Modeling flame extinction and reignition in large eddy simulations with fast chemistry

Area of Science:

• Computational fluid dynamics
• Fire safety engineering
• Combustion science

Background:

• Large eddy simulation (LES) models are vital for simulating fire suppression.
• Accurate prediction of flame extinction and preventing reignition are critical challenges in fire modeling.
• Realistic fire scenarios require robust combustion models that handle oxygen-dilution effects.

Purpose of the Study:

• To validate LES models for fire suppression, specifically focusing on flame extinction and reignition.
• To evaluate critical-flame-temperature-based extinction and reignition models within the Fire Dynamics Simulator (FDS).
• To assess the impact of different reignition treatments on model accuracy.

Main Methods:

• Simulation of a buoyant, turbulent methane diffusion flame with a co-flowing oxidizer using a fast chemistry, mixing-controlled combustion model.
• Experimental measurements including thermocouple temperature, oxygen mole fraction, combustion efficiency, and limiting oxygen index.
• Evaluation of FDS performance using various extinction and reignition model configurations.

Main Results:

• Models incorporating mechanisms to prevent spurious reignition demonstrated excellent agreement with experimental data.
• A baseline model without explicit reignition treatment failed to accurately predict flame extinction.
• Oxygen-dilution conditions in the oxidizer were shown to induce flame extinction.

Conclusions:

• Effective prevention of spurious reignition is essential for accurate LES prediction of flame extinction in fire suppression.
• The validated models provide improved capabilities for simulating realistic fire scenarios.
• This research supports the development of more reliable fire suppression simulations.