1979-02-01

Review of the Automotive Torque Converter 790046

With the big gains in automobile fuel economy already accomplished, primarily with off-shelf technology, further improvements above that expected by further downsizing will now require advanced technology. One area in which advancing the state of the art may not only benefit fuel economy but preserve drive-ability is in the fluid dynamic performance of torque converters. While lockup clutches may preclude the need for higher converter efficiency, improved performance in the primary gears where lockup is inhibited would still benefit fuel economy. The gains, however, would be less, but driveability would be improved by the higher coupling efficiency.Detailed fluid dynamic investigations were performed on a three-element torque converter. These investigations were based on computer solutions that have been successfully applied in the design of gas turbines. Using a numerical solution, surface velocities were computed along the reactor blade based on a two-dimensional flow field. These velocities were computed for an existing reactor blade and a proposed blade with a shortened axial chord. The reduced chord was intended for a more compact converter circuit design. Diffusion factors and exit fluid angles of the short chord design were maintained within the limits of the existing long chord design. Based on an approximation to the three-dimensional flow field, a computer program for the design of centrifugal Impellers was modified for application to impellers with axial flow discharge such as used in converter circuits. The results indicated the presence of negative and highly non-uniform velocities in the impeller. If these negative velocities or backflows could be removed and more uniform velocity gradients could be maintained, higher efficiency should be expected. Recommendations are made for further investigations.

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