Use of Experimentally Measured In-Cylinder Flow Field Data at IVC as Initial Conditions to CFD Simulations of Compression Stroke in I.C. Engines - A Feasibility Study

The feasibility of using experimentally determined flow fields at intake valve closing, IVC, as initial conditions for computing the in-cylinder flow dynamics during the compression stroke is demonstrated by means of a computer simulation of the overall approach. A commercial CFD code, STARCD, was used for this purpose. The study involved two steps. First, in order to establish a basis for comparison, the in-cylinder flow field throughout the intake and compression strokes, from intake valve opening, IVO, to top dead center, TDC, was computed for a simple engine geometry. Second, experimental initial conditions were simulated by randomly selecting and perturbing a set of velocity vectors from the computed flow field at IVC. These represent random sampling of velocity vectors and experimental errors from such techniques as 3-D PTV (3-D Particle Tracking Velocimetry), 2-D PIV (2-D Particle Imaging Velocimetry), LDV (Laser Doppler Velocimetry), ... The number of selected vectors as well as the magnitude of the imposed errors was varied systematically to determine the limitations of the approach. Using the interpolated field of the chosen subsets, the computation was then restarted and continued throughout the compression stroke. Comparisons with the base calculations were made to estimate the accuracy and limitations of the approach.