694 



HYDKAULICS AND ITS APPLICATIONS 



may become considerably less than that of the atmosphere. A chamber 

 surrounding J is connected to the supply of water to be pumped, by the 

 suction pipe S. The reduction of pressure in this chamber is then 

 accompanied by a flow of water along the suction pipe, which, meeting 

 the high pressure jet, is carried forward as a combined stream into the 

 diverging discharge pipe D. Here its kinetic energy is partially recon- 

 verted into pressure energy, which is utilized in overcoming the head to 

 be pumped against. 



Let /?i = height of supply head above jet in feet. 



,, li g = height of jet above suction supply 



H d = height of delivery head above jet ,, 



| j High Pressure Supply 



FIG. 338. Jet Pump. 



Prf , ^) 



W' V 2;;f 



Let h d = \ ~1 + 9 " r = H d + losses between point D and delivery. 



i = area of nozzle in square feet. 



,, a s = area of annular suction pipe in plane of nozzle, square feet. 



,, a d = area of mixing chamber at throat, square feet. 



Q = volume passing per second, v = velocity, and p the pressure 



in Ibs. per square foot at the point denoted by a suffix. 

 On the assumption that the sides of the mixing chamber are sensibly 

 parallel from the nozzle until the jets have attained a common velocity 

 and pressure at D, so that, neglecting friction, the sides of the chamber 

 exert no force on the water, we may apply the equation of momentum, 

 which now becomes : 



9 



_ I Qv 

 ' (~ 9 



Qi vi _ Pi 

 : 9 



Pd <*d 



