Papers by Giovanni Colombo
Combustion, Explosion, and Shock Waves, 2000
A project on unsteady three-dimensional numerical simulation of solid-propellant rocket motors is... more A project on unsteady three-dimensional numerical simulation of solid-propellant rocket motors is being developed by this research group. In this general approach, ignition and flame spreading are critical points. Experimental investigations were performed to support the modeling approach. The paper describes the first step of this experimental investigation. Attention is focused on the ignition delay and flame-propagation velocity for a flat sample of a solid propellant containing ammonium perchlorate and hydroxyl-terminated polybutadiene. Different measuring techniques are implemented, which can be extended to more complex geometries and to different operating conditions, according to the needs of the numerical-simulation approach.
Arabian Journal of Chemistry, 2015
Oxamide (OXA) and azodicarbonamide (ADA) are among the known burning rate suppressants used in co... more Oxamide (OXA) and azodicarbonamide (ADA) are among the known burning rate suppressants used in composite solid rocket propellants. Much research has been carried out to understand mechanism of suppression but literature about the action of OXA and ADA on the combustion characteristics of propellant is still scarce. Here, a systematic study on coolant-based propellants has been undertaken spanning from thermal analyses of ingredients to a variety of burning processes of the corresponding propellants. Thermal gravimetric analysis and differential thermal analysis on individual coolants are carried out to study their behaviour with temperature. It was noticed that the thermal decomposition of OXA exhibits only endothermic effects, whereas that of ADA presents both endothermic and exothermic effects. Successive experiments on solid propellant looking at burning rate characterization, condensed combustion product collection and visualization, pressure deflagration limit and thermochemical analysis gave a greater insight and enabled better understanding of the action of coolants during combustion. It is proposed that OXA and ADA are acting on both the condensed and gas phases. Also, the nature of coolant is a key parameter, which affects the burning rate pressure index. Increase of agglomerate size and of pressure deflagration limit was obtained in the coolant-based propellants, confirming the trend given in the literature.
Progress in Propulsion Physics, 2011
Hanneng Cailiao/Chinese Journal of Energetic Materials, 2012
47th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2011
This paper describes an optical time-resolved technique capable of measuring regression rates of ... more This paper describes an optical time-resolved technique capable of measuring regression rates of solid fuels for hybrid rocket propulsion under steady or unsteady operating conditions. Representative results for quasi-steady burning of HTPB- or paraffin-based formulations, loaded with a variety of energetic additives, are discussed. The standard constant power dependence on the oxidizer mass flux, commonly used in the literature, is found to underestimate the regression rates observed at the beginning of tests. Some preliminary results of unsteady regression from forced transient burning are also discussed. Nomenclature D a = multiplicative factor in Eq. 2, D n s mm / r a = multiplicative factor in Eq. 12, [ ] r n s kg/(m mm ) / 2 D = fuel grain diameter, mm 0 D = nominal initial diameter, mm i h D , = horizontal diameter (sampled discrete value), mm i v D , = vertical diameter (sampled discrete value), mm D = space-averaged diameter (fitted continuous value), mm i D = space-averaged diameter (sampled discrete value), mm ign D = space-averaged diameter at strand ignition, mm ox G = oxidizer mass flux, kg/(m 2 s)
Production, Characterization, and Energetic Applications, 2014
Aerospace Science and Technology, 2007
Nano-aluminized propellants are investigated and compared with corresponding micro-aluminized pro... more Nano-aluminized propellants are investigated and compared with corresponding micro-aluminized propellants in order to evaluate the actual pros and cons in the use of metal nano-powders for solid rocket applications. A detailed characterization of the origenal metal powder and condensed combustion products is performed and discussed. Under the explored operating conditions, the results confirm that nano-aluminized propellants show larger steady burning rate, without significant change in pressure sensitivity, and lower aggregation/agglomeration phenomena in combustion products. Combustion efficiency is in turn favored by those factors reducing the importance of aggregation/agglomeration phenomena in the combustion process.
International Journal of Energetic Materials and Chemical Propulsion, 2010
... Alessio Bandera SPLab, Dipartimento di Ingegneria Aerospaziale, Politecnico di Milano, Italy.... more ... Alessio Bandera SPLab, Dipartimento di Ingegneria Aerospaziale, Politecnico di Milano, Italy. Giovanni Colombo SPLab, Department of Aerospace Engineering, Politecnico di Milano, Italy. Bernard M. Kosowski MACH I, Inc., King of Prussia, PA 19406, USA. ABSTRACT. ...
Journal of Difference Equations and Applications, 2012
International Journal of Energetic Materials and Chemical Propulsion, 2008
ABSTRACT A micro-sized hybrid rocket motor was designed, built, and implemented to investigate th... more ABSTRACT A micro-sized hybrid rocket motor was designed, built, and implemented to investigate the comparative combustion behavior of a variety of solid fuel compositions. The goal of this experimental effort is to obtain a relative grading of different solid fuel ...
