Cavitation Detection in Automotive Torque Converters Using Nearfield Acoustical Measurements

As automotive torque converters decrease in both diameter and axial length, the effects of cavitation in the torque converter becomes increasingly important on noise, efficiency, and performance goals. Cavitation is the formation and collapse of vapor bubbles in a working fluid when local static pressure falls below the vapor pressure of the working fluid. A technique to detect cavitation in automotive torque converters using nearfield acoustical measurements is presented. The technique concentrates on high frequency noise that is associated with the collapse of vapor bubbles. The nearfield acoustical technique is compared to two other techniques using static pressure measurements inside the torque converter; one on the torque converter stator blades and the other on the torque converter pump blades. A microwave telemetry transmitter was used to obtain data from inside the torque converter in both previous investigations. The nearfield acoustical technique is demonstrated to be valid on a torque converter dynamometer test stand and in the bell housing of an operating vehicle. Using the nearfield acoustical technique, the effects of temperature and charge pressure on cavitation are shown. These effects are shown to agree with typical cavitation behaviors. The results for different performance torque converters are compared in the vehicle and on the dynamometer test stand. The results from in-vehicle tests show the same trends as test stand results. The nearfield acoustical technique provides a simple, relatively inexpensive procedure that can be utilized on a test stand as well as in the vehicle to determine the onset of cavitation in automotive torque converters.