Page:Model steam turbines; how to design and build them (IA modelsteamturbin00harrrich).pdf/17

 CHAPTER II.

PRESSURE DEVELOPED ON SURFACES BY AN IMPINGING JET. VELOCITY AND FLOW OF STEAM THROUGH ORIFICES.

IT has been seen from Chapter I. that if a body of mass $W/g$ traveling at velocity of v feet per second, receives a push or impulse P during time t seconds, the velocity, and consequently the energy, of the body is increased.

In fig. 3 a piston is shown mounted in a cylinder, the back end of which terminates in a nozzle. The cylinder is filled with water which, the piston being moved to the right, leaves the nozzle with a certain velocity V, and impinges on the flat stationary surface. On striking the plate its velocity in the direction of flow is nil, and the whole change of velocity is V. Hence

P = $W/g$ V. . .  .  .  .  .  (1)

where P is the pressure in lbs. per square inch, W weight of fluid or has discharged per second, and V the original velocity of the jet. 13