Page 199 - Handbook of Energy Engineering Calculations

4. Compute the friction hp of the engine
For an internal-combustion engine, the friction horsepower is fhp = ihp −
bhp. In this engine, fhp = 588 − 500 = 88 fhp (65.6 kW).

Related Calculations. Use a similar procedure to determine the indicated
engine efficiency e = e /e, where e = ideal cycle efficiency; brake engine
ei
i
efficiency, e = e e; combined engine efficiency or overall engine thermal
b
eb
efficiency, e = e = e e. Note that each of these three efficiencies is an
o
o
eo
engine efficiency and corresponds to an actual thermal efficiency, e , e , and
b
i
e .
o
Engine efficiency e = e /e, where e = actual engine thermal efficiency.
i
e
t
Where desired, the respective actual indicated brake, or overall, output can be
substituted for e , e , and e in the numerator of the above equations if the
i
b
o
ideal output is substituted in the denominator. The result will be the
respective engine efficiency. Output can be expressed in Btu per unit time, or
horsepower. Also, e = actual mep/ideal mep, and e = imep/ideal mep; e =
e
ei
eb
bmep/ideal mep; e = overall mep/ideal mep. Further, e = e e , and bmep =
eo
m i
b
e (imep). Where the actual heat supplied by the fuel, HHV Btu/lb, is known,
m
compute e e and e by the method given in the previous calculation
o
i
b
procedure. The above relations apply to any reciprocating internal-
combustion engine using any fuel.
ENERGY ANALYSIS I-C INDUSTRIAL ENGINE CHOICE

Select an internal-combustion engine to drive a centrifugal pump handling
2000 gal/min (126.2 L/s) of water at a total head of 350 ft (106.7 m). The

pump speed will be 1750 r/min, and it will run continuously. The engine and
pump are located at sea level.

Calculation Procedure:

1. Compute the power input to the pump
The power required to pump water is hp 8.33 GH/33,000e, where G = water