Rapid Characterization of I.C. Engine In-Cylinder Flow at Spark: A Synergistic Approach Using Experimental and Numerical Simulations

A new methodology for rapidly characterizing the in-cylinder flow field at spark ignition for internal combustion engines is described in this paper. The process involves the use of 3-D particle tracking velocimetry to measure the flow field at intake valve closing (IVC) in a water analog engine simulation, and the use of CFD to compute the evolution of the measured flow field during the compression stroke, by using the experimental 3-D PTV results at IVC as the initial condition for the calculations.

The technique has been applied to investigate the in-cylinder flow field of a typical 4 valve engine operating in two different modes; one or two intake ports active. The results indicate that in either mode the flow field at IVC is dominated by a different large scale structure: tumble in the case where both intake ports are active and swirl in the case where only one port is active. The results also indicate that these structures evolve differently during the compression stroke. While swirl decays monotonically during the compression stroke, tumble appears to gain in strength during the early stages of the compression before it starts decaying at a faster rate.

In addition, an initial comparison of the results obtained by this hybrid approach with engine combustion data indicates that the burn rate increases with increasing levels of in-cylinder turbulence, which is the expected trend based on combustion entrainment models.