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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

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

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3 VORTEX RING-LIKE STUCTURES IN ENGINES

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4 A typical spray in Diesel engines

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

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

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

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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

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

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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

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11 The region of maximal vorticity,

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12 VORTEX RING MODELS,

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13 Schematic view of a vortex ring

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Formulation of the problem, ring-to-core radius

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Approximate solution

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Velocity of the centroid at r=0,

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17 Velocity of the centroid at r=0,

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

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

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20 Velocity of the region of maximal vorticity,

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

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22 MODELLING VERSUS EXPERIMENTS

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23 Velocity of the region of maximal vorticity,

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24 Velocity of the region of maximal vorticity,

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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.

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26 OTHER RECENT RESULTS

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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

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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

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

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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

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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

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

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

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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

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