Schmiechen 



3.3 Internal Efficiency 



The second factor of the hydraulic efficiency, the internal efficiency may 

 either be considered at a pump efficiency or, in the presence of a ducting sys- 

 tem, as the product 



"^INT - ^DUCT '^PUMP V^^) 



of the duct efficiency and the pump efficiency proper. 



Introducing the energy flows Ej^ and e^q across some appropriately chosen 

 internal fluid surfaces s^q and s^q , respectively, we may define the mean mass- 

 specific energies 



the inlet efficiency (see Sec. 4.2) 



^10 = Eio/PQ • (41) 



^INL = Eio/Ei = ei,/ei , (42) 



and the outlet efficiency 



''^OUTL ~ ^2/^20 = ^2/^20 ■ ('*3) 



In terms of these magnitudes, the duct efficiency 



^DUCT = (^2 - ^l)/(e20 - ^10) (44) 



becomes 



^DUCT = (1 - O/(l/^0UTL - ^INL ^) ' (45) 



and the pump efficiency is defined as 



^PUMP = (^20 - ^lo)/^ ■ (46) 



After all our basic performance criterion may be rendered in the form 



^HYD ~ ^PROp/'^IDEAL " '^JET '^DUCT ^PUMP (4*) 



with the flow efficiency 



■^FLOW - ^JET "^DUCT 



= (1 - M^)/(1/770UTF "^OUTL " ^INL ^Vt^j^f) 



(48) 



showing the link-up of the various component efficiencies introduced. Once 

 again, neither the duct nor the flow efficiency may be split into factors account- 

 ing for the inflow and outflow separately. 



1092 



