The Influence of Cylindrical Spray Chamber Geometry on the Evolution of High Pressure Diesel Sprays

Abstract

While much is known on the effect of combustion chamber geometry on spray evolution in engines, less is known about its role in laboratory combustion chambers. This paper reports on a study, which investigates the effect of internal chamber geometry on the penetration and spreading angle of common rail nonreacting diesel sprays at room temperature conditions in a cylindrical constant volume chamber. This chamber has dimensions similar to those used in the literature. Spray chamber geometry was modified to yield three different chamber height-to-diameter ratios and two different nozzle stand-off distances. Sprays from three nozzles, two single-hole nozzles with different diameter and one twin-hole nozzle (THN), were examined for two injection pressures of 100 MPa and 150 MPa into two chamber pressures of 0.1 MPa and 5 MPa. To characterize the spray structure, a volume illumination method was used to study the spray tip penetration/speed and spread angle. For both injection pressures used with chamber pressure of 5 MPa, little sensitivity to vessel geometry was found in penetration distance and tip speed for variation in height to diameter ratio from 0.6 to 2.6 and variation in nozzle stand-off distance from 2 mm to 54 mm. For atmospheric chamber pressure, sensitivity to chamber geometry was evident and found to vary with nozzle type. Spread angle was found more largely affected by the calculation method and very sensitive to the image intensity threshold value for the cases investigated.