Estimate the lower calorific value of a marine fuel from a short assay (density, water, sulphur, ash) per ASTM D4868 / ISO 8217 Annex G. The IMO DCS fallback when direct bomb-calorimeter data is missing.
Formula
$$ \text{GCV} = 46.423 - 8.792 \rho_{15}^2 \cdot 10^{-6} - 3.170 \rho_{15} \cdot 10^{-3} $$
$$ \text{LCV} = \text{GCV} \cdot (1 - 0.01(w + s + a)) - 0.0212 H - 0.0245 w $$
Symbol legend
| Symbol | Meaning | Unit | Source |
|---|---|---|---|
| $\text{GCV}$ | Gross (higher) calorific value | MJ / kg | intermediate |
| $\text{LCV}$ | Lower (net) calorific value - used in MRV/DCS energy | MJ / kg | result |
| $\rho_{15}$ | Density at 15 °C | kg / m³ | BDN certificate |
| $w$ | Water content | % m/m | ISO 3733 |
| $s$ | Sulphur content | % m/m | ISO 8754 / 14596 |
| $a$ | Ash content | % m/m | ISO 6245 |
| $H$ | Hydrogen content - approximated $26 - 15\rho/1000$ for residuals | % m/m | empirical |
The estimator is accurate to ±0.5 MJ/kg for ISO 8217 RMG/RMK grades. For distillates it under-reads slightly; prefer a bomb-calorimeter test where available.
Sources
- ASTM D4868 - standard test method for gross heat of combustion.
- ISO 8217 - marine fuels specification, Annex G.