi

2015

Aerospace Science and Technology

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Please cite this article in press as: A. Baietta, F. Maggi, Parallel packing code for propellant microstructure analysis, Aerosp. Sci. Technol. (2015), http://dx.doi.org/10.1016/j.ast. 2015.08.012 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Parallel AbstractIn recent years, packing codes have become a successful alternative to experimental data collection for microstructure investigation of heterogeneous materials. Composite solid rocket propellants are interesting representatives of this category, consisting of a mix of fuel and oxidizer powders embedded in a polymeric binder. Their macroscopic properties are strictly dependent on the peculiar microstructure, which influences mechanical, combustion, as well as physical features. This work addresses algorithm development, validation, and scalability of POLIPack, a parallel packing code based on the Lubachevsky-Stillinger algorithm, developed at the Space Propulsion Laboratory (SPLab) of Politecnico di Milano. The application can reproduce the organization of spheres of any diameter inside a cube with periodic boundary. In addition to the general code description, the paper identifies a collision condition not addressed by the original Lubachevsky's algorithm (here called back impact), introduces a novel post-impact handling granting a minimum separation velocity between particles, and presents a parallelization approach based on OpenMP shared memory paradigm. Monomodal and bimodal packs have been compared to experimental data through statistic descriptors and packing maps.

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“…It characterizes the reciprocal position of spheres, identifying repetitive structures in assemblies, or clusters in multimodal blends [12]. It does not supply a directional information.…”

Section: Monomodal Packsmentioning

confidence: 99%

“…More recently, the concept was generalized to random microstructures via statistical methodologies. [9][10][11][12].…”

Section: Introductionmentioning

confidence: 99%

Parallel packing code for propellant microstructure analysis

Baietta

Maggi

2015

Aerospace Science and Technology

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“…An in §uence between ¦ne AP fraction and aluminum can be inferred if the pseudopropellant contained in the pocket structure is targeted, following the concept of Cohen [15] or of Maggi and coauthors [16]. The computed §ame temperature, considering binder and FAP as reacting mixture (assuming inert aluminum), are reported in Fig.…”

Section: Discussionmentioning

confidence: 99%

Exploratory investigations on metal-based fuels for air-breathing propulsion

Maggi

Colciago

Paravan

et al. 2019

Progress in Propulsion Physics – Volume 11

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Air-breathing solid fueled propulsion devices represent rugged, cheap, and rather simple options, out of the ramjet (RJ) category, which can contribute to volume containment and structural weight reduction. In the case of a ducted rocket, a fuel-rich propellant is burned in a primary combustion chamber and part of the oxidizer is taken from the atmosphere to complete the combustion inside a ram burner before exhaust. The use of metal additives contributes to the development of high-energy density materials, featuring better volumetric specific impulse. Metal powders are characterized by high energetic content per unit volume but can feature issues of difficult ignition, generation of condensed combustion products (CCPs), and incomplete combustion. The present work discusses a series of exploratory investigations on aluminum-based pyrolants. Thermochemical analyses, calorimetric investigations, and combustion tests will be considered, looking at improvements introduced by metal addition.

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“…A larger agglomerate particle size and mass fraction results in higher performance losses due to incomplete combustion and two-phase flow [17]. Experimental and numerical studies on the Al combustion in solid propellant formulations were discussed in References [75][76][77][78][79][80][81][82][83].…”

Section: Aluminized Solid Fuel Formulations: Aggregation and Agglomermentioning

confidence: 99%

Nano-Sized and Mechanically Activated Composites: Perspectives for Enhanced Mass Burning Rate in Aluminized Solid Fuels for Hybrid Rocket Propulsion

Paravan

2019

Aerospace

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This work provides a lab-scale investigation of the ballistics of solid fuel formulations based on hydroxyl-terminated polybutadiene and loaded with Al-based energetic additives. Tested metal-based fillers span from micron- to nano-sized powders and include oxidizer-containing fuel-rich composites. The latter are obtained by chemical and mechanical processes providing reduced diffusion distance between Al and the oxidizing species source. A thorough pre-burning characterization of the additives is performed. The combustion behaviors of the tested formulations are analyzed considering the solid fuel regression rate and the mass burning rate as the main parameters of interest. A non-metallized formulation is taken as baseline for the relative grading of the tested fuels. Instantaneous and time-average regression rate data are determined by an optical time-resolved technique. The ballistic responses of the fuels are analyzed together with high-speed visualizations of the regressing surface. The fuel formulation loaded with 10 wt.% nano-sized aluminum (ALEX-100) shows a mass burning rate enhancement over the baseline of 55% ± 11% for an oxygen mass flux of 325 ± 20 kg/(m2∙s), but this performance increase nearly disappears as combustion proceeds. Captured high-speed images of the regressing surface show the critical issue of aggregation affecting the ALEX-100-loaded formulation and hindering the metal combustion. The oxidizer-containing composite additives promote metal ignition and (partial) burning in the oxidizer-lean region of the reacting boundary layer. Fuels loaded with 10 wt.% fluoropolymer-coated nano-Al show mass burning rate enhancement over the baseline >40% for oxygen mass flux in the range 325 to 155 kg/(m2∙s). The regression rate data of the fuel composition loaded with nano-sized Al-ammonium perchlorate composite show similar results. In these formulations, the oxidizer content in the fuel grain is <2 wt.%, but it plays a key role in performance enhancement thanks to the reduced metal–oxidizer diffusion distance. Formulations loaded with mechanically activated ALEX-100–polytetrafluoroethylene composites show mass burning rate increases up to 140% ± 20% with metal mass fractions of 30%. This performance is achieved with the fluoropolymer mass fraction in the additive of 45%.

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Pocket Model for Aluminum Agglomeration Based on Propellant Microstructure

Cited by 27 publications

References 27 publications

Parallel packing code for propellant microstructure analysis

Parallel packing code for propellant microstructure analysis

Exploratory investigations on metal-based fuels for air-breathing propulsion

Nano-Sized and Mechanically Activated Composites: Perspectives for Enhanced Mass Burning Rate in Aluminized Solid Fuels for Hybrid Rocket Propulsion

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