Characteristics of Fuel Sprays from Specially Shaped and Impinging Flow Nozzles

Two ways to attain low emission diesel combustion, which are capable of meeting future regulations, are the so-called two-stage “rich and lean” combustion and ‘lean” diesel combustion. To actually achieve these types of combustion, homogeneous lean air-fuel mixture formation is very important In this study, two methods of producing a desirable air-fuel mixture axe investigated experimentally by observing fuel sprays from several unique injection nozzles in a high-pressure vessel. One was a slit shaped hole nozzle, which might result in increased air entrainment into the spray because of the larger surface area. The other was impinging flow nozzle, which generated a more homogeneous mixture by its high turbulence.

It was observed that with the slit shaped hole nozzle, the cross-sectional shape of the spray was unexpectedly circular, which was attributed to a greater dispersion of the spray perpendicular to the lengthwise slit axis. With the impinging flow nozzle, the fuel spray tended to spread out to a greater extent perpendicular to the plane containing the two nozzle holes. The high fuel concentration area which is typically observed at the center of the spray with a conventional nozzle was made leaner and the distribution was made more homogeneous.