A fuel spray induced vortex ring S.S. Sazhin a, * , F. Kaplanski b , G. Feng a , M.R. Heikal a , P.J. Bowen c a Department of Mechanical Engineering, School of Engineering, Faculty of Science and Engineering, University of Brighton, Cockroft Building, Lewes Road, Brighton BN2 4GJ, UK b Department of Aeromechanics, Estonian Energy Research Institute, Paldiski mnt. 1, Tallinn 10137, Estonia c School of Engineering, University of Wales, Cardiff CF1 3NS, UK Received 4 December 2000; accepted 13 March 2001 Abstract Itisdemonstratedthatatypicalgasolinefuelinjectionprocesscanbeaccompaniedbythedevelopmentofafountainstructureconsisting of a spray jet and a vortex ring. In the case of a typical injection process lasting 3 ms, the vortex-like structures were observed starting t < 2msafterthestartofinjectionandlastinguntilabout t  4:5ms: Thevortexringmovedinthedirectionofthejetanditsdistancefrom theaxisofthesprayincreasedwithtime.Theaxialsprayvelocityinitiallyincreasedwithincreasingdistancefromtheaxis,thensubsequently decreased. The observed velocity of the vortex ring and the proportionality of its radius and axial displacement are shown to be consistent with the concept of a time dependent turbulent eddy viscosity. q 2001 Elsevier Science Ltd. All rights reserved. Keywords: Fuel spray; Turbulence; Vortex ring 1. Introduction The problem of spray formation and dynamics is well recognised, especially in view of its application to Diesel and G-DI gasoline direct injection) engines [1±5]. The primary focus so far has been on the problem of spray formation and spray penetration, along with the associated problem of spray evaporation and combustion [6]. Much less attention has been devoted to the interaction of liquid spray with the gas phase leading to the formation of vortex rings, or the problem of penetration accompanied by the formationofvortexrings[7,8].However,onewouldexpect the formation of the vortex ring to have a signi®cant in¯u- enceonmanyaspectsofspraydynamics,reducingthespray penetration [9±11] for example, and in¯uencing the liquid evaporation rate. In the case of sprays in Diesel and G-DI engines, this would inevitably in¯uence the dynamics of combustion processes [12,13]. Only recently [5,14,15] have temporally based studies of GDI and Diesel sprays facilitatedstudiesofvortex-ringformation.Inthisformative study, the emphasis concerns developing an understanding of the phenomenon of vortex ring formation and dynamics related to fuel spray injection, and to consider theoretical interpretation of some of these results. In-depth analyses of experimental and theoretical studies of vortex rings in general are provided in review papers [7,8] and a number of original references [16±24]. In Section 2, the experimental set-up used to provide the temporally based data is described brie¯y, and the ®ndings are summarised. In Section 3, an interpretation of some experimental results is proposed based on the concept of timedependentturbulentviscosityassuggestedbyLugovtsov [25,26]. The main conclusions of the paper are summarised in Section 4. 2. Experimental results TheinjectorusedintheexperimentswasastandardG-DI injector with a nominal cone angle of 358. The duration of injection was 3 ms, during which time 20 mg of liquid fuel gasoline)wasinjected.Fuelwassuppliedatinjectionpres- sure of 100 bar and injected into the atmosphere at room temperature 208C). Fuel density was 725.1 kg/m 3 and its kinematic viscosity was 0.672 £ 10 26 m 2 /s. Following the spray injection, fuel droplet velocities were measured using the standard Laser Doppler Anemometry LDA) technique in the plane containing the axis of spray, but utilising a phase-averaging approach to derive temporal information. Inthetimeintervalbetween0and3ms,measurementswere averaged over a 0.25 ms timestep. Subsequently, they were averaged every 0.5 ms timestep Ð see Ref. [5] for a more Fuel 80 2001) 1871±1883 0016-2361/01/$ - see front matter q 2001 Elsevier Science Ltd. All rights reserved. PII:S0016-236101)00068-0 www.fuel®rst.com * Corresponding author. Tel.: 144-1273-642677; fax: 144-1273- 642301. E-mail address: s.sazhin@bton.ac.uk S.S. Sazhin).