FUND Project

The aim of the FUND Project is to improve the use of numerical simulation tools (Computational Fluid Dynamics (CFD) models) for the assessment of fire risk applications in nuclear fields. In particular, the objective of this study is to develop finite-rate chemistry models that can be used to better predict the so-called under-ventilated combustion regimes, encountered in nuclear facilities (and in buildings and or industries). Nowadays, two of the main challenges for CFD tools for compartment fire modeling are the assessment of the transition to under-ventilated combustion and the numerical capability of the model to predict the presence and concentration of flammable vapors (unburned fuel) inside the fire compartment. In this context of improving fire modeling for nuclear applications, the collaborative FUND project joins the numerical skills of the Ghent University team and the experimental skills of ASNR.

A series of fire tests were carried out using the NYX apparatus. The tests consisted of reproducing the combustion of a propane gas burner in a closed and mechanically ventilated chamber. The test parameters were the propane flow rate, the ventilation flow rate and the position of the air inlet. The test apparatus is instrumented to measure the ventilation flow rates, the propane flow rate, the temperature in the chamber and the concentration of the chemical species O2, CO2 and CO. The duration of the experiment is about 30 minutes.

About 40 experiments have been performed. No major difficulties were encountered. The experiments were successfully completed. For each experiment, the measurements are recorded and processed.

The implementation of this test campaign has made it possible to study the behaviour of a combustion process in a confined and mechanically ventilated situation, focusing on the production of carbon monoxide (CO). The results confirm the existence of two combustion regimes, one is controlled by the fuel flow rate, and the other is by the ventilation rate. The transition between the two regimes corresponds to the most critical situation in terms of fire risk, where the combustion is at the extinguishing limit, resulting in the highest temperature. The CO production is also at its maximum when the oxygen concentration is close to the extinction limit. The results highlight the influence of the ratio of fuel flow rate to ventilation flow rate on CO production. Additionally, the results provide new insights into the mechanisms of CO production. Furthermore, it will help the validation of the simulation model to predict these mechanisms. This work will be promoted through scientific publications in major fire risk and combustion science journals.

Research could be useful for the activities of the following:

Industries:

• Process-plant Industries (Honeywell UOP, Zeeco)
• Power generations (Siemens, EDF)

Research institutes:

• Fire research institutes (FM, NIST, UL FSRI)

Universities:

• Universities with compartment fire research (Lund University, University of Edinburgh, University of Poitiers)