Frozen action.

Last night, after dark, I went down to my turbine with a camera, which was loaned to me, to take pictures I've been longing to take for ages.

The reason for it being after dark was so the speed of the flash, rather than the speed of the shutter, froze the action.

Inevitably, a lot of water sprayed onto the camera lens and that has taken away some of the quality I was hoping for, but the pictures do show nicely how: 

• the cups cut into the jet and chop it up 
• the jet is carved in two by the splitter ridge
• the notch in each cup ensures the splitter ridge is the first part to enter the jet 
• water then passes down and around the floor of the cup 
• water is thrown up and away by the side walls
• pulses of water are created exiting to the side

The photos were made possible only by choosing carefully how to capture them. I use an SMA Windy Boy inverter to connect to the grid, and it takes 4 minutes from the time it first receives power before connecting to the grid. During this time, the pelton overspeeds and causes exhaust water to exit in a different way to when it's at its operational speed. A line of approach relatively free of spray is created which gives a good view of the jet.

The rotational speed in the photos was 1270 rpm, giving a linear velocity for the runner at the pcd (pitch circle diameter) of about 15 m/s. 

At this speed, the time taken for a cup to move to the position of the cup ahead of it is about one 400th of a second.

The nozzle orifice was 6.48 mm diameter, the flow 0.91 l/s and the jet velocity about 31 m/s.

The camera was a Sony Cybershot DSG TX10.  It is water proof, - and it needed to be !