Electrical conductivity surface sensor for two-phase flow imaging in a hydrodynamic coupling

For the measurement of fluid distributions inside a hydrodynamic coupling we have developed a high-speed surface sensor based on the measurement of the electrical conductivity. Two sensors are placed on the pressure-side and the suction-side walls of a blade channel inside the coupling. The sensors are composed by approximately 1000 interdigitated sensing structures. The system is supplied by a battery and has a wireless link to communicate with a PC. Sensor and electronics have been so designed that the whole system can rotate together with the coupling pump wheel. The electronics measures the conductivity of the liquid of each sensing structure in a multiplexed manner which effectively gives images of the instantaneous liquid distribution over the sensor surface. Frame frequencies of up to 10,000 images per second can be reached. We have applied the surface sensor to measure the fluid distribution in a test coupling for different slip conditions. Initial results are presented and discussed.