Modeling and Experimental Determination of the Axisymmetric Flow in a Diesel Engine Cylinder

Internal air motion in a Detroit Diesel 6V-92 two-stroke engine cylinder was determined by an idealized axisymmetric finite difference model under steady flow conditions. This model was used to compute axial and tangential velocities with entrance angles of 25 and 40 deg. Laser Doppler anemometer measurements were made in one plane for comparison under steady flow bench test conditions using actual engine hardware. Calculations and measurements showed that the swirl induced by the angled inlet flow was responsible for the nonuniform axial velocity profiles. These profiles exhibited large peaks in the midradius region (between cylinder center and wall). Increasing the inlet angle from 25 to 40 deg sharpened the axial velocity peak and shifted it toward the cylinder wall. The measurements indicated nearly isotropic turbulence across the measurement plane. A better understanding of the relationship between design and internal flow is expected to lead to improved combustion, scavenging tradeoffs.