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A multidimensional model of scavenging in a loop-scavenged two-stroke-cycle engine has been validated through detailed comparisons between computed and measured mean and rms velocities in a commercially available engine under motored operating conditions. The laser-Doppler velocimetry (LDV) measurement database constitutes one of the most complete characterizations of in-cylinder flows currently available. A novel feature of the calculations is that flow in the coupled intake-port/in-cylinder/exhaust-port system including a simplified crankcase is calculated. Through systematic variations in initial conditions and geometric configuration, the modeling suggests plausible explanations for some of the (at first sight) unexpected features found in the LDV measurements.

Three-dimensional transient computations of flow in variable-displacement vane pumps and in gear pumps have been completed. Several innovations were required for this new application of computational fluid dynamics (CFD). New physical insight into the pumping process has been extracted by exercising the model. Likely cavitation sites have been identified, the importance of fluid compressibility has been established, and reductions in flow losses and noise have been realized. Based on these computations, design changes have been proposed and evaluated in hardware for automatic transmission variable- displacement vane pumps. The same methodology is being applied to fixed- displacement gear pumps. These findings have relevance to both the Transmission Designer and the Transmission Analyst.