1. VORTEX RING-LIKE STRUCTURES IN GASOLINE FUEL SPRAYS: MODELLING AND OBSERVATIONS Sergei SAZHIN*, Felix KAPLANSKI**, Steven BEGG*, Morgan HEIKAL* * Sir Harry Ricardo Laboratories, Internal Combustion Engines Group, School of Environment and Technology, Faculty of Science and Engineering, University of Brighton, Brighton, BN2 4GJ, UK ** Laboratory of Multiphase Physics, Tallinn University of Technology, Tallinn 19086, Estonia

2. 2 Presentation overview VORTEX RING-LIKE STUCTURES IN ENGINES VORTEX RING MODELS MODELLING VERSUS EXPERIMENTS OTHER RECENT RESULTS

3. 3 VORTEX RING-LIKE STUCTURES IN ENGINES

4. 4 A typical spray in Diesel engines

5. 5 Typical vortex ring-like structure in a gasoline fuel spray Piston crown position

6. 6 Schematic view of vortex ring generator (Gharib et al.,1998 )

7. 7 Formation stage (Gharib et al.,1998 )L/D<4 L/D>4 L/D  4 ‘optimal’ ring

8. 8 Gasoline engine injectors Injector AB Fuel injector type Port (PFI)Direct (G-DI) Nominal fuel pressure3.5 bar100 bar Fuel temperature22 °C22 °C Fuel type Iso-octane (2,2,4 TMP) Iso-octane (2,2,4 TMP) Injection frequency1 Hz 1 Hz Injection duration5 ms2 ms Air pressure1 bar1 bar Air temperature20 °C20 °C Orifice size 200 μm 250 μm

9. 9 VORTEX RING-LIKE STRUCTURE IS GASOLINE ENGINE (injector A),

10. 10 VORTEX RING-LIKE STRUCTURE IS GASOLINE ENGINE (injector B), Injector axis Penetration depth Spray width V x1 V x3 V x2 2R o x r l

11. 11 The region of maximal vorticity,

12. 12 VORTEX RING MODELS,

13. 13 Schematic view of a vortex ring

14. Formulation of the problem, ring-to-core radius

15. Approximate solution

16. Velocity of the centroid at r=0,

17. 17 Velocity of the centroid at r=0,

18. 18 Velocity of the centroid at r=0 (short times), γ ≈ 0.57721566 is the Euler constant, ψ(x) is the di-gamma function

19. 19 Velocity of the centroid at r=0 (long times),

20. 20 Velocity of the region of maximal vorticity,

21. 21 Velocity of the region of maximal vorticity at long times, Θ 3 ~ t -3b

22. 22 MODELLING VERSUS EXPERIMENTS

23. 23 Velocity of the region of maximal vorticity,

24. 24 Velocity of the region of maximal vorticity,

25. 25 Conclusions 1. A generalised vortex ring model is based on the assumption that the time dependence of the vortex ring thickness ℓ is given by the relation atb, where a is an arbitrary positive number, and 1/4 ≤b ≤ 1/2 is suggested. 2. The predictions of the model are compared with the results of experimental studies of vortex ring-like structures in gasoline engine-like conditions with a high pressure (100 bar) G-DI injector and a low-pressure (3.5 bar) port fuel injector (PFI). The G-DI results has shown good agreement with the model. In contrast, the agreement of the PFI results with the model has been poor.

26. 26 OTHER RECENT RESULTS

27. 27 Transient heating of a semitransparent spherical body Sazhin, S.S., Krutitskii, P.A., Martynov, S.B., Mason, D., Heikal, M.R., Sazhina, E.M. (2007) Transient heating of a semitransparent spherical body, Int J Thermal Science, 46(5), 444-457. when R RdRd when R d <R<R g

28. 28 Evaporation of droplets into a background gas: kinetic modelling Sazhin, S.S., Shishkova, I.N., Kryukov, A.P., Levashov, V.Yu., Heikal, M.R. (2007) Evaporation of droplets into a background gas: kinetic modelling, Int J Heat Mass Transfer, 50, 2675-2691. 1 2 T s,  s x T Rd,  Kinetic region Hydrodynamic region Rd  j V q

29. 29 Approximate analysis of thermal radiation absorption in fuel droplets when R RdRd when R d <R<R g

30. 30 Approximate analysis of thermal radiation absorption in fuel droplets Sazhin, S.S., Kristyadi T., Abdelghaffar, W.A., Begg, S., Heikal, M.R., Mikhalovsky, S.V., Meikle S.T., Al- Hanbali, O. (2007) Approximate analysis of thermal radiation absorption in fuel droplets, ASME J Heat Transfer, 129, 1246-1255. where θ R is the radiation temperature, R d is the droplet radius, θ R can be assumed equal to the external temperature T ext in the case of an optically thin gas in the whole domain. The coefficients depend on the range of radii

31. 31 Particle grouping in oscillating flows. Sazhin S.S., Shakked, T., Sobolev, V., Katoshevski, D. (2008) Particle grouping in oscillating flows, European J of Mechanics B/Fluids, 27, 131-149. Katoshevski, D., Shakked, T., Sazhin, S.S., Crua, C., Heikal, M.R. (2008) Grouping and trapping of evaporating droplets in an oscillating gas flow, International J of Heat and Fluid Flow, 29, 415- 426. V d (m/s) X (mm)X (mm) Velocities are normalised by ω/k, the distance by 1/k and the time by 1/ω

32. 32 Acknowledgements The authors are grateful to EPSRC (Project EP/E047912/1) for financial support.

33. 33 Thank you for your attention Any comments or suggestions would be highly appreciated

34. VORTEX RING-LIKE STRUCTURES IN GASOLINE FUEL SPRAYS: MODELLING AND OBSERVATIONS Sergei SAZHIN*, Felix KAPLANSKI**, Steven BEGG*, Morgan HEIKAL* * Sir Harry Ricardo Laboratories, Internal Combustion Engines Group, School of Environment and Technology, Faculty of Science and Engineering, University of Brighton, Brighton, BN2 4GJ, UK ** Laboratory of Multiphase Physics, Tallinn University of Technology, Tallinn 19086, Estonia

35. 35