A Concave Electrode Based Capacitive Sensor for Cavitation Monitoring-Experimental Evaluation

Monitoring cavitation in the flow channel of industries like hydro-power plants and industries with large liquid cooling systems, is an important and crucial task. Cavitation is responsible majorly for the metal loss of turbine blades, erosion of the internal walls of pipes/penstock, and when the bubble explodes it creates impulse waves which create disturbance in measurement of flow. Also, the cavitation is the major source of vibration in the pipes while handling a high-speed fluid flow. Measuring cavitation in the pipes can help to schedule the regular maintenance and repairs of the affected system. In present work, the design of a simple non-invasive concave capacitive sensor is presented to measure the cavitation in terms of void fraction. The sensor is designed with the grounded guard electrodes and grounded shield, so it is immune to the stray electrical fields. Electrical models of the capacitive sensor are presented in different cases of void fractions. The proposed sensor is designed and experimentally validated by another concave capacitive sensor and the standard wire mesh sensor. The wire mesh sensor is designed along with its interface circuit. All three sensors are mounted on the same hardware setup, and the experiment is performed multiple times. The capacitance value changes from 16.58pF to 43.43pF for void fraction change of 100& x0025; to 0& x0025;. The uncertainty analysis is also done and the uncertainty of measurement budget is presented. The standard uncertainty of the proposed capacitive sensor is less than 0.372 pF for the whole range of measurement.