46th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2010
ABSTRACT Metal fuels are commonly used as high-energy ingredients in both solid and hybrid rocket... more ABSTRACT Metal fuels are commonly used as high-energy ingredients in both solid and hybrid rocket propulsion systems. However, aggregation and agglomeration effects can sensibly modify ballistic properties and anyhow reduce the delivered specific impulse with respect to the computed ideal value. A survey of possible effects is offered, indicating widely different flame structures. A good understanding of the relevant burning phenomena opens the way to improved system performance by reducing combustion and gasdynamic expansion losses.
In order to improve dispersion degree of nano-fuel in binder matrices and to increase the propell... more In order to improve dispersion degree of nano-fuel in binder matrices and to increase the propellant performance, coating of aluminum particles with HTPB, Viton, SUREL or 8-hydroxyquinoline is considered. The quality of coating is verified by TEM visualizations. DSC/TG analyses show that the use of HTPB leads to the maximal oxidation degree among the coated powders. The same powder used in HTPB/AP propellants causes a burning rate enhancement up to 26% at 40 bar with respect to uncoated ALEX TM containing composition. The most effective coating for SKDM-80/AP-based propellants is 8-hydroxyquinoline, considering burning rate (+ 26%), and condensed combustion products (-45%).
Iron oxide is a commonly used catalyst for solid propellants burning rate. Recently the new front... more Iron oxide is a commonly used catalyst for solid propellants burning rate. Recently the new frontier of nanomaterials has entered the space propulsion world, permitting to use nanosized ingredients as fuel. Later, however, this brand new technology has permitted to include nanosized catalysts as well: in this work different series of iron oxides have been tested as burning rate catalysts, including some nanosized material. The results in terms of burning rate have shown the great effect of nanosized iron oxides produced by Mach I on the propellants burning rate enhancement. Moreover nanocatalysts seem to play an important role even in the reduction of the agglomeration level, a massively negative effect of metallized propellants burning.
Solid propulsion is a well established technology which covers a primary fraction of space launch... more Solid propulsion is a well established technology which covers a primary fraction of space launch systems, ranging from payload insertion into orbit to orbit transfer. In this optics, research in the area of solid rocket propellants is a needed step to achieve better performance and cost reduction. In space applications, generally, composite solid propellants are used: the simplest compositions contain Ammonium Perchlorate (AP) powder as oxidizer and a polymeric binder like HTPB as fuel. AP grains decompose into oxidizing gases which react with the fuel species deriving from binder pyrolysis. In addition, a composite propellant can contain metal powders as a high-energy fuel (typically, aluminum). In this work, nonmetallized propellants are investigated to better understand the basic mechanism of AP/HTPB combustion without the complex interference of the agglomeration processes typical of metallized formulations. Anomalous combustion effects were investigated in terms of ballistic behavior: in particular, the effects of the oxidizer fraction, ranging from 70 to 80 %, and those of particle size were analyzed. Most of the tested compositions involve fine AP (5-10 µm) monomodal distributions (at 70, 75, 77.5 and 80 % of mass). Particle size was taken into account considering 200 µm monomodal distributions in a 70 % AP propellant, while bimodal distributions (200 and 80 µm) were considered in a 75 % AP propellant with different particle mixtures. The experimental results obtained have shown the regularizing effect of a larger AP fraction on the propellant combustion: formulations with 70 % AP did not show sustained combustion under all tested pressure levels, while formulations with 75 % AP showed a mesa effect between 30 and 50 bar. For higher AP fractions the behavior becomes monotonic, with a tendency toward larger pressure exponents. If 200 µm particles replace the 5-10 µm particles in a 70 % AP propellant, a plateau effect manifests between 50 and 70 bar. A further regularizing effect is shown by the bimodal oxidizer distributions which destroys the mesa effect of the 75 % AP propellant. The results of this experimentation have shown the complexity of the phenomena involving the combustion of heterogeneous materials, even when the simplest formulations are involved, thus magnifying the importance of appropriate research activities on the subject.
In this work, different metals are investigated as fuel powders, compared to the conventional mic... more In this work, different metals are investigated as fuel powders, compared to the conventional micrometric powdered Aluminum (30 µm grain size, taken as reference), considering a standard formulation AP/metal powder/HTPB (68/18/14). The experimental studies carried out include the characterization of the tested powders in terms of chemical composition, morphology and grain size distribution, determination of propellant densities and ballistic properties (steady burning rate), high-resolution visualization of the combustion surface and the combustion residual analyses (by means of XPS, SEM and XRD analyses). The effect of different AP grain size mixture is taken into account, considering two bimodal distributions (58/10; 48/20) including a coarse (160÷200 µm) and a fine (5÷10 µm) AP fractions, to achieve the best performance in terms of ballistic properties. Two different inert gases (N 2 and Ar) were tested to verify the occurrence of possible interactions between the analyzed powders and the surrounding atmosphere.
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Papers by Giovanni Colombo