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City Heat: Heavy or Bio?

The CPCU (Paris City Heating Company) is considering replacement of Heavy Fuel Oil (HFO) by Biodiesel in a number of HFO-fired furnaces. Following an extensive measurement campaign, CFD simulations were commissioned to further assess the impact of this change in fuel type. Dacolt has worked with Laborelec, a GDF-Suez competence centre in electrical power technology, to realize the CFD simulations.

Internals of one of the HFO-fired furnaces at CPCU.

CFD model

The CFD simulations were realized with ANSYS® FLUENT® using the FGM (Flamelet Generated Manifold) combustion model. Surrogate model fuels were defined for HFO and Biodiesel. Detailed chemistry tables were generated with Tabkin®, Dacolt’s dedicated software package for combustion chemistry look-up table generation. With the selected approach, the differences between the fuels, both in liquid properties and in chemical kinetics, were modeled with state-of-the-art techniques.


The FGM method with Tabkin tables allowed to predict a lifted diffusion flame, stabilised in the correct location. Advanced Fluent models were used to model the steam-assisted fuel atomisation.

Flame stabilisationFuel and steam injection


 Left: Temperature contours showing the lifted diffusion flame. Right: Steam-assisted fuel atomisation.

The simulation results are in line with the findings from the measurement campaign; the difference in flame topology is illustrated by the images below. The results strengthened the conclusions on the impact of the change in fuel type, supporting the decision making process.

Heavy Fuel OilBiodiesel

Flame contours colored by temperature. Left: Heavy Fuel Oil, right: Biodiesel.