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Combustion of coarse monodisperse titanium particles in air

1. O. G. Glotov. Combustion of coarse monodisperse titanium particles in air. Institute of Chemical Kinetics and Combustion, Russian Academy of Sciences, Novosibirsk, Russia. 2. Content.

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Combustion of coarse monodisperse titanium particles in air

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  1. 1 O. G. Glotov Combustion of coarse monodisperse titanium particles in air Institute of Chemical Kinetics and Combustion, Russian Academy of Sciences, Novosibirsk, Russia

  2. 2 Content  Introduction\ Ti is unusual interesting object \ production of nanosized photocatalytic TiO2 particles in situ  Experiment \ creation of monodisperse burning titanium particles \ techniques: video record, quenching & sampling, SEM & EDS • Results\ evolution events \ motion law \ fragmentation \ condensed combustion products • Conclusions\ 300, 390 and 480 micron are identical\ heterogeneous reaction \ fir-branch fragmentation \ full metal consumption

  3. 3 Ti Refractory nonvolatile metal with с refractory oxide Melting point: Ti 1939 K , TiO2 2130 К Oxide density lower than metal density Density: Ti 4.506g/cm3, TiO2 4.250g/cm3 Oxide protects metalagainst oxidation up to 500-550°С. Then oxidedissolves in metal. Ti - interesting objectfor metal combustion theory Ti considerably differfromAl, Mg, B  Engineering material  Metallic fuel

  4. 4 50 cm It is necessary to study the mechanism of Ti particles combustion in air To optimize the burning process for achieving highest completeness of metal combustion and high yield of smoke-like oxide with demanded parameters …

  5. 5 5 Typical pyrotechnicTipowder 85 %mass < 50 micron [Evgeny Shafirovich, Soon Kay Teoh, Arvind Varma. Combustion of levitated titanium particles in air / Combustion and Flame.2008. V.152,P. 262–271.] Sieves20–25, 25–32, …, 90–106, 106–125micron, electromagnetic levitation, laser ignition. [I. E. Molodetsky, E. P. Vicenzi, E. L. Dreizin, C. K. Law. Phases of Titanium Combustion in Air // Combustion and Flame.1998. V. 112, P. 522–532. ] Spark micro arc, ignited spheres240и 280micron [T. A. Andrzejak, E. Shafirovich, A. Varma. On the Mechanisms of Titanium Particle Reactions in O2/N2 and O2/Ar Atmospheres // Prop. Explos. Pyrotech. 2009, V. 34, P. 53–58.] Cylindrical sample 3.1253.125 mm. Laser heating. Thermocouple wires Pt/Rh 200 micronare welded to lateral surface.

  6. 6 Specimen, producing the burning monodisperse spherical Ti particles Non-metalizedcomposition-matrixwithinsertedinclusionsmade of metalizedcomposition Inclusionstransform into burning particles(agglomerate) Matrix ignites and ejects the particles Number and size of the burning particles are predetermined bynumber and parameters of inclusions

  7. 7 Specimen preparation Inclusions:69 % Ti, 31 % energetic binder

  8. 8 Specimen preparation Matrix: 27 % energetic binder, 50 % HMX, 23 % AP

  9. 9 Experiment Specimen Catchpot filled with Ar 1 – body 2 – funnel 3 – Petri dish D = 390 micron, L = 115 cm

  10. 10 Treatment of video records • Events • Time moment • Coordinate • Velosity • Parameters of movement • x(t) • v(t) • Parameters offragments’ scatter • r • vr

  11. Events and scenarios 11 e z b Events: «b» (begin) – fragmentation starts «e» (end) – fragmentation is over «s» (stop) – forced quenching of a particle in the catchpot «z» (zero) – particle disappears \ vanishes «z» – “star” shape fragmentation Scenariobez

  12. Parameters of b, e, z events 12

  13. Size and morphology evolution 13

  14. 14 Particles motion v(t) x(t) Approximation Cd = A/Re A(D)= –7+0.126·D v0 = 139–0.202·D, v0in cm/s, Din 300-480 micron A(D)

  15. 15 A new shape of fragmentation – «fir branch» Al starfir branch for particles D> 300 micron

  16. 16 Sampling of the condensed combustion products specimen stainless steel tube580 см Petri dish

  17. 17 Condensed combustion products Numerical size distribution mother Data for 300-micron burning mother particles

  18. 18 EDSdata

  19. 19 EDS data  No shell-kernel structure

  20. 20 EDSdata set TiO2.76upon the average

  21. Conclusions-1 21 The technique for creation the monodisperse burning Ti particles with size of hundred microns has been developed to investigate the Ti combustion mechanism For the first time the evolution of particles of titanium with size of 300, 390 and 480 microns formed by merging a great number of small particles has been examined Qualitative features of that size particles behavior are identical

  22. 22 Conclusions-2 Formation of a spherical particle occurs due to heterogeneous reaction and at an initial stage is accompanied by a bright luminescence Motion of a burning particle can be described with use of drag coefficient exceeding classical Stokes’ coefficient (Cd 50/Re for 480-micron particles) Prominent feature of the Ti particle evolution is fragmentation which in this specific case is performed with preservation of a mother particle (projection of splinters reminds a fir-tree branch). During fragmentation, there is an appreciable loss of weight and decrease in speed of a particle After the combustion termination as a result of full metal consumption the residual particle consists of various oxides – from TiO to TiO5; its diameter is by 1.5-2 times less than initial one

  23. 23 Thank you for attention !

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