Burning aluminum particles inside a laboratory-scale solid rocket motor

Melcher, John C.; Krier, Herman; Burton, Rodney L.

doi:10.2514/6.2001-3947

Cited by 16 publications

(9 citation statements)

References 6 publications

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“…Many studies of burning aluminum particles have been conducted [1][2][3][4]. Furthermore, many studies of burning time [5], ignition delay time [6], mechanism of agglomeration, and diameter of agglomerate of aluminum particles [7][8][9][10][11][12][13][14] have been conducted using various procedures, mostly experimental, but also analytical, to clarify the mechanism of agglomeration [15][16][17][18].…”

Section: Introductionmentioning

confidence: 99%

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Agglomeration Characteristics of Aluminum Particles in AP/AN Composite Propellants

Takahashi

Oide

Kuwahara

2013

Propellants Explo Pyrotec

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Most solid rockets are powered by ammonium perchlorate (AP) composite propellant including aluminum particles. As aluminized composite propellant burns, aluminum particles agglomerate as large as above 100 μm diameter on the burning surface, which in turn affects propellant combustion characteristics. The development of composite propellants has a long history. Many studies of aluminum particle combustion have been conducted. Optical observations indicate that aluminum particles form agglomerates on the burning surface of aluminized composite propellant. They ignite on leaving the burning surface. Because the temperature gradient in the reaction zone near a burning surface influences the burning rate of a composite propellant, details of aluminum particle agglomeration, agglomerate ignition, and their effects on the temperature gradient must be investigated. In our previous studies, we measured the aluminum particle agglomerate diameter by optical observation and collecting particles. We observed particles on the burning surface, the reaction zone, and the luminous flame zone of an ammonium perchlorate (AP)/ammonium nitrate (AN) composite propellant. We confirmed that agglomeration occurred in the reaction zone and that the agglomerate diameter decreased with increasing the burning rate. In this study, observing aluminum particles in the reaction zone near the burning surface, we investigated the relation between the agglomerates and the burning rate. A decreased burning rate and increased added amount of aluminum particles caused a larger agglomerate diameter. Defining the extent of the distributed aluminum particles before they agglomerate as an agglomerate range, we found that the agglomerate range was constant irrespective of the added amount of aluminum particles. Furthermore, the agglomerate diameter was ascertained from the density of the added amount of aluminum particles in the agglomerate range. We concluded from the heat balance around the burning surface that the product of the agglomerate range and the burning rate was nearly constant irrespective of the added amount of aluminum particles. Moreover, the reduced burning rate increased the agglomerate range.

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Section: Introductionmentioning

confidence: 99%

“…Collection of agglomerated aluminum particles emitted from burning propellant has been done under different pressures. Their particle diameters have been reported [7][8][9][10][11][12][13][14]. Aluminum particles added to AP composite propellant are known to form agglomerates on the burning surface during melting [1,2].…”

Section: Introductionmentioning

confidence: 99%

Agglomeration Characteristics of Aluminum Particles in AP/AN Composite Propellants

Takahashi

Oide

Kuwahara

2013

Propellants Explo Pyrotec

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“…In some experiments the AlO emission was dominated by the black body continuum emission [46][47][48][49], and in the case of nano-aluminum a weak emission signal was measured [40]. To quantify the amount of AlO during nano-aluminum combustion, absorption spectroscopy was used [50,51].…”

Section: Introductionmentioning

confidence: 99%

On AlO Emission Spectroscopy as a Diagnostic in Energetic Materials Testing

Peuker

Lynch

Krier

et al. 2013

Propellants Explo Pyrotec

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The emission of AlO is commonly observed in tests involving aluminum combustion in propellants and explosives. Such emission has been used as a signature of combustion, as a tool for measuring ignition and reaction times, and as a thermometer. This paper provides a critical review of methodologies exploiting AlO emission spectroscopy as a quantitative tool in energetics testing. Controlled tests involving aluminized explosives, as well as those using added alumina, are conducted, in which AlO emission is quantified and compared to total oxidation in the final residue. Experimental parameters such as optical depth and fireball confinement are systematically varied to examine the effect on AlO emission. We find that thermometry using AlO remains valid, and a new approach to using low resolution spectra is proposed. However, AlO emission spectroscopy or photometry can be quantitatively correlated to ignition and burning time, or used to infer the presence or absence of aluminum combustion, only under a limited set of circumstances. Factors that limit the ability to use AlO emission quantitatively are discussed in depth.

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“…As aluminum particles reach the burning surface, theyc an agglomerate into larger droplets, or form larged roplets throughc oalescem echanisms. Because RDX melts at around 480 Ka nd it is lower than typical propellant surface temperature (approx.900 K) [27] and the aluminum melting temperature is about 960 K [ 28],t he combustionw aves can affect the condensedp hase down to approximately 100 mmb eneath the burning surface [4].T his distancei s much larger than the 5-36 mml iquid layer thickness of AP particles [29][30][31].T hus, aluminum agglomeration can occur as combustion wavet ransmission and agglomerate may form on the burning surface or in the pocket geometry. The agglomerate may ignite as it is next to an AP/binder flame, where oxidizing speciesa re available for ignition.…”

Section: Effect Of Percent Rdxmentioning

confidence: 99%

Aluminum Agglomeration on Burning Surface of NEPE Propellants at 3-5 MPa

Liu

et al. 2016

Prop., Explos., Pyrotech.

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Aluminum agglomeration and agglomerate sizes of NEPE propellants were studied by cinephotomicrography at pressures of 3 and 5 MPa. Accumulation, aggregation, and agglomeration of aluminum particles similar to that at pressures below 1 MPa were observed. Coalescence of two agglomerates on the burning surface is obtained for the first time. A decrease in the burning rate from 8 to 5 mm s−1 leads to about 20 % increase in the agglomerate diameter. The pressure is found to have no direct influence on the agglomerate diameter when the burning rate is kept constant. The evolution of the agglomerate diameter according to the increase of the virgin aluminum size from 16 to 36 μm is convex in shape and reached its maximum at a particle diameter of 29 μm. Increasing the amount of RDX crystals added in the propellants causes a larger agglomerate diameter. The experimental mass average agglomerate diameters were compared with various agglomeration models. It is found that Hermsen and Salita empirical models have a higher accuracy for NEPE propellants rather than Becksted, Liu, or pocket models.

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Burning aluminum particles inside a laboratory-scale solid rocket motor

Cited by 16 publications

References 6 publications

Agglomeration Characteristics of Aluminum Particles in AP/AN Composite Propellants

Agglomeration Characteristics of Aluminum Particles in AP/AN Composite Propellants

On AlO Emission Spectroscopy as a Diagnostic in Energetic Materials Testing

Aluminum Agglomeration on Burning Surface of NEPE Propellants at 3-5 MPa

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