Impact of Altitude & Ambient Temperature on Diesel Engine Power

Air-cooled diesel engines are highly dependent on air density for combustion and cooling. Higher altitude and temperature reduce air density, leading to power de-rating.

1. Altitude

· Effect: Thinner air reduces oxygen available for combustion, leading to incomplete burning, power loss, and increased smoke.

· General Rule: Power de-rates by approximately 3.5% for every 300 meters (1000 ft) above sea level.

· Formula (Approximation):

 Power Correction Factor (Altitude) ≈ 1 - (0.035 × (Altitude in meters / 300))

2. Ambient Temperature

· Effect: Hotter air is less dense, reducing oxygen mass per intake cycle and limiting engine cooling efficiency.

· General Rule: Power de-rates by approximately 2% for every 5.6°C (10°F) above 25°C (77°F).

· Formula (Approximation):

 Power Correction Factor (Temperature) ≈ 1 - (0.02 × ((Ambient Temp in °C - 25) / 5.6))

Combined Effect Formula

To find the Corrected Available Power, multiply the engine's rated power at sea level/standard conditions by the combined correction factor:

Corrected Power = Rated Power × (Power Correction Factor (Altitude) × Power Correction Factor (Temperature))

Example:

For a 10kW engine at 1500m and 35°C:

· Altitude Factor: 1 - (0.035 × (1500 / 300)) = 0.825

· Temperature Factor: 1 - (0.02 × ((35 - 25) / 5.6)) ≈ 0.964

· Corrected Power: 10kW × (0.825 × 0.964) ≈ 7.95kW