Continuum Modeling and Simulation of Microscopic, Multi-phase, Reactive Processes of Reactants at the Nano- and Microscale

Moshe Matalon, Caterpillar ProfessorD. Scott Stewart, Shao Lee Soo Professor

matalon@illinois.edu (217) 244 8746dss@illinois.edu (217) 332 7947

Sept 18th, 2014

Overview/Outline of Recent Illinois work (2103-14) (for the Sept 18th talk)

A) Detailed analysis of a generic three-components counterflow flame supported by condensed phase, temperature dependent reaction and diffusion processes

(with applications propellant and energetic material ingredients to Ti + B, Al + AP, Al + Binder, Ti + Si and alike)

B) Model development that allows consideration of more complex

reaction diffusion pathways in condensed liquids/solids

(with more than 3 species and with phase transition)

C) Initial modeling steps for a theory of condensed phase combustion front comprised of the dynamic combustion of separated reactants associated with the manufactured microstructure.

(consideration of coherent rapid phase change and combustion in localized spots and the effective front behavior)

Multi-component, model for separated reactants Condensed phase diffusion flames

A) Detailed analysis of a generic three-components counterflow flame

Counterflow sub-models:

Analysis of a generic three-components counterflow flame configuration of the form

R1 + R2 → Products

An important aspect that distinguishes these types of problem from classical gaseous combustion is the diffusion properties of the reactants.

The use of generalized Fickian diffusivities requires the determination of the diffusion coefficients and their dependence on the (more fundamental) binary diffusivities.

These generally are concentration and temperature dependent.

We are examining a hierarchical of complexities starting with

(i) constant diffusion coefficients, (ii) coefficients that are concentration dependent and (iii) coefficients that are also highly temperature-dependent.

B) Model development that allows consideration of more complex reaction diffusion pathways in condensed liquids/solids

First example: Formulation of more complex condensed phasereaction/diffusion mechanisms (Al, CuO burning)

• Overall 2 Al + 3 CuO => Al2O3 + 3 Cu• EIGHT (8) condensed phase species Al(s) Al(liq) CuO(s) CuO(liq) Cu(s) Al(s) Al(liq) Al2O3(s) Al2O3(liq)

• Simplified multicomponent diffusion• Phase change• Chemical reaction

Exp Results: Shown forstoichiometric Al/CuO thermite (N. Glumac UIUC Glumac-Stewart DTRA grant)

Imaging and video sequences show progression of the reaction

Initial densification can be observed

Propagation and flame speed can be examined

C) Model of condensed phase combustion front made of separated reactants associated with the manufactured microstructure.

7

8

Test 6 Al-CuO Stoich

Movie and details to be added

Extraction of a Slice of the observed view field, Test 6 (CuO/Al)

Cut-outs images that correspond to the image in the yellow section.

The red circle at 30.43 ms isolates a single rapid ignition/extinction even on the scale of 100 micron

Cut-outs of images of a approximately 1.5 mm x 2 mm region that show a rapid ignition/extinction event.

The values image intensity of the bright spot is approximately but shown at the measure elapsed time.

Evident of a reaction diffusioncontrolled condensed phase flame ignition

Thermal time scale (millisec)Chemical time scale (~ 10 to 100 μsec)

To be compared with model calculations