Velocity, mechanical energy efficiency

Figure 12. Mechanical energy efficiency as a function of roll velocity for high...

Vehicle fuel economy is normally measured in miles per gallon. At any given instant, it depends on the energy content of a gallon of fuel (Qf), the vehicle velocity (V.,) and power required (P,-5q), the thermal efficiency with which the engine converts fuel energy into useful output work (rj,.), and the mechanical efficiency with which the driveline delivers that work to the vehicle wheels (r j). Specifically,... 

The mechanical efficiency of a fan is the ratio of the horsepower output to the horsepower input at the fan shaft. The input horsepower to drive the fan consists of the air horsepower, the energy losses in the fan, fluid dynamic losses, shock losses, leakage, disk friction, and bearing losses (all as horsepower), The fan oudet velocity pressure loss has been included in the fluid dynamic losses. 

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