1 / 19

Stochastic modeling of primary atomization : application to Diesel spray .

CNRS – UNIVERSITE et INSA de Rouen. Stochastic modeling of primary atomization : application to Diesel spray. J. Jouanguy & A. Chtab & M. Gorokhovski. Introduction. Atomization : main phenomena: Turbulence in liquid and gaz phase, cavitation, cycle by cycle variations

yuval
Télécharger la présentation

Stochastic modeling of primary atomization : application to Diesel spray .

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. CNRS – UNIVERSITE et INSA de Rouen Stochastic modeling of primary atomization : application to Diesel spray. J. Jouanguy & A. Chtab & M. Gorokhovski

  2. Introduction. Atomization: main phenomena: • Turbulence in liquid and gaz phase, cavitation, cycle by cycle variations • Deterministic description of such atomization is very diffcult task. • Stochastic approach => Application to primary atomization. Sacadura,CORIA

  3. Time t1 Time t2 radial direction radial direction r Liq. r Liq. axial direction axial direction radial direction radial direction Liq. r Liq. r axial direction radial direction axial direction radial direction Liq. r Liq. r axial direction axial direction Floating cutter particles.

  4. Scaling symetry for thickness of liquid core. • Life time. • Ensemble of n particles. y Fragmentation intensity spectrum r(x,t) r(x,t) r(x,t) r(x,t + dt ) liq. x The main asumption: scaling symetry for thickness.

  5. Knowledge of and Equation for the distribution function Theory of Fragmentation under Scaling symetry (Gorokhovski & Saveliev 2003, Phys. Fluids). Evolution equation Knowledge of Fokker Planck type equation Log brownian stochastic process Langevin type equation Equation for one realisation y rc =critical length scale r* =typical length scale liq x

  6. Time scale Identifiction of main parameters. Transverse instability = Rayleigh Taylor instability Liquid Formation of droplets through a minimal size rcr Shearing instability rc =critical radiusrcr r* =Rayleigh Taylor scale => (Reitz 1987)

  7. Radial direction Path of stochastic particle Grid Stochastic particle position Liquid zone Injector radius Gaz zone Axial direction Realization of stochastic process; « Stochastic floating cutter particles ». Motion of particules In the radial direction: In the axial direction: Staitistics of liquid core boundary =>

  8. Experimental setup. C. Arcoumanis, M. Gavaises, B. French SAE Technical Paper Series, 970799 (1997). Gaz initial conditions: Atmospheric conditions Liquid initial conditions:

  9. Injection of droplets Radius: Radius of the injector Injection velocity Probability to get liquid core; formation of discret blobs using presumed distribution: Statistics of liquid core boundary Mass flow rate conservation Motion of droplets => Standard KIVA procedure with velocity conditionned on the presence of liquid Initial conditions

  10. Example of distribution of formed blobs.

  11. Computed mean sauter diameter. Sauter Mean Diameter

  12. Symbols = experiment Line = simulation Centerline droplet mean axial velocity.

  13. Symbols = experiment Line = simulation Centerline Sauter Mean Diameter (SMD).

  14. Ug = 60 m/s, Ul = 1.36 m/s Ug = 60 m/s, Ul = 0.68 m/s Application to Air-Blast atomization. Experiment => mean liquid volume fraction (Stepowski & Werquin 2001) Simulation => statistics of liquid core boundary Key parameter:

  15. f Drag coefficient , Stp particle Stokes number Drop injection and lagrangian tracking. Typical size resulting from primary atomization Motion of the drops injected. Modification of the gas velocity field: Lagrangian tracking : Pl probability of presence of liquid

  16. Distribution of formed blobs. Experiments(Lasheras & al 1998) Ug = 140 m/s Ul = 0.13 m/s Examples of instantaneous distribution of formed droplets with instantaneous conditionned velocity of gaz and liquid core Ul = 2.8 m/s

  17. Shearing Turbulence Collisions Computation in the far field. => Secondary processes: Fragmentation or coalescence Example of instantaneous distribution of formed droplets ug = 140 m/s , ul = 0.55 m/s

  18. Comparison in the far field. Ug = 140 m/s

  19. Conclusion. • Simple enginering model for primary atomization is proposed. • This allows to form the blobs in the near-injector region. Future work. • Comparison with experiments in Brighton (trying different main mechanisms for fragmentation).

More Related