Thrust Specific Fuel Consumption Calculator Formula
Understand the math behind the thrust specific fuel consumption calculator. Each variable explained with a worked example.
Formulas Used
TSFC
tsfc_kg_kn_h = fuel_flow / thrustTSFC (SI)
tsfc_g_kn_s = fuel_flow / thrust / 3.6Variables
| Variable | Description | Default |
|---|---|---|
fuel_flow | Fuel Flow Rate(kg/h) | 2500 |
thrust | Net Thrust(kN) | 100 |
thrust_n | Derived value= thrust * 1000 | calculated |
How It Works
Thrust Specific Fuel Consumption
TSFC measures how efficiently a jet engine converts fuel into thrust. Lower values indicate better fuel economy.
Formula
TSFC = fuel_flow / Thrust
where fuel_flow is in kg/h and thrust in kN for the common industry unit of kg/(kN·h). Modern high-bypass turbofans achieve TSFC values around 15-20 g/(kN·s). Turbojet engines are less efficient at about 25-30 g/(kN·s).
Worked Example
A turbofan engine producing 100 kN of thrust while burning 2500 kg/h of fuel.
- 01TSFC = 2500 kg/h ÷ 100 kN = 25 kg/(kN·h)
- 02Convert to SI: 25 / 3.6 = 6.944 g/(kN·s)
Frequently Asked Questions
What is a good TSFC value?
Modern high-bypass turbofans have TSFC around 15-17 g/(kN·s) at cruise. Lower TSFC means better fuel efficiency. Older turbojet designs may have TSFC of 25-30 g/(kN·s).
How does TSFC vary with altitude?
TSFC generally improves (decreases) at higher altitudes due to lower air temperature improving the thermodynamic cycle efficiency. However, thrust also decreases with altitude.
What is the difference between TSFC and BSFC?
TSFC applies to jet engines and relates fuel consumption to thrust. BSFC (brake specific fuel consumption) applies to piston and turboprop engines and relates fuel consumption to shaft power.
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