Effects of Pelton Turbine Needle Eccentricity on Jet Quality

In hydropower with high heads, the Pelton turbine is the most used impulse turbine due to its high efficiency. However, the efficiency of the power generation from the Pelton turbines depends significantly on the jet quality. One of the major reasons for poor jet quality is a misalignment of the needle and nozzle of the Pelton injector, as it results in deviation of the jet from its path. With an increase in the jet deviation, the quality of the jet further reduces leading to more power generation loss and vibration. In addition to the extent of needle eccentricity, the jet deviation also depends on the nozzle opening. Here, various needle eccentricities (0, 2, 5, and 8%) and nozzle openings (25, 40, 50, 65, and 90%) are considered to study their effects on the jet deviation, i.e., the jet quality numerically. For 40% nozzle opening, as the needle eccentricity increases from 2 to 8%, the injector efficiency is found to reduce by 13.56% and the deviation of jet center, measured at a distance of 2.32 times the nozzle diameter from the nozzle exit, is found to increase three times. Further, for 5% needle eccentricity, as the nozzle opening reduces from 50 to 25%, the deviation of the jet center increases two times. This study demonstrates the need for checking Pelton needle eccentricity, especially after maintenance.