25.P.21 Construction of the explosion waves theory for combustible aerosols

J. Aerosol Sci., Vol. 25. Suppl. I, pp. $391-$392. 1994 Copyrillht~)199~, Elsevier Science lad Printed in Great Britain. All rights reserved

Pergamon

25 P 21 CONSTRUCTIOI{ OF THE E X P L O S I O N WAVES THEORY FOR COMBUSTIBLE AEROSOLS S.K. A S L A N O V Faculty of Mathematlcs and Mechanlcs Odessa State Unlverslty, Petra VellKogo Sir. 2 UKralne, 270057, Odessa

KEYWORDS Exploslon; TwO-phase Medium; Drop; Kinetics; Instabllity

Breal~-up;

P h e n o m e n o n of the exPloslon in a e r o s u s p e n s l o n from combustible drops, liquid h y d r o c a r b o n s especlally, is connected w l t h c o m p l i c a t e d set of mechanical and phYsicochemlcal proceses. As the most important of them, the process of brea/4-up for the Inltlal aerosol particles behlnd the moving shocE waves to the small daughter drops, W h i c h determine the next processes of the intensive e v a p o r a t i o n and combustion of the forming mlxture Is found experimentally. M e c h a n l s m of the local hydrodynamical instability of the drop surface layer was taKen by us before as a base ~or theoretlcal explanation o~ the viscous !lqUld ~'op crushing under the aerodynamlcal a c c e l e r a t i o n In the h i g h - s P e e d gas flow. Such an approach made it possible to find a n a l y t l c a l l Y the expresslon for the range of the desription of the drop mass r e d u c t i o n bY the breal~-up, that very well corresponds to the Known emperlcal law. In present wor~ the p o i n t e d analytical results are used for the c o n s t r u c t i o n of the closed theory for the self-sustaining exploslve waves In llqUld aerosols. W l t h thls alm they are introduced to the P r o P o s e d by us thermodYnamlcal c a l c u l a t e d scheme ~or numerical modelling of m o t i o n o~ the t w o - s p e e d two-phase m e d i u m of the detonating aerosol, consisting o{ the gaseous oxldlzer, steams o~ combustible, products of combustion and liquid drops. Secondary d i s p e r s i o n is cosldered non-inertlal because of the small particle size. The process o~ evaporatlon is o r d e r e d by the ~nown law of the constance of the speed for the drop surface area chan-

$391

$392

S.K. ASLANOV

glng, K i n e t i c s of chemical r e a c t i o n s is d e s c r i b e d by A r r e n l u s d e p e n d e n c e of the c o r r e s p o n d i n g i n d u c t i o n perlod. I n t e g r a t i o n of the e q u a t i o n set b e h i n d the inltlal shock front is c l o s e d b y the r e q u i r e m e n t of a c h i e v e ment of sonic s p e e d by the g a s - p h a s e flow. I n d e f i n i t e c o n s t a n t of the drops c r u s h i n g E l n e t l c s A, over w h i c h time for the full drop breaK-up is expressed, will come as a parameter and will define the whole family of the explosive regimes, Condition of the self-sustaining explosive wave, connected with the possibility of transforming of the subsonic gas flow into the supersonic one, makes it POSSible to, s e l e c t o n l y two r e g i m e s of its Prop a g a t i o n , - w i t h m a x i m u m and minlml.lm velocities. C o i n c i d e nee of thl,~ minimum ..a.,..c~!a,.~d value O~. .......... experimental data serves for the single-valued definition o f the b r e a K - u p p a r a m e t e r A, The constructed theory is realised at the example of the monodisperslve suspension of Kerosene in oxygen (stec h e o m e t r l c a l c o m p o s i t i o n ) w i t h the drop d i a m e t e r d o :0, 29; 0,90; 2,60 mm, C o r r e s p o n d i n g c a l c u l a t e d v a l u e s of the exP l o s l v e wave s p e e d D ~ . ~ . = 1 8 8 0 ; 1 7 0 0 ; 1 6 ~ 0 m/s d i f f e r f r o m the e x p e r i m e n t a l r e s u l t s o n l y at some per cent (they are overstated f o r d o : 2 , 5 mm a n d t h e y a r e u n d e r s t a t e d fop do: ~ 0 , 2 9 mm ), ~T~e c l a r l f l c a t e d details of the explosive wave structure explain the reducting character of the dependence D ~ L . (do),

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