DISCHARGE COEFFICIENT 



611 



experiments by Professor John Goodman, the increase in this coefficient 

 at the knocking speed in his pump, varying from 58 per cent, with a 

 delivery pressure of 10 Ibs. per square inch to 5 per cent, with a pressure 

 of 70 Ibs. per square inch. 



Although this increases the capacity of the pump, yet, as might be 

 expected, its efficiency is lowered, due to the increased losses by shock. 

 The experiments showed that in this particular pump an increase in the 



FIG. 291. Theoretical Diagram of Piston Pressures during Delivery Stroke of 



Reciprocating Pump. 



discharge coefficient from 1*059 to 1'517, was accompanied by a decrease 

 of 10 per cent, in the efficiency. 



A theoretical pressure diagram for the delivery side of the pump is 

 shown in Fig. 291, where, however, the' line A' H A, representing the 

 acceleration pressure, has been drawn to take into account the effect of 

 the obliquity of the connecting rod. 



Also, since frictional resistances now increase the head on the piston, 

 the friction line A' B A is drawn below the acceleration line. 



R n 2 



