Fluid Dynamics Investigation of a GDI Fuel Spray by Particle Image Velocimetry

In this work, result of experimental investigation on interaction of fuel spray generated by a swirled type injector,with air motion in a prototype cylinder are presented. experiments were carried out by planar imaging and particleimage velocimetry (piv) techniques in order to provide information about the spray structure evolution andinstantaneous velocity distribution of air motion and fuel spray at different operating condition. the experimentalsetup includes an engine head and a prototype cylinder with optical access suitable to stabilize conditions of tumbleflow close to the real sim engines. a common rail injection system was used with a swirled type injector of a nominalcone angle 50° and a nozzle diameter 0.55 mm. a blower, under steady state condition, supplies a suitable intake flowrate to simulate that one evolves in real engines at different operating conditions. tests were carried out by setting thepressure drop between the intake manifold and cylinder of 350 mm h20 , valve lifts h , == 5 and 9 mm and injectionpressure 10 mpa. the measurement, have been done on a plane across the cylinder and injector axis with a field ofview of 47 mm in diameter. piv of air motion shows a fluid dynamics structure clockwise rotating with homogenousstructure. the velocity profiles show 30% increasing of maximum velocity at operating condition of h v =9 mm withrespect to h v =5 mm. at the first stage of injection, results of planar imaging show a fuel spray that depicts a solidstructure with a penetration axis primarily controlled by the fuel momentum at later time; the fuel spray depicts a lesscone angle with respect to those obtained by analyzing the spray under air flow quiescent condition. then, because oftumble motion, the fuel spray is distorted and disintegrated. images show the formation of large clusters of fuel whichare transferred in wide region within the cylinder. at the first stage of injection, piv results of instantaneous velocitydistribution of fuel spray show a strong exchange of momentum with air motion evolving inside the cylinder. at latertime, velocity profiles of fuel droplets indicate a strong correlation with tumble motion that becomes the parameterregulating breaking, dispersion and transferring liquid fuel in the periphery cylinder.