LASER VELOCIMETER MEASUREMENTS IN THE TURBINE OF AN AUTOMOTIVE TORQUECONVERTER .2. UNSTEADY MEASUREMENTS

The unsteady velocity field found in the turbine of an automotive torq ue converter was measured using laser velocimetry. Velocities in the i nlet, quarter, mild and exit planes of the turbine were investigated a t two significantly different turbine/pump rotational speed ratios: 0. 065 and 0.800. A data organization method was developed to visualize t he 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 w ere employed to obtain the instantaneous angular position of the torqu e converter pump and turbine at the instant of laser velocimeter data acquisition. By proper ''registration'' of the velocity darn, visualiz ing the transient interaction effects between the turbine, pump, and s tator 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 throughflow velocity were 3.6 m/s. quarter and midplane velocity f luctuations 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, a nd output torque per blade passage were calculated. Incidence angles w ere 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 outpu t torque per blade passage fluctuated by 0.05 Nm for the 0.800 speed r atio and 0.13 Nm for the 0.065 speed ratio.