Design and Development of High-Velocity Submerged Water Jet Cavitation Erosion Test Rig

Abstract

Several hydro-machinery components such as impellers of submersible pump, draft tubes and turbine blades generally suffer from cavitation erosion (CE) during their operation, and due to this, service life and capability of such parts are reduced. During the design and development of these components, test rigs are usually required to evaluate their performance. In the present research work, keeping in view the economic aspects, out of different test rigs available, it is proposed to use high-velocity submerged water jet cavitation erosion test rig. The test rig was designed with flexibility in cavitation erosion parameters (velocity, angle of attack, stand-off distance, nozzle diameter) and fabricated with an aim to test the cavitation erosion of hydro-machinery steel under different cavitation erosion parameters. Calibration of the test rig was done for jet velocity, stand-off distance (SOD) and angle of attack. The CE rate of steel SS410 was evaluated using the fabricated test rig under different operating parameters consists of 3 velocities and 3 stand-off distance, keeping the other parameters like angle of attack as 90° and nozzle diameter as 3 mm. The test rig was capable of producing CE as observed from the specimen microstructure. From the microstructure analysis, the pits produced during the CE are clearly visible. The CE rate was found to be maximum for a parametric combination consist of maximum velocity (35 m/sec) and stand-off distance (10 cm). With an increase in velocity, the amount of water bubbles increases in the cavitation cloud, which contributes to maximum erosion. The cavitation erosion rate is enhanced by increasing the stand-off distance from 5 cm to 10 cm, followed by a decrement when moving from 10 to 15 cm.