MEASUREMENTS OF DROPLET VELOCITY AND SIZE DOWNSTREAM OF THE MOVING VALVES OF A 4-VALVE ENGINE WITH MANIFOLD INJECTION, OPERATED UNDER ISOTHERMAL STEADY SUCTION CONDITIONS

The four-valve head of a VTEC engine was mounted on an open cylinder a nd the valves and fuel injection system operated as in the engine with a rotational speed of 1200 rpm. Local measurements of droplet charact eristics were obtained with a phase-Doppler velocimeter and iso-octane injected over 5 ms intervals, corresponding to 36 crank angle degrees , with manifold depression of 20 mbar. The results show that most of t he fuel droplets were located close to the liner and on the side of th e cylinder adjacent to the exhaust valves. In the plane of the measure ment, 10 mm below TDC, the liquid flux diminished as the initiation of injection Mas advanced before opening of the inlet valves. With injec tion with the inlet valves closed, there were two waves of droplets, o ne from each of the two valves and separated by 60 deg CA and both wit h the Sauter mean diameter of about 120 mu m. With injection with the infer valves open, most of the droplets emerged from the main inlet va lve and with Sauter mean diameters of about 50 mu m, smaller than thos e of the unconfined spray.