EFFECT OF CAVITATION SOURCES ON COMBINED EROSION OF SANDY WATER AND CAVITATION EROSION

Based on the computational fluid dynamics (CFD) method, simulating the actual working conditions of turbines, the internal vapour-liquid-solid flow fields (total pressure and volume fraction of vapour phase) on the test turntable surfaces with six preset cavitation source holes in different diameters are numerically calculated under the combined erosion of sandy water and cavitation erosion. The vapour-liquid-solid combined erosion is tested on the reconstructive rotary wear test rig, and the macro photos and the SEM photos of the turntable are analysed. The erosion area of the combined erosion is predicted. The numerical results show that the regions of minimum and maximum pressure on the front surface of the turntable appear in the vicinity of the side of the cavitation holes, and the vapour phase looks like a big long comet tail and spreads along the direction of the water flow. Vapour phase volume is proportional to the diameter of cavitation source hole. The experimental results show that the shape of each erosion scar near each cavitation hole is similar, and the erosion regions are mainly concentrated near the cavitation holes along the direction of the water flow. Two deep ditches are formed on the upper and lower sides of the cavitation hole. When the diameters of the cavitation holes are increased, the erosion wedge pits near the cavitation holes gradually grow longer and deeper, and the extent of damage is strengthened, and the erosion scars are changed from order to disorder. The experimental results basically coincide with the calculated results.