1991-02-01

High Frame Rate Flow Visualization and LDV Measurements in a Steady Flow Cylinder Head Assembly 910473

The purpose of this work was to develop a high speed flow visualization system which could be used to observe the behavior of the air flow in a steady flow cylinder head assembly. This type of experimental rig has been used by engineers for many years to evaluate valve discharge coefficients. This study is believed to be the first high speed flow visualization of the air flow in a system of this type. Particular emphasis was placed on the characterization of intake generated swirl and tumble motions within the cylinder. A 40 watt copper vapor laser was used to expose motion picture films at 5000 frames per second. The light scattering medium was phenolic microballoons.Based on the flow visualization results, selected LDV measurements were made to quantify the visual observations. A propylene glycol aerosol was used for seeding in the LDV experiments. The observed and measured back-flow from the downstream plenum into the cylinder casts serious doubt on the usefulness of using tumble, and to some extent swirl measurements in a steady flow rig to estimate these conditions in real engines. This observation provides evidence of a fundamental difference which can exist between the steady flow field and that of a motored piston cylinder assembly. The flow visualization confirmed that the choice of a solid body rotation model would be inappropriate for a description of tumble or swirl in this assembly.

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