Laser Velocimeter Measurements in the Turbine of an Automotive Torque Converter: Part II—Unsteady Measurements

Abstract

The unsteady velocity field found in the turbine of an automotive torque converter was measured using laser velocimetry. Velocities in the inlet, quarter, mild, and exit planes of the turbine were investigated at two significantly different turbine/pump rotational speed ratios: 0.065 and 0.800. A data organization method was developed to visualize the three-dimensional, periodic unsteady velocity field in the rotating frame. For this method, the acquired data are assumed to be periodic at synchronous and blade interaction frequencies. Two shaft encoders were employed to obtain the instantaneous angular position of the torque converter pump and turbine at the instant of laser velocimeter data acquisition. By proper “registration” of the velocity data, visualizing the transient interaction effects between the turbine, pump, and stator was possible. Results showed strong cyclic velocity fluctuations in the turbine inlet plane as a function of the relative turbine-pump position. These fluctuations are due to the passing of upstream pump blades by the slower rotating turbine blades. Typical fluctuations in the through flow velocity were 3.6 m/s. Quarter and midplane velocity fluctuations were seen to be lower; typical values were 1.5 m/s and 0.8 m/s, respectively. The flow field in the turbine exit plane was seen to be relatively steady with negligible fluctuations of less than 0.03 m/s. From the velocity data, the fluctuations of turbine performance parameters such as flow inlet angles, root-mean-square unsteadiness, and output torque per blade passage were calculated. Incidence angles were seen to vary by 3 and 6 deg for the 0.800 and 0.065 speed ratios, respectively, while the exit angles remained steady. The turbine output torque per blade passage fluctuated by 0.05 Nm for the 0.800 speed ratio and 0.13 Nm for the 0.065 speed ratio.