Characterization and Comparison of Steady-Flow Techniques Used for Engine Airflow Development

This paper compares bulk impulse-torque and 2D planar PIV steady flow-field measurements created by an engine cylinder head and intake system model using a steady-flow bench and evaluates operational aspects of the steady-flow test system. The model included a full-sized intake manifold and cylinder head section from a Chrysler 2.4L PFI four-valve per cylinder engine mounted to an optical cylinder. Two test system operational aspects were evaluated: (1) upstream versus downstream engine location relative to the flowbench (operational modes corresponding to flow bench pulling or pushing through the system), (2) PIV seeding particulate choice. Several dry and oil fog particulates were assessed however, of the options tested, only laboratory grade glass and consumer grade talc allowed long enough operation for practical data acquisition. Tests were performed over lift-over-diameter (L/D) ratios spanning from 0.1 to 0.3. The results indicate that for the setup evaluated, the flowbench operational mode effects are not larger than the standard repeatability of each test point. This result is significant because pushing the air through the test components allows the seeding to be introduced downstream of the flow bench which avoids damaging and potentially dangerous accumulation of particulate within it. Commercial grade talc seeded PIV provides comparable trend-wise results to the glass particulate at the low and high L/D ratios but indicated a transition to high lift structures at a later L/D than the glass particulate. Angular momentum calculated by integrating the PIV flow fields predicted the measurements made using the impulse torque meter through the flow transition better when using the glass particles, deviating a maximum of 13% with glass but as much as 60% using the talc. This is primarily attributable to the vastly different characteristics of the flow after the transition and the very narrow range of L/D where it occurs.