1994-03-01

Application of LIPA (Laser Induced Photochemical Anemometry) to the Water Analog Model of a Four-Stroke IC Engine 940282

Our research contributes to the overall attempt to gain knowledge of the fluid dynamical processes in engines by applying a new measurement technique called LIPA (Laser Induced Photochemical Anemometry). It concentrates on detecting fundamental flow and mixing mechanisms by performing experiments on the induction stroke in an axisymmetric motored water analog model of a four stroke IC engine. We present results of the investigations done at an engine speed of 20 RPM in water (corresponding to 340 RPM in air) at three different valve lifts (3, 6, and 9 mm). Maps containing velocity vectors depict in 2D a toroidal recirculation pattern that scales with cylinder volume and they suggest that the recirculation pattern possesses the highest degree of order -- thus least mixing -- for 9 mm valve lift and the lowest for 3 mm valve lift. A fluid dynamic model on the basis of freestream jet characteristics has been proposed to account for this phenomenon. Ensemble averaged velocity data demonstrates the stability and repeatability of the averaged flow field pattern in the investigated area for the second half of the induction stroke. A brief introduction is given on the additional potential of LIPA by discussing data of velocity fluctuations, by including information of a velocity-vs-time plot for one location in the flow field, and data of vorticity distributions as contours in 3D diagrams.

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