Segment V12.2: Self-Propelled Lawn Sprinkler

(Related to Textbook Section 12.3 - Basic Angular Momentum Considerations)

Turbomachine shaft work can be calculated from the moment-of-momentum equation which expresses the relationship between angular momentum of a fluid about an axis of rotation and torque.

Although water enters the lawn sprinkler in the axial direction with zero angular momentum about the axis of rotation, the water exits with angular momentum about that axis (the exiting jets are not in the radial direction). The sprinkler arm, which is connected to the drive wheels through a set of gears, does not rotate until the flowrate is increased to provide sufficient torque. Some of the torque is used to power the sprinkler across the yard. The device is a turbine.