Page 202 - Handbook of Energy Engineering Calculations

2. Compute the engine output at the elevated temperature
When the intake air is at a temperature greater than 90°F (32.3°C), a
temperature correction factor must be applied. Then output = (sea-level hp)

(altitude correction factor)(intake-air-temperature correction factor), or output
= (800)(0.68)(0.95) = 516 hp (384.9 kW), with 110°F (43.3°C) intake air.

3. Compute the output of a supercharged engine
A different altitude correction is used for a supercharged engine, but the same

temperature-correction factor is applied. Table 2 lists the altitude-correction
factors for supercharged diesel engines. Thus, for this supercharged engine at
10,000-ft (3048-m) altitude with 80°F (26.7°C) intake air, output = (sea-level
hp)(altitude correction factor) = (800)(0.74) = 592 hp (441.6 kW).

At 10,000-ft (3048-m) altitude with 110°F (43.3°C) inlet air, output = (sea-
level hp)(altitude correction factor)(temperature correction factor) = (800)
(0.74)(0.95) = 563 hp (420.1 kW).

Related Calculations. Use the same procedure for gasoline, gas, oil, and

liquefied-petroleum gas engines. Where altitude-correction factors are not
available for the type of engine being used, other than a diesel, multiply the
engine sea-level brake horsepower by the ratio of the altitude-level
atmospheric pressure to the atmospheric pressure at sea level. Table 3 lists
the atmospheric pressure at various altitudes.

TABLE 3 Atmospheric Pressure at Various Altitudes