Fuel Mass Flow Rate Calculator
Calculation Result
Mass Flow Rate: 0 kg/hr
How to Calculate Fuel Mass Flow Rate
Understanding fuel mass flow rate is critical in automotive engineering, aviation, and industrial fluid dynamics. Unlike volume flow rate, which changes with temperature due to expansion and contraction, mass flow rate remains constant regardless of temperature or pressure changes. This makes it the most accurate metric for determining fuel delivery to an engine.
What is Fuel Mass Flow Rate?
Fuel mass flow rate, denoted typically as ṁ (m-dot), represents the mass of fuel that passes through a given cross-section per unit of time. It is essentially a measure of the "weight" of fuel consumed by an engine every hour or second. The standard SI unit is kilograms per hour (kg/hr) or kilograms per second (kg/s).
Formula 1: Using Volume Flow and Density
The most direct way to calculate mass flow rate is by knowing the volume of fuel flowing and the density of that specific fuel. Since fuel pumps and flow meters often measure volume (Liters or Gallons), this formula converts that volume into mass.
Formula:
ṁ = Q × ρ
- ṁ = Mass Flow Rate (kg/hr)
- Q = Volume Flow Rate (Liters/hr)
- ρ (rho) = Fuel Density (kg/L)
Example: If an engine consumes 50 Liters of gasoline per hour and the density of gasoline is 0.74 kg/L, the mass flow rate is 50 × 0.74 = 37 kg/hr.
Formula 2: Using Engine Power and BSFC
Engineers often need to estimate fuel flow based on engine performance data. Brake Specific Fuel Consumption (BSFC) is a measure of fuel efficiency that indicates how much fuel mass is consumed to produce one unit of power energy.
Formula:
ṁ = (P × BSFC) / 1000
- ṁ = Mass Flow Rate (kg/hr)
- P = Engine Power output (kW)
- BSFC = Brake Specific Fuel Consumption (grams per kilowatt-hour, g/kWh)
- 1000 = Conversion factor from grams to kilograms
Example: A 100 kW engine running at a BSFC of 240 g/kWh would consume (100 × 240) / 1000 = 24 kg of fuel per hour.
Why Fuel Density Matters
Fuel density varies significantly by type and temperature.
- Gasoline: Approx. 0.71 – 0.77 kg/L
- Diesel: Approx. 0.82 – 0.85 kg/L
- Jet A-1: Approx. 0.804 kg/L
Because diesel is denser than gasoline, a liter of diesel contains more mass (and therefore more chemical energy) than a liter of gasoline. This is why mass flow rate calculations are essential for accurate efficiency comparisons and stoichiometric tuning.