according as the disk is parallel-sided or coned. The water enters the wheel radially with the velocity ui, and
uo = Q / 2πrodo.
(3)
| Fig. 211. |
Fig. 211 shows the notation adopted for the velocities. Suppose the water enters the wheel with the velocity vi, while the velocity of the wheel is Vi. Completing the parallelogram, vri is the relative velocity of the water and wheel, and is the proper direction of the wheel vanes. Also, by resolving, ui and wi are the component velocities of flow and velocities of whir of the velocity vi of the water. At the outlet surface, vo is the final velocity of discharge, and the rest of the notation is similar to that for the inlet surface.
Usually the water flows equally in all directions in the eye of the wheel, in that case vi is radial. Then, in normal conditions of working, at the inlet surface,
| vi = ui wi = 0 tan θ = ui / Vi vri = ui cosec θ = √ (ui2 + Vi2). |
(4)
If the pump is raising less or more than its proper quantity, θ will not satisfy the last condition, and there is then some loss of head in shock.
At the outer circumference of the wheel or outlet surface,