MLA Citation: Bloomfield, Louis A. "Question 1117"
How Everything Works 22 Jul 2018. 22 Jul 2018 <>.
1117. What is the general theory of operation of a hydraulic turbine? — GS, Fort Worth, Texas
A hydraulic turbine is essentially a fan run backward—while a fan adds energy to a passing fluid, a turbine extracts energy from a passing fluid. You can think of the fluid's effects on the turbine blades in two different but equivalent ways. In one view, the fluid is deflected by its encounter with the canted turbine blades and as the blades push the fluid in one direction, the fluid pushes the blades in the opposite direction. This reaction force that the fluid exerts on the blades causes those blades to spin and does work on them—energy is transferred from the fluid to the blades.

In the other view, the blades "fly" through the fluid like the wings of an airplane. The fluid flow around each blade is such that the pressure is higher on one side of the blade than the other and the blade experiences a net force toward the lower pressure side. The blades move in the direction of this force, so the passing fluid does work on them—energy is transferred from the fluid to the blades.

These two views are completely equivalent. The fluid leaves the turbine blades traveling more slowly or at lower pressure, and it acquires a rotation in the direction opposite the turbine's rotation.

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