Effect of shape of silt particles on erosive wear of pelton turbine bucket

The efficiency of the turbine decreases with the increase in the erosive wear. This problem is a major concern in the case of small hydro power plants, as most of these plants are run-of-river schemes and situated in steep hilly terrains. Erosive wear of hydro turbine components depends on different parameters such as size, composition, concentration and shape of silt particles, velocity of flow and impingement angle, and properties of the base material. Under the present study an experimental investigation was carried out on a small scale Pelton turbine in actual flow conditions to investigate the effect of shape of silt particles on the erosive wear of Pelton turbine bucket. For the investigation, sand was collected from the head work of one of the most silt affected power houses. The sand particles were sieved to different sizes. Sand particles of average size 215 micron (i.e. sand sieved between 180 micron and 250 micron sieve) were arbitrarily chosen for the experiment. Sand particles mixed with the tank of water to be circulated through the Pelton turbine used for the experiment. A number of tests were conducted. Each test was conducted for different time periods and the sand particles were collected after each test. The micrographs of silt particles before and after the test were obtained by using SEM. The shape of the sand particles was examined by using Image J software. The average value of ten particles was considered for analysis. From the analysis, it was observed that the sand particles gaining circularity with the recirculation time of the sand water mixer. The wear rate decreased exponentially with the gain in circularity of silt particles and eroding capacity of angular particles are more than the circular particles.