Page 238 - Handbook of Energy Engineering Calculations

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(1200/2)/60 = 2.952 ft /s (0.0084 m /s).
Then, the volumetric efficiency of this engine = actual charge drawn into
the cylinder/engine displacement = 2.45/2.952 = 0.8299, or 82.99 percent.

Related Calculations. Use this general procedure to determine the volumetric
efficiency of reciprocating internal-combustion engines—both gasoline and

diesel. The procedure is also used for determining the fuel consumption of
such engines, using test data from actual engine runs.

AIR-COOLED I-C ENGINE CHOICE FOR INDUSTRIAL
USES

Choose a suitable air-cooled gasoline engine to replace a 10-hp (7.46-kW)

electric motor driving a municipal service sanitary pump at an elevation of
8000 ft (2438 m) where the ambient temperature is 90°F (32.2°C). Find the
expected load duty for this engine; construct a typical load curve for it.

Calculation Procedure:

1. Determine the horsepower (kW) rating required of the engine
Electric motors are rated on an entirely different basis than are internal-
combustion engines. Most electric motors will deliver 25 percent more power
than their rating during a period of 1 or 2 hours. For short periods many
electric motors may carry 50 percent overload.

Gasoline engines, by comparison, are rated at the maximum power that a
new engine will develop on a dynamometer test conducted at an ambient
temperature of 60°F (15.6°C) and a sea-level barometric pressure of 29.92 in

(759.97 mm) of mercury. For every 10°F (5.56°C) rise in the intake ambient
air temperature there will be a 1 percent reduction in the power output. And
for every 1-in (2.5-cm) drop in barometric pressure there will be a 3.5 percent
power output loss. For every 1000 ft (304.8 m) of altitude above sea level a
3.5 percent loss in power output also occurs.

Thus, for average atmospheric conditions, the actual power of a gasoline
engine is about 5 to 7 percent less than the standard rating. And if altitude is a
factor, the loss can be appreciable, reaching 35 percent at 10,000-ft (3048-m)