ماشین حساب پارامترهای موتور

Brake Specific Fuel Consumption is the fuel consumed per unit power per hour, in g/kWh. It directly indicates engine efficiency:

• Small high-speed diesel: 230–270 g/kWh
• Medium-speed diesel: 195–230 g/kWh
• Large slow-speed marine: 160–175 g/kWh
• Gas engine (lean burn): 230–280 g/kWh equivalent

Lower BSFC = higher efficiency = less fuel per kW.

BMEP (Brake Mean Effective Pressure) is the hypothetical constant pressure acting on the piston that would produce the same net work per cycle. It normalizes performance independent of engine size.

• Naturally aspirated diesel: 7–10 bar
• Turbocharged diesel: 15–25 bar
• High-performance racing: 25–30+ bar

Higher BMEP means more power from a given displacement — a measure of specific output.

ISO 3046-1 defines four standard power ratings for reciprocating IC engines:

• COP: Continuous Power — unlimited running at constant load
• PRP: Prime Power — unlimited hours at variable load (avg ≤ 80%)
• LTP: Limited Time Power — max 500 h/year at 100%
• ESP: Emergency Standby — max 200 h/year

Reference conditions: 25°C, 100 kPa, 30% relative humidity.

Per ISO 3046-1, engine power must be derated when operating above reference conditions:

• Altitude: ~3.5% per 300 m above 300 m elevation
• Temperature: ~2% per 5.5°C above 25°C ambient
• Humidity: minor effect, usually neglected

Example: at 1500 m altitude and 40°C, derating ≈ 3.5%×4 + 2%×2.7 ≈ 19.4%.

Diesel engines are inherently more efficient (35–52%) due to higher compression ratios (15–22:1) and lean combustion. Gas engines (28–42%) use lower compression (10–14:1) but produce less NOx.

For the same power output, gas engines consume more fuel (by energy) but produce ~25% less CO₂ per kWh due to the hydrogen content of methane.