How does the Kaplan turbine regulate flow at part load conditions?

The Kaplan turbine regulates flow at part load conditions by adjusting both the wicket gates and the runner blade angles to maintain high efficiency and stable operation. At part load, the amount of water flowing through the turbine is reduced to match the lower electrical demand. Simply closing the wicket gates would cause the water to impinge on the runner blades at a non-optimal angle, leading to increased turbulence and reduced efficiency. To compensate for this, the Kaplan turbine's control system adjusts the runner blade angle in coordination with the wicket gate opening. The control system aims to maintain the optimal angle of attack between the water flow and the runner blades, minimizing energy losses and maximizing power extraction. The relationship between wicket gate opening and runner blade angle is typically defined by a "cam curve" or similar control strategy. This coordinated adjustment of wicket gates and runner blades allows the Kaplan turbine to maintain relatively high efficiency over a wide range of flow rates, including part-load conditions. For example, if the electrical demand drops to 50% of the turbine's capacity, the wicket gates will be partially closed, and the runner blades will be adjusted to a flatter angle to efficiently capture the reduced water flow. This ability to adjust both the wicket gates and runner blades is a key advantage of Kaplan turbines, making them well-suited for applications with variable water flow.