Fundamental Analysis of the Secondary Flows and Jet-Wake in a Torque Converter Pump: Part 1 — Model and Flow in a Rotating Passage

Previously, experimental results for the velocity field in a torque converter pump showed strong jet/wake characteristics including backflows and circulatory secondary flows. To understand the fundamental flow behavior simplified analytical/numerical Navier-Stokes flow models were developed herein to independently analyze the pump pressure-to-suction side jet/wake flow, the core-to-shell side jet/wake flow, and the secondary flows. Parametric studies were undertaken to evaluate the effect that operating conditions and geometry had on the characteristics. Two relatively simple models were employed: (i) a rotating 2-D straight-walled duct to model the pressure-to-suction side jet/wake flow due to rotational Coriolis forces and (ii) a 180° flow bend to model the core-to-shell side jet/wake flow due to rapid radial/axial flow turning. The formation and development of the pump jet/wake flow was studied in detail. Results showed that the core side wake and the suction side wake, both of which drive the formation of 3-D jet/wake flow in a mixed flow impeller were primarily dependent on two non-dimensional force parameters: the modified Rossby number and the Reynolds number. The suction side wake, which was due to the counter-rotational tangential Coriolis force, was almost only a function of the modified Rossby number and independent of the Reynolds number, while the core side wake, which was due to flow separation caused by rapid radial flow turning, was primarily a function of the Reynolds number. Increasing the modified Rossby number increased the pressure-to-suction side jet/wake flow; similarly, increasing the Reynolds number increased the core-to-shell side jet/wake flow. The geometric parameters that were seen to affect the pump flow were the back-weeping angle for the pressure-to-suction side jet/wake, and the passage length (or curvature) for the core-to-shell jet/wake. Results showed that using backswept blades can completely eliminate the pressure-to-suction side jet/wake flow effect. Other geometrical parameters were tested but only a small to moderate influence on the jet/wake flow phenomena was found. Predicted trends compared favorably with experimental results.