Engine & Turbine Fuel Consumption Estimation
| Driver Type | Heat Rate (HHV) | Typical Size | Fuel Use (MCF/hr per 1000 HP) | Application |
|---|---|---|---|---|
| Gas Engine (Rich-burn) | 7,500–8,500 BTU/BHP-hr | 100–3,500 HP | ~7.5 | Field, gathering |
| Gas Engine (Lean-burn) | 7,000–7,800 BTU/BHP-hr | 500–5,000 HP | ~7.0 | Pipeline, process |
| Gas Turbine (Industrial) | 9,500–11,000 BTU/BHP-hr | 3,000–30,000 HP | ~10.0 | Pipeline mainline |
| Gas Turbine (Aero) | 8,500–9,500 BTU/BHP-hr | 5,000–50,000 HP | ~9.0 | LNG, offshore |
| Electric Motor | N/A (use kWh) | Any | N/A | All; zero on-site emissions |
Gas engine vs turbine selection, derating factors, fuel conditioning, and emissions regulations (RICE MACT, NSPS JJJJ).
Multiply rated brake horsepower by load factor and BSFC heat rate, then divide by fuel HHV to get SCF/hr: Q = BHP × LF × BSFC / HHV. A 1,000 BHP gas engine at 85% load with 7,500 BTU/BHP-hr BSFC and 1,020 BTU/SCF gas burns about 6,400 SCF/hr or 153 MSCFD.
Lean-burn gas engines run 7,000–8,500 BTU/BHP-hr (HHV); rich-burn engines 7,500–9,000; industrial gas turbines 9,500–11,000; aeroderivative turbines 8,500–9,500. Always confirm whether the OEM curve is on HHV or LHV basis — they differ by about 11% for natural gas.
Gas engines lose roughly 3% per 1,000 ft of elevation and 1% per 10°F above ISO 59°F. Gas turbines are more sensitive: about 3.5% per 1,000 ft and 0.5% per °F above ISO. A turbine rated 10,000 HP at sea level may deliver only 6,500–7,000 HP at 5,000 ft and 100°F.
Use HHV (higher heating value) consistently for both fuel and heat rate. Engine OEMs often quote heat rate on LHV basis (about 90% of HHV for natural gas), so convert before calculating: HR_HHV = HR_LHV × (HHV / LHV). Mixing HHV gas with an LHV heat rate underestimates fuel use by ~10%.
GPSA Engineering Data Book Section 15 covers driver selection and fuel calculations. API 616 (gas turbines) and API 618 (reciprocating compressors) cover the equipment. RICE MACT (40 CFR 63 Subpart ZZZZ) and NSPS JJJJ (40 CFR 60) govern emissions from stationary engines used as compressor drivers.