scholarly journals Thermal theory of aluminum particle ignition in continuum, free-molecular, and transition heat transfer regimes

2018 ◽  
Vol 124 (5) ◽  
pp. 054301 ◽  
Author(s):  
Alexandre Ermoline
Keyword(s):  
Heat Transfer ◽  
Aluminum Particle ◽  
Thermal Theory ◽  
Particle Ignition ◽  
Transition Heat

scholarly journals Measurements in Solid Propellant Plumes at Ambient Conditions

2011 ◽  
Author(s):  
Jonathan L. Height ◽  
Burl A. Donaldson ◽  
Walter Gill ◽  
Christian G. Parigger
Keyword(s):  
Temperature Distribution ◽  
Solid Propellant ◽  
Aluminum Particle ◽  
Burning Surface ◽  
Ambient Conditions ◽  
Aluminum Particles ◽  
Open Atmosphere ◽  
Particle Ignition ◽  
Accident Scenarios ◽  
Color Pyrometer

The study of aluminum particle ignition in an open atmosphere propellant burn is of particular interest when considering accident scenarios for rockets carrying high-value payloads. This study investigates the temperature of an open atmosphere Atlas V solid propellant burn as a function of height from the burning surface. Two instruments were used to infer this temperature: a two-color pyrometer and a spectrometer. The spectra were fitted to a model of energy states for aluminum monoxide. The temperature which provided the best match between the model and data was taken as the reaction temperature. Emissions above 30 inches from the surface of the propellant were not sufficiently strong for data reduction, perhaps obscured by the alumina smoke cloud. The temperature distribution in the plume increased slightly with distance from the burning surface, presumably indicating the delay in ignition and heat release from the larger aluminum particles in the propellant. The pyrometer and spectrometer results were found to be in excellent agreement indicating plume temperatures in the range of 2300K to 3000K.

Thermal Theory of Metal Particle Ignition

AIAA Journal ◽  
1975 ◽  
Vol 13 (2) ◽  
pp. 209-214 ◽  
Author(s):  
A.G. MERZHANOV
Keyword(s):  
Metal Particle ◽  
Thermal Theory ◽  
Particle Ignition

scholarly journals Experimental Research on the Thermal Performance of Composite PCM Hollow Block Walls and Validation of Phase Transition Heat Transfer Models

2016 ◽  
Vol 2016 ◽  
pp. 1-15 ◽  
Author(s):  
Yuan Zhang ◽  
Sunqi Zhuang ◽  
Qian Wang ◽  
Jiapeng He
Keyword(s):  
Heat Transfer ◽  
Phase Transition ◽  
Thermal Performance ◽  
Heat Transfer Process ◽  
Unsteady State ◽  
Typical Structure ◽  
Hollow Block ◽  
Change Material ◽  
Capacity Method ◽  
Transition Heat

A type of concrete hollow block with typical structure and a common phase change material (PCM) were adopted. The PCM was filled into the hollow blocks by which the multiform composite PCM hollow blocks were made. The temperature-changing hot chamber method was used to test the thermal performance of block walls. The enthalpy method and the effective heat capacity method were used to calculate the heat transfer process. The results of the two methods can both reach the reasonable agreement with the experimental data. The unsteady-state thermal performance of the PCM hollow block walls is markedly higher than that of the wall without PCM. Furthermore, if the temperature of the PCM in the wall does not exceed its phase transition temperature range, the PCM wall can reach high thermal performance.

Aluminum Particle Ignition Studies

2012 ◽  
Author(s):  
Michael S. Cornelius ◽  
Burl Donaldson
Keyword(s):  
Atmospheric Pressure ◽  
Molten Aluminum ◽  
Pressure Pulse ◽  
Aluminum Particle ◽  
Oxide Shell ◽  
Ignition Process ◽  
Particle Sizes ◽  
Aluminum Particles ◽  
Particle Ignition ◽  
Arc Heating

Experiments have been performed to study the combustion criteria of aluminum particles at atmospheric pressure. The primary goal is to quantify the outcome for a particle into which thermal energy has been deposited. Experiments utilized instantaneous joule heating of an aluminum wire. Once the particle was generated, it fell under gravity and the flight was recorded by video; in some cases, the ignited particle quenched or fragmented, and the residue was collected for SEM and EDS imaging. This provided information related to the aluminum oxide shell which was formed when combustion occurred. These experiments produced particles of approximately 150450 microns in the arc heating tests. In a second set of experiments, particles were produced under more observable time scales. This provided observation of the oxide skin, which is known to influence the ignition process. This experiment utilized a pressure pulse to eject a small droplet of molten aluminum through a small orifice. From this experiment, particle sizes ranging 2–3 mm were produced.

Heating and Ignition of Metal Particles in the Transition Heat Transfer Regime

2008 ◽  
Vol 130 (10) ◽  
Author(s):  
Salil Mohan ◽  
Mikhaylo A. Trunov ◽  
Edward L. Dreizin
Keyword(s):  
Heat Transfer ◽  
Temperature Difference ◽  
Particle Diameter ◽  
Accommodation Coefficient ◽  
Heat Transfer Model ◽  
Heat Transfer Analysis ◽  
Transfer Model ◽  
Metallic Particles ◽  
The Continuum ◽  
Transition Heat

This paper considers the heating and ignition of small metallic particles in hot gases for a range of Knudsen numbers, for which the continuum description of heat transfer is not valid. Modified Fuchs’ model for the transition heat transfer analysis was adapted to treat diatomic gas with properties changing as a function of temperature. The dimensionless heat transfer coefficient, Nusselt number, was calculated as a function of the particle diameter for the transition heat transfer regime. Heat transfer rates in the transition regime are somewhat different from one another for the cases of particle heating and cooling while the absolute values of the particle-gas temperature difference are the same. This effect does not exist for the continuum heat transfer model. It is observed that the applicability of the continuum heat transfer model for particles of different sizes depends on pressure and particle-air temperature difference. For example, for particles at 300K heated in air at 2000K, the continuum heat transfer model can be used for particle diameters greater than 10μm and 1μm at the pressures of 1bar and 10bars, respectively. Transition heat transfer model must be used for the analysis of heat transfer for nanosized particles. For calculating the ignition delay, the continuum model remains useful for particle diameters greater than 18μm and 2μm for 1bar and 10bars, respectively. The sensitivity of the transition heat transfer model to the accommodation coefficient is evaluated. It is found that for metallic particles, the accommodation coefficient has a relatively weak effect on the heat transfer rate.

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