As the name indicates, An Impulse Turbine is running by the impulse of water. In an impulse turbine, the water from the dam flows through the pipeline. Then through guide mechanism and finally through the nozzles.
In this transportation process of water from the dam to turbine, the entire available energy of the water is converted into Kinetic Energy by passing through nozzles.
These nozzles are kept as much as close to the runner. The water enters the running wheel in the form of Jets, which impinges on the buckets, fixed on the outer periphery of the wheel.
The energy to the runner is imparted by the jet of water impinges on the buckets with high velocity. Hence the pressure of water at entering and leaving the vanes is atmospheric.
So, Here are the Different Efficiencies of Impulse Turbine